symtab.go

     1  // Inferno utils/6l/span.c
     2  // https://bitbucket.org/inferno-os/inferno-os/src/master/utils/6l/span.c
     3  //
     4  //	Copyright © 1994-1999 Lucent Technologies Inc.  All rights reserved.
     5  //	Portions Copyright © 1995-1997 C H Forsyth (forsyth@terzarima.net)
     6  //	Portions Copyright © 1997-1999 Vita Nuova Limited
     7  //	Portions Copyright © 2000-2007 Vita Nuova Holdings Limited (www.vitanuova.com)
     8  //	Portions Copyright © 2004,2006 Bruce Ellis
     9  //	Portions Copyright © 2005-2007 C H Forsyth (forsyth@terzarima.net)
    10  //	Revisions Copyright © 2000-2007 Lucent Technologies Inc. and others
    11  //	Portions Copyright © 2009 The Go Authors. All rights reserved.
    12  //
    13  // Permission is hereby granted, free of charge, to any person obtaining a copy
    14  // of this software and associated documentation files (the "Software"), to deal
    15  // in the Software without restriction, including without limitation the rights
    16  // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
    17  // copies of the Software, and to permit persons to whom the Software is
    18  // furnished to do so, subject to the following conditions:
    19  //
    20  // The above copyright notice and this permission notice shall be included in
    21  // all copies or substantial portions of the Software.
    22  //
    23  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    24  // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    25  // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
    26  // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
    27  // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
    28  // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
    29  // THE SOFTWARE.
    30  
    31  package ld
    32  
    33  import (
    34  	"cmd/internal/obj"
    35  	"cmd/internal/objabi"
    36  	"cmd/link/internal/loader"
    37  	"cmd/link/internal/sym"
    38  	"debug/elf"
    39  	"fmt"
    40  	"internal/buildcfg"
    41  	"path/filepath"
    42  	"strings"
    43  )
    44  
    45  // Symbol table.
    46  
    47  func putelfstr(s string) int {
    48  	if len(elfstrdat) == 0 && s != "" {
    49  		// first entry must be empty string
    50  		putelfstr("")
    51  	}
    52  
    53  	off := len(elfstrdat)
    54  	elfstrdat = append(elfstrdat, s...)
    55  	elfstrdat = append(elfstrdat, 0)
    56  	return off
    57  }
    58  
    59  func putelfsyment(out *OutBuf, off int, addr int64, size int64, info uint8, shndx elf.SectionIndex, other int) {
    60  	if elf64 {
    61  		out.Write32(uint32(off))
    62  		out.Write8(info)
    63  		out.Write8(uint8(other))
    64  		out.Write16(uint16(shndx))
    65  		out.Write64(uint64(addr))
    66  		out.Write64(uint64(size))
    67  		symSize += ELF64SYMSIZE
    68  	} else {
    69  		out.Write32(uint32(off))
    70  		out.Write32(uint32(addr))
    71  		out.Write32(uint32(size))
    72  		out.Write8(info)
    73  		out.Write8(uint8(other))
    74  		out.Write16(uint16(shndx))
    75  		symSize += ELF32SYMSIZE
    76  	}
    77  }
    78  
    79  func putelfsym(ctxt *Link, x loader.Sym, typ elf.SymType, curbind elf.SymBind) {
    80  	ldr := ctxt.loader
    81  	addr := ldr.SymValue(x)
    82  	size := ldr.SymSize(x)
    83  
    84  	xo := x
    85  	if ldr.OuterSym(x) != 0 {
    86  		xo = ldr.OuterSym(x)
    87  	}
    88  	xot := ldr.SymType(xo)
    89  	xosect := ldr.SymSect(xo)
    90  
    91  	var elfshnum elf.SectionIndex
    92  	if xot == sym.SDYNIMPORT || xot == sym.SHOSTOBJ || xot == sym.SUNDEFEXT {
    93  		elfshnum = elf.SHN_UNDEF
    94  		size = 0
    95  	} else {
    96  		if xosect == nil {
    97  			ldr.Errorf(x, "missing section in putelfsym")
    98  			return
    99  		}
   100  		if xosect.Elfsect == nil {
   101  			ldr.Errorf(x, "missing ELF section in putelfsym")
   102  			return
   103  		}
   104  		elfshnum = elfShdrShnum(xosect.Elfsect.(*ElfShdr))
   105  	}
   106  
   107  	sname := ldr.SymExtname(x)
   108  	sname = mangleABIName(ctxt, ldr, x, sname)
   109  
   110  	// One pass for each binding: elf.STB_LOCAL, elf.STB_GLOBAL,
   111  	// maybe one day elf.STB_WEAK.
   112  	bind := elf.STB_GLOBAL
   113  	if ldr.IsFileLocal(x) && !isStaticTmp(sname) || ldr.AttrVisibilityHidden(x) || ldr.AttrLocal(x) {
   114  		// Static tmp is package local, but a package can be shared among multiple DSOs.
   115  		// They need to have a single view of the static tmp that are writable.
   116  		bind = elf.STB_LOCAL
   117  	}
   118  
   119  	// In external linking mode, we have to invoke gcc with -rdynamic
   120  	// to get the exported symbols put into the dynamic symbol table.
   121  	// To avoid filling the dynamic table with lots of unnecessary symbols,
   122  	// mark all Go symbols local (not global) in the final executable.
   123  	// But when we're dynamically linking, we need all those global symbols.
   124  	if !ctxt.DynlinkingGo() && ctxt.IsExternal() && !ldr.AttrCgoExportStatic(x) && elfshnum != elf.SHN_UNDEF {
   125  		bind = elf.STB_LOCAL
   126  	}
   127  
   128  	if ctxt.LinkMode == LinkExternal && elfshnum != elf.SHN_UNDEF {
   129  		addr -= int64(xosect.Vaddr)
   130  	}
   131  	other := int(elf.STV_DEFAULT)
   132  	if ldr.AttrVisibilityHidden(x) {
   133  		// TODO(mwhudson): We only set AttrVisibilityHidden in ldelf, i.e. when
   134  		// internally linking. But STV_HIDDEN visibility only matters in object
   135  		// files and shared libraries, and as we are a long way from implementing
   136  		// internal linking for shared libraries and only create object files when
   137  		// externally linking, I don't think this makes a lot of sense.
   138  		other = int(elf.STV_HIDDEN)
   139  	}
   140  	if ctxt.IsPPC64() && typ == elf.STT_FUNC && ldr.AttrShared(x) {
   141  		// On ppc64 the top three bits of the st_other field indicate how many
   142  		// bytes separate the global and local entry points. For non-PCrel shared
   143  		// symbols this is always 8 bytes except for some special functions.
   144  		hasPCrel := buildcfg.GOPPC64 >= 10 && buildcfg.GOOS == "linux"
   145  
   146  		// This should match the preprocessing behavior in cmd/internal/obj/ppc64/obj9.go
   147  		// where the distinct global entry is inserted.
   148  		if !hasPCrel && ldr.SymName(x) != "runtime.duffzero" && ldr.SymName(x) != "runtime.duffcopy" {
   149  			other |= 3 << 5
   150  		}
   151  	}
   152  
   153  	// When dynamically linking, we create Symbols by reading the names from
   154  	// the symbol tables of the shared libraries and so the names need to
   155  	// match exactly. Tools like DTrace will have to wait for now.
   156  	if !ctxt.DynlinkingGo() {
   157  		// Rewrite · to . for ASCII-only tools like DTrace (sigh)
   158  		sname = strings.ReplaceAll(sname, "·", ".")
   159  	}
   160  
   161  	if ctxt.DynlinkingGo() && bind == elf.STB_GLOBAL && curbind == elf.STB_LOCAL && ldr.SymType(x).IsText() {
   162  		// When dynamically linking, we want references to functions defined
   163  		// in this module to always be to the function object, not to the
   164  		// PLT. We force this by writing an additional local symbol for every
   165  		// global function symbol and making all relocations against the
   166  		// global symbol refer to this local symbol instead (see
   167  		// (*sym.Symbol).ElfsymForReloc). This is approximately equivalent to the
   168  		// ELF linker -Bsymbolic-functions option, but that is buggy on
   169  		// several platforms.
   170  		putelfsyment(ctxt.Out, putelfstr("local."+sname), addr, size, elf.ST_INFO(elf.STB_LOCAL, typ), elfshnum, other)
   171  		ldr.SetSymLocalElfSym(x, int32(ctxt.numelfsym))
   172  		ctxt.numelfsym++
   173  		return
   174  	} else if bind != curbind {
   175  		return
   176  	}
   177  
   178  	putelfsyment(ctxt.Out, putelfstr(sname), addr, size, elf.ST_INFO(bind, typ), elfshnum, other)
   179  	ldr.SetSymElfSym(x, int32(ctxt.numelfsym))
   180  	ctxt.numelfsym++
   181  }
   182  
   183  func putelfsectionsym(ctxt *Link, out *OutBuf, s loader.Sym, shndx elf.SectionIndex) {
   184  	putelfsyment(out, 0, 0, 0, elf.ST_INFO(elf.STB_LOCAL, elf.STT_SECTION), shndx, 0)
   185  	ctxt.loader.SetSymElfSym(s, int32(ctxt.numelfsym))
   186  	ctxt.numelfsym++
   187  }
   188  
   189  func genelfsym(ctxt *Link, elfbind elf.SymBind) {
   190  	ldr := ctxt.loader
   191  
   192  	// runtime.text marker symbol(s).
   193  	s := ldr.Lookup("runtime.text", 0)
   194  	putelfsym(ctxt, s, elf.STT_FUNC, elfbind)
   195  	for k, sect := range Segtext.Sections[1:] {
   196  		n := k + 1
   197  		if sect.Name != ".text" || (ctxt.IsAIX() && ctxt.IsExternal()) {
   198  			// On AIX, runtime.text.X are symbols already in the symtab.
   199  			break
   200  		}
   201  		s = ldr.Lookup(fmt.Sprintf("runtime.text.%d", n), 0)
   202  		if s == 0 {
   203  			break
   204  		}
   205  		if !ldr.SymType(s).IsText() {
   206  			panic("unexpected type for runtime.text symbol")
   207  		}
   208  		putelfsym(ctxt, s, elf.STT_FUNC, elfbind)
   209  	}
   210  
   211  	// Text symbols.
   212  	for _, s := range ctxt.Textp {
   213  		putelfsym(ctxt, s, elf.STT_FUNC, elfbind)
   214  	}
   215  
   216  	// runtime.etext marker symbol.
   217  	s = ldr.Lookup("runtime.etext", 0)
   218  	if ldr.SymType(s).IsText() {
   219  		putelfsym(ctxt, s, elf.STT_FUNC, elfbind)
   220  	}
   221  
   222  	shouldBeInSymbolTable := func(s loader.Sym) bool {
   223  		if ldr.AttrNotInSymbolTable(s) {
   224  			return false
   225  		}
   226  		// FIXME: avoid having to do name inspections here.
   227  		// NB: the restrictions below on file local symbols are a bit
   228  		// arbitrary -- if it turns out we need nameless static
   229  		// symbols they could be relaxed/removed.
   230  		sn := ldr.SymName(s)
   231  		if (sn == "" || sn[0] == '.') && ldr.IsFileLocal(s) {
   232  			panic(fmt.Sprintf("unexpected file local symbol %d %s<%d>\n",
   233  				s, sn, ldr.SymVersion(s)))
   234  		}
   235  		if (sn == "" || sn[0] == '.') && !ldr.IsFileLocal(s) {
   236  			return false
   237  		}
   238  		return true
   239  	}
   240  
   241  	// Data symbols.
   242  	for s := loader.Sym(1); s < loader.Sym(ldr.NSym()); s++ {
   243  		if !ldr.AttrReachable(s) {
   244  			continue
   245  		}
   246  		st := ldr.SymType(s)
   247  		if st >= sym.SELFRXSECT && st < sym.SFirstUnallocated {
   248  			typ := elf.STT_OBJECT
   249  			if st == sym.STLSBSS {
   250  				if ctxt.IsInternal() {
   251  					continue
   252  				}
   253  				typ = elf.STT_TLS
   254  			}
   255  			if !shouldBeInSymbolTable(s) {
   256  				continue
   257  			}
   258  			putelfsym(ctxt, s, typ, elfbind)
   259  			continue
   260  		}
   261  		if st == sym.SHOSTOBJ || st == sym.SDYNIMPORT || st == sym.SUNDEFEXT {
   262  			putelfsym(ctxt, s, ldr.SymElfType(s), elfbind)
   263  		}
   264  	}
   265  }
   266  
   267  func asmElfSym(ctxt *Link) {
   268  
   269  	// the first symbol entry is reserved
   270  	putelfsyment(ctxt.Out, 0, 0, 0, elf.ST_INFO(elf.STB_LOCAL, elf.STT_NOTYPE), 0, 0)
   271  
   272  	dwarfaddelfsectionsyms(ctxt)
   273  
   274  	// Some linkers will add a FILE sym if one is not present.
   275  	// Avoid having the working directory inserted into the symbol table.
   276  	// It is added with a name to avoid problems with external linking
   277  	// encountered on some versions of Solaris. See issue #14957.
   278  	putelfsyment(ctxt.Out, putelfstr("go.go"), 0, 0, elf.ST_INFO(elf.STB_LOCAL, elf.STT_FILE), elf.SHN_ABS, 0)
   279  	ctxt.numelfsym++
   280  
   281  	bindings := []elf.SymBind{elf.STB_LOCAL, elf.STB_GLOBAL}
   282  	for _, elfbind := range bindings {
   283  		if elfbind == elf.STB_GLOBAL {
   284  			elfglobalsymndx = ctxt.numelfsym
   285  		}
   286  		genelfsym(ctxt, elfbind)
   287  	}
   288  }
   289  
   290  func putplan9sym(ctxt *Link, ldr *loader.Loader, s loader.Sym, char SymbolType) {
   291  	t := int(char)
   292  	if ldr.IsFileLocal(s) {
   293  		t += 'a' - 'A'
   294  	}
   295  	l := 4
   296  	addr := ldr.SymValue(s)
   297  	if ctxt.IsAMD64() && !flag8 {
   298  		ctxt.Out.Write32b(uint32(addr >> 32))
   299  		l = 8
   300  	}
   301  
   302  	ctxt.Out.Write32b(uint32(addr))
   303  	ctxt.Out.Write8(uint8(t + 0x80)) /* 0x80 is variable length */
   304  
   305  	name := ldr.SymName(s)
   306  	name = mangleABIName(ctxt, ldr, s, name)
   307  	ctxt.Out.WriteString(name)
   308  	ctxt.Out.Write8(0)
   309  
   310  	symSize += int32(l) + 1 + int32(len(name)) + 1
   311  }
   312  
   313  func asmbPlan9Sym(ctxt *Link) {
   314  	ldr := ctxt.loader
   315  
   316  	// Add special runtime.text and runtime.etext symbols.
   317  	s := ldr.Lookup("runtime.text", 0)
   318  	if ldr.SymType(s).IsText() {
   319  		putplan9sym(ctxt, ldr, s, TextSym)
   320  	}
   321  	s = ldr.Lookup("runtime.etext", 0)
   322  	if ldr.SymType(s).IsText() {
   323  		putplan9sym(ctxt, ldr, s, TextSym)
   324  	}
   325  
   326  	// Add text symbols.
   327  	for _, s := range ctxt.Textp {
   328  		putplan9sym(ctxt, ldr, s, TextSym)
   329  	}
   330  
   331  	shouldBeInSymbolTable := func(s loader.Sym) bool {
   332  		if ldr.AttrNotInSymbolTable(s) {
   333  			return false
   334  		}
   335  		name := ldr.SymName(s) // TODO: try not to read the name
   336  		if name == "" || name[0] == '.' {
   337  			return false
   338  		}
   339  		return true
   340  	}
   341  
   342  	// Add data symbols and external references.
   343  	for s := loader.Sym(1); s < loader.Sym(ldr.NSym()); s++ {
   344  		if !ldr.AttrReachable(s) {
   345  			continue
   346  		}
   347  		t := ldr.SymType(s)
   348  		if t >= sym.SELFRXSECT && t < sym.SFirstUnallocated { // data sections handled in dodata
   349  			if t == sym.STLSBSS {
   350  				continue
   351  			}
   352  			if !shouldBeInSymbolTable(s) {
   353  				continue
   354  			}
   355  			char := DataSym
   356  			if t == sym.SBSS || t == sym.SNOPTRBSS {
   357  				char = BSSSym
   358  			}
   359  			putplan9sym(ctxt, ldr, s, char)
   360  		}
   361  	}
   362  }
   363  
   364  // Create a table with information on the text sections.
   365  // Return the symbol of the table, and number of sections.
   366  func textsectionmap(ctxt *Link) (loader.Sym, uint32) {
   367  	ldr := ctxt.loader
   368  	t := ldr.CreateSymForUpdate("runtime.textsectionmap", 0)
   369  	t.SetType(sym.SRODATA)
   370  	nsections := int64(0)
   371  
   372  	for _, sect := range Segtext.Sections {
   373  		if sect.Name == ".text" {
   374  			nsections++
   375  		} else {
   376  			break
   377  		}
   378  	}
   379  	t.Grow(3 * nsections * int64(ctxt.Arch.PtrSize))
   380  
   381  	off := int64(0)
   382  	n := 0
   383  
   384  	// The vaddr for each text section is the difference between the section's
   385  	// Vaddr and the Vaddr for the first text section as determined at compile
   386  	// time.
   387  
   388  	// The symbol for the first text section is named runtime.text as before.
   389  	// Additional text sections are named runtime.text.n where n is the
   390  	// order of creation starting with 1. These symbols provide the section's
   391  	// address after relocation by the linker.
   392  
   393  	textbase := Segtext.Sections[0].Vaddr
   394  	for _, sect := range Segtext.Sections {
   395  		if sect.Name != ".text" {
   396  			break
   397  		}
   398  		// The fields written should match runtime/symtab.go:textsect.
   399  		// They are designed to minimize runtime calculations.
   400  		vaddr := sect.Vaddr - textbase
   401  		off = t.SetUint(ctxt.Arch, off, vaddr) // field vaddr
   402  		end := vaddr + sect.Length
   403  		off = t.SetUint(ctxt.Arch, off, end) // field end
   404  		name := "runtime.text"
   405  		if n != 0 {
   406  			name = fmt.Sprintf("runtime.text.%d", n)
   407  		}
   408  		s := ldr.Lookup(name, 0)
   409  		if s == 0 {
   410  			ctxt.Errorf(s, "Unable to find symbol %s\n", name)
   411  		}
   412  		off = t.SetAddr(ctxt.Arch, off, s) // field baseaddr
   413  		n++
   414  	}
   415  	return t.Sym(), uint32(n)
   416  }
   417  
   418  func (ctxt *Link) symtab(pcln *pclntab) []sym.SymKind {
   419  	ldr := ctxt.loader
   420  
   421  	if !ctxt.IsAIX() && !ctxt.IsWasm() {
   422  		switch ctxt.BuildMode {
   423  		case BuildModeCArchive, BuildModeCShared:
   424  			s := ldr.Lookup(*flagEntrySymbol, sym.SymVerABI0)
   425  			if s != 0 {
   426  				addinitarrdata(ctxt, ldr, s)
   427  			}
   428  		}
   429  	}
   430  
   431  	// Define these so that they'll get put into the symbol table.
   432  	// data.c:/^address will provide the actual values.
   433  	ctxt.xdefine("runtime.rodata", sym.SRODATA, 0)
   434  	ctxt.xdefine("runtime.erodata", sym.SRODATAEND, 0)
   435  	ctxt.xdefine("runtime.types", sym.SRODATA, 0)
   436  	ctxt.xdefine("runtime.etypes", sym.SRODATA, 0)
   437  	ctxt.xdefine("runtime.noptrdata", sym.SNOPTRDATA, 0)
   438  	ctxt.xdefine("runtime.enoptrdata", sym.SNOPTRDATAEND, 0)
   439  	ctxt.xdefine("runtime.data", sym.SDATA, 0)
   440  	ctxt.xdefine("runtime.edata", sym.SDATAEND, 0)
   441  	ctxt.xdefine("runtime.bss", sym.SBSS, 0)
   442  	ctxt.xdefine("runtime.ebss", sym.SBSS, 0)
   443  	ctxt.xdefine("runtime.noptrbss", sym.SNOPTRBSS, 0)
   444  	ctxt.xdefine("runtime.enoptrbss", sym.SNOPTRBSS, 0)
   445  	ctxt.xdefine("runtime.gcmask.*", sym.SNOPTRBSS, 0)
   446  	ctxt.xdefine("runtime.covctrs", sym.SNOPTRBSS, 0)
   447  	ctxt.xdefine("runtime.ecovctrs", sym.SNOPTRBSS, 0)
   448  	ctxt.xdefine("runtime.end", sym.SBSS, 0)
   449  	ctxt.xdefine("runtime.epclntab", sym.SRODATA, 0)
   450  
   451  	// garbage collection symbols
   452  	s := ldr.CreateSymForUpdate("runtime.gcdata", 0)
   453  	s.SetType(sym.SRODATA)
   454  	s.SetSize(0)
   455  	ctxt.xdefine("runtime.egcdata", sym.SRODATA, 0)
   456  
   457  	s = ldr.CreateSymForUpdate("runtime.gcbss", 0)
   458  	s.SetType(sym.SRODATA)
   459  	s.SetSize(0)
   460  	ctxt.xdefine("runtime.egcbss", sym.SRODATA, 0)
   461  
   462  	// pseudo-symbols to mark locations of type, string, and go string data.
   463  	s = ldr.CreateSymForUpdate("type:*", 0)
   464  	s.SetType(sym.STYPE)
   465  	s.SetSize(0)
   466  	s.SetAlign(int32(ctxt.Arch.PtrSize))
   467  	symtype := s.Sym()
   468  	setCarrierSym(sym.STYPE, symtype)
   469  
   470  	groupSym := func(name string, t sym.SymKind) loader.Sym {
   471  		s := ldr.CreateSymForUpdate(name, 0)
   472  		s.SetType(t)
   473  		s.SetSize(0)
   474  		s.SetAlign(int32(ctxt.Arch.PtrSize))
   475  		s.SetLocal(true)
   476  		setCarrierSym(t, s.Sym())
   477  		return s.Sym()
   478  	}
   479  	var (
   480  		symgostring = groupSym("go:string.*", sym.SGOSTRING)
   481  		symgofunc   = groupSym("go:funcdesc", sym.SGOFUNC)
   482  		symgcbits   = groupSym("runtime.gcbits.*", sym.SGCBITS)
   483  		symgcmask   = groupSym("runtime.gcmask.*", sym.SGCMASK)
   484  	)
   485  
   486  	// assign specific types so that they sort together.
   487  	// within a type they sort by size, so the .* symbols
   488  	// just defined above will be first.
   489  	// hide the specific symbols.
   490  	// Some of these symbol section conditions are duplicated
   491  	// in cmd/internal/obj.contentHashSection.
   492  	nsym := loader.Sym(ldr.NSym())
   493  	symGroupType := make([]sym.SymKind, nsym)
   494  	for s := loader.Sym(1); s < nsym; s++ {
   495  		if (!ctxt.IsExternal() && ldr.IsFileLocal(s) && !ldr.IsFromAssembly(s) && ldr.SymPkg(s) != "") || (ctxt.LinkMode == LinkInternal && ldr.SymType(s) == sym.SCOVERAGE_COUNTER) {
   496  			ldr.SetAttrNotInSymbolTable(s, true)
   497  		}
   498  
   499  		if !ldr.AttrReachable(s) || ldr.AttrSpecial(s) {
   500  			continue
   501  		}
   502  
   503  		if ldr.SymType(s) == sym.SNOPTRBSS && strings.HasPrefix(ldr.SymName(s), "type:.gcmask.") {
   504  			symGroupType[s] = sym.SGCMASK
   505  			ldr.SetAttrNotInSymbolTable(s, true)
   506  			ldr.SetCarrierSym(s, symgcmask)
   507  			continue
   508  		}
   509  
   510  		if ldr.SymType(s) != sym.SRODATA && ldr.SymType(s) != sym.SGOFUNC {
   511  			continue
   512  		}
   513  
   514  		name := ldr.SymName(s)
   515  		switch {
   516  		case strings.HasPrefix(name, "go:string."):
   517  			symGroupType[s] = sym.SGOSTRING
   518  			ldr.SetAttrNotInSymbolTable(s, true)
   519  			ldr.SetCarrierSym(s, symgostring)
   520  
   521  		case strings.HasPrefix(name, "runtime.gcbits."):
   522  			symGroupType[s] = sym.SGCBITS
   523  			ldr.SetAttrNotInSymbolTable(s, true)
   524  			ldr.SetCarrierSym(s, symgcbits)
   525  
   526  		case strings.HasSuffix(name, "·f"):
   527  			if !ctxt.DynlinkingGo() {
   528  				ldr.SetAttrNotInSymbolTable(s, true)
   529  				ldr.SetCarrierSym(s, symgofunc)
   530  			}
   531  			symGroupType[s] = sym.SGOFUNC
   532  
   533  		case strings.HasPrefix(name, "type:"):
   534  			if !ctxt.DynlinkingGo() {
   535  				ldr.SetAttrNotInSymbolTable(s, true)
   536  				ldr.SetCarrierSym(s, symtype)
   537  			}
   538  			symGroupType[s] = sym.STYPE
   539  
   540  		case ldr.IsItab(s):
   541  			if !ctxt.DynlinkingGo() {
   542  				ldr.SetAttrNotInSymbolTable(s, true)
   543  				ldr.SetCarrierSym(s, symtype)
   544  			}
   545  			symGroupType[s] = sym.STYPE
   546  		}
   547  	}
   548  
   549  	if ctxt.BuildMode == BuildModeShared {
   550  		abihashgostr := ldr.CreateSymForUpdate("go:link.abihash."+filepath.Base(*flagOutfile), 0)
   551  		abihashgostr.SetType(sym.SRODATA)
   552  		hashsym := ldr.LookupOrCreateSym("go:link.abihashbytes", 0)
   553  		abihashgostr.AddAddr(ctxt.Arch, hashsym)
   554  		abihashgostr.AddUint(ctxt.Arch, uint64(ldr.SymSize(hashsym)))
   555  	}
   556  	if ctxt.BuildMode == BuildModePlugin || ctxt.CanUsePlugins() {
   557  		for _, l := range ctxt.Library {
   558  			s := ldr.CreateSymForUpdate("go:link.pkghashbytes."+l.Pkg, 0)
   559  			s.SetType(sym.SRODATA)
   560  			s.SetSize(int64(len(l.Fingerprint)))
   561  			s.SetData(l.Fingerprint[:])
   562  			str := ldr.CreateSymForUpdate("go:link.pkghash."+l.Pkg, 0)
   563  			str.SetType(sym.SRODATA)
   564  			str.AddAddr(ctxt.Arch, s.Sym())
   565  			str.AddUint(ctxt.Arch, uint64(len(l.Fingerprint)))
   566  		}
   567  	}
   568  
   569  	textsectionmapSym, nsections := textsectionmap(ctxt)
   570  
   571  	// Information about the layout of the executable image for the
   572  	// runtime to use. Any changes here must be matched by changes to
   573  	// the definition of moduledata in runtime/symtab.go.
   574  	// This code uses several global variables that are set by pcln.go:pclntab.
   575  	moduledata := ldr.MakeSymbolUpdater(ctxt.Moduledata)
   576  
   577  	slice := func(sym loader.Sym, len uint64) {
   578  		moduledata.AddAddr(ctxt.Arch, sym)
   579  		moduledata.AddUint(ctxt.Arch, len)
   580  		moduledata.AddUint(ctxt.Arch, len)
   581  	}
   582  
   583  	sliceSym := func(sym loader.Sym) {
   584  		slice(sym, uint64(ldr.SymSize(sym)))
   585  	}
   586  
   587  	nilSlice := func() {
   588  		moduledata.AddUint(ctxt.Arch, 0)
   589  		moduledata.AddUint(ctxt.Arch, 0)
   590  		moduledata.AddUint(ctxt.Arch, 0)
   591  	}
   592  
   593  	// The pcHeader
   594  	moduledata.AddAddr(ctxt.Arch, pcln.pcheader)
   595  
   596  	// The function name slice
   597  	sliceSym(pcln.funcnametab)
   598  
   599  	// The cutab slice
   600  	slice(pcln.cutab, uint64(ldr.SymSize(pcln.cutab))/4)
   601  
   602  	// The filetab slice
   603  	sliceSym(pcln.filetab)
   604  
   605  	// The pctab slice
   606  	sliceSym(pcln.pctab)
   607  
   608  	// The pclntab slice
   609  	sliceSym(pcln.pclntab)
   610  
   611  	// The ftab slice
   612  	slice(pcln.pclntab, uint64(pcln.nfunc+1))
   613  
   614  	// findfunctab
   615  	moduledata.AddAddr(ctxt.Arch, pcln.findfunctab)
   616  	// minpc, maxpc
   617  	moduledata.AddAddr(ctxt.Arch, pcln.firstFunc)
   618  	moduledata.AddAddrPlus(ctxt.Arch, pcln.lastFunc, ldr.SymSize(pcln.lastFunc))
   619  	// pointers to specific parts of the module
   620  	moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.text", 0))
   621  	moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.etext", 0))
   622  	moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.noptrdata", 0))
   623  	moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.enoptrdata", 0))
   624  	moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.data", 0))
   625  	moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.edata", 0))
   626  	moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.bss", 0))
   627  	moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.ebss", 0))
   628  	moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.noptrbss", 0))
   629  	moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.enoptrbss", 0))
   630  	moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.covctrs", 0))
   631  	moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.ecovctrs", 0))
   632  	moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.end", 0))
   633  	moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.gcdata", 0))
   634  	moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.gcbss", 0))
   635  	moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.types", 0))
   636  	ctxt.moduledataTypeDescOffset = moduledata.Size()
   637  	moduledata.AddUint(ctxt.Arch, 0) // filled in by dodataSect
   638  	moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.etypes", 0))
   639  	ctxt.moduledataItabOffset = moduledata.Size()
   640  	moduledata.AddUint(ctxt.Arch, 0) // filled in by dodataSect
   641  	ctxt.moduledataItabSizeOffset = moduledata.Size()
   642  	moduledata.AddUint(ctxt.Arch, 0) // filled in by dodataSect
   643  	moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.rodata", 0))
   644  	moduledata.AddAddr(ctxt.Arch, ldr.Lookup("go:func.*", 0))
   645  	moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.epclntab", 0))
   646  
   647  	if ctxt.IsAIX() && ctxt.IsExternal() {
   648  		// Add R_XCOFFREF relocation to prevent ld's garbage collection of
   649  		// the following symbols. They might not be referenced in the program.
   650  		addRef := func(name string) {
   651  			s := ldr.Lookup(name, 0)
   652  			if s == 0 {
   653  				return
   654  			}
   655  			r, _ := moduledata.AddRel(objabi.R_XCOFFREF)
   656  			r.SetSym(s)
   657  			r.SetSiz(uint8(ctxt.Arch.PtrSize))
   658  		}
   659  		addRef("runtime.rodata")
   660  		addRef("runtime.erodata")
   661  		addRef("runtime.epclntab")
   662  		addRef("go:func.*")
   663  		// As we use relative addressing for text symbols in functab, it is
   664  		// important that the offsets we computed stay unchanged by the external
   665  		// linker, i.e. all symbols in Textp should not be removed.
   666  		// Most of them are actually referenced (our deadcode pass ensures that),
   667  		// except go:buildid which is generated late and not used by the program.
   668  		addRef("go:buildid")
   669  	}
   670  	if ctxt.IsAIX() {
   671  		// On AIX, an R_ADDR relocation from an RODATA symbol to a DATA symbol
   672  		// does not work. See data.go:relocsym, case R_ADDR.
   673  		// Here we record the unrelocated address in aixStaticDataBase (it is
   674  		// unrelocated as it is in RODATA) so we can compute the delta at
   675  		// run time.
   676  		sb := ldr.CreateSymForUpdate("runtime.aixStaticDataBase", 0)
   677  		sb.SetSize(0)
   678  		sb.AddAddr(ctxt.Arch, ldr.Lookup("runtime.data", 0))
   679  		sb.SetType(sym.SRODATA)
   680  	}
   681  
   682  	// text section information
   683  	slice(textsectionmapSym, uint64(nsections))
   684  
   685  	// The ptab slice
   686  	if ptab := ldr.Lookup("go:plugin.tabs", 0); ptab != 0 && ldr.AttrReachable(ptab) {
   687  		ldr.SetAttrLocal(ptab, true)
   688  		if ldr.SymType(ptab) != sym.SRODATA {
   689  			panic(fmt.Sprintf("go:plugin.tabs is %v, not SRODATA", ldr.SymType(ptab)))
   690  		}
   691  		nentries := uint64(len(ldr.Data(ptab)) / 8) // sizeof(nameOff) + sizeof(typeOff)
   692  		slice(ptab, nentries)
   693  	} else {
   694  		nilSlice()
   695  	}
   696  
   697  	if ctxt.BuildMode == BuildModePlugin {
   698  		addgostring(ctxt, ldr, moduledata, "go:link.thispluginpath", objabi.PathToPrefix(*flagPluginPath))
   699  
   700  		pkghashes := ldr.CreateSymForUpdate("go:link.pkghashes", 0)
   701  		pkghashes.SetLocal(true)
   702  		pkghashes.SetType(sym.SRODATA)
   703  
   704  		for i, l := range ctxt.Library {
   705  			// pkghashes[i].name
   706  			addgostring(ctxt, ldr, pkghashes, fmt.Sprintf("go:link.pkgname.%d", i), l.Pkg)
   707  			// pkghashes[i].linktimehash
   708  			addgostring(ctxt, ldr, pkghashes, fmt.Sprintf("go:link.pkglinkhash.%d", i), string(l.Fingerprint[:]))
   709  			// pkghashes[i].runtimehash
   710  			hash := ldr.Lookup("go:link.pkghash."+l.Pkg, 0)
   711  			pkghashes.AddAddr(ctxt.Arch, hash)
   712  		}
   713  		slice(pkghashes.Sym(), uint64(len(ctxt.Library)))
   714  	} else {
   715  		moduledata.AddUint(ctxt.Arch, 0) // pluginpath
   716  		moduledata.AddUint(ctxt.Arch, 0)
   717  		nilSlice() // pkghashes slice
   718  	}
   719  	// Add inittasks slice
   720  	t := ctxt.mainInittasks
   721  	if t != 0 {
   722  		moduledata.AddAddr(ctxt.Arch, t)
   723  		moduledata.AddUint(ctxt.Arch, uint64(ldr.SymSize(t)/int64(ctxt.Arch.PtrSize)))
   724  		moduledata.AddUint(ctxt.Arch, uint64(ldr.SymSize(t)/int64(ctxt.Arch.PtrSize)))
   725  	} else {
   726  		// Some build modes have no inittasks, like a shared library.
   727  		// Its inittask list will be constructed by a higher-level
   728  		// linking step.
   729  		// This branch can also happen if there are no init tasks at all.
   730  		moduledata.AddUint(ctxt.Arch, 0)
   731  		moduledata.AddUint(ctxt.Arch, 0)
   732  		moduledata.AddUint(ctxt.Arch, 0)
   733  	}
   734  
   735  	if len(ctxt.Shlibs) > 0 {
   736  		thismodulename := filepath.Base(*flagOutfile)
   737  		switch ctxt.BuildMode {
   738  		case BuildModeExe, BuildModePIE:
   739  			// When linking an executable, outfile is just "a.out". Make
   740  			// it something slightly more comprehensible.
   741  			thismodulename = "the executable"
   742  		}
   743  		addgostring(ctxt, ldr, moduledata, "go:link.thismodulename", thismodulename)
   744  
   745  		modulehashes := ldr.CreateSymForUpdate("go:link.abihashes", 0)
   746  		modulehashes.SetLocal(true)
   747  		modulehashes.SetType(sym.SRODATA)
   748  
   749  		for i, shlib := range ctxt.Shlibs {
   750  			// modulehashes[i].modulename
   751  			modulename := filepath.Base(shlib.Path)
   752  			addgostring(ctxt, ldr, modulehashes, fmt.Sprintf("go:link.libname.%d", i), modulename)
   753  
   754  			// modulehashes[i].linktimehash
   755  			addgostring(ctxt, ldr, modulehashes, fmt.Sprintf("go:link.linkhash.%d", i), string(shlib.Hash))
   756  
   757  			// modulehashes[i].runtimehash
   758  			abihash := ldr.LookupOrCreateSym("go:link.abihash."+modulename, 0)
   759  			ldr.SetAttrReachable(abihash, true)
   760  			modulehashes.AddAddr(ctxt.Arch, abihash)
   761  		}
   762  
   763  		slice(modulehashes.Sym(), uint64(len(ctxt.Shlibs)))
   764  	} else {
   765  		moduledata.AddUint(ctxt.Arch, 0) // modulename
   766  		moduledata.AddUint(ctxt.Arch, 0)
   767  		nilSlice() // moduleshashes slice
   768  	}
   769  
   770  	hasmain := ctxt.BuildMode == BuildModeExe || ctxt.BuildMode == BuildModePIE
   771  	if hasmain {
   772  		moduledata.AddUint8(1)
   773  	} else {
   774  		moduledata.AddUint8(0)
   775  	}
   776  
   777  	// The rest of moduledata is zero initialized.
   778  	// When linking an object that does not contain the runtime we are
   779  	// creating the moduledata from scratch and it does not have a
   780  	// compiler-provided size, so read it from the type data.
   781  	moduledatatype := ldr.Lookup("type:runtime.moduledata", 0)
   782  	moduledata.SetSize(decodetypeSize(ctxt.Arch, ldr.Data(moduledatatype)))
   783  	moduledata.Grow(moduledata.Size())
   784  
   785  	lastmoduledatap := ldr.CreateSymForUpdate("runtime.lastmoduledatap", 0)
   786  	if lastmoduledatap.Type() != sym.SDYNIMPORT {
   787  		lastmoduledatap.SetType(sym.SNOPTRDATA)
   788  		lastmoduledatap.SetSize(0) // overwrite existing value
   789  		lastmoduledatap.SetData(nil)
   790  		lastmoduledatap.AddAddr(ctxt.Arch, moduledata.Sym())
   791  	}
   792  	return symGroupType
   793  }
   794  
   795  // CarrierSymByType tracks carrier symbols and their sizes.
   796  var CarrierSymByType [sym.SFirstUnallocated]struct {
   797  	Sym  loader.Sym
   798  	Size int64
   799  }
   800  
   801  func setCarrierSym(typ sym.SymKind, s loader.Sym) {
   802  	if CarrierSymByType[typ].Sym != 0 {
   803  		panic(fmt.Sprintf("carrier symbol for type %v already set", typ))
   804  	}
   805  	CarrierSymByType[typ].Sym = s
   806  }
   807  
   808  func setCarrierSize(typ sym.SymKind, sz int64) {
   809  	if typ == sym.Sxxx {
   810  		panic("setCarrierSize(Sxxx)")
   811  	}
   812  	if CarrierSymByType[typ].Size != 0 {
   813  		panic(fmt.Sprintf("carrier symbol size for type %v already set", typ))
   814  	}
   815  	CarrierSymByType[typ].Size = sz
   816  }
   817  
   818  func isStaticTmp(name string) bool {
   819  	return strings.Contains(name, "."+obj.StaticNamePrefix)
   820  }
   821  
   822  // Mangle function name with ABI information.
   823  func mangleABIName(ctxt *Link, ldr *loader.Loader, x loader.Sym, name string) string {
   824  	// For functions with ABI wrappers, we have to make sure that we
   825  	// don't wind up with two symbol table entries with the same
   826  	// name (since this will generated an error from the external
   827  	// linker). If we have wrappers, keep the ABIInternal name
   828  	// unmangled since we want cross-load-module calls to target
   829  	// ABIInternal, and rename other symbols.
   830  	//
   831  	// TODO: avoid the ldr.Lookup calls below by instead using an aux
   832  	// sym or marker relocation to associate the wrapper with the
   833  	// wrapped function.
   834  	if !buildcfg.Experiment.RegabiWrappers {
   835  		return name
   836  	}
   837  
   838  	if ldr.SymType(x).IsText() && ldr.SymVersion(x) != sym.SymVerABIInternal && ldr.SymVersion(x) < sym.SymVerStatic {
   839  		if s2 := ldr.Lookup(name, sym.SymVerABIInternal); s2 != 0 && ldr.SymType(s2).IsText() {
   840  			name = fmt.Sprintf("%s.abi%d", name, ldr.SymVersion(x))
   841  		}
   842  	}
   843  
   844  	// When loading a shared library, if a symbol has only one ABI,
   845  	// and the name is not mangled, we don't know what ABI it is.
   846  	// So we always mangle ABIInternal function name in shared linkage,
   847  	// except symbols that are exported to C. Type symbols are always
   848  	// ABIInternal so they are not mangled.
   849  	if ctxt.IsShared() {
   850  		if ldr.SymType(x).IsText() && ldr.SymVersion(x) == sym.SymVerABIInternal && !ldr.AttrCgoExport(x) && !strings.HasPrefix(name, "type:") {
   851  			name = fmt.Sprintf("%s.abiinternal", name)
   852  		}
   853  	}
   854  
   855  	return name
   856  }
   857
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