Source file src/cmd/link/internal/ld/dwarf.go

     1  // Copyright 2019 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  // TODO/NICETOHAVE:
     6  //   - eliminate DW_CLS_ if not used
     7  //   - package info in compilation units
     8  //   - assign types to their packages
     9  //   - gdb uses c syntax, meaning clumsy quoting is needed for go identifiers. eg
    10  //     ptype struct '[]uint8' and qualifiers need to be quoted away
    11  //   - file:line info for variables
    12  //   - make strings a typedef so prettyprinters can see the underlying string type
    13  
    14  package ld
    15  
    16  import (
    17  	"cmd/internal/dwarf"
    18  	"cmd/internal/obj"
    19  	"cmd/internal/objabi"
    20  	"cmd/internal/src"
    21  	"cmd/internal/sys"
    22  	"cmd/link/internal/loader"
    23  	"cmd/link/internal/sym"
    24  	"cmp"
    25  	"fmt"
    26  	"internal/abi"
    27  	"internal/buildcfg"
    28  	"log"
    29  	"path"
    30  	"runtime"
    31  	"slices"
    32  	"strings"
    33  	"sync"
    34  )
    35  
    36  // dwctxt is a wrapper intended to satisfy the method set of
    37  // dwarf.Context, so that functions like dwarf.PutAttrs will work with
    38  // DIEs that use loader.Sym as opposed to *sym.Symbol. It is also
    39  // being used as a place to store tables/maps that are useful as part
    40  // of type conversion (this is just a convenience; it would be easy to
    41  // split these things out into another type if need be).
    42  type dwctxt struct {
    43  	linkctxt *Link
    44  	ldr      *loader.Loader
    45  	arch     *sys.Arch
    46  
    47  	// This maps type name string (e.g. "uintptr") to loader symbol for
    48  	// the DWARF DIE for that type (e.g. "go:info.type.uintptr")
    49  	tmap map[string]loader.Sym
    50  
    51  	// This maps loader symbol for the DWARF DIE symbol generated for
    52  	// a type (e.g. "go:info.uintptr") to the type symbol itself
    53  	// ("type:uintptr").
    54  	// FIXME: try converting this map (and the next one) to a single
    55  	// array indexed by loader.Sym -- this may perform better.
    56  	rtmap map[loader.Sym]loader.Sym
    57  
    58  	// This maps Go type symbol (e.g. "type:XXX") to loader symbol for
    59  	// the typedef DIE for that type (e.g. "go:info.XXX..def")
    60  	tdmap map[loader.Sym]loader.Sym
    61  
    62  	// Cache these type symbols, so as to avoid repeatedly looking them up
    63  	typeRuntimeEface loader.Sym
    64  	typeRuntimeIface loader.Sym
    65  	uintptrInfoSym   loader.Sym
    66  
    67  	// Used at various points in that parallel portion of DWARF gen to
    68  	// protect against conflicting updates to globals (such as "gdbscript")
    69  	dwmu *sync.Mutex
    70  }
    71  
    72  // dwSym wraps a loader.Sym; this type is meant to obey the interface
    73  // rules for dwarf.Sym from the cmd/internal/dwarf package. DwDie and
    74  // DwAttr objects contain references to symbols via this type.
    75  type dwSym loader.Sym
    76  
    77  func (c dwctxt) PtrSize() int {
    78  	return c.arch.PtrSize
    79  }
    80  
    81  func (c dwctxt) Size(s dwarf.Sym) int64 {
    82  	return int64(len(c.ldr.Data(loader.Sym(s.(dwSym)))))
    83  }
    84  
    85  func (c dwctxt) AddInt(s dwarf.Sym, size int, i int64) {
    86  	ds := loader.Sym(s.(dwSym))
    87  	dsu := c.ldr.MakeSymbolUpdater(ds)
    88  	dsu.AddUintXX(c.arch, uint64(i), size)
    89  }
    90  
    91  func (c dwctxt) AddBytes(s dwarf.Sym, b []byte) {
    92  	ds := loader.Sym(s.(dwSym))
    93  	dsu := c.ldr.MakeSymbolUpdater(ds)
    94  	dsu.AddBytes(b)
    95  }
    96  
    97  func (c dwctxt) AddString(s dwarf.Sym, v string) {
    98  	ds := loader.Sym(s.(dwSym))
    99  	dsu := c.ldr.MakeSymbolUpdater(ds)
   100  	dsu.Addstring(v)
   101  }
   102  
   103  func (c dwctxt) AddAddress(s dwarf.Sym, data interface{}, value int64) {
   104  	ds := loader.Sym(s.(dwSym))
   105  	dsu := c.ldr.MakeSymbolUpdater(ds)
   106  	if value != 0 {
   107  		value -= dsu.Value()
   108  	}
   109  	tgtds := loader.Sym(data.(dwSym))
   110  	dsu.AddAddrPlus(c.arch, tgtds, value)
   111  }
   112  
   113  func (c dwctxt) AddCURelativeAddress(s dwarf.Sym, data interface{}, value int64) {
   114  	ds := loader.Sym(s.(dwSym))
   115  	dsu := c.ldr.MakeSymbolUpdater(ds)
   116  	if value != 0 {
   117  		value -= dsu.Value()
   118  	}
   119  	tgtds := loader.Sym(data.(dwSym))
   120  	dsu.AddCURelativeAddrPlus(c.arch, tgtds, value)
   121  }
   122  
   123  func (c dwctxt) AddSectionOffset(s dwarf.Sym, size int, t interface{}, ofs int64) {
   124  	ds := loader.Sym(s.(dwSym))
   125  	dsu := c.ldr.MakeSymbolUpdater(ds)
   126  	tds := loader.Sym(t.(dwSym))
   127  	switch size {
   128  	default:
   129  		c.linkctxt.Errorf(ds, "invalid size %d in adddwarfref\n", size)
   130  	case c.arch.PtrSize, 4:
   131  	}
   132  	dsu.AddSymRef(c.arch, tds, ofs, objabi.R_ADDROFF, size)
   133  }
   134  
   135  func (c dwctxt) AddDWARFAddrSectionOffset(s dwarf.Sym, t interface{}, ofs int64) {
   136  	size := 4
   137  	if isDwarf64(c.linkctxt) {
   138  		size = 8
   139  	}
   140  	ds := loader.Sym(s.(dwSym))
   141  	dsu := c.ldr.MakeSymbolUpdater(ds)
   142  	tds := loader.Sym(t.(dwSym))
   143  	switch size {
   144  	default:
   145  		c.linkctxt.Errorf(ds, "invalid size %d in adddwarfref\n", size)
   146  	case c.arch.PtrSize, 4:
   147  	}
   148  	dsu.AddSymRef(c.arch, tds, ofs, objabi.R_DWARFSECREF, size)
   149  }
   150  
   151  func (c dwctxt) AddIndirectTextRef(s dwarf.Sym, t interface{}) {
   152  	ds := loader.Sym(s.(dwSym))
   153  	dsu := c.ldr.MakeSymbolUpdater(ds)
   154  	tds := loader.Sym(t.(dwSym))
   155  	dsu.AddSymRef(c.arch, tds, 0, objabi.R_DWTXTADDR_U4, 4)
   156  }
   157  
   158  func (c dwctxt) Logf(format string, args ...interface{}) {
   159  	c.linkctxt.Logf(format, args...)
   160  }
   161  
   162  // At the moment these interfaces are only used in the compiler.
   163  
   164  func (c dwctxt) CurrentOffset(s dwarf.Sym) int64 {
   165  	panic("should be used only in the compiler")
   166  }
   167  
   168  func (c dwctxt) RecordDclReference(s dwarf.Sym, t dwarf.Sym, dclIdx int, inlIndex int) {
   169  	panic("should be used only in the compiler")
   170  }
   171  
   172  func (c dwctxt) RecordChildDieOffsets(s dwarf.Sym, vars []*dwarf.Var, offsets []int32) {
   173  	panic("should be used only in the compiler")
   174  }
   175  
   176  func isDwarf64(ctxt *Link) bool {
   177  	return ctxt.HeadType == objabi.Haix
   178  }
   179  
   180  // https://sourceware.org/gdb/onlinedocs/gdb/dotdebug_005fgdb_005fscripts-section.html
   181  // Each entry inside .debug_gdb_scripts section begins with a non-null prefix
   182  // byte that specifies the kind of entry. The following entries are supported:
   183  const (
   184  	GdbScriptPythonFileId = 1
   185  	GdbScriptSchemeFileId = 3
   186  	GdbScriptPythonTextId = 4
   187  	GdbScriptSchemeTextId = 6
   188  )
   189  
   190  var gdbscript string
   191  
   192  // dwarfSecInfo holds information about a DWARF output section,
   193  // specifically a section symbol and a list of symbols contained in
   194  // that section. On the syms list, the first symbol will always be the
   195  // section symbol, then any remaining symbols (if any) will be
   196  // sub-symbols in that section. Note that for some sections (eg:
   197  // .debug_abbrev), the section symbol is all there is (all content is
   198  // contained in it). For other sections (eg: .debug_info), the section
   199  // symbol is empty and all the content is in the sub-symbols. Finally
   200  // there are some sections (eg: .debug_ranges) where it is a mix (both
   201  // the section symbol and the sub-symbols have content)
   202  type dwarfSecInfo struct {
   203  	syms []loader.Sym
   204  }
   205  
   206  // secSym returns the section symbol for the section.
   207  func (dsi *dwarfSecInfo) secSym() loader.Sym {
   208  	if len(dsi.syms) == 0 {
   209  		return 0
   210  	}
   211  	return dsi.syms[0]
   212  }
   213  
   214  // subSyms returns a list of sub-symbols for the section.
   215  func (dsi *dwarfSecInfo) subSyms() []loader.Sym {
   216  	if len(dsi.syms) == 0 {
   217  		return []loader.Sym{}
   218  	}
   219  	return dsi.syms[1:]
   220  }
   221  
   222  // dwarfp stores the collected DWARF symbols created during
   223  // dwarf generation.
   224  var dwarfp []dwarfSecInfo
   225  
   226  func (d *dwctxt) writeabbrev() dwarfSecInfo {
   227  	abrvs := d.ldr.CreateSymForUpdate(".debug_abbrev", 0)
   228  	abrvs.SetType(sym.SDWARFSECT)
   229  	abrvs.AddBytes(dwarf.GetAbbrev())
   230  	return dwarfSecInfo{syms: []loader.Sym{abrvs.Sym()}}
   231  }
   232  
   233  var dwtypes dwarf.DWDie
   234  
   235  // newattr attaches a new attribute to the specified DIE.
   236  //
   237  // FIXME: at the moment attributes are stored in a linked list in a
   238  // fairly space-inefficient way -- it might be better to instead look
   239  // up all attrs in a single large table, then store indices into the
   240  // table in the DIE. This would allow us to common up storage for
   241  // attributes that are shared by many DIEs (ex: byte size of N).
   242  func newattr(die *dwarf.DWDie, attr uint16, cls int, value int64, data interface{}) {
   243  	a := new(dwarf.DWAttr)
   244  	a.Link = die.Attr
   245  	die.Attr = a
   246  	a.Atr = attr
   247  	a.Cls = uint8(cls)
   248  	a.Value = value
   249  	a.Data = data
   250  }
   251  
   252  // Each DIE (except the root ones) has at least 1 attribute: its
   253  // name. getattr moves the desired one to the front so
   254  // frequently searched ones are found faster.
   255  func getattr(die *dwarf.DWDie, attr uint16) *dwarf.DWAttr {
   256  	if die.Attr.Atr == attr {
   257  		return die.Attr
   258  	}
   259  
   260  	a := die.Attr
   261  	b := a.Link
   262  	for b != nil {
   263  		if b.Atr == attr {
   264  			a.Link = b.Link
   265  			b.Link = die.Attr
   266  			die.Attr = b
   267  			return b
   268  		}
   269  
   270  		a = b
   271  		b = b.Link
   272  	}
   273  
   274  	return nil
   275  }
   276  
   277  // Every DIE manufactured by the linker has at least an AT_name
   278  // attribute (but it will only be written out if it is listed in the abbrev).
   279  // The compiler does create nameless DWARF DIEs (ex: concrete subprogram
   280  // instance).
   281  // FIXME: it would be more efficient to bulk-allocate DIEs.
   282  func (d *dwctxt) newdie(parent *dwarf.DWDie, abbrev int, name string) *dwarf.DWDie {
   283  	die := new(dwarf.DWDie)
   284  	die.Abbrev = abbrev
   285  	die.Link = parent.Child
   286  	parent.Child = die
   287  
   288  	newattr(die, dwarf.DW_AT_name, dwarf.DW_CLS_STRING, int64(len(name)), name)
   289  
   290  	// Sanity check: all DIEs created in the linker should be named.
   291  	if name == "" {
   292  		panic("nameless DWARF DIE")
   293  	}
   294  
   295  	var st sym.SymKind
   296  	switch abbrev {
   297  	case dwarf.DW_ABRV_FUNCTYPEPARAM, dwarf.DW_ABRV_FUNCTYPEOUTPARAM, dwarf.DW_ABRV_DOTDOTDOT, dwarf.DW_ABRV_STRUCTFIELD, dwarf.DW_ABRV_ARRAYRANGE:
   298  		// There are no relocations against these dies, and their names
   299  		// are not unique, so don't create a symbol.
   300  		return die
   301  	case dwarf.DW_ABRV_COMPUNIT, dwarf.DW_ABRV_COMPUNIT_TEXTLESS:
   302  		// Avoid collisions with "real" symbol names.
   303  		name = fmt.Sprintf(".pkg.%s.%d", name, len(d.linkctxt.compUnits))
   304  		st = sym.SDWARFCUINFO
   305  	case dwarf.DW_ABRV_VARIABLE:
   306  		st = sym.SDWARFVAR
   307  	default:
   308  		// Everything else is assigned a type of SDWARFTYPE. that
   309  		// this also includes loose ends such as STRUCT_FIELD.
   310  		st = sym.SDWARFTYPE
   311  	}
   312  	ds := d.ldr.LookupOrCreateSym(dwarf.InfoPrefix+name, 0)
   313  	dsu := d.ldr.MakeSymbolUpdater(ds)
   314  	dsu.SetType(st)
   315  	d.ldr.SetAttrNotInSymbolTable(ds, true)
   316  	d.ldr.SetAttrReachable(ds, true)
   317  	die.Sym = dwSym(ds)
   318  	if abbrev >= dwarf.DW_ABRV_NULLTYPE && abbrev <= dwarf.DW_ABRV_TYPEDECL {
   319  		d.tmap[name] = ds
   320  	}
   321  
   322  	return die
   323  }
   324  
   325  func walktypedef(die *dwarf.DWDie) *dwarf.DWDie {
   326  	if die == nil {
   327  		return nil
   328  	}
   329  	// Resolve typedef if present.
   330  	if die.Abbrev == dwarf.DW_ABRV_TYPEDECL {
   331  		for attr := die.Attr; attr != nil; attr = attr.Link {
   332  			if attr.Atr == dwarf.DW_AT_type && attr.Cls == dwarf.DW_CLS_REFERENCE && attr.Data != nil {
   333  				return attr.Data.(*dwarf.DWDie)
   334  			}
   335  		}
   336  	}
   337  
   338  	return die
   339  }
   340  
   341  func (d *dwctxt) walksymtypedef(symIdx loader.Sym) loader.Sym {
   342  
   343  	// We're being given the loader symbol for the type DIE, e.g.
   344  	// "go:info.type.uintptr". Map that first to the type symbol (e.g.
   345  	// "type:uintptr") and then to the typedef DIE for the type.
   346  	// FIXME: this seems clunky, maybe there is a better way to do this.
   347  
   348  	if ts, ok := d.rtmap[symIdx]; ok {
   349  		if def, ok := d.tdmap[ts]; ok {
   350  			return def
   351  		}
   352  		d.linkctxt.Errorf(ts, "internal error: no entry for sym %d in tdmap\n", ts)
   353  		return 0
   354  	}
   355  	d.linkctxt.Errorf(symIdx, "internal error: no entry for sym %d in rtmap\n", symIdx)
   356  	return 0
   357  }
   358  
   359  // Find child by AT_name using hashtable if available or linear scan
   360  // if not.
   361  func findchild(die *dwarf.DWDie, name string) *dwarf.DWDie {
   362  	var prev *dwarf.DWDie
   363  	for ; die != prev; prev, die = die, walktypedef(die) {
   364  		for a := die.Child; a != nil; a = a.Link {
   365  			if name == getattr(a, dwarf.DW_AT_name).Data {
   366  				return a
   367  			}
   368  		}
   369  		continue
   370  	}
   371  	return nil
   372  }
   373  
   374  // find looks up the loader symbol for the DWARF DIE generated for the
   375  // type with the specified name.
   376  func (d *dwctxt) find(name string) loader.Sym {
   377  	return d.tmap[name]
   378  }
   379  
   380  func (d *dwctxt) mustFind(name string) loader.Sym {
   381  	r := d.find(name)
   382  	if r == 0 {
   383  		Exitf("dwarf find: cannot find %s", name)
   384  	}
   385  	return r
   386  }
   387  
   388  func (d *dwctxt) adddwarfref(sb *loader.SymbolBuilder, t loader.Sym, size int) {
   389  	switch size {
   390  	default:
   391  		d.linkctxt.Errorf(sb.Sym(), "invalid size %d in adddwarfref\n", size)
   392  	case d.arch.PtrSize, 4:
   393  	}
   394  	sb.AddSymRef(d.arch, t, 0, objabi.R_DWARFSECREF, size)
   395  }
   396  
   397  func (d *dwctxt) newrefattr(die *dwarf.DWDie, attr uint16, ref loader.Sym) {
   398  	if ref == 0 {
   399  		return
   400  	}
   401  	newattr(die, attr, dwarf.DW_CLS_REFERENCE, 0, dwSym(ref))
   402  }
   403  
   404  func (d *dwctxt) dtolsym(s dwarf.Sym) loader.Sym {
   405  	if s == nil {
   406  		return 0
   407  	}
   408  	dws := loader.Sym(s.(dwSym))
   409  	return dws
   410  }
   411  
   412  func (d *dwctxt) putdie(syms []loader.Sym, die *dwarf.DWDie) []loader.Sym {
   413  	s := d.dtolsym(die.Sym)
   414  	if s == 0 {
   415  		s = syms[len(syms)-1]
   416  	} else {
   417  		syms = append(syms, s)
   418  	}
   419  	sDwsym := dwSym(s)
   420  	dwarf.Uleb128put(d, sDwsym, int64(die.Abbrev))
   421  	dwarf.PutAttrs(d, sDwsym, die.Abbrev, die.Attr)
   422  	if dwarf.HasChildren(die) {
   423  		for die := die.Child; die != nil; die = die.Link {
   424  			syms = d.putdie(syms, die)
   425  		}
   426  		dsu := d.ldr.MakeSymbolUpdater(syms[len(syms)-1])
   427  		dsu.AddUint8(0)
   428  	}
   429  	return syms
   430  }
   431  
   432  func reverselist(list **dwarf.DWDie) {
   433  	curr := *list
   434  	var prev *dwarf.DWDie
   435  	for curr != nil {
   436  		next := curr.Link
   437  		curr.Link = prev
   438  		prev = curr
   439  		curr = next
   440  	}
   441  
   442  	*list = prev
   443  }
   444  
   445  func reversetree(list **dwarf.DWDie) {
   446  	reverselist(list)
   447  	for die := *list; die != nil; die = die.Link {
   448  		if dwarf.HasChildren(die) {
   449  			reversetree(&die.Child)
   450  		}
   451  	}
   452  }
   453  
   454  func newmemberoffsetattr(die *dwarf.DWDie, offs int32) {
   455  	newattr(die, dwarf.DW_AT_data_member_location, dwarf.DW_CLS_CONSTANT, int64(offs), nil)
   456  }
   457  
   458  func (d *dwctxt) lookupOrDiag(n string) loader.Sym {
   459  	symIdx := d.ldr.Lookup(n, 0)
   460  	if symIdx == 0 {
   461  		Exitf("dwarf: missing type: %s", n)
   462  	}
   463  	if len(d.ldr.Data(symIdx)) == 0 {
   464  		Exitf("dwarf: missing type (no data): %s", n)
   465  	}
   466  
   467  	return symIdx
   468  }
   469  
   470  func (d *dwctxt) dotypedef(parent *dwarf.DWDie, name string, def *dwarf.DWDie) *dwarf.DWDie {
   471  	// Only emit typedefs for real names.
   472  	if strings.HasPrefix(name, "map[") {
   473  		return nil
   474  	}
   475  	if strings.HasPrefix(name, "struct {") {
   476  		return nil
   477  	}
   478  	// cmd/compile uses "noalg.struct {...}" as type name when hash and eq algorithm generation of
   479  	// this struct type is suppressed.
   480  	if strings.HasPrefix(name, "noalg.struct {") {
   481  		return nil
   482  	}
   483  	if strings.HasPrefix(name, "chan ") {
   484  		return nil
   485  	}
   486  	if name[0] == '[' || name[0] == '*' {
   487  		return nil
   488  	}
   489  	if def == nil {
   490  		Errorf("dwarf: bad def in dotypedef")
   491  	}
   492  
   493  	// Create a new loader symbol for the typedef. We no longer
   494  	// do lookups of typedef symbols by name, so this is going
   495  	// to be an anonymous symbol (we want this for perf reasons).
   496  	tds := d.ldr.CreateExtSym("", 0)
   497  	tdsu := d.ldr.MakeSymbolUpdater(tds)
   498  	tdsu.SetType(sym.SDWARFTYPE)
   499  	def.Sym = dwSym(tds)
   500  	d.ldr.SetAttrNotInSymbolTable(tds, true)
   501  	d.ldr.SetAttrReachable(tds, true)
   502  
   503  	// The typedef entry must be created after the def,
   504  	// so that future lookups will find the typedef instead
   505  	// of the real definition. This hooks the typedef into any
   506  	// circular definition loops, so that gdb can understand them.
   507  	die := d.newdie(parent, dwarf.DW_ABRV_TYPEDECL, name)
   508  
   509  	d.newrefattr(die, dwarf.DW_AT_type, tds)
   510  
   511  	return die
   512  }
   513  
   514  // Define gotype, for composite ones recurse into constituents.
   515  func (d *dwctxt) defgotype(gotype loader.Sym) loader.Sym {
   516  	if gotype == 0 {
   517  		return d.mustFind("<unspecified>")
   518  	}
   519  
   520  	// If we already have a tdmap entry for the gotype, return it.
   521  	if ds, ok := d.tdmap[gotype]; ok {
   522  		return ds
   523  	}
   524  
   525  	sn := d.ldr.SymName(gotype)
   526  	if !strings.HasPrefix(sn, "type:") {
   527  		d.linkctxt.Errorf(gotype, "dwarf: type name doesn't start with \"type:\"")
   528  		return d.mustFind("<unspecified>")
   529  	}
   530  	name := sn[len("type:"):] // could also decode from Type.string
   531  
   532  	sdie := d.find(name)
   533  	if sdie != 0 {
   534  		return sdie
   535  	}
   536  
   537  	gtdwSym := d.newtype(gotype)
   538  	d.tdmap[gotype] = loader.Sym(gtdwSym.Sym.(dwSym))
   539  	return loader.Sym(gtdwSym.Sym.(dwSym))
   540  }
   541  
   542  func (d *dwctxt) newtype(gotype loader.Sym) *dwarf.DWDie {
   543  	sn := d.ldr.SymName(gotype)
   544  	name := sn[len("type:"):] // could also decode from Type.string
   545  	tdata := d.ldr.Data(gotype)
   546  	if len(tdata) == 0 {
   547  		d.linkctxt.Errorf(gotype, "missing type")
   548  	}
   549  	kind := decodetypeKind(d.arch, tdata)
   550  	bytesize := decodetypeSize(d.arch, tdata)
   551  
   552  	var die, typedefdie *dwarf.DWDie
   553  	switch kind {
   554  	case abi.Bool:
   555  		die = d.newdie(&dwtypes, dwarf.DW_ABRV_BASETYPE, name)
   556  		newattr(die, dwarf.DW_AT_encoding, dwarf.DW_CLS_CONSTANT, dwarf.DW_ATE_boolean, 0)
   557  		newattr(die, dwarf.DW_AT_byte_size, dwarf.DW_CLS_CONSTANT, bytesize, 0)
   558  
   559  	case abi.Int,
   560  		abi.Int8,
   561  		abi.Int16,
   562  		abi.Int32,
   563  		abi.Int64:
   564  		die = d.newdie(&dwtypes, dwarf.DW_ABRV_BASETYPE, name)
   565  		newattr(die, dwarf.DW_AT_encoding, dwarf.DW_CLS_CONSTANT, dwarf.DW_ATE_signed, 0)
   566  		newattr(die, dwarf.DW_AT_byte_size, dwarf.DW_CLS_CONSTANT, bytesize, 0)
   567  
   568  	case abi.Uint,
   569  		abi.Uint8,
   570  		abi.Uint16,
   571  		abi.Uint32,
   572  		abi.Uint64,
   573  		abi.Uintptr:
   574  		die = d.newdie(&dwtypes, dwarf.DW_ABRV_BASETYPE, name)
   575  		newattr(die, dwarf.DW_AT_encoding, dwarf.DW_CLS_CONSTANT, dwarf.DW_ATE_unsigned, 0)
   576  		newattr(die, dwarf.DW_AT_byte_size, dwarf.DW_CLS_CONSTANT, bytesize, 0)
   577  
   578  	case abi.Float32,
   579  		abi.Float64:
   580  		die = d.newdie(&dwtypes, dwarf.DW_ABRV_BASETYPE, name)
   581  		newattr(die, dwarf.DW_AT_encoding, dwarf.DW_CLS_CONSTANT, dwarf.DW_ATE_float, 0)
   582  		newattr(die, dwarf.DW_AT_byte_size, dwarf.DW_CLS_CONSTANT, bytesize, 0)
   583  
   584  	case abi.Complex64,
   585  		abi.Complex128:
   586  		die = d.newdie(&dwtypes, dwarf.DW_ABRV_BASETYPE, name)
   587  		newattr(die, dwarf.DW_AT_encoding, dwarf.DW_CLS_CONSTANT, dwarf.DW_ATE_complex_float, 0)
   588  		newattr(die, dwarf.DW_AT_byte_size, dwarf.DW_CLS_CONSTANT, bytesize, 0)
   589  
   590  	case abi.Array:
   591  		die = d.newdie(&dwtypes, dwarf.DW_ABRV_ARRAYTYPE, name)
   592  		typedefdie = d.dotypedef(&dwtypes, name, die)
   593  		newattr(die, dwarf.DW_AT_byte_size, dwarf.DW_CLS_CONSTANT, bytesize, 0)
   594  		s := decodetypeArrayElem(d.linkctxt, d.arch, gotype)
   595  		d.newrefattr(die, dwarf.DW_AT_type, d.defgotype(s))
   596  		fld := d.newdie(die, dwarf.DW_ABRV_ARRAYRANGE, "range")
   597  
   598  		// use actual length not upper bound; correct for 0-length arrays.
   599  		newattr(fld, dwarf.DW_AT_count, dwarf.DW_CLS_CONSTANT, decodetypeArrayLen(d.ldr, d.arch, gotype), 0)
   600  
   601  		d.newrefattr(fld, dwarf.DW_AT_type, d.uintptrInfoSym)
   602  
   603  	case abi.Chan:
   604  		die = d.newdie(&dwtypes, dwarf.DW_ABRV_CHANTYPE, name)
   605  		s := decodetypeChanElem(d.ldr, d.arch, gotype)
   606  		d.newrefattr(die, dwarf.DW_AT_go_elem, d.defgotype(s))
   607  		// Save elem type for synthesizechantypes. We could synthesize here
   608  		// but that would change the order of DIEs we output.
   609  		d.newrefattr(die, dwarf.DW_AT_type, s)
   610  
   611  	case abi.Func:
   612  		die = d.newdie(&dwtypes, dwarf.DW_ABRV_FUNCTYPE, name)
   613  		newattr(die, dwarf.DW_AT_byte_size, dwarf.DW_CLS_CONSTANT, bytesize, 0)
   614  		typedefdie = d.dotypedef(&dwtypes, name, die)
   615  		data := d.ldr.Data(gotype)
   616  		// FIXME: add caching or reuse reloc slice.
   617  		relocs := d.ldr.Relocs(gotype)
   618  		nfields := decodetypeFuncInCount(d.arch, data)
   619  		for i := 0; i < nfields; i++ {
   620  			s := decodetypeFuncInType(d.ldr, d.arch, gotype, &relocs, i)
   621  			sn := d.ldr.SymName(s)
   622  			fld := d.newdie(die, dwarf.DW_ABRV_FUNCTYPEPARAM, sn[5:])
   623  			d.newrefattr(fld, dwarf.DW_AT_type, d.defgotype(s))
   624  		}
   625  
   626  		if decodetypeFuncDotdotdot(d.arch, data) {
   627  			d.newdie(die, dwarf.DW_ABRV_DOTDOTDOT, "...")
   628  		}
   629  		nfields = decodetypeFuncOutCount(d.arch, data)
   630  		for i := 0; i < nfields; i++ {
   631  			s := decodetypeFuncOutType(d.ldr, d.arch, gotype, &relocs, i)
   632  			sn := d.ldr.SymName(s)
   633  			fld := d.newdie(die, dwarf.DW_ABRV_FUNCTYPEOUTPARAM, sn[5:])
   634  			newattr(fld, dwarf.DW_AT_variable_parameter, dwarf.DW_CLS_FLAG, 1, 0)
   635  			d.newrefattr(fld, dwarf.DW_AT_type, d.defgotype(s))
   636  		}
   637  
   638  	case abi.Interface:
   639  		die = d.newdie(&dwtypes, dwarf.DW_ABRV_IFACETYPE, name)
   640  		typedefdie = d.dotypedef(&dwtypes, name, die)
   641  		data := d.ldr.Data(gotype)
   642  		nfields := int(decodetypeIfaceMethodCount(d.arch, data))
   643  		var s loader.Sym
   644  		if nfields == 0 {
   645  			s = d.typeRuntimeEface
   646  		} else {
   647  			s = d.typeRuntimeIface
   648  		}
   649  		d.newrefattr(die, dwarf.DW_AT_type, d.defgotype(s))
   650  
   651  	case abi.Map:
   652  		die = d.newdie(&dwtypes, dwarf.DW_ABRV_MAPTYPE, name)
   653  		s := decodetypeMapKey(d.ldr, d.arch, gotype)
   654  		d.newrefattr(die, dwarf.DW_AT_go_key, d.defgotype(s))
   655  		s = decodetypeMapValue(d.ldr, d.arch, gotype)
   656  		d.newrefattr(die, dwarf.DW_AT_go_elem, d.defgotype(s))
   657  		// Save gotype for use in synthesizemaptypes. We could synthesize here,
   658  		// but that would change the order of the DIEs.
   659  		d.newrefattr(die, dwarf.DW_AT_type, gotype)
   660  
   661  	case abi.Pointer:
   662  		die = d.newdie(&dwtypes, dwarf.DW_ABRV_PTRTYPE, name)
   663  		typedefdie = d.dotypedef(&dwtypes, name, die)
   664  		s := decodetypePtrElem(d.ldr, d.arch, gotype)
   665  		d.newrefattr(die, dwarf.DW_AT_type, d.defgotype(s))
   666  
   667  	case abi.Slice:
   668  		die = d.newdie(&dwtypes, dwarf.DW_ABRV_SLICETYPE, name)
   669  		typedefdie = d.dotypedef(&dwtypes, name, die)
   670  		newattr(die, dwarf.DW_AT_byte_size, dwarf.DW_CLS_CONSTANT, bytesize, 0)
   671  		s := decodetypeArrayElem(d.linkctxt, d.arch, gotype)
   672  		elem := d.defgotype(s)
   673  		d.newrefattr(die, dwarf.DW_AT_go_elem, elem)
   674  
   675  	case abi.String:
   676  		die = d.newdie(&dwtypes, dwarf.DW_ABRV_STRINGTYPE, name)
   677  		newattr(die, dwarf.DW_AT_byte_size, dwarf.DW_CLS_CONSTANT, bytesize, 0)
   678  
   679  	case abi.Struct:
   680  		die = d.newdie(&dwtypes, dwarf.DW_ABRV_STRUCTTYPE, name)
   681  		typedefdie = d.dotypedef(&dwtypes, name, die)
   682  		newattr(die, dwarf.DW_AT_byte_size, dwarf.DW_CLS_CONSTANT, bytesize, 0)
   683  		nfields := decodetypeStructFieldCount(d.ldr, d.arch, gotype)
   684  		for i := 0; i < nfields; i++ {
   685  			f := decodetypeStructFieldName(d.ldr, d.arch, gotype, i)
   686  			s := decodetypeStructFieldType(d.linkctxt, d.arch, gotype, i)
   687  			if f == "" {
   688  				sn := d.ldr.SymName(s)
   689  				f = sn[5:] // skip "type:"
   690  			}
   691  			fld := d.newdie(die, dwarf.DW_ABRV_STRUCTFIELD, f)
   692  			d.newrefattr(fld, dwarf.DW_AT_type, d.defgotype(s))
   693  			offset := decodetypeStructFieldOffset(d.ldr, d.arch, gotype, i)
   694  			newmemberoffsetattr(fld, int32(offset))
   695  			if decodetypeStructFieldEmbedded(d.ldr, d.arch, gotype, i) {
   696  				newattr(fld, dwarf.DW_AT_go_embedded_field, dwarf.DW_CLS_FLAG, 1, 0)
   697  			}
   698  		}
   699  
   700  	case abi.UnsafePointer:
   701  		die = d.newdie(&dwtypes, dwarf.DW_ABRV_BARE_PTRTYPE, name)
   702  
   703  	default:
   704  		d.linkctxt.Errorf(gotype, "dwarf: definition of unknown kind %d", kind)
   705  		die = d.newdie(&dwtypes, dwarf.DW_ABRV_TYPEDECL, name)
   706  		d.newrefattr(die, dwarf.DW_AT_type, d.mustFind("<unspecified>"))
   707  	}
   708  
   709  	newattr(die, dwarf.DW_AT_go_kind, dwarf.DW_CLS_CONSTANT, int64(kind), 0)
   710  
   711  	if d.ldr.AttrReachable(gotype) {
   712  		newattr(die, dwarf.DW_AT_go_runtime_type, dwarf.DW_CLS_GO_TYPEREF, 0, dwSym(gotype))
   713  	}
   714  
   715  	// Sanity check.
   716  	if _, ok := d.rtmap[gotype]; ok {
   717  		log.Fatalf("internal error: rtmap entry already installed\n")
   718  	}
   719  
   720  	ds := loader.Sym(die.Sym.(dwSym))
   721  	if typedefdie != nil {
   722  		ds = loader.Sym(typedefdie.Sym.(dwSym))
   723  	}
   724  	d.rtmap[ds] = gotype
   725  
   726  	if _, ok := prototypedies[sn]; ok {
   727  		prototypedies[sn] = die
   728  	}
   729  
   730  	if typedefdie != nil {
   731  		return typedefdie
   732  	}
   733  	return die
   734  }
   735  
   736  func (d *dwctxt) nameFromDIESym(dwtypeDIESym loader.Sym) string {
   737  	sn := d.ldr.SymName(dwtypeDIESym)
   738  	return sn[len(dwarf.InfoPrefix):]
   739  }
   740  
   741  func (d *dwctxt) defptrto(dwtype loader.Sym) loader.Sym {
   742  
   743  	// FIXME: it would be nice if the compiler attached an aux symbol
   744  	// ref from the element type to the pointer type -- it would be
   745  	// more efficient to do it this way as opposed to via name lookups.
   746  
   747  	ptrname := "*" + d.nameFromDIESym(dwtype)
   748  	if die := d.find(ptrname); die != 0 {
   749  		return die
   750  	}
   751  
   752  	pdie := d.newdie(&dwtypes, dwarf.DW_ABRV_PTRTYPE, ptrname)
   753  	d.newrefattr(pdie, dwarf.DW_AT_type, dwtype)
   754  
   755  	// The DWARF info synthesizes pointer types that don't exist at the
   756  	// language level, like *hash<...> and *bucket<...>, and the data
   757  	// pointers of slices. Link to the ones we can find.
   758  	gts := d.ldr.Lookup("type:"+ptrname, 0)
   759  	if gts != 0 && d.ldr.AttrReachable(gts) {
   760  		newattr(pdie, dwarf.DW_AT_go_kind, dwarf.DW_CLS_CONSTANT, int64(abi.Pointer), 0)
   761  		newattr(pdie, dwarf.DW_AT_go_runtime_type, dwarf.DW_CLS_GO_TYPEREF, 0, dwSym(gts))
   762  	}
   763  
   764  	if gts != 0 {
   765  		ds := loader.Sym(pdie.Sym.(dwSym))
   766  		d.rtmap[ds] = gts
   767  		d.tdmap[gts] = ds
   768  	}
   769  
   770  	return d.dtolsym(pdie.Sym)
   771  }
   772  
   773  // Copies src's children into dst. Copies attributes by value.
   774  // DWAttr.data is copied as pointer only. If except is one of
   775  // the top-level children, it will not be copied.
   776  func (d *dwctxt) copychildrenexcept(ctxt *Link, dst *dwarf.DWDie, src *dwarf.DWDie, except *dwarf.DWDie) {
   777  	for src = src.Child; src != nil; src = src.Link {
   778  		if src == except {
   779  			continue
   780  		}
   781  		c := d.newdie(dst, src.Abbrev, getattr(src, dwarf.DW_AT_name).Data.(string))
   782  		for a := src.Attr; a != nil; a = a.Link {
   783  			newattr(c, a.Atr, int(a.Cls), a.Value, a.Data)
   784  		}
   785  		d.copychildrenexcept(ctxt, c, src, nil)
   786  	}
   787  
   788  	reverselist(&dst.Child)
   789  }
   790  
   791  func (d *dwctxt) copychildren(ctxt *Link, dst *dwarf.DWDie, src *dwarf.DWDie) {
   792  	d.copychildrenexcept(ctxt, dst, src, nil)
   793  }
   794  
   795  // Search children (assumed to have TAG_member) for the one named
   796  // field and set its AT_type to dwtype
   797  func (d *dwctxt) substitutetype(structdie *dwarf.DWDie, field string, dwtype loader.Sym) {
   798  	child := findchild(structdie, field)
   799  	if child == nil {
   800  		Exitf("dwarf substitutetype: %s does not have member %s",
   801  			getattr(structdie, dwarf.DW_AT_name).Data, field)
   802  		return
   803  	}
   804  
   805  	a := getattr(child, dwarf.DW_AT_type)
   806  	if a != nil {
   807  		a.Data = dwSym(dwtype)
   808  	} else {
   809  		d.newrefattr(child, dwarf.DW_AT_type, dwtype)
   810  	}
   811  }
   812  
   813  func (d *dwctxt) findprotodie(ctxt *Link, name string) *dwarf.DWDie {
   814  	die, ok := prototypedies[name]
   815  	if ok && die == nil {
   816  		d.defgotype(d.lookupOrDiag(name))
   817  		die = prototypedies[name]
   818  	}
   819  	if die == nil {
   820  		log.Fatalf("internal error: DIE generation failed for %s\n", name)
   821  	}
   822  	return die
   823  }
   824  
   825  func (d *dwctxt) synthesizestringtypes(ctxt *Link, die *dwarf.DWDie) {
   826  	prototype := walktypedef(d.findprotodie(ctxt, "type:runtime.stringStructDWARF"))
   827  	if prototype == nil {
   828  		return
   829  	}
   830  
   831  	for ; die != nil; die = die.Link {
   832  		if die.Abbrev != dwarf.DW_ABRV_STRINGTYPE {
   833  			continue
   834  		}
   835  		d.copychildren(ctxt, die, prototype)
   836  	}
   837  }
   838  
   839  func (d *dwctxt) synthesizeslicetypes(ctxt *Link, die *dwarf.DWDie) {
   840  	prototype := walktypedef(d.findprotodie(ctxt, "type:runtime.slice"))
   841  	if prototype == nil {
   842  		return
   843  	}
   844  
   845  	for ; die != nil; die = die.Link {
   846  		if die.Abbrev != dwarf.DW_ABRV_SLICETYPE {
   847  			continue
   848  		}
   849  		d.copychildren(ctxt, die, prototype)
   850  		elem := loader.Sym(getattr(die, dwarf.DW_AT_go_elem).Data.(dwSym))
   851  		d.substitutetype(die, "array", d.defptrto(elem))
   852  	}
   853  }
   854  
   855  func mkinternaltypename(base string, arg1 string, arg2 string) string {
   856  	if arg2 == "" {
   857  		return fmt.Sprintf("%s<%s>", base, arg1)
   858  	}
   859  	return fmt.Sprintf("%s<%s,%s>", base, arg1, arg2)
   860  }
   861  
   862  func (d *dwctxt) mkinternaltype(ctxt *Link, abbrev int, typename, keyname, valname string, f func(*dwarf.DWDie)) loader.Sym {
   863  	name := mkinternaltypename(typename, keyname, valname)
   864  	symname := dwarf.InfoPrefix + name
   865  	s := d.ldr.Lookup(symname, 0)
   866  	if s != 0 && d.ldr.SymType(s) == sym.SDWARFTYPE {
   867  		return s
   868  	}
   869  	die := d.newdie(&dwtypes, abbrev, name)
   870  	f(die)
   871  	return d.dtolsym(die.Sym)
   872  }
   873  
   874  func (d *dwctxt) synthesizemaptypes(ctxt *Link, die *dwarf.DWDie) {
   875  	mapType := walktypedef(d.findprotodie(ctxt, "type:internal/runtime/maps.Map"))
   876  	tableType := walktypedef(d.findprotodie(ctxt, "type:internal/runtime/maps.table"))
   877  	groupsReferenceType := walktypedef(d.findprotodie(ctxt, "type:internal/runtime/maps.groupsReference"))
   878  
   879  	for ; die != nil; die = die.Link {
   880  		if die.Abbrev != dwarf.DW_ABRV_MAPTYPE {
   881  			continue
   882  		}
   883  		gotype := loader.Sym(getattr(die, dwarf.DW_AT_type).Data.(dwSym))
   884  
   885  		keyType := decodetypeMapKey(d.ldr, d.arch, gotype)
   886  		valType := decodetypeMapValue(d.ldr, d.arch, gotype)
   887  		groupType := decodetypeMapGroup(d.ldr, d.arch, gotype)
   888  
   889  		keyType = d.walksymtypedef(d.defgotype(keyType))
   890  		valType = d.walksymtypedef(d.defgotype(valType))
   891  		groupType = d.walksymtypedef(d.defgotype(groupType))
   892  
   893  		keyName := d.nameFromDIESym(keyType)
   894  		valName := d.nameFromDIESym(valType)
   895  
   896  		// Construct groupsReference[K,V]
   897  		dwGroupsReference := d.mkinternaltype(ctxt, dwarf.DW_ABRV_STRUCTTYPE, "groupReference", keyName, valName, func(dwh *dwarf.DWDie) {
   898  			d.copychildren(ctxt, dwh, groupsReferenceType)
   899  			// data *group[K,V]
   900  			//
   901  			// This is actually a pointer to an array
   902  			// *[lengthMask+1]group[K,V], but the length is
   903  			// variable, so we can't statically record the length.
   904  			d.substitutetype(dwh, "data", d.defptrto(groupType))
   905  			newattr(dwh, dwarf.DW_AT_byte_size, dwarf.DW_CLS_CONSTANT, getattr(groupsReferenceType, dwarf.DW_AT_byte_size).Value, nil)
   906  			newattr(dwh, dwarf.DW_AT_go_kind, dwarf.DW_CLS_CONSTANT, int64(abi.Struct), 0)
   907  		})
   908  
   909  		// Construct table[K,V]
   910  		dwTable := d.mkinternaltype(ctxt, dwarf.DW_ABRV_STRUCTTYPE, "table", keyName, valName, func(dwh *dwarf.DWDie) {
   911  			d.copychildren(ctxt, dwh, tableType)
   912  			d.substitutetype(dwh, "groups", dwGroupsReference)
   913  			newattr(dwh, dwarf.DW_AT_byte_size, dwarf.DW_CLS_CONSTANT, getattr(tableType, dwarf.DW_AT_byte_size).Value, nil)
   914  			newattr(dwh, dwarf.DW_AT_go_kind, dwarf.DW_CLS_CONSTANT, int64(abi.Struct), 0)
   915  		})
   916  
   917  		// Construct map[K,V]
   918  		dwMap := d.mkinternaltype(ctxt, dwarf.DW_ABRV_STRUCTTYPE, "map", keyName, valName, func(dwh *dwarf.DWDie) {
   919  			d.copychildren(ctxt, dwh, mapType)
   920  			// dirPtr is a pointer to a variable-length array of
   921  			// *table[K,V], of length dirLen.
   922  			//
   923  			// Since we can't directly define a variable-length
   924  			// array, store this as **table[K,V]. i.e., pointer to
   925  			// the first entry in the array.
   926  			d.substitutetype(dwh, "dirPtr", d.defptrto(d.defptrto(dwTable)))
   927  			newattr(dwh, dwarf.DW_AT_byte_size, dwarf.DW_CLS_CONSTANT, getattr(mapType, dwarf.DW_AT_byte_size).Value, nil)
   928  			newattr(dwh, dwarf.DW_AT_go_kind, dwarf.DW_CLS_CONSTANT, int64(abi.Struct), 0)
   929  		})
   930  
   931  		// make map type a pointer to map[K,V]
   932  		d.newrefattr(die, dwarf.DW_AT_type, d.defptrto(dwMap))
   933  	}
   934  }
   935  
   936  func (d *dwctxt) synthesizechantypes(ctxt *Link, die *dwarf.DWDie) {
   937  	sudog := walktypedef(d.findprotodie(ctxt, "type:runtime.sudog"))
   938  	waitq := walktypedef(d.findprotodie(ctxt, "type:runtime.waitq"))
   939  	hchan := walktypedef(d.findprotodie(ctxt, "type:runtime.hchan"))
   940  	if sudog == nil || waitq == nil || hchan == nil {
   941  		return
   942  	}
   943  
   944  	sudogsize := int(getattr(sudog, dwarf.DW_AT_byte_size).Value)
   945  
   946  	for ; die != nil; die = die.Link {
   947  		if die.Abbrev != dwarf.DW_ABRV_CHANTYPE {
   948  			continue
   949  		}
   950  		elemgotype := loader.Sym(getattr(die, dwarf.DW_AT_type).Data.(dwSym))
   951  		tname := d.ldr.SymName(elemgotype)
   952  		elemname := tname[5:]
   953  		elemtype := d.walksymtypedef(d.defgotype(d.lookupOrDiag(tname)))
   954  
   955  		// sudog<T>
   956  		dwss := d.mkinternaltype(ctxt, dwarf.DW_ABRV_STRUCTTYPE, "sudog", elemname, "", func(dws *dwarf.DWDie) {
   957  			d.copychildren(ctxt, dws, sudog)
   958  			d.substitutetype(dws, "elem", d.defptrto(elemtype))
   959  			newattr(dws, dwarf.DW_AT_byte_size, dwarf.DW_CLS_CONSTANT, int64(sudogsize), nil)
   960  		})
   961  
   962  		// waitq<T>
   963  		dwws := d.mkinternaltype(ctxt, dwarf.DW_ABRV_STRUCTTYPE, "waitq", elemname, "", func(dww *dwarf.DWDie) {
   964  
   965  			d.copychildren(ctxt, dww, waitq)
   966  			d.substitutetype(dww, "first", d.defptrto(dwss))
   967  			d.substitutetype(dww, "last", d.defptrto(dwss))
   968  			newattr(dww, dwarf.DW_AT_byte_size, dwarf.DW_CLS_CONSTANT, getattr(waitq, dwarf.DW_AT_byte_size).Value, nil)
   969  		})
   970  
   971  		// hchan<T>
   972  		dwhs := d.mkinternaltype(ctxt, dwarf.DW_ABRV_STRUCTTYPE, "hchan", elemname, "", func(dwh *dwarf.DWDie) {
   973  			d.copychildren(ctxt, dwh, hchan)
   974  			d.substitutetype(dwh, "recvq", dwws)
   975  			d.substitutetype(dwh, "sendq", dwws)
   976  			newattr(dwh, dwarf.DW_AT_byte_size, dwarf.DW_CLS_CONSTANT, getattr(hchan, dwarf.DW_AT_byte_size).Value, nil)
   977  		})
   978  
   979  		d.newrefattr(die, dwarf.DW_AT_type, d.defptrto(dwhs))
   980  	}
   981  }
   982  
   983  // createUnitLength creates the initial length field with value v and update
   984  // offset of unit_length if needed.
   985  func (d *dwctxt) createUnitLength(su *loader.SymbolBuilder, v uint64) {
   986  	if isDwarf64(d.linkctxt) {
   987  		su.AddUint32(d.arch, 0xFFFFFFFF)
   988  	}
   989  	d.addDwarfAddrField(su, v)
   990  }
   991  
   992  // addDwarfAddrField adds a DWARF field in DWARF 64bits or 32bits.
   993  func (d *dwctxt) addDwarfAddrField(sb *loader.SymbolBuilder, v uint64) {
   994  	if isDwarf64(d.linkctxt) {
   995  		sb.AddUint(d.arch, v)
   996  	} else {
   997  		sb.AddUint32(d.arch, uint32(v))
   998  	}
   999  }
  1000  
  1001  // addDwarfAddrRef adds a DWARF pointer in DWARF 64bits or 32bits.
  1002  func (d *dwctxt) addDwarfAddrRef(sb *loader.SymbolBuilder, t loader.Sym) {
  1003  	if isDwarf64(d.linkctxt) {
  1004  		d.adddwarfref(sb, t, 8)
  1005  	} else {
  1006  		d.adddwarfref(sb, t, 4)
  1007  	}
  1008  }
  1009  
  1010  // calcCompUnitRanges calculates the PC ranges of the compilation units.
  1011  func (d *dwctxt) calcCompUnitRanges() {
  1012  	var prevUnit *sym.CompilationUnit
  1013  	for _, s := range d.linkctxt.Textp {
  1014  		sym := loader.Sym(s)
  1015  
  1016  		fi := d.ldr.FuncInfo(sym)
  1017  		if !fi.Valid() {
  1018  			continue
  1019  		}
  1020  
  1021  		// Skip linker-created functions (ex: runtime.addmoduledata), since they
  1022  		// don't have DWARF to begin with.
  1023  		unit := d.ldr.SymUnit(sym)
  1024  		if unit == nil {
  1025  			continue
  1026  		}
  1027  
  1028  		// Update PC ranges.
  1029  		//
  1030  		// We don't simply compare the end of the previous
  1031  		// symbol with the start of the next because there's
  1032  		// often a little padding between them. Instead, we
  1033  		// only create boundaries between symbols from
  1034  		// different units.
  1035  		sval := d.ldr.SymValue(sym)
  1036  		u0val := d.ldr.SymValue(loader.Sym(unit.Textp[0]))
  1037  		if prevUnit != unit {
  1038  			unit.PCs = append(unit.PCs, dwarf.Range{Start: sval - u0val})
  1039  			prevUnit = unit
  1040  		}
  1041  		unit.PCs[len(unit.PCs)-1].End = sval - u0val + int64(len(d.ldr.Data(sym)))
  1042  	}
  1043  }
  1044  
  1045  func movetomodule(ctxt *Link, parent *dwarf.DWDie) {
  1046  	die := ctxt.runtimeCU.DWInfo.Child
  1047  	if die == nil {
  1048  		ctxt.runtimeCU.DWInfo.Child = parent.Child
  1049  		return
  1050  	}
  1051  	for die.Link != nil {
  1052  		die = die.Link
  1053  	}
  1054  	die.Link = parent.Child
  1055  }
  1056  
  1057  /*
  1058   * Generate a sequence of opcodes that is as short as possible.
  1059   * See section 6.2.5
  1060   */
  1061  const (
  1062  	LINE_BASE   = -4
  1063  	LINE_RANGE  = 10
  1064  	PC_RANGE    = (255 - OPCODE_BASE) / LINE_RANGE
  1065  	OPCODE_BASE = 11
  1066  )
  1067  
  1068  /*
  1069   * Walk prog table, emit line program and build DIE tree.
  1070   */
  1071  
  1072  func getCompilationDir() string {
  1073  	// OSX requires this be set to something, but it's not easy to choose
  1074  	// a value. Linking takes place in a temporary directory, so there's
  1075  	// no point including it here. Paths in the file table are usually
  1076  	// absolute, in which case debuggers will ignore this value. -trimpath
  1077  	// produces relative paths, but we don't know where they start, so
  1078  	// all we can do here is try not to make things worse.
  1079  	return "."
  1080  }
  1081  
  1082  func (d *dwctxt) importInfoSymbol(dsym loader.Sym) {
  1083  	d.ldr.SetAttrReachable(dsym, true)
  1084  	d.ldr.SetAttrNotInSymbolTable(dsym, true)
  1085  	dst := d.ldr.SymType(dsym)
  1086  	if dst != sym.SDWARFCONST && dst != sym.SDWARFABSFCN {
  1087  		log.Fatalf("error: DWARF info sym %d/%s with incorrect type %s", dsym, d.ldr.SymName(dsym), d.ldr.SymType(dsym).String())
  1088  	}
  1089  	relocs := d.ldr.Relocs(dsym)
  1090  	for i := 0; i < relocs.Count(); i++ {
  1091  		r := relocs.At(i)
  1092  		if r.Type() != objabi.R_DWARFSECREF {
  1093  			continue
  1094  		}
  1095  		rsym := r.Sym()
  1096  		// If there is an entry for the symbol in our rtmap, then it
  1097  		// means we've processed the type already, and can skip this one.
  1098  		if _, ok := d.rtmap[rsym]; ok {
  1099  			// type already generated
  1100  			continue
  1101  		}
  1102  		// FIXME: is there a way we could avoid materializing the
  1103  		// symbol name here?
  1104  		sn := d.ldr.SymName(rsym)
  1105  		tn := sn[len(dwarf.InfoPrefix):]
  1106  		ts := d.ldr.Lookup("type:"+tn, 0)
  1107  		d.defgotype(ts)
  1108  	}
  1109  }
  1110  
  1111  func expandFile(fname string) string {
  1112  	fname = strings.TrimPrefix(fname, src.FileSymPrefix)
  1113  	return expandGoroot(fname)
  1114  }
  1115  
  1116  // writeDirFileTables emits the portion of the DWARF line table
  1117  // prologue containing the include directories and file names,
  1118  // described in section 6.2.4 of the DWARF standard. It walks the
  1119  // filepaths for the unit to discover any common directories, which
  1120  // are emitted to the directory table first, then the file table is
  1121  // emitted after that.
  1122  //
  1123  // Note that there are some differences betwen DWARF versions 4 and 5
  1124  // regarding how files and directories are handled; the chief item is
  1125  // that in version 4 we have an implicit directory index 0 that holds
  1126  // the compilation dir, and an implicit file index 0 that holds the
  1127  // "primary" source file being compiled (with the assumption that
  1128  // we'll get these two pieces of info from attributes on the
  1129  // compilation unit DIE). DWARF version 5 does away with these
  1130  // implicit entries; if you want to refer to a file or dir, you have
  1131  // to mention it explicitly.
  1132  //
  1133  // So, let's say we have a Go package with import path
  1134  // "github.com/fruit/bowl" with two source files, "apple.go" and
  1135  // "orange.go". The directory and file table in version 4 might look
  1136  // like:
  1137  //
  1138  //	Dir Table:
  1139  //	1		github.com/fruit/bowl
  1140  //
  1141  //	File Table:
  1142  //	Entry	Dir	Time	Size	Name
  1143  //	1		0	0		0		<autogenerated>
  1144  //	2		1	0		0		apple.go
  1145  //	3		1	0		0		orange.go
  1146  //
  1147  // With DWARF version 5, the file and directory tables might look like
  1148  //
  1149  //	Dir Table:
  1150  //	0		.
  1151  //	1		github.com/fruit/bowl
  1152  //
  1153  //	File Table:
  1154  //	Entry	Dir	  Name
  1155  //	0		0	  ?                /* see remark below about this entry */
  1156  //	1		0	  <autogenerated>
  1157  //	2		1	  apple.go
  1158  //	3		1	  orange.go
  1159  //
  1160  // Also worth noting that the line table prolog allows you to control
  1161  // what items or fields appear in file and die entries (as opposed
  1162  // to the fixed dir/time/size/name format for files in DWARF 4).
  1163  func (d *dwctxt) writeDirFileTables(unit *sym.CompilationUnit, lsu *loader.SymbolBuilder) {
  1164  	type fileDir struct {
  1165  		base string
  1166  		dir  int
  1167  	}
  1168  	dirNums := make(map[string]int)
  1169  	dirs := []string{"."}
  1170  	dirNums["."] = 0
  1171  	files := []fileDir{}
  1172  	if buildcfg.Experiment.Dwarf5 {
  1173  		// Add a dummy zero entry (not used for anything) so as to
  1174  		// ensure that the first useful file index is 1, since that's
  1175  		// the default value of the line table file register).  Note
  1176  		// the "?"; this was originally an empty string, but doing
  1177  		// this triggers crashes in some versions of GDB, see
  1178  		// https://sourceware.org/bugzilla/show_bug.cgi?id=30357 for
  1179  		// the details.
  1180  		files = append(files, fileDir{base: "?", dir: 0})
  1181  	}
  1182  
  1183  	// Preprocess files to collect directories. This assumes that the
  1184  	// file table is already de-duped.
  1185  	for i, name := range unit.FileTable {
  1186  		name := expandFile(name)
  1187  		if len(name) == 0 {
  1188  			// Can't have empty filenames, and having a unique
  1189  			// filename is quite useful for debugging.
  1190  			name = fmt.Sprintf("<missing>_%d", i)
  1191  		}
  1192  		// Note the use of "path" here and not "filepath". The compiler
  1193  		// hard-codes to use "/" in DWARF paths (even for Windows), so we
  1194  		// want to maintain that here.
  1195  		file := path.Base(name)
  1196  		dir := path.Dir(name)
  1197  		dirIdx, ok := dirNums[dir]
  1198  		if !ok && dir != "." {
  1199  			dirIdx = len(dirNums)
  1200  			dirNums[dir] = dirIdx
  1201  			dirs = append(dirs, dir)
  1202  		}
  1203  		files = append(files, fileDir{base: file, dir: dirIdx})
  1204  
  1205  		// We can't use something that may be dead-code
  1206  		// eliminated from a binary here. proc.go contains
  1207  		// main and the scheduler, so it's not going anywhere.
  1208  		if i := strings.Index(name, "runtime/proc.go"); i >= 0 && unit.Lib.Pkg == "runtime" {
  1209  			d.dwmu.Lock()
  1210  			if gdbscript == "" {
  1211  				k := strings.Index(name, "runtime/proc.go")
  1212  				gdbscript = name[:k] + "runtime/runtime-gdb.py"
  1213  			}
  1214  			d.dwmu.Unlock()
  1215  		}
  1216  	}
  1217  
  1218  	lsDwsym := dwSym(lsu.Sym())
  1219  	if buildcfg.Experiment.Dwarf5 {
  1220  		// Emit DWARF5 directory and file sections. The key added
  1221  		// element here for version 5 is that we emit a small prolog
  1222  		// describing the format of each file/dir entry, then a count
  1223  		// of the entries, then the entries themselves.
  1224  
  1225  		// Dir table first...
  1226  		lsu.AddUint8(1) // directory_entry_format_count
  1227  		// each directory entry is just a single path string.
  1228  		dwarf.Uleb128put(d, lsDwsym, dwarf.DW_LNCT_path)
  1229  		dwarf.Uleb128put(d, lsDwsym, dwarf.DW_FORM_string)
  1230  		// emit count, then dirs
  1231  		dwarf.Uleb128put(d, lsDwsym, int64(len(dirs)))
  1232  		for k := 0; k < len(dirs); k++ {
  1233  			d.AddString(lsDwsym, dirs[k])
  1234  		}
  1235  
  1236  		// ... now file table.  With DWARF version 5 we put out a
  1237  		// prolog that describes the format of each file entry; our
  1238  		// chosen format is a pair <F,D> where F is the file and D is
  1239  		// the dir index (zero-based).
  1240  		lsu.AddUint8(2) // file_entry_format_count
  1241  		// each file entry is just a file path followed by dir index.
  1242  		dwarf.Uleb128put(d, lsDwsym, dwarf.DW_LNCT_path)
  1243  		dwarf.Uleb128put(d, lsDwsym, dwarf.DW_FORM_string)
  1244  		dwarf.Uleb128put(d, lsDwsym, dwarf.DW_LNCT_directory_index)
  1245  		dwarf.Uleb128put(d, lsDwsym, dwarf.DW_FORM_udata)
  1246  		// emit count, then files
  1247  		dwarf.Uleb128put(d, lsDwsym, int64(len(files)))
  1248  		for k := 0; k < len(files); k++ {
  1249  			d.AddString(lsDwsym, files[k].base)
  1250  			dwarf.Uleb128put(d, lsDwsym, int64(files[k].dir))
  1251  		}
  1252  	} else {
  1253  		// Emit DWARF4 directory and file sections.
  1254  
  1255  		// Dir table first. This just a series of nul terminated
  1256  		// strings, followed by a single zero byte.
  1257  		for k := 1; k < len(dirs); k++ {
  1258  			d.AddString(lsDwsym, dirs[k])
  1259  		}
  1260  		lsu.AddUint8(0) // terminator needed in V4 case.
  1261  
  1262  		// File table next. This is a series of
  1263  		// file/dirindex/mtime/length tuples (where dirindex is
  1264  		// 1-based) followed by a single zero byte.
  1265  		for k := 0; k < len(files); k++ {
  1266  			d.AddString(lsDwsym, files[k].base)
  1267  			dwarf.Uleb128put(d, lsDwsym, int64(files[k].dir))
  1268  			lsu.AddUint8(0) // mtime
  1269  			lsu.AddUint8(0) // length
  1270  		}
  1271  		lsu.AddUint8(0) // terminator
  1272  	}
  1273  }
  1274  
  1275  // writelines collects up and chains together the symbols needed to
  1276  // form the DWARF line table for the specified compilation unit,
  1277  // returning a list of symbols. The returned list will include an
  1278  // initial symbol containing the line table header and prologue (with
  1279  // file table), then a series of compiler-emitted line table symbols
  1280  // (one per live function), and finally an epilog symbol containing an
  1281  // end-of-sequence operator. The prologue and epilog symbols are passed
  1282  // in (having been created earlier); here we add content to them.
  1283  func (d *dwctxt) writelines(unit *sym.CompilationUnit, lineProlog loader.Sym) []loader.Sym {
  1284  	is_stmt := uint8(1) // initially = recommended default_is_stmt = 1, tracks is_stmt toggles.
  1285  
  1286  	unitstart := int64(-1)
  1287  	headerstart := int64(-1)
  1288  	headerend := int64(-1)
  1289  
  1290  	syms := make([]loader.Sym, 0, len(unit.Textp)+2)
  1291  	syms = append(syms, lineProlog)
  1292  	lsu := d.ldr.MakeSymbolUpdater(lineProlog)
  1293  	lsDwsym := dwSym(lineProlog)
  1294  	newattr(unit.DWInfo, dwarf.DW_AT_stmt_list, dwarf.DW_CLS_PTR, 0, lsDwsym)
  1295  
  1296  	// Write .debug_line Line Number Program Header (sec 6.2.4)
  1297  	// Fields marked with (*) must be changed for 64-bit dwarf
  1298  	unitLengthOffset := lsu.Size()
  1299  	d.createUnitLength(lsu, 0) // unit_length (*), filled in at end
  1300  	unitstart = lsu.Size()
  1301  	if buildcfg.Experiment.Dwarf5 {
  1302  		lsu.AddUint16(d.arch, 5)
  1303  		// DWARF5 requires address_size and segment selector sizes
  1304  		// here, both ubyte format.
  1305  		lsu.AddUint8(uint8(d.arch.PtrSize))
  1306  		lsu.AddUint8(0)
  1307  	} else {
  1308  		lsu.AddUint16(d.arch, 2) // dwarf version (appendix F) -- version 3 is incompatible w/ XCode 9.0's dsymutil, latest supported on OSX 10.12 as of 2018-05
  1309  	}
  1310  	headerLengthOffset := lsu.Size()
  1311  	d.addDwarfAddrField(lsu, 0) // header_length (*), filled in at end
  1312  	headerstart = lsu.Size()
  1313  
  1314  	lsu.AddUint8(1) // minimum_instruction_length
  1315  	if buildcfg.Experiment.Dwarf5 {
  1316  		lsu.AddUint8(1) // maximum_operations_per_instruction
  1317  	}
  1318  	lsu.AddUint8(is_stmt)          // default_is_stmt
  1319  	lsu.AddUint8(LINE_BASE & 0xFF) // line_base
  1320  	lsu.AddUint8(LINE_RANGE)       // line_range
  1321  	lsu.AddUint8(OPCODE_BASE)      // opcode_base
  1322  	lsu.AddUint8(0)                // standard_opcode_lengths[1]
  1323  	lsu.AddUint8(1)                // standard_opcode_lengths[2]
  1324  	lsu.AddUint8(1)                // standard_opcode_lengths[3]
  1325  	lsu.AddUint8(1)                // standard_opcode_lengths[4]
  1326  	lsu.AddUint8(1)                // standard_opcode_lengths[5]
  1327  	lsu.AddUint8(0)                // standard_opcode_lengths[6]
  1328  	lsu.AddUint8(0)                // standard_opcode_lengths[7]
  1329  	lsu.AddUint8(0)                // standard_opcode_lengths[8]
  1330  	lsu.AddUint8(1)                // standard_opcode_lengths[9]
  1331  	lsu.AddUint8(0)                // standard_opcode_lengths[10]
  1332  
  1333  	// Call helper to emit dir and file sections.
  1334  	d.writeDirFileTables(unit, lsu)
  1335  
  1336  	// capture length at end of file names.
  1337  	headerend = lsu.Size()
  1338  	unitlen := lsu.Size() - unitstart
  1339  
  1340  	// Output the state machine for each function remaining.
  1341  	for _, s := range unit.Textp {
  1342  		fnSym := loader.Sym(s)
  1343  		_, _, _, lines := d.ldr.GetFuncDwarfAuxSyms(fnSym)
  1344  
  1345  		// Chain the line symbol onto the list.
  1346  		if lines != 0 {
  1347  			syms = append(syms, lines)
  1348  			unitlen += int64(len(d.ldr.Data(lines)))
  1349  		}
  1350  	}
  1351  
  1352  	if d.linkctxt.HeadType == objabi.Haix {
  1353  		addDwsectCUSize(".debug_line", unit.Lib.Pkg, uint64(unitlen))
  1354  	}
  1355  
  1356  	if isDwarf64(d.linkctxt) {
  1357  		lsu.SetUint(d.arch, unitLengthOffset+4, uint64(unitlen)) // +4 because of 0xFFFFFFFF
  1358  		lsu.SetUint(d.arch, headerLengthOffset, uint64(headerend-headerstart))
  1359  	} else {
  1360  		lsu.SetUint32(d.arch, unitLengthOffset, uint32(unitlen))
  1361  		lsu.SetUint32(d.arch, headerLengthOffset, uint32(headerend-headerstart))
  1362  	}
  1363  
  1364  	return syms
  1365  }
  1366  
  1367  // writepcranges generates the DW_AT_ranges table for compilation unit
  1368  // "unit", and returns a collection of ranges symbols (one for the
  1369  // compilation unit DIE itself and the remainder from functions in the unit).
  1370  func (d *dwctxt) writepcranges(unit *sym.CompilationUnit, base loader.Sym, pcs []dwarf.Range, rangeProlog loader.Sym, debugaddrsym loader.Sym) []loader.Sym {
  1371  
  1372  	syms := make([]loader.Sym, 0, len(unit.RangeSyms)+1)
  1373  	syms = append(syms, rangeProlog)
  1374  	rsu := d.ldr.MakeSymbolUpdater(rangeProlog)
  1375  	rDwSym := dwSym(rangeProlog)
  1376  
  1377  	// Create PC ranges for the compilation unit DIE.
  1378  	newattr(unit.DWInfo, dwarf.DW_AT_ranges, dwarf.DW_CLS_PTR, rsu.Size(), rDwSym)
  1379  	newattr(unit.DWInfo, dwarf.DW_AT_low_pc, dwarf.DW_CLS_ADDRESS, 0, dwSym(base))
  1380  	if buildcfg.Experiment.Dwarf5 && debugaddrsym != 0 {
  1381  		debugaddr := d.ldr.MakeSymbolUpdater(debugaddrsym)
  1382  		// Write DWARF5-based ranges for the unit. This will introduce
  1383  		// a series of new R_DWTXTADDR_* relocs, which we'll process
  1384  		// in the loop immediately following this call.
  1385  		dwarf.PutRngListRanges(d, rDwSym, dwSym(base), pcs)
  1386  		drelocs := d.ldr.Relocs(rangeProlog)
  1387  		for ri := 0; ri < drelocs.Count(); ri++ {
  1388  			r := drelocs.At(ri)
  1389  			if !r.Type().IsDwTxtAddr() {
  1390  				continue
  1391  			}
  1392  			cusym := d.dtolsym(unit.DWInfo.Sym)
  1393  			d.assignDebugAddrSlot(unit, cusym, r, debugaddr)
  1394  		}
  1395  	} else {
  1396  		dwarf.PutBasedRanges(d, rDwSym, pcs)
  1397  	}
  1398  
  1399  	// Collect up the ranges for functions in the unit.
  1400  	rsize := uint64(rsu.Size())
  1401  	for _, ls := range unit.RangeSyms {
  1402  		s := loader.Sym(ls)
  1403  		syms = append(syms, s)
  1404  		rsize += uint64(d.ldr.SymSize(s))
  1405  	}
  1406  
  1407  	if d.linkctxt.HeadType == objabi.Haix {
  1408  		addDwsectCUSize(".debug_ranges", unit.Lib.Pkg, rsize)
  1409  	}
  1410  
  1411  	return syms
  1412  }
  1413  
  1414  /*
  1415   *  Emit .debug_frame
  1416   */
  1417  const (
  1418  	dataAlignmentFactor = -4
  1419  )
  1420  
  1421  // appendPCDeltaCFA appends per-PC CFA deltas to b and returns the final slice.
  1422  func appendPCDeltaCFA(arch *sys.Arch, b []byte, deltapc, cfa int64) []byte {
  1423  	b = append(b, dwarf.DW_CFA_def_cfa_offset_sf)
  1424  	b = dwarf.AppendSleb128(b, cfa/dataAlignmentFactor)
  1425  
  1426  	switch {
  1427  	case deltapc < 0x40:
  1428  		b = append(b, uint8(dwarf.DW_CFA_advance_loc+deltapc))
  1429  	case deltapc < 0x100:
  1430  		b = append(b, dwarf.DW_CFA_advance_loc1)
  1431  		b = append(b, uint8(deltapc))
  1432  	case deltapc < 0x10000:
  1433  		b = append(b, dwarf.DW_CFA_advance_loc2, 0, 0)
  1434  		arch.ByteOrder.PutUint16(b[len(b)-2:], uint16(deltapc))
  1435  	default:
  1436  		b = append(b, dwarf.DW_CFA_advance_loc4, 0, 0, 0, 0)
  1437  		arch.ByteOrder.PutUint32(b[len(b)-4:], uint32(deltapc))
  1438  	}
  1439  	return b
  1440  }
  1441  
  1442  func (d *dwctxt) writeframes(fs loader.Sym) dwarfSecInfo {
  1443  	fsd := dwSym(fs)
  1444  	fsu := d.ldr.MakeSymbolUpdater(fs)
  1445  	fsu.SetType(sym.SDWARFSECT)
  1446  	isdw64 := isDwarf64(d.linkctxt)
  1447  	haslr := d.linkctxt.Arch.HasLR
  1448  
  1449  	// Length field is 4 bytes on Dwarf32 and 12 bytes on Dwarf64
  1450  	lengthFieldSize := int64(4)
  1451  	if isdw64 {
  1452  		lengthFieldSize += 8
  1453  	}
  1454  
  1455  	// Emit the CIE, Section 6.4.1
  1456  	cieReserve := uint32(16)
  1457  	if haslr {
  1458  		cieReserve = 32
  1459  	}
  1460  	if isdw64 {
  1461  		cieReserve += 4 // 4 bytes added for cid
  1462  	}
  1463  	d.createUnitLength(fsu, uint64(cieReserve))         // initial length, must be multiple of thearch.ptrsize
  1464  	d.addDwarfAddrField(fsu, ^uint64(0))                // cid
  1465  	fsu.AddUint8(3)                                     // dwarf version (appendix F)
  1466  	fsu.AddUint8(0)                                     // augmentation ""
  1467  	dwarf.Uleb128put(d, fsd, 1)                         // code_alignment_factor
  1468  	dwarf.Sleb128put(d, fsd, dataAlignmentFactor)       // all CFI offset calculations include multiplication with this factor
  1469  	dwarf.Uleb128put(d, fsd, int64(thearch.Dwarfreglr)) // return_address_register
  1470  
  1471  	fsu.AddUint8(dwarf.DW_CFA_def_cfa)                  // Set the current frame address..
  1472  	dwarf.Uleb128put(d, fsd, int64(thearch.Dwarfregsp)) // ...to use the value in the platform's SP register (defined in l.go)...
  1473  	if haslr {
  1474  		dwarf.Uleb128put(d, fsd, int64(0)) // ...plus a 0 offset.
  1475  
  1476  		fsu.AddUint8(dwarf.DW_CFA_same_value) // The platform's link register is unchanged during the prologue.
  1477  		dwarf.Uleb128put(d, fsd, int64(thearch.Dwarfreglr))
  1478  
  1479  		fsu.AddUint8(dwarf.DW_CFA_val_offset)               // The previous value...
  1480  		dwarf.Uleb128put(d, fsd, int64(thearch.Dwarfregsp)) // ...of the platform's SP register...
  1481  		dwarf.Uleb128put(d, fsd, int64(0))                  // ...is CFA+0.
  1482  	} else {
  1483  		dwarf.Uleb128put(d, fsd, int64(d.arch.PtrSize)) // ...plus the word size (because the call instruction implicitly adds one word to the frame).
  1484  
  1485  		fsu.AddUint8(dwarf.DW_CFA_offset_extended)                           // The previous value...
  1486  		dwarf.Uleb128put(d, fsd, int64(thearch.Dwarfreglr))                  // ...of the return address...
  1487  		dwarf.Uleb128put(d, fsd, int64(-d.arch.PtrSize)/dataAlignmentFactor) // ...is saved at [CFA - (PtrSize/4)].
  1488  	}
  1489  
  1490  	pad := int64(cieReserve) + lengthFieldSize - int64(len(d.ldr.Data(fs)))
  1491  
  1492  	if pad < 0 {
  1493  		Exitf("dwarf: cieReserve too small by %d bytes.", -pad)
  1494  	}
  1495  
  1496  	internalExec := d.linkctxt.BuildMode == BuildModeExe && d.linkctxt.IsInternal()
  1497  	addAddrPlus := loader.GenAddAddrPlusFunc(internalExec)
  1498  
  1499  	fsu.AddBytes(zeros[:pad])
  1500  
  1501  	var deltaBuf []byte
  1502  	pcsp := obj.NewPCIter(uint32(d.arch.MinLC))
  1503  	for _, s := range d.linkctxt.Textp {
  1504  		fn := loader.Sym(s)
  1505  		fi := d.ldr.FuncInfo(fn)
  1506  		if !fi.Valid() {
  1507  			continue
  1508  		}
  1509  		fpcsp := d.ldr.Pcsp(s)
  1510  
  1511  		// Emit a FDE, Section 6.4.1.
  1512  		// First build the section contents into a byte buffer.
  1513  		deltaBuf = deltaBuf[:0]
  1514  		if haslr && fi.TopFrame() {
  1515  			// Mark the link register as having an undefined value.
  1516  			// This stops call stack unwinders progressing any further.
  1517  			// TODO: similar mark on non-LR architectures.
  1518  			deltaBuf = append(deltaBuf, dwarf.DW_CFA_undefined)
  1519  			deltaBuf = dwarf.AppendUleb128(deltaBuf, uint64(thearch.Dwarfreglr))
  1520  		}
  1521  
  1522  		for pcsp.Init(d.linkctxt.loader.Data(fpcsp)); !pcsp.Done; pcsp.Next() {
  1523  			nextpc := pcsp.NextPC
  1524  
  1525  			// pciterinit goes up to the end of the function,
  1526  			// but DWARF expects us to stop just before the end.
  1527  			if int64(nextpc) == int64(len(d.ldr.Data(fn))) {
  1528  				nextpc--
  1529  				if nextpc < pcsp.PC {
  1530  					continue
  1531  				}
  1532  			}
  1533  
  1534  			spdelta := int64(pcsp.Value)
  1535  			if !haslr {
  1536  				// Return address has been pushed onto stack.
  1537  				spdelta += int64(d.arch.PtrSize)
  1538  			}
  1539  
  1540  			if haslr && !fi.TopFrame() {
  1541  				// TODO(bryanpkc): This is imprecise. In general, the instruction
  1542  				// that stores the return address to the stack frame is not the
  1543  				// same one that allocates the frame.
  1544  				if pcsp.Value > 0 {
  1545  					// The return address is preserved at (CFA-frame_size)
  1546  					// after a stack frame has been allocated.
  1547  					deltaBuf = append(deltaBuf, dwarf.DW_CFA_offset_extended_sf)
  1548  					deltaBuf = dwarf.AppendUleb128(deltaBuf, uint64(thearch.Dwarfreglr))
  1549  					deltaBuf = dwarf.AppendSleb128(deltaBuf, -spdelta/dataAlignmentFactor)
  1550  				} else {
  1551  					// The return address is restored into the link register
  1552  					// when a stack frame has been de-allocated.
  1553  					deltaBuf = append(deltaBuf, dwarf.DW_CFA_same_value)
  1554  					deltaBuf = dwarf.AppendUleb128(deltaBuf, uint64(thearch.Dwarfreglr))
  1555  				}
  1556  			}
  1557  
  1558  			deltaBuf = appendPCDeltaCFA(d.arch, deltaBuf, int64(nextpc)-int64(pcsp.PC), spdelta)
  1559  		}
  1560  		pad := int(Rnd(int64(len(deltaBuf)), int64(d.arch.PtrSize))) - len(deltaBuf)
  1561  		deltaBuf = append(deltaBuf, zeros[:pad]...)
  1562  
  1563  		// Emit the FDE header, Section 6.4.1.
  1564  		//	4 bytes: length, must be multiple of thearch.ptrsize
  1565  		//	4/8 bytes: Pointer to the CIE above, at offset 0
  1566  		//	ptrsize: initial location
  1567  		//	ptrsize: address range
  1568  
  1569  		fdeLength := uint64(4 + 2*d.arch.PtrSize + len(deltaBuf))
  1570  		if isdw64 {
  1571  			fdeLength += 4 // 4 bytes added for CIE pointer
  1572  		}
  1573  		d.createUnitLength(fsu, fdeLength)
  1574  
  1575  		if d.linkctxt.LinkMode == LinkExternal {
  1576  			d.addDwarfAddrRef(fsu, fs)
  1577  		} else {
  1578  			d.addDwarfAddrField(fsu, 0) // CIE offset
  1579  		}
  1580  		addAddrPlus(fsu, d.arch, s, 0)
  1581  		fsu.AddUintXX(d.arch, uint64(len(d.ldr.Data(fn))), d.arch.PtrSize) // address range
  1582  		fsu.AddBytes(deltaBuf)
  1583  
  1584  		if d.linkctxt.HeadType == objabi.Haix {
  1585  			addDwsectCUSize(".debug_frame", d.ldr.SymPkg(fn), fdeLength+uint64(lengthFieldSize))
  1586  		}
  1587  	}
  1588  
  1589  	return dwarfSecInfo{syms: []loader.Sym{fs}}
  1590  }
  1591  
  1592  /*
  1593   *  Walk DWarfDebugInfoEntries, and emit .debug_info
  1594   */
  1595  
  1596  func (d *dwctxt) writeUnitInfo(u *sym.CompilationUnit, abbrevsym loader.Sym, addrsym loader.Sym, infoEpilog loader.Sym) []loader.Sym {
  1597  	syms := []loader.Sym{}
  1598  	if len(u.Textp) == 0 && u.DWInfo.Child == nil && len(u.VarDIEs) == 0 {
  1599  		return syms
  1600  	}
  1601  
  1602  	compunit := u.DWInfo
  1603  	s := d.dtolsym(compunit.Sym)
  1604  	su := d.ldr.MakeSymbolUpdater(s)
  1605  
  1606  	// Write .debug_info Compilation Unit Header (sec 7.5.1)
  1607  	// Fields marked with (*) must be changed for 64-bit dwarf
  1608  	d.createUnitLength(su, 0) // unit_length (*), will be filled in later.
  1609  	dwver := 4
  1610  	if buildcfg.Experiment.Dwarf5 {
  1611  		dwver = 5
  1612  	}
  1613  	su.AddUint16(d.arch, uint16(dwver)) // dwarf version (appendix F)
  1614  
  1615  	if buildcfg.Experiment.Dwarf5 {
  1616  		// DWARF5 at this point requires
  1617  		// 1. unit type
  1618  		// 2. address size
  1619  		// 3. abbrev offset
  1620  		su.AddUint8(uint8(dwarf.DW_UT_compile))
  1621  		su.AddUint8(uint8(d.arch.PtrSize))
  1622  		d.addDwarfAddrRef(su, abbrevsym)
  1623  	} else {
  1624  		// DWARF4 requires
  1625  		// 1. abbrev offset
  1626  		// 2. address size
  1627  		d.addDwarfAddrRef(su, abbrevsym)
  1628  		su.AddUint8(uint8(d.arch.PtrSize))
  1629  	}
  1630  
  1631  	ds := dwSym(s)
  1632  	dwarf.Uleb128put(d, ds, int64(compunit.Abbrev))
  1633  	if buildcfg.Experiment.Dwarf5 {
  1634  		// If this CU has functions, update the DW_AT_addr_base
  1635  		// attribute to point to the correct section symbol.
  1636  		abattr := getattr(compunit, dwarf.DW_AT_addr_base)
  1637  		if abattr != nil {
  1638  			abattr.Data = dwSym(addrsym)
  1639  		}
  1640  	}
  1641  	dwarf.PutAttrs(d, ds, compunit.Abbrev, compunit.Attr)
  1642  
  1643  	// This is an under-estimate; more will be needed for type DIEs.
  1644  	cu := make([]loader.Sym, 0, len(u.AbsFnDIEs)+len(u.FuncDIEs))
  1645  	cu = append(cu, s)
  1646  	cu = append(cu, u.AbsFnDIEs...)
  1647  	cu = append(cu, u.FuncDIEs...)
  1648  	if u.Consts != 0 {
  1649  		cu = append(cu, loader.Sym(u.Consts))
  1650  	}
  1651  	cu = append(cu, u.VarDIEs...)
  1652  	var cusize int64
  1653  	for _, child := range cu {
  1654  		cusize += int64(len(d.ldr.Data(child)))
  1655  	}
  1656  
  1657  	for die := compunit.Child; die != nil; die = die.Link {
  1658  		l := len(cu)
  1659  		lastSymSz := int64(len(d.ldr.Data(cu[l-1])))
  1660  		cu = d.putdie(cu, die)
  1661  		if lastSymSz != int64(len(d.ldr.Data(cu[l-1]))) {
  1662  			// putdie will sometimes append directly to the last symbol of the list
  1663  			cusize = cusize - lastSymSz + int64(len(d.ldr.Data(cu[l-1])))
  1664  		}
  1665  		for _, child := range cu[l:] {
  1666  			cusize += int64(len(d.ldr.Data(child)))
  1667  		}
  1668  	}
  1669  
  1670  	culu := d.ldr.MakeSymbolUpdater(infoEpilog)
  1671  	culu.AddUint8(0) // closes compilation unit DIE
  1672  	cu = append(cu, infoEpilog)
  1673  	cusize++
  1674  
  1675  	// Save size for AIX symbol table.
  1676  	if d.linkctxt.HeadType == objabi.Haix {
  1677  		addDwsectCUSize(".debug_info", d.getPkgFromCUSym(s), uint64(cusize))
  1678  	}
  1679  	if isDwarf64(d.linkctxt) {
  1680  		cusize -= 12                          // exclude the length field.
  1681  		su.SetUint(d.arch, 4, uint64(cusize)) // 4 because of 0XFFFFFFFF
  1682  	} else {
  1683  		cusize -= 4 // exclude the length field.
  1684  		su.SetUint32(d.arch, 0, uint32(cusize))
  1685  	}
  1686  	return append(syms, cu...)
  1687  }
  1688  
  1689  func (d *dwctxt) writegdbscript() dwarfSecInfo {
  1690  	// TODO (aix): make it available
  1691  	if d.linkctxt.HeadType == objabi.Haix {
  1692  		return dwarfSecInfo{}
  1693  	}
  1694  	if d.linkctxt.LinkMode == LinkExternal && d.linkctxt.HeadType == objabi.Hwindows && d.linkctxt.BuildMode == BuildModeCArchive {
  1695  		// gcc on Windows places .debug_gdb_scripts in the wrong location, which
  1696  		// causes the program not to run. See https://golang.org/issue/20183
  1697  		// Non c-archives can avoid this issue via a linker script
  1698  		// (see fix near writeGDBLinkerScript).
  1699  		// c-archive users would need to specify the linker script manually.
  1700  		// For UX it's better not to deal with this.
  1701  		return dwarfSecInfo{}
  1702  	}
  1703  	if gdbscript == "" {
  1704  		return dwarfSecInfo{}
  1705  	}
  1706  
  1707  	gs := d.ldr.CreateSymForUpdate(".debug_gdb_scripts", 0)
  1708  	gs.SetType(sym.SDWARFSECT)
  1709  
  1710  	gs.AddUint8(GdbScriptPythonFileId)
  1711  	gs.Addstring(gdbscript)
  1712  	return dwarfSecInfo{syms: []loader.Sym{gs.Sym()}}
  1713  }
  1714  
  1715  // FIXME: might be worth looking replacing this map with a function
  1716  // that switches based on symbol instead.
  1717  
  1718  var prototypedies map[string]*dwarf.DWDie
  1719  
  1720  func dwarfEnabled(ctxt *Link) bool {
  1721  	if *FlagW { // disable dwarf
  1722  		return false
  1723  	}
  1724  	if ctxt.HeadType == objabi.Hplan9 || ctxt.HeadType == objabi.Hjs || ctxt.HeadType == objabi.Hwasip1 {
  1725  		return false
  1726  	}
  1727  
  1728  	if ctxt.LinkMode == LinkExternal {
  1729  		switch {
  1730  		case ctxt.IsELF:
  1731  		case ctxt.HeadType == objabi.Hdarwin:
  1732  		case ctxt.HeadType == objabi.Hwindows:
  1733  		case ctxt.HeadType == objabi.Haix:
  1734  			res, err := dwarf.IsDWARFEnabledOnAIXLd(ctxt.extld())
  1735  			if err != nil {
  1736  				Exitf("%v", err)
  1737  			}
  1738  			return res
  1739  		default:
  1740  			return false
  1741  		}
  1742  	}
  1743  
  1744  	return true
  1745  }
  1746  
  1747  // mkBuiltinType populates the dwctxt2 sym lookup maps for the
  1748  // newly created builtin type DIE 'typeDie'.
  1749  func (d *dwctxt) mkBuiltinType(ctxt *Link, abrv int, tname string) *dwarf.DWDie {
  1750  	// create type DIE
  1751  	die := d.newdie(&dwtypes, abrv, tname)
  1752  
  1753  	// Look up type symbol.
  1754  	gotype := d.lookupOrDiag("type:" + tname)
  1755  
  1756  	// Map from die sym to type sym
  1757  	ds := loader.Sym(die.Sym.(dwSym))
  1758  	d.rtmap[ds] = gotype
  1759  
  1760  	// Map from type to def sym
  1761  	d.tdmap[gotype] = ds
  1762  
  1763  	return die
  1764  }
  1765  
  1766  // assignDebugAddrSlot assigns a slot (if needed) in the .debug_addr
  1767  // section fragment of the specified unit for the function pointed to
  1768  // by R_DWTXTADDR_* relocation r.  The slot index selected will be
  1769  // filled in when the relocation is actually applied/resolved.
  1770  func (d *dwctxt) assignDebugAddrSlot(unit *sym.CompilationUnit, fnsym loader.Sym, r loader.Reloc, sb *loader.SymbolBuilder) {
  1771  	rsym := r.Sym()
  1772  	if unit.Addrs == nil {
  1773  		unit.Addrs = make(map[sym.LoaderSym]uint32)
  1774  	}
  1775  	if _, ok := unit.Addrs[sym.LoaderSym(rsym)]; ok {
  1776  		// already present, no work needed
  1777  	} else {
  1778  		sl := len(unit.Addrs)
  1779  		rt := r.Type()
  1780  		lim, _ := rt.DwTxtAddrRelocParams()
  1781  		if sl > lim {
  1782  			log.Fatalf("internal error: %s relocation overflow on infosym for %s", rt.String(), d.ldr.SymName(fnsym))
  1783  		}
  1784  		unit.Addrs[sym.LoaderSym(rsym)] = uint32(sl)
  1785  		sb.AddAddrPlus(d.arch, rsym, 0)
  1786  		data := sb.Data()
  1787  		if d.arch.PtrSize == 4 {
  1788  			d.arch.ByteOrder.PutUint32(data[len(data)-4:], uint32(d.ldr.SymValue(rsym)))
  1789  		} else {
  1790  			d.arch.ByteOrder.PutUint64(data[len(data)-8:], uint64(d.ldr.SymValue(rsym)))
  1791  		}
  1792  	}
  1793  }
  1794  
  1795  // dwarfVisitFunction takes a function (text) symbol and processes the
  1796  // subprogram DIE for the function and picks up any other DIEs
  1797  // (absfns, types) that it references.
  1798  func (d *dwctxt) dwarfVisitFunction(fnSym loader.Sym, unit *sym.CompilationUnit) {
  1799  	// The DWARF subprogram DIE symbol is listed as an aux sym
  1800  	// of the text (fcn) symbol, so ask the loader to retrieve it,
  1801  	// as well as the associated range symbol.
  1802  	infosym, _, rangesym, _ := d.ldr.GetFuncDwarfAuxSyms(fnSym)
  1803  	if infosym == 0 {
  1804  		return
  1805  	}
  1806  	d.ldr.SetAttrNotInSymbolTable(infosym, true)
  1807  	d.ldr.SetAttrReachable(infosym, true)
  1808  	unit.FuncDIEs = append(unit.FuncDIEs, sym.LoaderSym(infosym))
  1809  	if rangesym != 0 {
  1810  		d.ldr.SetAttrNotInSymbolTable(rangesym, true)
  1811  		d.ldr.SetAttrReachable(rangesym, true)
  1812  		unit.RangeSyms = append(unit.RangeSyms, sym.LoaderSym(rangesym))
  1813  	}
  1814  
  1815  	// Walk the relocations of the subprogram DIE symbol to discover
  1816  	// references to abstract function DIEs, Go type DIES, and
  1817  	// (via R_USETYPE relocs) types that were originally assigned to
  1818  	// locals/params but were optimized away.
  1819  	drelocs := d.ldr.Relocs(infosym)
  1820  	for ri := 0; ri < drelocs.Count(); ri++ {
  1821  		r := drelocs.At(ri)
  1822  		// Look for "use type" relocs.
  1823  		if r.Type() == objabi.R_USETYPE {
  1824  			d.defgotype(r.Sym())
  1825  			continue
  1826  		}
  1827  		if r.Type() != objabi.R_DWARFSECREF {
  1828  			continue
  1829  		}
  1830  
  1831  		rsym := r.Sym()
  1832  		rst := d.ldr.SymType(rsym)
  1833  
  1834  		// Look for abstract function references.
  1835  		if rst == sym.SDWARFABSFCN {
  1836  			if !d.ldr.AttrOnList(rsym) {
  1837  				// abstract function
  1838  				d.ldr.SetAttrOnList(rsym, true)
  1839  				unit.AbsFnDIEs = append(unit.AbsFnDIEs, sym.LoaderSym(rsym))
  1840  				d.importInfoSymbol(rsym)
  1841  			}
  1842  			continue
  1843  		}
  1844  
  1845  		// Look for type references.
  1846  		if rst != sym.SDWARFTYPE && rst != sym.Sxxx {
  1847  			continue
  1848  		}
  1849  		if _, ok := d.rtmap[rsym]; ok {
  1850  			// type already generated
  1851  			continue
  1852  		}
  1853  
  1854  		rsn := d.ldr.SymName(rsym)
  1855  		tn := rsn[len(dwarf.InfoPrefix):]
  1856  		ts := d.ldr.Lookup("type:"+tn, 0)
  1857  		d.defgotype(ts)
  1858  	}
  1859  }
  1860  
  1861  // dwarfGenerateDebugInfo generated debug info entries for all types,
  1862  // variables and functions in the program.
  1863  // Along with dwarfGenerateDebugSyms they are the two main entry points into
  1864  // dwarf generation: dwarfGenerateDebugInfo does all the work that should be
  1865  // done before symbol names are mangled while dwarfGenerateDebugSyms does
  1866  // all the work that can only be done after addresses have been assigned to
  1867  // text symbols.
  1868  func dwarfGenerateDebugInfo(ctxt *Link) {
  1869  	if !dwarfEnabled(ctxt) {
  1870  		return
  1871  	}
  1872  
  1873  	d := &dwctxt{
  1874  		linkctxt: ctxt,
  1875  		ldr:      ctxt.loader,
  1876  		arch:     ctxt.Arch,
  1877  		tmap:     make(map[string]loader.Sym),
  1878  		tdmap:    make(map[loader.Sym]loader.Sym),
  1879  		rtmap:    make(map[loader.Sym]loader.Sym),
  1880  	}
  1881  	d.typeRuntimeEface = d.lookupOrDiag("type:runtime.eface")
  1882  	d.typeRuntimeIface = d.lookupOrDiag("type:runtime.iface")
  1883  
  1884  	if ctxt.HeadType == objabi.Haix {
  1885  		// Initial map used to store package size for each DWARF section.
  1886  		dwsectCUSize = make(map[string]uint64)
  1887  	}
  1888  
  1889  	// For ctxt.Diagnostic messages.
  1890  	newattr(&dwtypes, dwarf.DW_AT_name, dwarf.DW_CLS_STRING, int64(len("dwtypes")), "dwtypes")
  1891  
  1892  	// Unspecified type. There are no references to this in the symbol table.
  1893  	d.newdie(&dwtypes, dwarf.DW_ABRV_NULLTYPE, "<unspecified>")
  1894  
  1895  	// Some types that must exist to define other ones (uintptr in particular
  1896  	// is needed for array size)
  1897  	unsafeptrDie := d.mkBuiltinType(ctxt, dwarf.DW_ABRV_BARE_PTRTYPE, "unsafe.Pointer")
  1898  	newattr(unsafeptrDie, dwarf.DW_AT_go_runtime_type, dwarf.DW_CLS_GO_TYPEREF, 0, dwSym(d.lookupOrDiag("type:unsafe.Pointer")))
  1899  	uintptrDie := d.mkBuiltinType(ctxt, dwarf.DW_ABRV_BASETYPE, "uintptr")
  1900  	newattr(uintptrDie, dwarf.DW_AT_encoding, dwarf.DW_CLS_CONSTANT, dwarf.DW_ATE_unsigned, 0)
  1901  	newattr(uintptrDie, dwarf.DW_AT_byte_size, dwarf.DW_CLS_CONSTANT, int64(d.arch.PtrSize), 0)
  1902  	newattr(uintptrDie, dwarf.DW_AT_go_kind, dwarf.DW_CLS_CONSTANT, int64(abi.Uintptr), 0)
  1903  	newattr(uintptrDie, dwarf.DW_AT_go_runtime_type, dwarf.DW_CLS_GO_TYPEREF, 0, dwSym(d.lookupOrDiag("type:uintptr")))
  1904  
  1905  	d.uintptrInfoSym = d.mustFind("uintptr")
  1906  
  1907  	// Prototypes needed for type synthesis.
  1908  	prototypedies = map[string]*dwarf.DWDie{
  1909  		"type:runtime.stringStructDWARF":             nil,
  1910  		"type:runtime.slice":                         nil,
  1911  		"type:runtime.sudog":                         nil,
  1912  		"type:runtime.waitq":                         nil,
  1913  		"type:runtime.hchan":                         nil,
  1914  		"type:internal/runtime/maps.Map":             nil,
  1915  		"type:internal/runtime/maps.table":           nil,
  1916  		"type:internal/runtime/maps.groupsReference": nil,
  1917  	}
  1918  
  1919  	// Needed by the prettyprinter code for interface inspection.
  1920  	for _, typ := range []string{
  1921  		"type:internal/abi.Type",
  1922  		"type:internal/abi.ArrayType",
  1923  		"type:internal/abi.ChanType",
  1924  		"type:internal/abi.FuncType",
  1925  		"type:internal/abi.MapType",
  1926  		"type:internal/abi.PtrType",
  1927  		"type:internal/abi.SliceType",
  1928  		"type:internal/abi.StructType",
  1929  		"type:internal/abi.InterfaceType",
  1930  		"type:internal/abi.ITab",
  1931  		"type:internal/abi.Imethod"} {
  1932  		d.defgotype(d.lookupOrDiag(typ))
  1933  	}
  1934  
  1935  	// fake root DIE for compile unit DIEs
  1936  	var dwroot dwarf.DWDie
  1937  	flagVariants := make(map[string]bool)
  1938  
  1939  	for _, lib := range ctxt.Library {
  1940  
  1941  		consts := d.ldr.Lookup(dwarf.ConstInfoPrefix+lib.Pkg, 0)
  1942  		for _, unit := range lib.Units {
  1943  			// We drop the constants into the first CU.
  1944  			if consts != 0 {
  1945  				unit.Consts = sym.LoaderSym(consts)
  1946  				d.importInfoSymbol(consts)
  1947  				consts = 0
  1948  			}
  1949  			ctxt.compUnits = append(ctxt.compUnits, unit)
  1950  
  1951  			// We need at least one runtime unit.
  1952  			if unit.Lib.Pkg == "runtime" {
  1953  				ctxt.runtimeCU = unit
  1954  			}
  1955  
  1956  			cuabrv := dwarf.DW_ABRV_COMPUNIT
  1957  			if len(unit.Textp) == 0 {
  1958  				cuabrv = dwarf.DW_ABRV_COMPUNIT_TEXTLESS
  1959  			}
  1960  			unit.DWInfo = d.newdie(&dwroot, cuabrv, unit.Lib.Pkg)
  1961  			newattr(unit.DWInfo, dwarf.DW_AT_language, dwarf.DW_CLS_CONSTANT, int64(dwarf.DW_LANG_Go), 0)
  1962  			// OS X linker requires compilation dir or absolute path in comp unit name to output debug info.
  1963  			compDir := getCompilationDir()
  1964  			// TODO: Make this be the actual compilation directory, not
  1965  			// the linker directory. If we move CU construction into the
  1966  			// compiler, this should happen naturally.
  1967  			newattr(unit.DWInfo, dwarf.DW_AT_comp_dir, dwarf.DW_CLS_STRING, int64(len(compDir)), compDir)
  1968  
  1969  			var peData []byte
  1970  			if producerExtra := d.ldr.Lookup(dwarf.CUInfoPrefix+"producer."+unit.Lib.Pkg, 0); producerExtra != 0 {
  1971  				peData = d.ldr.Data(producerExtra)
  1972  			}
  1973  			producer := "Go cmd/compile " + buildcfg.Version
  1974  			if len(peData) > 0 {
  1975  				// We put a semicolon before the flags to clearly
  1976  				// separate them from the version, which can be long
  1977  				// and have lots of weird things in it in development
  1978  				// versions. We promise not to put a semicolon in the
  1979  				// version, so it should be safe for readers to scan
  1980  				// forward to the semicolon.
  1981  				producer += "; " + string(peData)
  1982  				flagVariants[string(peData)] = true
  1983  			} else {
  1984  				flagVariants[""] = true
  1985  			}
  1986  
  1987  			newattr(unit.DWInfo, dwarf.DW_AT_producer, dwarf.DW_CLS_STRING, int64(len(producer)), producer)
  1988  
  1989  			var pkgname string
  1990  			if pnSymIdx := d.ldr.Lookup(dwarf.CUInfoPrefix+"packagename."+unit.Lib.Pkg, 0); pnSymIdx != 0 {
  1991  				pnsData := d.ldr.Data(pnSymIdx)
  1992  				pkgname = string(pnsData)
  1993  			}
  1994  			newattr(unit.DWInfo, dwarf.DW_AT_go_package_name, dwarf.DW_CLS_STRING, int64(len(pkgname)), pkgname)
  1995  
  1996  			if buildcfg.Experiment.Dwarf5 && cuabrv == dwarf.DW_ABRV_COMPUNIT {
  1997  				// For DWARF5, the CU die will have an attribute that
  1998  				// points to the offset into the .debug_addr section
  1999  				// that contains the compilation unit's
  2000  				// contributions. Add this attribute now. Note that
  2001  				// we'll later on update the Data field in this attr
  2002  				// once we know the .debug_addr sym for the unit.
  2003  				newattr(unit.DWInfo, dwarf.DW_AT_addr_base, dwarf.DW_CLS_REFERENCE, 0, 0)
  2004  			}
  2005  
  2006  			// Scan all functions in this compilation unit, create
  2007  			// DIEs for all referenced types, find all referenced
  2008  			// abstract functions, visit range symbols. Note that
  2009  			// Textp has been dead-code-eliminated already.
  2010  			for _, s := range unit.Textp {
  2011  				d.dwarfVisitFunction(loader.Sym(s), unit)
  2012  			}
  2013  		}
  2014  	}
  2015  
  2016  	// Fix for 31034: if the objects feeding into this link were compiled
  2017  	// with different sets of flags, then don't issue an error if
  2018  	// the -strictdups checks fail.
  2019  	if checkStrictDups > 1 && len(flagVariants) > 1 {
  2020  		checkStrictDups = 1
  2021  	}
  2022  
  2023  	// Make a pass through all data symbols, looking for those
  2024  	// corresponding to reachable, Go-generated, user-visible
  2025  	// global variables. For each global of this sort, locate
  2026  	// the corresponding compiler-generated DIE symbol and tack
  2027  	// it onto the list associated with the unit.
  2028  	// Also looks for dictionary symbols and generates DIE symbols for each
  2029  	// type they reference.
  2030  	for idx := loader.Sym(1); idx < loader.Sym(d.ldr.NDef()); idx++ {
  2031  		if !d.ldr.AttrReachable(idx) ||
  2032  			d.ldr.AttrNotInSymbolTable(idx) ||
  2033  			d.ldr.SymVersion(idx) >= sym.SymVerStatic {
  2034  			continue
  2035  		}
  2036  		t := d.ldr.SymType(idx)
  2037  		switch {
  2038  		case t.IsRODATA(), t.IsDATA(), t.IsNOPTRDATA(),
  2039  			t == sym.STYPE, t == sym.SBSS, t == sym.SNOPTRBSS, t == sym.STLSBSS:
  2040  			// ok
  2041  		default:
  2042  			continue
  2043  		}
  2044  		// Skip things with no type, unless it's a dictionary
  2045  		gt := d.ldr.SymGoType(idx)
  2046  		if gt == 0 {
  2047  			if t == sym.SRODATA {
  2048  				if d.ldr.IsDict(idx) {
  2049  					// This is a dictionary, make sure that all types referenced by this dictionary are reachable
  2050  					relocs := d.ldr.Relocs(idx)
  2051  					for i := 0; i < relocs.Count(); i++ {
  2052  						reloc := relocs.At(i)
  2053  						if reloc.Type() == objabi.R_USEIFACE {
  2054  							d.defgotype(reloc.Sym())
  2055  						}
  2056  					}
  2057  				}
  2058  			}
  2059  			continue
  2060  		}
  2061  		// Skip file local symbols (this includes static tmps, stack
  2062  		// object symbols, and local symbols in assembler src files).
  2063  		if d.ldr.IsFileLocal(idx) {
  2064  			continue
  2065  		}
  2066  
  2067  		// Find compiler-generated DWARF info sym for global in question,
  2068  		// and tack it onto the appropriate unit.  Note that there are
  2069  		// circumstances under which we can't find the compiler-generated
  2070  		// symbol-- this typically happens as a result of compiler options
  2071  		// (e.g. compile package X with "-dwarf=0").
  2072  		varDIE := d.ldr.GetVarDwarfAuxSym(idx)
  2073  		if varDIE != 0 {
  2074  			unit := d.ldr.SymUnit(idx)
  2075  			d.defgotype(gt)
  2076  			unit.VarDIEs = append(unit.VarDIEs, sym.LoaderSym(varDIE))
  2077  		}
  2078  	}
  2079  
  2080  	d.synthesizestringtypes(ctxt, dwtypes.Child)
  2081  	d.synthesizeslicetypes(ctxt, dwtypes.Child)
  2082  	d.synthesizemaptypes(ctxt, dwtypes.Child)
  2083  	d.synthesizechantypes(ctxt, dwtypes.Child)
  2084  }
  2085  
  2086  // dwarfGenerateDebugSyms constructs debug_line, debug_frame, and
  2087  // debug_loc. It also writes out the debug_info section using symbols
  2088  // generated in dwarfGenerateDebugInfo.
  2089  func dwarfGenerateDebugSyms(ctxt *Link) {
  2090  	if !dwarfEnabled(ctxt) {
  2091  		return
  2092  	}
  2093  	d := &dwctxt{
  2094  		linkctxt: ctxt,
  2095  		ldr:      ctxt.loader,
  2096  		arch:     ctxt.Arch,
  2097  		dwmu:     new(sync.Mutex),
  2098  	}
  2099  	d.dwarfGenerateDebugSyms()
  2100  }
  2101  
  2102  // dwUnitSyms stores input and output symbols for DWARF generation
  2103  // for a given compilation unit.
  2104  type dwUnitSyms struct {
  2105  	// Inputs for a given unit.
  2106  	lineProlog  loader.Sym
  2107  	rangeProlog loader.Sym
  2108  	infoEpilog  loader.Sym
  2109  
  2110  	// Outputs for a given unit.
  2111  	linesyms   []loader.Sym
  2112  	infosyms   []loader.Sym
  2113  	locsyms    []loader.Sym
  2114  	rangessyms []loader.Sym
  2115  	addrsym    loader.Sym
  2116  }
  2117  
  2118  // dwUnitPortion assembles the DWARF content for a given comp unit:
  2119  // debug_info, debug_lines, debug_ranges(V4) or debug_rnglists (V5),
  2120  // debug_loc (V4) or debug_loclists (V5) and debug_addr (V5);
  2121  // debug_frame is handled elsewhere. Order is important; the calls to
  2122  // writelines and writepcranges below make updates to the compilation
  2123  // unit DIE, hence they have to happen before the call to
  2124  // writeUnitInfo.
  2125  func (d *dwctxt) dwUnitPortion(u *sym.CompilationUnit, abbrevsym loader.Sym, us *dwUnitSyms) {
  2126  	if u.DWInfo.Abbrev != dwarf.DW_ABRV_COMPUNIT_TEXTLESS {
  2127  		us.linesyms = d.writelines(u, us.lineProlog)
  2128  		base := loader.Sym(u.Textp[0])
  2129  		if buildcfg.Experiment.Dwarf5 {
  2130  			d.writedebugaddr(u, us.addrsym)
  2131  		}
  2132  		us.rangessyms = d.writepcranges(u, base, u.PCs, us.rangeProlog, us.addrsym)
  2133  		us.locsyms = d.collectUnitLocs(u)
  2134  	}
  2135  	us.infosyms = d.writeUnitInfo(u, abbrevsym, us.addrsym, us.infoEpilog)
  2136  }
  2137  
  2138  // writedebugaddr scans the symbols of interest in unit for
  2139  // R_DWTXTADDR_R* relocations and converts these into the material
  2140  // we'll need to generate the .debug_addr section for the unit. This
  2141  // will create a map within the unit (as a side effect), mapping func
  2142  // symbol to debug_addr slot.
  2143  func (d *dwctxt) writedebugaddr(unit *sym.CompilationUnit, debugaddr loader.Sym) {
  2144  	dasu := d.ldr.MakeSymbolUpdater(debugaddr)
  2145  
  2146  	var dsyms []loader.Sym
  2147  	for _, s := range unit.Textp {
  2148  		fnSym := loader.Sym(s)
  2149  		// NB: this looks at SDWARFFCN; it will need to also look
  2150  		// at range and loc when they get there.
  2151  		infosym, locsym, rangessym, _ := d.ldr.GetFuncDwarfAuxSyms(fnSym)
  2152  
  2153  		// Walk the relocations of the various DWARF symbols to
  2154  		// collect relocations corresponding to indirect function
  2155  		// references via .debug_addr.
  2156  		dsyms = dsyms[:0]
  2157  		dsyms = append(dsyms, infosym)
  2158  		if rangessym != 0 {
  2159  			dsyms = append(dsyms, rangessym)
  2160  		}
  2161  		if locsym != 0 {
  2162  			dsyms = append(dsyms, locsym)
  2163  		}
  2164  		for _, dsym := range dsyms {
  2165  			drelocs := d.ldr.Relocs(dsym)
  2166  			for ri := 0; ri < drelocs.Count(); ri++ {
  2167  				r := drelocs.At(ri)
  2168  				if !r.Type().IsDwTxtAddr() {
  2169  					continue
  2170  				}
  2171  				rsym := r.Sym()
  2172  				rst := d.ldr.SymType(rsym)
  2173  				// Do some consistency checks.
  2174  				if !rst.IsText() {
  2175  					// R_DWTXTADDR_* relocation should only refer to
  2176  					// text symbols, so something apparently went
  2177  					// wrong here.
  2178  					log.Fatalf("internal error: R_DWTXTADDR_* relocation on dwinfosym for %s against non-function %s type:%s", d.ldr.SymName(fnSym), d.ldr.SymName(rsym), rst.String())
  2179  				}
  2180  				if runit := d.ldr.SymUnit(rsym); runit != unit {
  2181  					log.Fatalf("internal error: R_DWTXTADDR_* relocation target text sym unit mismatch (want %q got %q)", unit.Lib.Pkg, runit.Lib.Pkg)
  2182  				}
  2183  				d.assignDebugAddrSlot(unit, fnSym, r, dasu)
  2184  			}
  2185  		}
  2186  	}
  2187  }
  2188  
  2189  func (d *dwctxt) dwarfGenerateDebugSyms() {
  2190  	abbrevSec := d.writeabbrev()
  2191  	dwarfp = append(dwarfp, abbrevSec)
  2192  	d.calcCompUnitRanges()
  2193  	slices.SortFunc(d.linkctxt.compUnits, compilationUnitByStartPCCmp)
  2194  
  2195  	// newdie adds DIEs to the *beginning* of the parent's DIE list.
  2196  	// Now that we're done creating DIEs, reverse the trees so DIEs
  2197  	// appear in the order they were created.
  2198  	for _, u := range d.linkctxt.compUnits {
  2199  		reversetree(&u.DWInfo.Child)
  2200  	}
  2201  	reversetree(&dwtypes.Child)
  2202  	movetomodule(d.linkctxt, &dwtypes)
  2203  
  2204  	mkSecSym := func(name string) loader.Sym {
  2205  		s := d.ldr.CreateSymForUpdate(name, 0)
  2206  		s.SetType(sym.SDWARFSECT)
  2207  		s.SetReachable(true)
  2208  		return s.Sym()
  2209  	}
  2210  
  2211  	mkAnonSym := func(kind sym.SymKind) loader.Sym {
  2212  		s := d.ldr.MakeSymbolUpdater(d.ldr.CreateExtSym("", 0))
  2213  		s.SetType(kind)
  2214  		s.SetReachable(true)
  2215  		return s.Sym()
  2216  	}
  2217  
  2218  	// Create the section symbols.
  2219  	frameSym := mkSecSym(".debug_frame")
  2220  	lineSym := mkSecSym(".debug_line")
  2221  	var rangesSym, locSym loader.Sym
  2222  	if buildcfg.Experiment.Dwarf5 {
  2223  		rangesSym = mkSecSym(".debug_rnglists")
  2224  		locSym = mkSecSym(".debug_loclists")
  2225  	} else {
  2226  		rangesSym = mkSecSym(".debug_ranges")
  2227  		locSym = mkSecSym(".debug_loc")
  2228  	}
  2229  	infoSym := mkSecSym(".debug_info")
  2230  	var addrSym loader.Sym
  2231  	if buildcfg.Experiment.Dwarf5 {
  2232  		addrSym = mkSecSym(".debug_addr")
  2233  	}
  2234  
  2235  	// Create the section objects
  2236  	lineSec := dwarfSecInfo{syms: []loader.Sym{lineSym}}
  2237  	frameSec := dwarfSecInfo{syms: []loader.Sym{frameSym}}
  2238  	infoSec := dwarfSecInfo{syms: []loader.Sym{infoSym}}
  2239  	var addrSec, rangesSec, locSec dwarfSecInfo
  2240  	if buildcfg.Experiment.Dwarf5 {
  2241  		addrHdr := d.writeDebugAddrHdr()
  2242  		addrSec.syms = []loader.Sym{addrSym, addrHdr}
  2243  		rnglistsHdr := d.writeDebugRngListsHdr()
  2244  		rangesSec.syms = []loader.Sym{rangesSym, rnglistsHdr}
  2245  		loclistsHdr := d.writeDebugLocListsHdr()
  2246  		locSec.syms = []loader.Sym{locSym, loclistsHdr}
  2247  	} else {
  2248  		rangesSec = dwarfSecInfo{syms: []loader.Sym{rangesSym}}
  2249  		locSec = dwarfSecInfo{syms: []loader.Sym{locSym}}
  2250  	}
  2251  
  2252  	// Create any new symbols that will be needed during the
  2253  	// parallel portion below.
  2254  	ncu := len(d.linkctxt.compUnits)
  2255  	unitSyms := make([]dwUnitSyms, ncu)
  2256  	for i := 0; i < ncu; i++ {
  2257  		us := &unitSyms[i]
  2258  		us.lineProlog = mkAnonSym(sym.SDWARFLINES)
  2259  		us.rangeProlog = mkAnonSym(sym.SDWARFRANGE)
  2260  		us.infoEpilog = mkAnonSym(sym.SDWARFFCN)
  2261  		us.addrsym = mkAnonSym(sym.SDWARFADDR)
  2262  	}
  2263  
  2264  	var wg sync.WaitGroup
  2265  	sema := make(chan struct{}, runtime.GOMAXPROCS(0))
  2266  
  2267  	// Kick off generation of .debug_frame, since it doesn't have
  2268  	// any entanglements and can be started right away.
  2269  	wg.Add(1)
  2270  	go func() {
  2271  		sema <- struct{}{}
  2272  		defer func() {
  2273  			<-sema
  2274  			wg.Done()
  2275  		}()
  2276  		frameSec = d.writeframes(frameSym)
  2277  	}()
  2278  
  2279  	// Create a goroutine per comp unit to handle the generation that
  2280  	// unit's portion of .debug_line, .debug_loc, .debug_ranges, and
  2281  	// .debug_info.
  2282  	wg.Add(len(d.linkctxt.compUnits))
  2283  	for i := 0; i < ncu; i++ {
  2284  		go func(u *sym.CompilationUnit, us *dwUnitSyms) {
  2285  			sema <- struct{}{}
  2286  			defer func() {
  2287  				<-sema
  2288  				wg.Done()
  2289  			}()
  2290  			d.dwUnitPortion(u, abbrevSec.secSym(), us)
  2291  		}(d.linkctxt.compUnits[i], &unitSyms[i])
  2292  	}
  2293  	wg.Wait()
  2294  
  2295  	markReachable := func(syms []loader.Sym) []loader.Sym {
  2296  		for _, s := range syms {
  2297  			d.ldr.SetAttrNotInSymbolTable(s, true)
  2298  			d.ldr.SetAttrReachable(s, true)
  2299  		}
  2300  		return syms
  2301  	}
  2302  
  2303  	patchHdr := func(sec *dwarfSecInfo, len uint64) {
  2304  		hdrsym := sec.syms[1]
  2305  		len += uint64(d.ldr.SymSize(hdrsym))
  2306  		su := d.ldr.MakeSymbolUpdater(hdrsym)
  2307  		if isDwarf64(d.linkctxt) {
  2308  			len -= 12                          // sub size of length field
  2309  			su.SetUint(d.arch, 4, uint64(len)) // 4 because of 0XFFFFFFFF
  2310  		} else {
  2311  			len -= 4 // subtract size of length field
  2312  			su.SetUint32(d.arch, 0, uint32(len))
  2313  		}
  2314  	}
  2315  
  2316  	if buildcfg.Experiment.Dwarf5 {
  2317  		// Compute total size of the DWARF5-specific .debug_* syms in
  2318  		// each compilation unit.
  2319  		var rltot, addrtot, loctot uint64
  2320  		for i := 0; i < ncu; i++ {
  2321  			addrtot += uint64(d.ldr.SymSize(unitSyms[i].addrsym))
  2322  			rs := unitSyms[i].rangessyms
  2323  			for _, s := range rs {
  2324  				rltot += uint64(d.ldr.SymSize(s))
  2325  			}
  2326  			loc := unitSyms[i].locsyms
  2327  			for _, s := range loc {
  2328  				loctot += uint64(d.ldr.SymSize(s))
  2329  			}
  2330  		}
  2331  		// Call a helper to patch the length field in the headers.
  2332  		patchHdr(&addrSec, addrtot)
  2333  		patchHdr(&rangesSec, rltot)
  2334  		patchHdr(&locSec, loctot)
  2335  	}
  2336  
  2337  	// Stitch together the results.
  2338  	for i := 0; i < ncu; i++ {
  2339  		r := &unitSyms[i]
  2340  		lineSec.syms = append(lineSec.syms, markReachable(r.linesyms)...)
  2341  		infoSec.syms = append(infoSec.syms, markReachable(r.infosyms)...)
  2342  		locSec.syms = append(locSec.syms, markReachable(r.locsyms)...)
  2343  		rangesSec.syms = append(rangesSec.syms, markReachable(r.rangessyms)...)
  2344  		if buildcfg.Experiment.Dwarf5 && r.addrsym != 0 {
  2345  			addrSec.syms = append(addrSec.syms, r.addrsym)
  2346  		}
  2347  	}
  2348  	dwarfp = append(dwarfp, lineSec)
  2349  	dwarfp = append(dwarfp, frameSec)
  2350  	gdbScriptSec := d.writegdbscript()
  2351  	if gdbScriptSec.secSym() != 0 {
  2352  		dwarfp = append(dwarfp, gdbScriptSec)
  2353  	}
  2354  	dwarfp = append(dwarfp, infoSec)
  2355  	if len(locSec.syms) > 1 {
  2356  		dwarfp = append(dwarfp, locSec)
  2357  	}
  2358  	dwarfp = append(dwarfp, rangesSec)
  2359  	if buildcfg.Experiment.Dwarf5 {
  2360  		dwarfp = append(dwarfp, addrSec)
  2361  	}
  2362  
  2363  	// Check to make sure we haven't listed any symbols more than once
  2364  	// in the info section. This used to be done by setting and
  2365  	// checking the OnList attribute in "putdie", but that strategy
  2366  	// was not friendly for concurrency.
  2367  	seen := loader.MakeBitmap(d.ldr.NSym())
  2368  	for _, s := range infoSec.syms {
  2369  		if seen.Has(s) {
  2370  			log.Fatalf("dwarf symbol %s listed multiple times",
  2371  				d.ldr.SymName(s))
  2372  		}
  2373  		seen.Set(s)
  2374  	}
  2375  }
  2376  
  2377  func (d *dwctxt) collectUnitLocs(u *sym.CompilationUnit) []loader.Sym {
  2378  	syms := []loader.Sym{}
  2379  	for _, fn := range u.FuncDIEs {
  2380  		relocs := d.ldr.Relocs(loader.Sym(fn))
  2381  		for i := 0; i < relocs.Count(); i++ {
  2382  			reloc := relocs.At(i)
  2383  			if reloc.Type() != objabi.R_DWARFSECREF {
  2384  				continue
  2385  			}
  2386  			rsym := reloc.Sym()
  2387  			if d.ldr.SymType(rsym) == sym.SDWARFLOC {
  2388  				syms = append(syms, rsym)
  2389  				// One location list entry per function, but many relocations to it. Don't duplicate.
  2390  				break
  2391  			}
  2392  		}
  2393  	}
  2394  	return syms
  2395  }
  2396  
  2397  // Add DWARF section names to the section header string table, by calling add
  2398  // on each name. ELF only.
  2399  func dwarfaddshstrings(ctxt *Link, add func(string)) {
  2400  	if *FlagW { // disable dwarf
  2401  		return
  2402  	}
  2403  
  2404  	secs := []string{"abbrev", "frame", "info", "loc", "line", "gdb_scripts"}
  2405  	if buildcfg.Experiment.Dwarf5 {
  2406  		secs = append(secs, "addr", "rnglists", "loclists")
  2407  	} else {
  2408  		secs = append(secs, "ranges", "loc")
  2409  	}
  2410  
  2411  	for _, sec := range secs {
  2412  		add(".debug_" + sec)
  2413  		if ctxt.IsExternal() {
  2414  			add(elfRelType + ".debug_" + sec)
  2415  		}
  2416  	}
  2417  }
  2418  
  2419  func dwarfaddelfsectionsyms(ctxt *Link) {
  2420  	if *FlagW { // disable dwarf
  2421  		return
  2422  	}
  2423  	if ctxt.LinkMode != LinkExternal {
  2424  		return
  2425  	}
  2426  
  2427  	ldr := ctxt.loader
  2428  	for _, si := range dwarfp {
  2429  		s := si.secSym()
  2430  		sect := ldr.SymSect(si.secSym())
  2431  		putelfsectionsym(ctxt, ctxt.Out, s, sect.Elfsect.(*ElfShdr).shnum)
  2432  	}
  2433  }
  2434  
  2435  // dwarfcompress compresses the DWARF sections. Relocations are applied
  2436  // on the fly. After this, dwarfp will contain a different (new) set of
  2437  // symbols, and sections may have been replaced.
  2438  func dwarfcompress(ctxt *Link) {
  2439  	// compressedSect is a helper type for parallelizing compression.
  2440  	type compressedSect struct {
  2441  		index      int
  2442  		compressed []byte
  2443  		syms       []loader.Sym
  2444  	}
  2445  
  2446  	supported := ctxt.IsELF || ctxt.IsWindows() || ctxt.IsDarwin()
  2447  	if !ctxt.compressDWARF || !supported || ctxt.IsExternal() {
  2448  		return
  2449  	}
  2450  
  2451  	var compressedCount int
  2452  	resChannel := make(chan compressedSect)
  2453  	for i := range dwarfp {
  2454  		go func(resIndex int, syms []loader.Sym) {
  2455  			resChannel <- compressedSect{resIndex, compressSyms(ctxt, syms), syms}
  2456  		}(compressedCount, dwarfp[i].syms)
  2457  		compressedCount++
  2458  	}
  2459  	res := make([]compressedSect, compressedCount)
  2460  	for ; compressedCount > 0; compressedCount-- {
  2461  		r := <-resChannel
  2462  		res[r.index] = r
  2463  	}
  2464  
  2465  	ldr := ctxt.loader
  2466  	var newDwarfp []dwarfSecInfo
  2467  	Segdwarf.Sections = Segdwarf.Sections[:0]
  2468  	for _, z := range res {
  2469  		s := z.syms[0]
  2470  		if z.compressed == nil {
  2471  			// Compression didn't help.
  2472  			ds := dwarfSecInfo{syms: z.syms}
  2473  			newDwarfp = append(newDwarfp, ds)
  2474  			Segdwarf.Sections = append(Segdwarf.Sections, ldr.SymSect(s))
  2475  		} else {
  2476  			var compressedSegName string
  2477  			if ctxt.IsELF {
  2478  				compressedSegName = ldr.SymSect(s).Name
  2479  			} else {
  2480  				compressedSegName = ".zdebug_" + ldr.SymSect(s).Name[len(".debug_"):]
  2481  			}
  2482  			sect := addsection(ctxt.loader, ctxt.Arch, &Segdwarf, compressedSegName, 04)
  2483  			sect.Align = int32(ctxt.Arch.Alignment)
  2484  			sect.Length = uint64(len(z.compressed))
  2485  			sect.Compressed = true
  2486  			newSym := ldr.MakeSymbolBuilder(compressedSegName)
  2487  			ldr.SetAttrReachable(s, true)
  2488  			newSym.SetData(z.compressed)
  2489  			newSym.SetSize(int64(len(z.compressed)))
  2490  			ldr.SetSymSect(newSym.Sym(), sect)
  2491  			ds := dwarfSecInfo{syms: []loader.Sym{newSym.Sym()}}
  2492  			newDwarfp = append(newDwarfp, ds)
  2493  
  2494  			// compressed symbols are no longer needed.
  2495  			for _, s := range z.syms {
  2496  				ldr.SetAttrReachable(s, false)
  2497  				ldr.FreeSym(s)
  2498  			}
  2499  		}
  2500  	}
  2501  	dwarfp = newDwarfp
  2502  
  2503  	// Re-compute the locations of the compressed DWARF symbols
  2504  	// and sections, since the layout of these within the file is
  2505  	// based on Section.Vaddr and Symbol.Value.
  2506  	pos := Segdwarf.Vaddr
  2507  	var prevSect *sym.Section
  2508  	for _, si := range dwarfp {
  2509  		for _, s := range si.syms {
  2510  			ldr.SetSymValue(s, int64(pos))
  2511  			sect := ldr.SymSect(s)
  2512  			if sect != prevSect {
  2513  				sect.Vaddr = uint64(pos)
  2514  				prevSect = sect
  2515  			}
  2516  			if ldr.SubSym(s) != 0 {
  2517  				log.Fatalf("%s: unexpected sub-symbols", ldr.SymName(s))
  2518  			}
  2519  			pos += uint64(ldr.SymSize(s))
  2520  			if ctxt.IsWindows() {
  2521  				pos = uint64(Rnd(int64(pos), PEFILEALIGN))
  2522  			}
  2523  		}
  2524  	}
  2525  	Segdwarf.Length = pos - Segdwarf.Vaddr
  2526  }
  2527  
  2528  func compilationUnitByStartPCCmp(a, b *sym.CompilationUnit) int {
  2529  	switch {
  2530  	case len(a.Textp) == 0 && len(b.Textp) == 0:
  2531  		return strings.Compare(a.Lib.Pkg, b.Lib.Pkg)
  2532  	case len(a.Textp) != 0 && len(b.Textp) == 0:
  2533  		return -1
  2534  	case len(a.Textp) == 0 && len(b.Textp) != 0:
  2535  		return +1
  2536  	default:
  2537  		return cmp.Compare(a.PCs[0].Start, b.PCs[0].Start)
  2538  	}
  2539  }
  2540  
  2541  // getPkgFromCUSym returns the package name for the compilation unit
  2542  // represented by s.
  2543  // The prefix dwarf.InfoPrefix+".pkg." needs to be removed in order to get
  2544  // the package name.
  2545  func (d *dwctxt) getPkgFromCUSym(s loader.Sym) string {
  2546  	return strings.TrimPrefix(d.ldr.SymName(s), dwarf.InfoPrefix+".pkg.")
  2547  }
  2548  
  2549  // On AIX, the symbol table needs to know where are the compilation units parts
  2550  // for a specific package in each .dw section.
  2551  // dwsectCUSize map will save the size of a compilation unit for
  2552  // the corresponding .dw section.
  2553  // This size can later be retrieved with the index "sectionName.pkgName".
  2554  var dwsectCUSizeMu sync.Mutex
  2555  var dwsectCUSize map[string]uint64
  2556  
  2557  // getDwsectCUSize retrieves the corresponding package size inside the current section.
  2558  func getDwsectCUSize(sname string, pkgname string) uint64 {
  2559  	return dwsectCUSize[sname+"."+pkgname]
  2560  }
  2561  
  2562  func addDwsectCUSize(sname string, pkgname string, size uint64) {
  2563  	dwsectCUSizeMu.Lock()
  2564  	defer dwsectCUSizeMu.Unlock()
  2565  	dwsectCUSize[sname+"."+pkgname] += size
  2566  }
  2567  
  2568  // writeDebugMiscSecHdr writes a header section for the new new DWARF5
  2569  // sections ".debug_addr", ".debug_loclists", and ".debug_rnglists".
  2570  // A description of the format/layout of these headers can be found in
  2571  // the DWARF5 spec in sections 7.27 (.debug_addr), 7.28
  2572  // (.debug_rnglists) and 7.29 (.debug_loclists).
  2573  func (d *dwctxt) writeDebugMiscSecHdr(st sym.SymKind, addOffsetEntryCount bool) loader.Sym {
  2574  	su := d.ldr.MakeSymbolUpdater(d.ldr.CreateExtSym("", 0))
  2575  	su.SetType(st)
  2576  	su.SetReachable(true)
  2577  	d.createUnitLength(su, 0)          // will be filled in later.
  2578  	su.AddUint16(d.arch, 5)            // dwarf version (appendix F)
  2579  	su.AddUint8(uint8(d.arch.PtrSize)) // address_size
  2580  	su.AddUint8(0)                     // segment selector
  2581  	if addOffsetEntryCount {
  2582  		su.AddUint32(d.arch, 0) // offset entry count (required but unused)
  2583  	}
  2584  	return su.Sym()
  2585  }
  2586  
  2587  func (d *dwctxt) writeDebugRngListsHdr() loader.Sym {
  2588  	return d.writeDebugMiscSecHdr(sym.SDWARFRANGE, true)
  2589  }
  2590  
  2591  func (d *dwctxt) writeDebugLocListsHdr() loader.Sym {
  2592  	return d.writeDebugMiscSecHdr(sym.SDWARFLOC, true)
  2593  }
  2594  
  2595  func (d *dwctxt) writeDebugAddrHdr() loader.Sym {
  2596  	return d.writeDebugMiscSecHdr(sym.SDWARFADDR, false)
  2597  }
  2598  

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