Source file src/cmd/link/internal/loadelf/ldelf.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  // Package loadelf implements an ELF file reader.
     6  package loadelf
     7  
     8  import (
     9  	"bytes"
    10  	"cmd/internal/bio"
    11  	"cmd/internal/objabi"
    12  	"cmd/internal/sys"
    13  	"cmd/link/internal/loader"
    14  	"cmd/link/internal/sym"
    15  	"debug/elf"
    16  	"encoding/binary"
    17  	"fmt"
    18  	"io"
    19  	"log"
    20  	"strings"
    21  )
    22  
    23  /*
    24  Derived from Plan 9 from User Space's src/libmach/elf.h, elf.c
    25  https://github.com/9fans/plan9port/tree/master/src/libmach/
    26  
    27  	Copyright © 2004 Russ Cox.
    28  	Portions Copyright © 2008-2010 Google Inc.
    29  	Portions Copyright © 2010 The Go Authors.
    30  
    31  Permission is hereby granted, free of charge, to any person obtaining a copy
    32  of this software and associated documentation files (the "Software"), to deal
    33  in the Software without restriction, including without limitation the rights
    34  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
    35  copies of the Software, and to permit persons to whom the Software is
    36  furnished to do so, subject to the following conditions:
    37  
    38  The above copyright notice and this permission notice shall be included in
    39  all copies or substantial portions of the Software.
    40  
    41  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    42  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    43  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
    44  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
    45  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
    46  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
    47  THE SOFTWARE.
    48  */
    49  
    50  const (
    51  	SHT_ARM_ATTRIBUTES = 0x70000003
    52  )
    53  
    54  type ElfSect struct {
    55  	name        string
    56  	nameoff     uint32
    57  	type_       elf.SectionType
    58  	flags       elf.SectionFlag
    59  	addr        uint64
    60  	off         uint64
    61  	size        uint64
    62  	link        uint32
    63  	info        uint32
    64  	align       uint64
    65  	entsize     uint64
    66  	base        []byte
    67  	readOnlyMem bool // Is this section in readonly memory?
    68  	sym         loader.Sym
    69  }
    70  
    71  type ElfObj struct {
    72  	f         *bio.Reader
    73  	base      int64 // offset in f where ELF begins
    74  	length    int64 // length of ELF
    75  	is64      int
    76  	name      string
    77  	e         binary.ByteOrder
    78  	sect      []ElfSect
    79  	nsect     uint
    80  	nsymtab   int
    81  	symtab    *ElfSect
    82  	symstr    *ElfSect
    83  	type_     uint32
    84  	machine   uint32
    85  	version   uint32
    86  	entry     uint64
    87  	phoff     uint64
    88  	shoff     uint64
    89  	flags     uint32
    90  	ehsize    uint32
    91  	phentsize uint32
    92  	phnum     uint32
    93  	shentsize uint32
    94  	shnum     uint32
    95  	shstrndx  uint32
    96  }
    97  
    98  type ElfSym struct {
    99  	name  string
   100  	value uint64
   101  	size  uint64
   102  	bind  elf.SymBind
   103  	type_ elf.SymType
   104  	other uint8
   105  	shndx elf.SectionIndex
   106  	sym   loader.Sym
   107  }
   108  
   109  const (
   110  	TagFile               = 1
   111  	TagCPUName            = 4
   112  	TagCPURawName         = 5
   113  	TagCompatibility      = 32
   114  	TagNoDefaults         = 64
   115  	TagAlsoCompatibleWith = 65
   116  	TagABIVFPArgs         = 28
   117  )
   118  
   119  type elfAttribute struct {
   120  	tag  uint64
   121  	sval string
   122  	ival uint64
   123  }
   124  
   125  type elfAttributeList struct {
   126  	data []byte
   127  	err  error
   128  }
   129  
   130  func (a *elfAttributeList) string() string {
   131  	if a.err != nil {
   132  		return ""
   133  	}
   134  	nul := bytes.IndexByte(a.data, 0)
   135  	if nul < 0 {
   136  		a.err = io.EOF
   137  		return ""
   138  	}
   139  	s := string(a.data[:nul])
   140  	a.data = a.data[nul+1:]
   141  	return s
   142  }
   143  
   144  func (a *elfAttributeList) uleb128() uint64 {
   145  	if a.err != nil {
   146  		return 0
   147  	}
   148  	v, size := binary.Uvarint(a.data)
   149  	a.data = a.data[size:]
   150  	return v
   151  }
   152  
   153  // Read an elfAttribute from the list following the rules used on ARM systems.
   154  func (a *elfAttributeList) armAttr() elfAttribute {
   155  	attr := elfAttribute{tag: a.uleb128()}
   156  	switch {
   157  	case attr.tag == TagCompatibility:
   158  		attr.ival = a.uleb128()
   159  		attr.sval = a.string()
   160  
   161  	case attr.tag == TagNoDefaults: // Tag_nodefaults has no argument
   162  
   163  	case attr.tag == TagAlsoCompatibleWith:
   164  		// Not really, but we don't actually care about this tag.
   165  		attr.sval = a.string()
   166  
   167  	// Tag with string argument
   168  	case attr.tag == TagCPUName || attr.tag == TagCPURawName || (attr.tag >= 32 && attr.tag&1 != 0):
   169  		attr.sval = a.string()
   170  
   171  	default: // Tag with integer argument
   172  		attr.ival = a.uleb128()
   173  	}
   174  	return attr
   175  }
   176  
   177  func (a *elfAttributeList) done() bool {
   178  	if a.err != nil || len(a.data) == 0 {
   179  		return true
   180  	}
   181  	return false
   182  }
   183  
   184  // Look for the attribute that indicates the object uses the hard-float ABI (a
   185  // file-level attribute with tag Tag_VFP_arch and value 1). Unfortunately the
   186  // format used means that we have to parse all of the file-level attributes to
   187  // find the one we are looking for. This format is slightly documented in "ELF
   188  // for the ARM Architecture" but mostly this is derived from reading the source
   189  // to gold and readelf.
   190  func parseArmAttributes(e binary.ByteOrder, data []byte) (found bool, ehdrFlags uint32, err error) {
   191  	found = false
   192  	if data[0] != 'A' {
   193  		return false, 0, fmt.Errorf(".ARM.attributes has unexpected format %c\n", data[0])
   194  	}
   195  	data = data[1:]
   196  	for len(data) != 0 {
   197  		sectionlength := e.Uint32(data)
   198  		sectiondata := data[4:sectionlength]
   199  		data = data[sectionlength:]
   200  
   201  		nulIndex := bytes.IndexByte(sectiondata, 0)
   202  		if nulIndex < 0 {
   203  			return false, 0, fmt.Errorf("corrupt .ARM.attributes (section name not NUL-terminated)\n")
   204  		}
   205  		name := string(sectiondata[:nulIndex])
   206  		sectiondata = sectiondata[nulIndex+1:]
   207  
   208  		if name != "aeabi" {
   209  			continue
   210  		}
   211  		for len(sectiondata) != 0 {
   212  			subsectiontag, sz := binary.Uvarint(sectiondata)
   213  			subsectionsize := e.Uint32(sectiondata[sz:])
   214  			subsectiondata := sectiondata[sz+4 : subsectionsize]
   215  			sectiondata = sectiondata[subsectionsize:]
   216  
   217  			if subsectiontag != TagFile {
   218  				continue
   219  			}
   220  			attrList := elfAttributeList{data: subsectiondata}
   221  			for !attrList.done() {
   222  				attr := attrList.armAttr()
   223  				if attr.tag == TagABIVFPArgs && attr.ival == 1 {
   224  					found = true
   225  					ehdrFlags = 0x5000402 // has entry point, Version5 EABI, hard-float ABI
   226  				}
   227  			}
   228  			if attrList.err != nil {
   229  				return false, 0, fmt.Errorf("could not parse .ARM.attributes\n")
   230  			}
   231  		}
   232  	}
   233  	return found, ehdrFlags, nil
   234  }
   235  
   236  // Load loads the ELF file pn from f.
   237  // Symbols are installed into the loader, and a slice of the text symbols is returned.
   238  //
   239  // On ARM systems, Load will attempt to determine what ELF header flags to
   240  // emit by scanning the attributes in the ELF file being loaded. The
   241  // parameter initEhdrFlags contains the current header flags for the output
   242  // object, and the returned ehdrFlags contains what this Load function computes.
   243  // TODO: find a better place for this logic.
   244  func Load(l *loader.Loader, arch *sys.Arch, localSymVersion int, f *bio.Reader, pkg string, length int64, pn string, initEhdrFlags uint32) (textp []loader.Sym, ehdrFlags uint32, err error) {
   245  	errorf := func(str string, args ...interface{}) ([]loader.Sym, uint32, error) {
   246  		return nil, 0, fmt.Errorf("loadelf: %s: %v", pn, fmt.Sprintf(str, args...))
   247  	}
   248  
   249  	ehdrFlags = initEhdrFlags
   250  
   251  	base := f.Offset()
   252  
   253  	var hdrbuf [64]byte
   254  	if _, err := io.ReadFull(f, hdrbuf[:]); err != nil {
   255  		return errorf("malformed elf file: %v", err)
   256  	}
   257  
   258  	var e binary.ByteOrder
   259  	switch elf.Data(hdrbuf[elf.EI_DATA]) {
   260  	case elf.ELFDATA2LSB:
   261  		e = binary.LittleEndian
   262  
   263  	case elf.ELFDATA2MSB:
   264  		e = binary.BigEndian
   265  
   266  	default:
   267  		return errorf("malformed elf file, unknown header")
   268  	}
   269  
   270  	hdr := new(elf.Header32)
   271  	binary.Read(bytes.NewReader(hdrbuf[:]), e, hdr)
   272  
   273  	if string(hdr.Ident[:elf.EI_CLASS]) != elf.ELFMAG {
   274  		return errorf("malformed elf file, bad header")
   275  	}
   276  
   277  	// read header
   278  	elfobj := new(ElfObj)
   279  
   280  	elfobj.e = e
   281  	elfobj.f = f
   282  	elfobj.base = base
   283  	elfobj.length = length
   284  	elfobj.name = pn
   285  
   286  	is64 := 0
   287  	class := elf.Class(hdrbuf[elf.EI_CLASS])
   288  	if class == elf.ELFCLASS64 {
   289  		is64 = 1
   290  		hdr := new(elf.Header64)
   291  		binary.Read(bytes.NewReader(hdrbuf[:]), e, hdr)
   292  		elfobj.type_ = uint32(hdr.Type)
   293  		elfobj.machine = uint32(hdr.Machine)
   294  		elfobj.version = hdr.Version
   295  		elfobj.entry = hdr.Entry
   296  		elfobj.phoff = hdr.Phoff
   297  		elfobj.shoff = hdr.Shoff
   298  		elfobj.flags = hdr.Flags
   299  		elfobj.ehsize = uint32(hdr.Ehsize)
   300  		elfobj.phentsize = uint32(hdr.Phentsize)
   301  		elfobj.phnum = uint32(hdr.Phnum)
   302  		elfobj.shentsize = uint32(hdr.Shentsize)
   303  		elfobj.shnum = uint32(hdr.Shnum)
   304  		elfobj.shstrndx = uint32(hdr.Shstrndx)
   305  	} else {
   306  		elfobj.type_ = uint32(hdr.Type)
   307  		elfobj.machine = uint32(hdr.Machine)
   308  		elfobj.version = hdr.Version
   309  		elfobj.entry = uint64(hdr.Entry)
   310  		elfobj.phoff = uint64(hdr.Phoff)
   311  		elfobj.shoff = uint64(hdr.Shoff)
   312  		elfobj.flags = hdr.Flags
   313  		elfobj.ehsize = uint32(hdr.Ehsize)
   314  		elfobj.phentsize = uint32(hdr.Phentsize)
   315  		elfobj.phnum = uint32(hdr.Phnum)
   316  		elfobj.shentsize = uint32(hdr.Shentsize)
   317  		elfobj.shnum = uint32(hdr.Shnum)
   318  		elfobj.shstrndx = uint32(hdr.Shstrndx)
   319  	}
   320  
   321  	elfobj.is64 = is64
   322  
   323  	if v := uint32(hdrbuf[elf.EI_VERSION]); v != elfobj.version {
   324  		return errorf("malformed elf version: got %d, want %d", v, elfobj.version)
   325  	}
   326  
   327  	if elf.Type(elfobj.type_) != elf.ET_REL {
   328  		return errorf("elf but not elf relocatable object")
   329  	}
   330  
   331  	mach := elf.Machine(elfobj.machine)
   332  	switch arch.Family {
   333  	default:
   334  		return errorf("elf %s unimplemented", arch.Name)
   335  
   336  	case sys.MIPS:
   337  		if mach != elf.EM_MIPS || class != elf.ELFCLASS32 {
   338  			return errorf("elf object but not mips")
   339  		}
   340  
   341  	case sys.MIPS64:
   342  		if mach != elf.EM_MIPS || class != elf.ELFCLASS64 {
   343  			return errorf("elf object but not mips64")
   344  		}
   345  	case sys.Loong64:
   346  		if mach != elf.EM_LOONGARCH || class != elf.ELFCLASS64 {
   347  			return errorf("elf object but not loong64")
   348  		}
   349  
   350  	case sys.ARM:
   351  		if e != binary.LittleEndian || mach != elf.EM_ARM || class != elf.ELFCLASS32 {
   352  			return errorf("elf object but not arm")
   353  		}
   354  
   355  	case sys.AMD64:
   356  		if e != binary.LittleEndian || mach != elf.EM_X86_64 || class != elf.ELFCLASS64 {
   357  			return errorf("elf object but not amd64")
   358  		}
   359  
   360  	case sys.ARM64:
   361  		if e != binary.LittleEndian || mach != elf.EM_AARCH64 || class != elf.ELFCLASS64 {
   362  			return errorf("elf object but not arm64")
   363  		}
   364  
   365  	case sys.I386:
   366  		if e != binary.LittleEndian || mach != elf.EM_386 || class != elf.ELFCLASS32 {
   367  			return errorf("elf object but not 386")
   368  		}
   369  
   370  	case sys.PPC64:
   371  		if mach != elf.EM_PPC64 || class != elf.ELFCLASS64 {
   372  			return errorf("elf object but not ppc64")
   373  		}
   374  
   375  	case sys.RISCV64:
   376  		if mach != elf.EM_RISCV || class != elf.ELFCLASS64 {
   377  			return errorf("elf object but not riscv64")
   378  		}
   379  
   380  	case sys.S390X:
   381  		if mach != elf.EM_S390 || class != elf.ELFCLASS64 {
   382  			return errorf("elf object but not s390x")
   383  		}
   384  	}
   385  
   386  	// load section list into memory.
   387  	elfobj.sect = make([]ElfSect, elfobj.shnum)
   388  
   389  	elfobj.nsect = uint(elfobj.shnum)
   390  	for i := 0; uint(i) < elfobj.nsect; i++ {
   391  		f.MustSeek(int64(uint64(base)+elfobj.shoff+uint64(int64(i)*int64(elfobj.shentsize))), 0)
   392  		sect := &elfobj.sect[i]
   393  		if is64 != 0 {
   394  			var b elf.Section64
   395  			if err := binary.Read(f, e, &b); err != nil {
   396  				return errorf("malformed elf file: %v", err)
   397  			}
   398  
   399  			sect.nameoff = b.Name
   400  			sect.type_ = elf.SectionType(b.Type)
   401  			sect.flags = elf.SectionFlag(b.Flags)
   402  			sect.addr = b.Addr
   403  			sect.off = b.Off
   404  			sect.size = b.Size
   405  			sect.link = b.Link
   406  			sect.info = b.Info
   407  			sect.align = b.Addralign
   408  			sect.entsize = b.Entsize
   409  		} else {
   410  			var b elf.Section32
   411  
   412  			if err := binary.Read(f, e, &b); err != nil {
   413  				return errorf("malformed elf file: %v", err)
   414  			}
   415  			sect.nameoff = b.Name
   416  			sect.type_ = elf.SectionType(b.Type)
   417  			sect.flags = elf.SectionFlag(b.Flags)
   418  			sect.addr = uint64(b.Addr)
   419  			sect.off = uint64(b.Off)
   420  			sect.size = uint64(b.Size)
   421  			sect.link = b.Link
   422  			sect.info = b.Info
   423  			sect.align = uint64(b.Addralign)
   424  			sect.entsize = uint64(b.Entsize)
   425  		}
   426  	}
   427  
   428  	// read section string table and translate names
   429  	if elfobj.shstrndx >= uint32(elfobj.nsect) {
   430  		return errorf("malformed elf file: shstrndx out of range %d >= %d", elfobj.shstrndx, elfobj.nsect)
   431  	}
   432  
   433  	sect := &elfobj.sect[elfobj.shstrndx]
   434  	if err := elfmap(elfobj, sect); err != nil {
   435  		return errorf("malformed elf file: %v", err)
   436  	}
   437  	for i := 0; uint(i) < elfobj.nsect; i++ {
   438  		if elfobj.sect[i].nameoff != 0 {
   439  			elfobj.sect[i].name = cstring(sect.base[elfobj.sect[i].nameoff:])
   440  		}
   441  	}
   442  
   443  	// load string table for symbols into memory.
   444  	elfobj.symtab = section(elfobj, ".symtab")
   445  
   446  	if elfobj.symtab == nil {
   447  		// our work is done here - no symbols means nothing can refer to this file
   448  		return
   449  	}
   450  
   451  	if elfobj.symtab.link <= 0 || elfobj.symtab.link >= uint32(elfobj.nsect) {
   452  		return errorf("elf object has symbol table with invalid string table link")
   453  	}
   454  
   455  	elfobj.symstr = &elfobj.sect[elfobj.symtab.link]
   456  	if is64 != 0 {
   457  		elfobj.nsymtab = int(elfobj.symtab.size / elf.Sym64Size)
   458  	} else {
   459  		elfobj.nsymtab = int(elfobj.symtab.size / elf.Sym32Size)
   460  	}
   461  
   462  	if err := elfmap(elfobj, elfobj.symtab); err != nil {
   463  		return errorf("malformed elf file: %v", err)
   464  	}
   465  	if err := elfmap(elfobj, elfobj.symstr); err != nil {
   466  		return errorf("malformed elf file: %v", err)
   467  	}
   468  
   469  	// load text and data segments into memory.
   470  	// they are not as small as the section lists, but we'll need
   471  	// the memory anyway for the symbol images, so we might
   472  	// as well use one large chunk.
   473  
   474  	// create symbols for elfmapped sections
   475  	sectsymNames := make(map[string]bool)
   476  	counter := 0
   477  	for i := 0; uint(i) < elfobj.nsect; i++ {
   478  		sect = &elfobj.sect[i]
   479  		if sect.type_ == SHT_ARM_ATTRIBUTES && sect.name == ".ARM.attributes" {
   480  			if err := elfmap(elfobj, sect); err != nil {
   481  				return errorf("%s: malformed elf file: %v", pn, err)
   482  			}
   483  			// We assume the soft-float ABI unless we see a tag indicating otherwise.
   484  			if initEhdrFlags == 0x5000002 {
   485  				ehdrFlags = 0x5000202
   486  			} else {
   487  				ehdrFlags = initEhdrFlags
   488  			}
   489  			found, newEhdrFlags, err := parseArmAttributes(e, sect.base[:sect.size])
   490  			if err != nil {
   491  				// TODO(dfc) should this return an error?
   492  				log.Printf("%s: %v", pn, err)
   493  			}
   494  			if found {
   495  				ehdrFlags = newEhdrFlags
   496  			}
   497  		}
   498  		if (sect.type_ != elf.SHT_PROGBITS && sect.type_ != elf.SHT_NOBITS) || sect.flags&elf.SHF_ALLOC == 0 {
   499  			continue
   500  		}
   501  		if sect.type_ != elf.SHT_NOBITS {
   502  			if err := elfmap(elfobj, sect); err != nil {
   503  				return errorf("%s: malformed elf file: %v", pn, err)
   504  			}
   505  		}
   506  
   507  		name := fmt.Sprintf("%s(%s)", pkg, sect.name)
   508  		for sectsymNames[name] {
   509  			counter++
   510  			name = fmt.Sprintf("%s(%s%d)", pkg, sect.name, counter)
   511  		}
   512  		sectsymNames[name] = true
   513  
   514  		sb := l.MakeSymbolUpdater(l.LookupOrCreateCgoExport(name, localSymVersion))
   515  
   516  		switch sect.flags & (elf.SHF_ALLOC | elf.SHF_WRITE | elf.SHF_EXECINSTR) {
   517  		default:
   518  			return errorf("%s: unexpected flags for ELF section %s", pn, sect.name)
   519  
   520  		case elf.SHF_ALLOC:
   521  			sb.SetType(sym.SRODATA)
   522  
   523  		case elf.SHF_ALLOC + elf.SHF_WRITE:
   524  			if sect.type_ == elf.SHT_NOBITS {
   525  				sb.SetType(sym.SNOPTRBSS)
   526  			} else {
   527  				sb.SetType(sym.SNOPTRDATA)
   528  			}
   529  
   530  		case elf.SHF_ALLOC + elf.SHF_EXECINSTR:
   531  			sb.SetType(sym.STEXT)
   532  		}
   533  
   534  		if sect.name == ".got" || sect.name == ".toc" {
   535  			sb.SetType(sym.SELFGOT)
   536  		}
   537  		if sect.type_ == elf.SHT_PROGBITS {
   538  			sb.SetData(sect.base[:sect.size])
   539  			sb.SetExternal(true)
   540  		}
   541  
   542  		sb.SetSize(int64(sect.size))
   543  		sb.SetAlign(int32(sect.align))
   544  		sb.SetReadOnly(sect.readOnlyMem)
   545  
   546  		sect.sym = sb.Sym()
   547  	}
   548  
   549  	// enter sub-symbols into symbol table.
   550  	// symbol 0 is the null symbol.
   551  	symbols := make([]loader.Sym, elfobj.nsymtab)
   552  
   553  	for i := 1; i < elfobj.nsymtab; i++ {
   554  		var elfsym ElfSym
   555  		if err := readelfsym(l, arch, elfobj, i, &elfsym, 1, localSymVersion); err != nil {
   556  			return errorf("%s: malformed elf file: %v", pn, err)
   557  		}
   558  		symbols[i] = elfsym.sym
   559  		if elfsym.type_ != elf.STT_FUNC && elfsym.type_ != elf.STT_OBJECT && elfsym.type_ != elf.STT_NOTYPE && elfsym.type_ != elf.STT_COMMON {
   560  			continue
   561  		}
   562  		if elfsym.shndx == elf.SHN_COMMON || elfsym.type_ == elf.STT_COMMON {
   563  			sb := l.MakeSymbolUpdater(elfsym.sym)
   564  			if uint64(sb.Size()) < elfsym.size {
   565  				sb.SetSize(int64(elfsym.size))
   566  			}
   567  			if sb.Type() == 0 || sb.Type() == sym.SXREF {
   568  				sb.SetType(sym.SNOPTRBSS)
   569  			}
   570  			continue
   571  		}
   572  
   573  		if uint(elfsym.shndx) >= elfobj.nsect || elfsym.shndx == 0 {
   574  			continue
   575  		}
   576  
   577  		// even when we pass needSym == 1 to readelfsym, it might still return nil to skip some unwanted symbols
   578  		if elfsym.sym == 0 {
   579  			continue
   580  		}
   581  		sect = &elfobj.sect[elfsym.shndx]
   582  		if sect.sym == 0 {
   583  			if elfsym.type_ == 0 {
   584  				if strings.HasPrefix(sect.name, ".debug_") && elfsym.name == "" {
   585  					// clang on arm and riscv64.
   586  					// This reportedly happens with clang 3.7 on ARM.
   587  					// See issue 13139.
   588  					continue
   589  				}
   590  				if strings.HasPrefix(elfsym.name, ".Ldebug_") || elfsym.name == ".L0 " {
   591  					// gcc on riscv64.
   592  					continue
   593  				}
   594  				if elfsym.name == ".Lline_table_start0" {
   595  					// clang on riscv64.
   596  					continue
   597  				}
   598  
   599  				if strings.HasPrefix(elfsym.name, "$d") && sect.name == ".debug_frame" {
   600  					// "$d" is a marker, not a real symbol.
   601  					// This happens with gcc on ARM64.
   602  					// See https://sourceware.org/bugzilla/show_bug.cgi?id=21809
   603  					continue
   604  				}
   605  			}
   606  
   607  			if strings.HasPrefix(elfsym.name, ".Linfo_string") {
   608  				// clang does this
   609  				continue
   610  			}
   611  
   612  			if strings.HasPrefix(elfsym.name, ".LASF") || strings.HasPrefix(elfsym.name, ".LLRL") || strings.HasPrefix(elfsym.name, ".LLST") {
   613  				// gcc on s390x and riscv64 does this.
   614  				continue
   615  			}
   616  
   617  			return errorf("%v: sym#%d (%q): ignoring symbol in section %d (%q) (type %d)", elfsym.sym, i, elfsym.name, elfsym.shndx, sect.name, elfsym.type_)
   618  		}
   619  
   620  		s := elfsym.sym
   621  		if l.OuterSym(s) != 0 {
   622  			if l.AttrDuplicateOK(s) {
   623  				continue
   624  			}
   625  			return errorf("duplicate symbol reference: %s in both %s and %s",
   626  				l.SymName(s), l.SymName(l.OuterSym(s)), l.SymName(sect.sym))
   627  		}
   628  
   629  		sectsb := l.MakeSymbolUpdater(sect.sym)
   630  		sb := l.MakeSymbolUpdater(s)
   631  
   632  		sb.SetType(sectsb.Type())
   633  		sectsb.AddInteriorSym(s)
   634  		if !l.AttrCgoExportDynamic(s) {
   635  			sb.SetDynimplib("") // satisfy dynimport
   636  		}
   637  		sb.SetValue(int64(elfsym.value))
   638  		sb.SetSize(int64(elfsym.size))
   639  		if sectsb.Type().IsText() {
   640  			if l.AttrExternal(s) && !l.AttrDuplicateOK(s) {
   641  				return errorf("%s: duplicate symbol definition", sb.Name())
   642  			}
   643  			l.SetAttrExternal(s, true)
   644  		}
   645  
   646  		if elf.Machine(elfobj.machine) == elf.EM_PPC64 {
   647  			flag := int(elfsym.other) >> 5
   648  			switch flag {
   649  			case 0:
   650  				// No local entry. R2 is preserved.
   651  			case 1:
   652  				// This is kind of a hack, but pass the hint about this symbol's
   653  				// usage of R2 (R2 is a caller-save register not a TOC pointer, and
   654  				// this function does not have a distinct local entry) by setting
   655  				// its SymLocalentry to 1.
   656  				l.SetSymLocalentry(s, 1)
   657  			case 7:
   658  				return errorf("%s: invalid sym.other 0x%x", sb.Name(), elfsym.other)
   659  			default:
   660  				// Convert the word sized offset into bytes.
   661  				l.SetSymLocalentry(s, 4<<uint(flag-2))
   662  			}
   663  		}
   664  	}
   665  
   666  	// Sort outer lists by address, adding to textp.
   667  	// This keeps textp in increasing address order.
   668  	for i := uint(0); i < elfobj.nsect; i++ {
   669  		s := elfobj.sect[i].sym
   670  		if s == 0 {
   671  			continue
   672  		}
   673  		sb := l.MakeSymbolUpdater(s)
   674  		if l.SubSym(s) != 0 {
   675  			sb.SortSub()
   676  		}
   677  		if sb.Type().IsText() {
   678  			if l.AttrOnList(s) {
   679  				return errorf("symbol %s listed multiple times",
   680  					l.SymName(s))
   681  			}
   682  			l.SetAttrOnList(s, true)
   683  			textp = append(textp, s)
   684  			for ss := l.SubSym(s); ss != 0; ss = l.SubSym(ss) {
   685  				if l.AttrOnList(ss) {
   686  					return errorf("symbol %s listed multiple times",
   687  						l.SymName(ss))
   688  				}
   689  				l.SetAttrOnList(ss, true)
   690  				textp = append(textp, ss)
   691  			}
   692  		}
   693  	}
   694  
   695  	// load relocations
   696  	for i := uint(0); i < elfobj.nsect; i++ {
   697  		rsect := &elfobj.sect[i]
   698  		if rsect.type_ != elf.SHT_RELA && rsect.type_ != elf.SHT_REL {
   699  			continue
   700  		}
   701  		if rsect.info >= uint32(elfobj.nsect) || elfobj.sect[rsect.info].base == nil {
   702  			continue
   703  		}
   704  		sect = &elfobj.sect[rsect.info]
   705  		if err := elfmap(elfobj, rsect); err != nil {
   706  			return errorf("malformed elf file: %v", err)
   707  		}
   708  		rela := 0
   709  		if rsect.type_ == elf.SHT_RELA {
   710  			rela = 1
   711  		}
   712  		n := int(rsect.size / uint64(4+4*is64) / uint64(2+rela))
   713  		p := rsect.base
   714  		sb := l.MakeSymbolUpdater(sect.sym)
   715  		for j := 0; j < n; j++ {
   716  			var add uint64
   717  			var symIdx int
   718  			var relocType uint64
   719  			var rOff int32
   720  			var rAdd int64
   721  			var rSym loader.Sym
   722  
   723  			if is64 != 0 {
   724  				// 64-bit rel/rela
   725  				rOff = int32(e.Uint64(p))
   726  
   727  				p = p[8:]
   728  				switch arch.Family {
   729  				case sys.MIPS64:
   730  					// https://www.linux-mips.org/pub/linux/mips/doc/ABI/elf64-2.4.pdf
   731  					// The doc shows it's different with general Linux ELF
   732  					symIdx = int(e.Uint32(p))
   733  					relocType = uint64(p[7])
   734  				default:
   735  					info := e.Uint64(p)
   736  					relocType = info & 0xffffffff
   737  					symIdx = int(info >> 32)
   738  				}
   739  				p = p[8:]
   740  				if rela != 0 {
   741  					add = e.Uint64(p)
   742  					p = p[8:]
   743  				}
   744  			} else {
   745  				// 32-bit rel/rela
   746  				rOff = int32(e.Uint32(p))
   747  
   748  				p = p[4:]
   749  				info := e.Uint32(p)
   750  				relocType = uint64(info & 0xff)
   751  				symIdx = int(info >> 8)
   752  				p = p[4:]
   753  				if rela != 0 {
   754  					add = uint64(e.Uint32(p))
   755  					p = p[4:]
   756  				}
   757  			}
   758  
   759  			if relocType == 0 { // skip R_*_NONE relocation
   760  				j--
   761  				n--
   762  				continue
   763  			}
   764  
   765  			if symIdx == 0 { // absolute relocation, don't bother reading the null symbol
   766  				rSym = 0
   767  			} else {
   768  				var elfsym ElfSym
   769  				if err := readelfsym(l, arch, elfobj, int(symIdx), &elfsym, 0, 0); err != nil {
   770  					return errorf("malformed elf file: %v", err)
   771  				}
   772  				elfsym.sym = symbols[symIdx]
   773  				if elfsym.sym == 0 {
   774  					return errorf("malformed elf file: %s#%d: reloc of invalid sym #%d %s shndx=%d type=%d", l.SymName(sect.sym), j, int(symIdx), elfsym.name, elfsym.shndx, elfsym.type_)
   775  				}
   776  
   777  				rSym = elfsym.sym
   778  			}
   779  
   780  			rType := objabi.ElfRelocOffset + objabi.RelocType(relocType)
   781  			rSize, addendSize, err := relSize(arch, pn, uint32(relocType))
   782  			if err != nil {
   783  				return nil, 0, err
   784  			}
   785  			if rela != 0 {
   786  				rAdd = int64(add)
   787  			} else {
   788  				// load addend from image
   789  				if rSize == 4 {
   790  					rAdd = int64(e.Uint32(sect.base[rOff:]))
   791  				} else if rSize == 8 {
   792  					rAdd = int64(e.Uint64(sect.base[rOff:]))
   793  				} else {
   794  					return errorf("invalid rela size %d", rSize)
   795  				}
   796  			}
   797  
   798  			if addendSize == 2 {
   799  				rAdd = int64(int16(rAdd))
   800  			}
   801  			if addendSize == 4 {
   802  				rAdd = int64(int32(rAdd))
   803  			}
   804  
   805  			r, _ := sb.AddRel(rType)
   806  			r.SetOff(rOff)
   807  			r.SetSiz(rSize)
   808  			r.SetSym(rSym)
   809  			r.SetAdd(rAdd)
   810  		}
   811  
   812  		sb.SortRelocs() // just in case
   813  	}
   814  
   815  	return textp, ehdrFlags, nil
   816  }
   817  
   818  func section(elfobj *ElfObj, name string) *ElfSect {
   819  	for i := 0; uint(i) < elfobj.nsect; i++ {
   820  		if elfobj.sect[i].name != "" && name != "" && elfobj.sect[i].name == name {
   821  			return &elfobj.sect[i]
   822  		}
   823  	}
   824  	return nil
   825  }
   826  
   827  func elfmap(elfobj *ElfObj, sect *ElfSect) (err error) {
   828  	if sect.base != nil {
   829  		return nil
   830  	}
   831  
   832  	if sect.off+sect.size > uint64(elfobj.length) {
   833  		err = fmt.Errorf("elf section past end of file")
   834  		return err
   835  	}
   836  
   837  	elfobj.f.MustSeek(int64(uint64(elfobj.base)+sect.off), 0)
   838  	sect.base, sect.readOnlyMem, err = elfobj.f.Slice(uint64(sect.size))
   839  	if err != nil {
   840  		return fmt.Errorf("short read: %v", err)
   841  	}
   842  
   843  	return nil
   844  }
   845  
   846  func readelfsym(l *loader.Loader, arch *sys.Arch, elfobj *ElfObj, i int, elfsym *ElfSym, needSym int, localSymVersion int) (err error) {
   847  	if i >= elfobj.nsymtab || i < 0 {
   848  		err = fmt.Errorf("invalid elf symbol index")
   849  		return err
   850  	}
   851  
   852  	if i == 0 {
   853  		return fmt.Errorf("readym: read null symbol!")
   854  	}
   855  
   856  	if elfobj.is64 != 0 {
   857  		b := new(elf.Sym64)
   858  		binary.Read(bytes.NewReader(elfobj.symtab.base[i*elf.Sym64Size:(i+1)*elf.Sym64Size]), elfobj.e, b)
   859  		elfsym.name = cstring(elfobj.symstr.base[b.Name:])
   860  		elfsym.value = b.Value
   861  		elfsym.size = b.Size
   862  		elfsym.shndx = elf.SectionIndex(b.Shndx)
   863  		elfsym.bind = elf.ST_BIND(b.Info)
   864  		elfsym.type_ = elf.ST_TYPE(b.Info)
   865  		elfsym.other = b.Other
   866  	} else {
   867  		b := new(elf.Sym32)
   868  		binary.Read(bytes.NewReader(elfobj.symtab.base[i*elf.Sym32Size:(i+1)*elf.Sym32Size]), elfobj.e, b)
   869  		elfsym.name = cstring(elfobj.symstr.base[b.Name:])
   870  		elfsym.value = uint64(b.Value)
   871  		elfsym.size = uint64(b.Size)
   872  		elfsym.shndx = elf.SectionIndex(b.Shndx)
   873  		elfsym.bind = elf.ST_BIND(b.Info)
   874  		elfsym.type_ = elf.ST_TYPE(b.Info)
   875  		elfsym.other = b.Other
   876  	}
   877  
   878  	var s loader.Sym
   879  
   880  	if elfsym.name == "_GLOBAL_OFFSET_TABLE_" {
   881  		elfsym.name = ".got"
   882  	}
   883  	if elfsym.name == ".TOC." {
   884  		// Magic symbol on ppc64.  Will be set to this object
   885  		// file's .got+0x8000.
   886  		elfsym.bind = elf.STB_LOCAL
   887  	}
   888  
   889  	switch elfsym.type_ {
   890  	case elf.STT_SECTION:
   891  		s = elfobj.sect[elfsym.shndx].sym
   892  
   893  	case elf.STT_OBJECT, elf.STT_FUNC, elf.STT_NOTYPE, elf.STT_COMMON:
   894  		switch elfsym.bind {
   895  		case elf.STB_GLOBAL:
   896  			if needSym != 0 {
   897  				s = l.LookupOrCreateCgoExport(elfsym.name, 0)
   898  
   899  				// for global scoped hidden symbols we should insert it into
   900  				// symbol hash table, but mark them as hidden.
   901  				// __i686.get_pc_thunk.bx is allowed to be duplicated, to
   902  				// workaround that we set dupok.
   903  				// TODO(minux): correctly handle __i686.get_pc_thunk.bx without
   904  				// set dupok generally. See https://golang.org/cl/5823055
   905  				// comment #5 for details.
   906  				if s != 0 && elfsym.other == 2 {
   907  					if !l.IsExternal(s) {
   908  						l.MakeSymbolUpdater(s)
   909  					}
   910  					l.SetAttrDuplicateOK(s, true)
   911  					l.SetAttrVisibilityHidden(s, true)
   912  				}
   913  			}
   914  
   915  		case elf.STB_LOCAL:
   916  			if (arch.Family == sys.ARM || arch.Family == sys.ARM64) && (strings.HasPrefix(elfsym.name, "$a") || strings.HasPrefix(elfsym.name, "$d") || strings.HasPrefix(elfsym.name, "$x")) {
   917  				// binutils for arm and arm64 generate these mapping
   918  				// symbols, ignore these
   919  				break
   920  			}
   921  
   922  			if elfsym.name == ".TOC." {
   923  				// We need to be able to look this up,
   924  				// so put it in the hash table.
   925  				if needSym != 0 {
   926  					s = l.LookupOrCreateCgoExport(elfsym.name, localSymVersion)
   927  					l.SetAttrVisibilityHidden(s, true)
   928  				}
   929  				break
   930  			}
   931  
   932  			if needSym != 0 {
   933  				// local names and hidden global names are unique
   934  				// and should only be referenced by their index, not name, so we
   935  				// don't bother to add them into the hash table
   936  				// FIXME: pass empty string here for name? This would
   937  				// reduce mem use, but also (possibly) make it harder
   938  				// to debug problems.
   939  				s = l.CreateStaticSym(elfsym.name)
   940  				l.SetAttrVisibilityHidden(s, true)
   941  			}
   942  
   943  		case elf.STB_WEAK:
   944  			if needSym != 0 {
   945  				s = l.LookupOrCreateCgoExport(elfsym.name, 0)
   946  				if elfsym.other == 2 {
   947  					l.SetAttrVisibilityHidden(s, true)
   948  				}
   949  
   950  				// Allow weak symbols to be duplicated when already defined.
   951  				if l.OuterSym(s) != 0 {
   952  					l.SetAttrDuplicateOK(s, true)
   953  				}
   954  			}
   955  
   956  		default:
   957  			err = fmt.Errorf("%s: invalid symbol binding %d", elfsym.name, elfsym.bind)
   958  			return err
   959  		}
   960  	}
   961  
   962  	if s != 0 && l.SymType(s) == 0 && elfsym.type_ != elf.STT_SECTION {
   963  		sb := l.MakeSymbolUpdater(s)
   964  		sb.SetType(sym.SXREF)
   965  	}
   966  	elfsym.sym = s
   967  
   968  	return nil
   969  }
   970  
   971  // Return the size of the relocated field, and the size of the addend as the first
   972  // and second values. Note, the addend may be larger than the relocation field in
   973  // some cases when a relocated value is split across multiple relocations.
   974  func relSize(arch *sys.Arch, pn string, elftype uint32) (uint8, uint8, error) {
   975  	// TODO(mdempsky): Replace this with a struct-valued switch statement
   976  	// once golang.org/issue/15164 is fixed or found to not impair cmd/link
   977  	// performance.
   978  
   979  	const (
   980  		AMD64   = uint32(sys.AMD64)
   981  		ARM     = uint32(sys.ARM)
   982  		ARM64   = uint32(sys.ARM64)
   983  		I386    = uint32(sys.I386)
   984  		LOONG64 = uint32(sys.Loong64)
   985  		MIPS    = uint32(sys.MIPS)
   986  		MIPS64  = uint32(sys.MIPS64)
   987  		PPC64   = uint32(sys.PPC64)
   988  		RISCV64 = uint32(sys.RISCV64)
   989  		S390X   = uint32(sys.S390X)
   990  	)
   991  
   992  	switch uint32(arch.Family) | elftype<<16 {
   993  	default:
   994  		return 0, 0, fmt.Errorf("%s: unknown relocation type %d; compiled without -fpic?", pn, elftype)
   995  
   996  	case MIPS | uint32(elf.R_MIPS_HI16)<<16,
   997  		MIPS | uint32(elf.R_MIPS_LO16)<<16,
   998  		MIPS | uint32(elf.R_MIPS_GOT16)<<16,
   999  		MIPS | uint32(elf.R_MIPS_GOT_HI16)<<16,
  1000  		MIPS | uint32(elf.R_MIPS_GOT_LO16)<<16,
  1001  		MIPS | uint32(elf.R_MIPS_GPREL16)<<16,
  1002  		MIPS | uint32(elf.R_MIPS_GOT_PAGE)<<16,
  1003  		MIPS | uint32(elf.R_MIPS_JALR)<<16,
  1004  		MIPS | uint32(elf.R_MIPS_GOT_OFST)<<16,
  1005  		MIPS64 | uint32(elf.R_MIPS_HI16)<<16,
  1006  		MIPS64 | uint32(elf.R_MIPS_LO16)<<16,
  1007  		MIPS64 | uint32(elf.R_MIPS_GOT16)<<16,
  1008  		MIPS64 | uint32(elf.R_MIPS_GOT_HI16)<<16,
  1009  		MIPS64 | uint32(elf.R_MIPS_GOT_LO16)<<16,
  1010  		MIPS64 | uint32(elf.R_MIPS_GPREL16)<<16,
  1011  		MIPS64 | uint32(elf.R_MIPS_GOT_PAGE)<<16,
  1012  		MIPS64 | uint32(elf.R_MIPS_JALR)<<16,
  1013  		MIPS64 | uint32(elf.R_MIPS_GOT_OFST)<<16,
  1014  		MIPS64 | uint32(elf.R_MIPS_CALL16)<<16,
  1015  		MIPS64 | uint32(elf.R_MIPS_GPREL32)<<16,
  1016  		MIPS64 | uint32(elf.R_MIPS_64)<<16,
  1017  		MIPS64 | uint32(elf.R_MIPS_GOT_DISP)<<16,
  1018  		MIPS64 | uint32(elf.R_MIPS_PC32)<<16:
  1019  		return 4, 4, nil
  1020  
  1021  	case LOONG64 | uint32(elf.R_LARCH_ADD8)<<16,
  1022  		LOONG64 | uint32(elf.R_LARCH_SUB8)<<16:
  1023  		return 1, 1, nil
  1024  
  1025  	case LOONG64 | uint32(elf.R_LARCH_ADD16)<<16,
  1026  		LOONG64 | uint32(elf.R_LARCH_SUB16)<<16:
  1027  		return 2, 2, nil
  1028  
  1029  	case LOONG64 | uint32(elf.R_LARCH_MARK_LA)<<16,
  1030  		LOONG64 | uint32(elf.R_LARCH_MARK_PCREL)<<16,
  1031  		LOONG64 | uint32(elf.R_LARCH_ADD24)<<16,
  1032  		LOONG64 | uint32(elf.R_LARCH_ADD32)<<16,
  1033  		LOONG64 | uint32(elf.R_LARCH_SUB24)<<16,
  1034  		LOONG64 | uint32(elf.R_LARCH_SUB32)<<16,
  1035  		LOONG64 | uint32(elf.R_LARCH_B26)<<16,
  1036  		LOONG64 | uint32(elf.R_LARCH_32_PCREL)<<16:
  1037  		return 4, 4, nil
  1038  
  1039  	case LOONG64 | uint32(elf.R_LARCH_64)<<16,
  1040  		LOONG64 | uint32(elf.R_LARCH_ADD64)<<16,
  1041  		LOONG64 | uint32(elf.R_LARCH_SUB64)<<16,
  1042  		LOONG64 | uint32(elf.R_LARCH_64_PCREL)<<16:
  1043  		return 8, 8, nil
  1044  
  1045  	case S390X | uint32(elf.R_390_8)<<16:
  1046  		return 1, 1, nil
  1047  
  1048  	case PPC64 | uint32(elf.R_PPC64_TOC16)<<16,
  1049  		S390X | uint32(elf.R_390_16)<<16,
  1050  		S390X | uint32(elf.R_390_GOT16)<<16,
  1051  		S390X | uint32(elf.R_390_PC16)<<16,
  1052  		S390X | uint32(elf.R_390_PC16DBL)<<16,
  1053  		S390X | uint32(elf.R_390_PLT16DBL)<<16:
  1054  		return 2, 2, nil
  1055  
  1056  	case ARM | uint32(elf.R_ARM_ABS32)<<16,
  1057  		ARM | uint32(elf.R_ARM_GOT32)<<16,
  1058  		ARM | uint32(elf.R_ARM_PLT32)<<16,
  1059  		ARM | uint32(elf.R_ARM_GOTOFF)<<16,
  1060  		ARM | uint32(elf.R_ARM_GOTPC)<<16,
  1061  		ARM | uint32(elf.R_ARM_THM_PC22)<<16,
  1062  		ARM | uint32(elf.R_ARM_REL32)<<16,
  1063  		ARM | uint32(elf.R_ARM_CALL)<<16,
  1064  		ARM | uint32(elf.R_ARM_V4BX)<<16,
  1065  		ARM | uint32(elf.R_ARM_GOT_PREL)<<16,
  1066  		ARM | uint32(elf.R_ARM_PC24)<<16,
  1067  		ARM | uint32(elf.R_ARM_JUMP24)<<16,
  1068  		ARM64 | uint32(elf.R_AARCH64_CALL26)<<16,
  1069  		ARM64 | uint32(elf.R_AARCH64_ADR_GOT_PAGE)<<16,
  1070  		ARM64 | uint32(elf.R_AARCH64_LD64_GOT_LO12_NC)<<16,
  1071  		ARM64 | uint32(elf.R_AARCH64_ADR_PREL_PG_HI21)<<16,
  1072  		ARM64 | uint32(elf.R_AARCH64_ADD_ABS_LO12_NC)<<16,
  1073  		ARM64 | uint32(elf.R_AARCH64_LDST8_ABS_LO12_NC)<<16,
  1074  		ARM64 | uint32(elf.R_AARCH64_LDST16_ABS_LO12_NC)<<16,
  1075  		ARM64 | uint32(elf.R_AARCH64_LDST32_ABS_LO12_NC)<<16,
  1076  		ARM64 | uint32(elf.R_AARCH64_LDST64_ABS_LO12_NC)<<16,
  1077  		ARM64 | uint32(elf.R_AARCH64_LDST128_ABS_LO12_NC)<<16,
  1078  		ARM64 | uint32(elf.R_AARCH64_PREL32)<<16,
  1079  		ARM64 | uint32(elf.R_AARCH64_JUMP26)<<16,
  1080  		AMD64 | uint32(elf.R_X86_64_PC32)<<16,
  1081  		AMD64 | uint32(elf.R_X86_64_PLT32)<<16,
  1082  		AMD64 | uint32(elf.R_X86_64_GOTPCREL)<<16,
  1083  		AMD64 | uint32(elf.R_X86_64_GOTPCRELX)<<16,
  1084  		AMD64 | uint32(elf.R_X86_64_REX_GOTPCRELX)<<16,
  1085  		I386 | uint32(elf.R_386_32)<<16,
  1086  		I386 | uint32(elf.R_386_PC32)<<16,
  1087  		I386 | uint32(elf.R_386_GOT32)<<16,
  1088  		I386 | uint32(elf.R_386_PLT32)<<16,
  1089  		I386 | uint32(elf.R_386_GOTOFF)<<16,
  1090  		I386 | uint32(elf.R_386_GOTPC)<<16,
  1091  		I386 | uint32(elf.R_386_GOT32X)<<16,
  1092  		PPC64 | uint32(elf.R_PPC64_REL24)<<16,
  1093  		PPC64 | uint32(elf.R_PPC64_REL24_NOTOC)<<16,
  1094  		PPC64 | uint32(elf.R_PPC64_REL24_P9NOTOC)<<16,
  1095  		PPC64 | uint32(elf.R_PPC_REL32)<<16,
  1096  		S390X | uint32(elf.R_390_32)<<16,
  1097  		S390X | uint32(elf.R_390_PC32)<<16,
  1098  		S390X | uint32(elf.R_390_GOT32)<<16,
  1099  		S390X | uint32(elf.R_390_PLT32)<<16,
  1100  		S390X | uint32(elf.R_390_PC32DBL)<<16,
  1101  		S390X | uint32(elf.R_390_PLT32DBL)<<16,
  1102  		S390X | uint32(elf.R_390_GOTPCDBL)<<16,
  1103  		S390X | uint32(elf.R_390_GOTENT)<<16:
  1104  		return 4, 4, nil
  1105  
  1106  	case AMD64 | uint32(elf.R_X86_64_64)<<16,
  1107  		AMD64 | uint32(elf.R_X86_64_PC64)<<16,
  1108  		ARM64 | uint32(elf.R_AARCH64_ABS64)<<16,
  1109  		ARM64 | uint32(elf.R_AARCH64_PREL64)<<16,
  1110  		PPC64 | uint32(elf.R_PPC64_ADDR64)<<16,
  1111  		PPC64 | uint32(elf.R_PPC64_PCREL34)<<16,
  1112  		PPC64 | uint32(elf.R_PPC64_GOT_PCREL34)<<16,
  1113  		PPC64 | uint32(elf.R_PPC64_PLT_PCREL34_NOTOC)<<16,
  1114  		S390X | uint32(elf.R_390_GLOB_DAT)<<16,
  1115  		S390X | uint32(elf.R_390_RELATIVE)<<16,
  1116  		S390X | uint32(elf.R_390_GOTOFF)<<16,
  1117  		S390X | uint32(elf.R_390_GOTPC)<<16,
  1118  		S390X | uint32(elf.R_390_64)<<16,
  1119  		S390X | uint32(elf.R_390_PC64)<<16,
  1120  		S390X | uint32(elf.R_390_GOT64)<<16,
  1121  		S390X | uint32(elf.R_390_PLT64)<<16:
  1122  		return 8, 8, nil
  1123  
  1124  	case RISCV64 | uint32(elf.R_RISCV_SET6)<<16,
  1125  		RISCV64 | uint32(elf.R_RISCV_SUB6)<<16,
  1126  		RISCV64 | uint32(elf.R_RISCV_SET8)<<16,
  1127  		RISCV64 | uint32(elf.R_RISCV_SUB8)<<16:
  1128  		return 1, 1, nil
  1129  
  1130  	case RISCV64 | uint32(elf.R_RISCV_RVC_BRANCH)<<16,
  1131  		RISCV64 | uint32(elf.R_RISCV_RVC_JUMP)<<16,
  1132  		RISCV64 | uint32(elf.R_RISCV_SET16)<<16,
  1133  		RISCV64 | uint32(elf.R_RISCV_SUB16)<<16:
  1134  		return 2, 2, nil
  1135  
  1136  	case RISCV64 | uint32(elf.R_RISCV_32)<<16,
  1137  		RISCV64 | uint32(elf.R_RISCV_BRANCH)<<16,
  1138  		RISCV64 | uint32(elf.R_RISCV_HI20)<<16,
  1139  		RISCV64 | uint32(elf.R_RISCV_LO12_I)<<16,
  1140  		RISCV64 | uint32(elf.R_RISCV_LO12_S)<<16,
  1141  		RISCV64 | uint32(elf.R_RISCV_GOT_HI20)<<16,
  1142  		RISCV64 | uint32(elf.R_RISCV_PCREL_HI20)<<16,
  1143  		RISCV64 | uint32(elf.R_RISCV_PCREL_LO12_I)<<16,
  1144  		RISCV64 | uint32(elf.R_RISCV_PCREL_LO12_S)<<16,
  1145  		RISCV64 | uint32(elf.R_RISCV_ADD32)<<16,
  1146  		RISCV64 | uint32(elf.R_RISCV_SET32)<<16,
  1147  		RISCV64 | uint32(elf.R_RISCV_SUB32)<<16,
  1148  		RISCV64 | uint32(elf.R_RISCV_32_PCREL)<<16,
  1149  		RISCV64 | uint32(elf.R_RISCV_RELAX)<<16:
  1150  		return 4, 4, nil
  1151  
  1152  	case RISCV64 | uint32(elf.R_RISCV_64)<<16,
  1153  		RISCV64 | uint32(elf.R_RISCV_CALL)<<16,
  1154  		RISCV64 | uint32(elf.R_RISCV_CALL_PLT)<<16:
  1155  		return 8, 8, nil
  1156  
  1157  	case PPC64 | uint32(elf.R_PPC64_TOC16_LO)<<16,
  1158  		PPC64 | uint32(elf.R_PPC64_TOC16_HI)<<16,
  1159  		PPC64 | uint32(elf.R_PPC64_TOC16_HA)<<16,
  1160  		PPC64 | uint32(elf.R_PPC64_TOC16_DS)<<16,
  1161  		PPC64 | uint32(elf.R_PPC64_TOC16_LO_DS)<<16,
  1162  		PPC64 | uint32(elf.R_PPC64_REL16_LO)<<16,
  1163  		PPC64 | uint32(elf.R_PPC64_REL16_HI)<<16,
  1164  		PPC64 | uint32(elf.R_PPC64_REL16_HA)<<16,
  1165  		PPC64 | uint32(elf.R_PPC64_PLT16_HA)<<16,
  1166  		PPC64 | uint32(elf.R_PPC64_PLT16_LO_DS)<<16:
  1167  		return 2, 4, nil
  1168  
  1169  	// PPC64 inline PLT sequence hint relocations (-fno-plt)
  1170  	// These are informational annotations to assist linker optimizations.
  1171  	case PPC64 | uint32(elf.R_PPC64_PLTSEQ)<<16,
  1172  		PPC64 | uint32(elf.R_PPC64_PLTCALL)<<16,
  1173  		PPC64 | uint32(elf.R_PPC64_PLTCALL_NOTOC)<<16,
  1174  		PPC64 | uint32(elf.R_PPC64_PLTSEQ_NOTOC)<<16:
  1175  		return 0, 0, nil
  1176  
  1177  	}
  1178  }
  1179  
  1180  func cstring(x []byte) string {
  1181  	i := bytes.IndexByte(x, '\x00')
  1182  	if i >= 0 {
  1183  		x = x[:i]
  1184  	}
  1185  	return string(x)
  1186  }
  1187  

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