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.covctrs", sym.SNOPTRBSS, 0)
   446  	ctxt.xdefine("runtime.ecovctrs", sym.SNOPTRBSS, 0)
   447  	ctxt.xdefine("runtime.end", sym.SBSS, 0)
   448  	ctxt.xdefine("runtime.epclntab", sym.SRODATA, 0)
   449  
   450  	// garbage collection symbols
   451  	s := ldr.CreateSymForUpdate("runtime.gcdata", 0)
   452  	s.SetType(sym.SRODATA)
   453  	s.SetSize(0)
   454  	ctxt.xdefine("runtime.egcdata", sym.SRODATA, 0)
   455  
   456  	s = ldr.CreateSymForUpdate("runtime.gcbss", 0)
   457  	s.SetType(sym.SRODATA)
   458  	s.SetSize(0)
   459  	ctxt.xdefine("runtime.egcbss", sym.SRODATA, 0)
   460  
   461  	// pseudo-symbols to mark locations of type, string, and go string data.
   462  	s = ldr.CreateSymForUpdate("type:*", 0)
   463  	s.SetType(sym.STYPE)
   464  	s.SetSize(0)
   465  	s.SetAlign(int32(ctxt.Arch.PtrSize))
   466  	symtype := s.Sym()
   467  	setCarrierSym(sym.STYPE, symtype)
   468  
   469  	groupSym := func(name string, t sym.SymKind) loader.Sym {
   470  		s := ldr.CreateSymForUpdate(name, 0)
   471  		s.SetType(t)
   472  		s.SetSize(0)
   473  		s.SetAlign(int32(ctxt.Arch.PtrSize))
   474  		s.SetLocal(true)
   475  		setCarrierSym(t, s.Sym())
   476  		return s.Sym()
   477  	}
   478  	var (
   479  		symgostring = groupSym("go:string.*", sym.SGOSTRING)
   480  		symgofunc   = groupSym("go:funcdesc", sym.SGOFUNC)
   481  		symgcbits   = groupSym("runtime.gcbits.*", sym.SGCBITS)
   482  	)
   483  
   484  	// assign specific types so that they sort together.
   485  	// within a type they sort by size, so the .* symbols
   486  	// just defined above will be first.
   487  	// hide the specific symbols.
   488  	// Some of these symbol section conditions are duplicated
   489  	// in cmd/internal/obj.contentHashSection.
   490  	nsym := loader.Sym(ldr.NSym())
   491  	symGroupType := make([]sym.SymKind, nsym)
   492  	for s := loader.Sym(1); s < nsym; s++ {
   493  		if (!ctxt.IsExternal() && ldr.IsFileLocal(s) && !ldr.IsFromAssembly(s) && ldr.SymPkg(s) != "") || (ctxt.LinkMode == LinkInternal && ldr.SymType(s) == sym.SCOVERAGE_COUNTER) {
   494  			ldr.SetAttrNotInSymbolTable(s, true)
   495  		}
   496  		if !ldr.AttrReachable(s) || ldr.AttrSpecial(s) || (ldr.SymType(s) != sym.SRODATA && ldr.SymType(s) != sym.SGOFUNC) {
   497  			continue
   498  		}
   499  
   500  		name := ldr.SymName(s)
   501  		switch {
   502  		case strings.HasPrefix(name, "go:string."):
   503  			symGroupType[s] = sym.SGOSTRING
   504  			ldr.SetAttrNotInSymbolTable(s, true)
   505  			ldr.SetCarrierSym(s, symgostring)
   506  
   507  		case strings.HasPrefix(name, "runtime.gcbits."),
   508  			strings.HasPrefix(name, "type:.gcprog."):
   509  			symGroupType[s] = sym.SGCBITS
   510  			ldr.SetAttrNotInSymbolTable(s, true)
   511  			ldr.SetCarrierSym(s, symgcbits)
   512  
   513  		case strings.HasSuffix(name, "·f"):
   514  			if !ctxt.DynlinkingGo() {
   515  				ldr.SetAttrNotInSymbolTable(s, true)
   516  				ldr.SetCarrierSym(s, symgofunc)
   517  			}
   518  			symGroupType[s] = sym.SGOFUNC
   519  
   520  		case strings.HasPrefix(name, "type:"):
   521  			if !ctxt.DynlinkingGo() {
   522  				ldr.SetAttrNotInSymbolTable(s, true)
   523  				ldr.SetCarrierSym(s, symtype)
   524  			}
   525  			symGroupType[s] = sym.STYPE
   526  
   527  		case ldr.IsItab(s):
   528  			if !ctxt.DynlinkingGo() {
   529  				ldr.SetAttrNotInSymbolTable(s, true)
   530  				ldr.SetCarrierSym(s, symtype)
   531  			}
   532  			symGroupType[s] = sym.STYPE
   533  		}
   534  	}
   535  
   536  	if ctxt.BuildMode == BuildModeShared {
   537  		abihashgostr := ldr.CreateSymForUpdate("go:link.abihash."+filepath.Base(*flagOutfile), 0)
   538  		abihashgostr.SetType(sym.SRODATA)
   539  		hashsym := ldr.LookupOrCreateSym("go:link.abihashbytes", 0)
   540  		abihashgostr.AddAddr(ctxt.Arch, hashsym)
   541  		abihashgostr.AddUint(ctxt.Arch, uint64(ldr.SymSize(hashsym)))
   542  	}
   543  	if ctxt.BuildMode == BuildModePlugin || ctxt.CanUsePlugins() {
   544  		for _, l := range ctxt.Library {
   545  			s := ldr.CreateSymForUpdate("go:link.pkghashbytes."+l.Pkg, 0)
   546  			s.SetType(sym.SRODATA)
   547  			s.SetSize(int64(len(l.Fingerprint)))
   548  			s.SetData(l.Fingerprint[:])
   549  			str := ldr.CreateSymForUpdate("go:link.pkghash."+l.Pkg, 0)
   550  			str.SetType(sym.SRODATA)
   551  			str.AddAddr(ctxt.Arch, s.Sym())
   552  			str.AddUint(ctxt.Arch, uint64(len(l.Fingerprint)))
   553  		}
   554  	}
   555  
   556  	textsectionmapSym, nsections := textsectionmap(ctxt)
   557  
   558  	// Information about the layout of the executable image for the
   559  	// runtime to use. Any changes here must be matched by changes to
   560  	// the definition of moduledata in runtime/symtab.go.
   561  	// This code uses several global variables that are set by pcln.go:pclntab.
   562  	moduledata := ldr.MakeSymbolUpdater(ctxt.Moduledata)
   563  
   564  	slice := func(sym loader.Sym, len uint64) {
   565  		moduledata.AddAddr(ctxt.Arch, sym)
   566  		moduledata.AddUint(ctxt.Arch, len)
   567  		moduledata.AddUint(ctxt.Arch, len)
   568  	}
   569  
   570  	sliceSym := func(sym loader.Sym) {
   571  		slice(sym, uint64(ldr.SymSize(sym)))
   572  	}
   573  
   574  	nilSlice := func() {
   575  		moduledata.AddUint(ctxt.Arch, 0)
   576  		moduledata.AddUint(ctxt.Arch, 0)
   577  		moduledata.AddUint(ctxt.Arch, 0)
   578  	}
   579  
   580  	// The pcHeader
   581  	moduledata.AddAddr(ctxt.Arch, pcln.pcheader)
   582  
   583  	// The function name slice
   584  	sliceSym(pcln.funcnametab)
   585  
   586  	// The cutab slice
   587  	slice(pcln.cutab, uint64(ldr.SymSize(pcln.cutab))/4)
   588  
   589  	// The filetab slice
   590  	sliceSym(pcln.filetab)
   591  
   592  	// The pctab slice
   593  	sliceSym(pcln.pctab)
   594  
   595  	// The pclntab slice
   596  	sliceSym(pcln.pclntab)
   597  
   598  	// The ftab slice
   599  	slice(pcln.pclntab, uint64(pcln.nfunc+1))
   600  
   601  	// findfunctab
   602  	moduledata.AddAddr(ctxt.Arch, pcln.findfunctab)
   603  	// minpc, maxpc
   604  	moduledata.AddAddr(ctxt.Arch, pcln.firstFunc)
   605  	moduledata.AddAddrPlus(ctxt.Arch, pcln.lastFunc, ldr.SymSize(pcln.lastFunc))
   606  	// pointers to specific parts of the module
   607  	moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.text", 0))
   608  	moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.etext", 0))
   609  	moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.noptrdata", 0))
   610  	moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.enoptrdata", 0))
   611  	moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.data", 0))
   612  	moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.edata", 0))
   613  	moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.bss", 0))
   614  	moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.ebss", 0))
   615  	moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.noptrbss", 0))
   616  	moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.enoptrbss", 0))
   617  	moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.covctrs", 0))
   618  	moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.ecovctrs", 0))
   619  	moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.end", 0))
   620  	moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.gcdata", 0))
   621  	moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.gcbss", 0))
   622  	moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.types", 0))
   623  	ctxt.moduledataTypeDescOffset = moduledata.Size()
   624  	moduledata.AddUint(ctxt.Arch, 0) // filled in by dodataSect
   625  	moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.etypes", 0))
   626  	moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.rodata", 0))
   627  	moduledata.AddAddr(ctxt.Arch, ldr.Lookup("go:func.*", 0))
   628  	moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.epclntab", 0))
   629  
   630  	if ctxt.IsAIX() && ctxt.IsExternal() {
   631  		// Add R_XCOFFREF relocation to prevent ld's garbage collection of
   632  		// the following symbols. They might not be referenced in the program.
   633  		addRef := func(name string) {
   634  			s := ldr.Lookup(name, 0)
   635  			if s == 0 {
   636  				return
   637  			}
   638  			r, _ := moduledata.AddRel(objabi.R_XCOFFREF)
   639  			r.SetSym(s)
   640  			r.SetSiz(uint8(ctxt.Arch.PtrSize))
   641  		}
   642  		addRef("runtime.rodata")
   643  		addRef("runtime.erodata")
   644  		addRef("runtime.epclntab")
   645  		addRef("go:func.*")
   646  		// As we use relative addressing for text symbols in functab, it is
   647  		// important that the offsets we computed stay unchanged by the external
   648  		// linker, i.e. all symbols in Textp should not be removed.
   649  		// Most of them are actually referenced (our deadcode pass ensures that),
   650  		// except go:buildid which is generated late and not used by the program.
   651  		addRef("go:buildid")
   652  	}
   653  	if ctxt.IsAIX() {
   654  		// On AIX, an R_ADDR relocation from an RODATA symbol to a DATA symbol
   655  		// does not work. See data.go:relocsym, case R_ADDR.
   656  		// Here we record the unrelocated address in aixStaticDataBase (it is
   657  		// unrelocated as it is in RODATA) so we can compute the delta at
   658  		// run time.
   659  		sb := ldr.CreateSymForUpdate("runtime.aixStaticDataBase", 0)
   660  		sb.SetSize(0)
   661  		sb.AddAddr(ctxt.Arch, ldr.Lookup("runtime.data", 0))
   662  		sb.SetType(sym.SRODATA)
   663  	}
   664  
   665  	// text section information
   666  	slice(textsectionmapSym, uint64(nsections))
   667  
   668  	// The itablinks slice
   669  	itablinkSym := ldr.Lookup("runtime.itablink", 0)
   670  	nitablinks := uint64(ldr.SymSize(itablinkSym)) / uint64(ctxt.Arch.PtrSize)
   671  	slice(itablinkSym, nitablinks)
   672  
   673  	// The ptab slice
   674  	if ptab := ldr.Lookup("go:plugin.tabs", 0); ptab != 0 && ldr.AttrReachable(ptab) {
   675  		ldr.SetAttrLocal(ptab, true)
   676  		if ldr.SymType(ptab) != sym.SRODATA {
   677  			panic(fmt.Sprintf("go:plugin.tabs is %v, not SRODATA", ldr.SymType(ptab)))
   678  		}
   679  		nentries := uint64(len(ldr.Data(ptab)) / 8) // sizeof(nameOff) + sizeof(typeOff)
   680  		slice(ptab, nentries)
   681  	} else {
   682  		nilSlice()
   683  	}
   684  
   685  	if ctxt.BuildMode == BuildModePlugin {
   686  		addgostring(ctxt, ldr, moduledata, "go:link.thispluginpath", objabi.PathToPrefix(*flagPluginPath))
   687  
   688  		pkghashes := ldr.CreateSymForUpdate("go:link.pkghashes", 0)
   689  		pkghashes.SetLocal(true)
   690  		pkghashes.SetType(sym.SRODATA)
   691  
   692  		for i, l := range ctxt.Library {
   693  			// pkghashes[i].name
   694  			addgostring(ctxt, ldr, pkghashes, fmt.Sprintf("go:link.pkgname.%d", i), l.Pkg)
   695  			// pkghashes[i].linktimehash
   696  			addgostring(ctxt, ldr, pkghashes, fmt.Sprintf("go:link.pkglinkhash.%d", i), string(l.Fingerprint[:]))
   697  			// pkghashes[i].runtimehash
   698  			hash := ldr.Lookup("go:link.pkghash."+l.Pkg, 0)
   699  			pkghashes.AddAddr(ctxt.Arch, hash)
   700  		}
   701  		slice(pkghashes.Sym(), uint64(len(ctxt.Library)))
   702  	} else {
   703  		moduledata.AddUint(ctxt.Arch, 0) // pluginpath
   704  		moduledata.AddUint(ctxt.Arch, 0)
   705  		nilSlice() // pkghashes slice
   706  	}
   707  	// Add inittasks slice
   708  	t := ctxt.mainInittasks
   709  	if t != 0 {
   710  		moduledata.AddAddr(ctxt.Arch, t)
   711  		moduledata.AddUint(ctxt.Arch, uint64(ldr.SymSize(t)/int64(ctxt.Arch.PtrSize)))
   712  		moduledata.AddUint(ctxt.Arch, uint64(ldr.SymSize(t)/int64(ctxt.Arch.PtrSize)))
   713  	} else {
   714  		// Some build modes have no inittasks, like a shared library.
   715  		// Its inittask list will be constructed by a higher-level
   716  		// linking step.
   717  		// This branch can also happen if there are no init tasks at all.
   718  		moduledata.AddUint(ctxt.Arch, 0)
   719  		moduledata.AddUint(ctxt.Arch, 0)
   720  		moduledata.AddUint(ctxt.Arch, 0)
   721  	}
   722  
   723  	if len(ctxt.Shlibs) > 0 {
   724  		thismodulename := filepath.Base(*flagOutfile)
   725  		switch ctxt.BuildMode {
   726  		case BuildModeExe, BuildModePIE:
   727  			// When linking an executable, outfile is just "a.out". Make
   728  			// it something slightly more comprehensible.
   729  			thismodulename = "the executable"
   730  		}
   731  		addgostring(ctxt, ldr, moduledata, "go:link.thismodulename", thismodulename)
   732  
   733  		modulehashes := ldr.CreateSymForUpdate("go:link.abihashes", 0)
   734  		modulehashes.SetLocal(true)
   735  		modulehashes.SetType(sym.SRODATA)
   736  
   737  		for i, shlib := range ctxt.Shlibs {
   738  			// modulehashes[i].modulename
   739  			modulename := filepath.Base(shlib.Path)
   740  			addgostring(ctxt, ldr, modulehashes, fmt.Sprintf("go:link.libname.%d", i), modulename)
   741  
   742  			// modulehashes[i].linktimehash
   743  			addgostring(ctxt, ldr, modulehashes, fmt.Sprintf("go:link.linkhash.%d", i), string(shlib.Hash))
   744  
   745  			// modulehashes[i].runtimehash
   746  			abihash := ldr.LookupOrCreateSym("go:link.abihash."+modulename, 0)
   747  			ldr.SetAttrReachable(abihash, true)
   748  			modulehashes.AddAddr(ctxt.Arch, abihash)
   749  		}
   750  
   751  		slice(modulehashes.Sym(), uint64(len(ctxt.Shlibs)))
   752  	} else {
   753  		moduledata.AddUint(ctxt.Arch, 0) // modulename
   754  		moduledata.AddUint(ctxt.Arch, 0)
   755  		nilSlice() // moduleshashes slice
   756  	}
   757  
   758  	hasmain := ctxt.BuildMode == BuildModeExe || ctxt.BuildMode == BuildModePIE
   759  	if hasmain {
   760  		moduledata.AddUint8(1)
   761  	} else {
   762  		moduledata.AddUint8(0)
   763  	}
   764  
   765  	// The rest of moduledata is zero initialized.
   766  	// When linking an object that does not contain the runtime we are
   767  	// creating the moduledata from scratch and it does not have a
   768  	// compiler-provided size, so read it from the type data.
   769  	moduledatatype := ldr.Lookup("type:runtime.moduledata", 0)
   770  	moduledata.SetSize(decodetypeSize(ctxt.Arch, ldr.Data(moduledatatype)))
   771  	moduledata.Grow(moduledata.Size())
   772  
   773  	lastmoduledatap := ldr.CreateSymForUpdate("runtime.lastmoduledatap", 0)
   774  	if lastmoduledatap.Type() != sym.SDYNIMPORT {
   775  		lastmoduledatap.SetType(sym.SNOPTRDATA)
   776  		lastmoduledatap.SetSize(0) // overwrite existing value
   777  		lastmoduledatap.SetData(nil)
   778  		lastmoduledatap.AddAddr(ctxt.Arch, moduledata.Sym())
   779  	}
   780  	return symGroupType
   781  }
   782  
   783  // CarrierSymByType tracks carrier symbols and their sizes.
   784  var CarrierSymByType [sym.SFirstUnallocated]struct {
   785  	Sym  loader.Sym
   786  	Size int64
   787  }
   788  
   789  func setCarrierSym(typ sym.SymKind, s loader.Sym) {
   790  	if CarrierSymByType[typ].Sym != 0 {
   791  		panic(fmt.Sprintf("carrier symbol for type %v already set", typ))
   792  	}
   793  	CarrierSymByType[typ].Sym = s
   794  }
   795  
   796  func setCarrierSize(typ sym.SymKind, sz int64) {
   797  	if typ == sym.Sxxx {
   798  		panic("setCarrierSize(Sxxx)")
   799  	}
   800  	if CarrierSymByType[typ].Size != 0 {
   801  		panic(fmt.Sprintf("carrier symbol size for type %v already set", typ))
   802  	}
   803  	CarrierSymByType[typ].Size = sz
   804  }
   805  
   806  func isStaticTmp(name string) bool {
   807  	return strings.Contains(name, "."+obj.StaticNamePrefix)
   808  }
   809  
   810  // Mangle function name with ABI information.
   811  func mangleABIName(ctxt *Link, ldr *loader.Loader, x loader.Sym, name string) string {
   812  	// For functions with ABI wrappers, we have to make sure that we
   813  	// don't wind up with two symbol table entries with the same
   814  	// name (since this will generated an error from the external
   815  	// linker). If we have wrappers, keep the ABIInternal name
   816  	// unmangled since we want cross-load-module calls to target
   817  	// ABIInternal, and rename other symbols.
   818  	//
   819  	// TODO: avoid the ldr.Lookup calls below by instead using an aux
   820  	// sym or marker relocation to associate the wrapper with the
   821  	// wrapped function.
   822  	if !buildcfg.Experiment.RegabiWrappers {
   823  		return name
   824  	}
   825  
   826  	if ldr.SymType(x).IsText() && ldr.SymVersion(x) != sym.SymVerABIInternal && ldr.SymVersion(x) < sym.SymVerStatic {
   827  		if s2 := ldr.Lookup(name, sym.SymVerABIInternal); s2 != 0 && ldr.SymType(s2).IsText() {
   828  			name = fmt.Sprintf("%s.abi%d", name, ldr.SymVersion(x))
   829  		}
   830  	}
   831  
   832  	// When loading a shared library, if a symbol has only one ABI,
   833  	// and the name is not mangled, we don't know what ABI it is.
   834  	// So we always mangle ABIInternal function name in shared linkage,
   835  	// except symbols that are exported to C. Type symbols are always
   836  	// ABIInternal so they are not mangled.
   837  	if ctxt.IsShared() {
   838  		if ldr.SymType(x).IsText() && ldr.SymVersion(x) == sym.SymVerABIInternal && !ldr.AttrCgoExport(x) && !strings.HasPrefix(name, "type:") {
   839  			name = fmt.Sprintf("%s.abiinternal", name)
   840  		}
   841  	}
   842  
   843  	return name
   844  }
   845
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