symbolbuilder.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 loader
     6  
     7  import (
     8  	"cmd/internal/goobj"
     9  	"cmd/internal/objabi"
    10  	"cmd/internal/sys"
    11  	"cmd/link/internal/sym"
    12  	"cmp"
    13  	"slices"
    14  )
    15  
    16  // SymbolBuilder is a helper designed to help with the construction
    17  // of new symbol contents.
    18  type SymbolBuilder struct {
    19  	*extSymPayload         // points to payload being updated
    20  	symIdx         Sym     // index of symbol being updated/constructed
    21  	l              *Loader // loader
    22  }
    23  
    24  // MakeSymbolBuilder creates a symbol builder for use in constructing
    25  // an entirely new symbol.
    26  func (l *Loader) MakeSymbolBuilder(name string) *SymbolBuilder {
    27  	// for now assume that any new sym is intended to be static
    28  	symIdx := l.CreateStaticSym(name)
    29  	sb := &SymbolBuilder{l: l, symIdx: symIdx}
    30  	sb.extSymPayload = l.getPayload(symIdx)
    31  	return sb
    32  }
    33  
    34  // MakeSymbolUpdater creates a symbol builder helper for an existing
    35  // symbol 'symIdx'. If 'symIdx' is not an external symbol, then create
    36  // a clone of it (copy name, properties, etc) fix things up so that
    37  // the lookup tables and caches point to the new version, not the old
    38  // version.
    39  func (l *Loader) MakeSymbolUpdater(symIdx Sym) *SymbolBuilder {
    40  	if symIdx == 0 {
    41  		panic("can't update the null symbol")
    42  	}
    43  	if !l.IsExternal(symIdx) {
    44  		// Create a clone with the same name/version/kind etc.
    45  		l.cloneToExternal(symIdx)
    46  	}
    47  
    48  	// Construct updater and return.
    49  	sb := &SymbolBuilder{l: l, symIdx: symIdx}
    50  	sb.extSymPayload = l.getPayload(symIdx)
    51  	return sb
    52  }
    53  
    54  // CreateSymForUpdate creates a symbol with given name and version,
    55  // returns a CreateSymForUpdate for update. If the symbol already
    56  // exists, it will update in-place.
    57  func (l *Loader) CreateSymForUpdate(name string, version int) *SymbolBuilder {
    58  	s := l.LookupOrCreateSym(name, version)
    59  	l.SetAttrReachable(s, true)
    60  	return l.MakeSymbolUpdater(s)
    61  }
    62  
    63  // Getters for properties of the symbol we're working on.
    64  
    65  func (sb *SymbolBuilder) Sym() Sym               { return sb.symIdx }
    66  func (sb *SymbolBuilder) Name() string           { return sb.name }
    67  func (sb *SymbolBuilder) Version() int           { return sb.ver }
    68  func (sb *SymbolBuilder) Type() sym.SymKind      { return sb.kind }
    69  func (sb *SymbolBuilder) Size() int64            { return sb.size }
    70  func (sb *SymbolBuilder) Data() []byte           { return sb.data }
    71  func (sb *SymbolBuilder) Value() int64           { return sb.l.SymValue(sb.symIdx) }
    72  func (sb *SymbolBuilder) Align() int32           { return sb.l.SymAlign(sb.symIdx) }
    73  func (sb *SymbolBuilder) Localentry() uint8      { return sb.l.SymLocalentry(sb.symIdx) }
    74  func (sb *SymbolBuilder) OnList() bool           { return sb.l.AttrOnList(sb.symIdx) }
    75  func (sb *SymbolBuilder) External() bool         { return sb.l.AttrExternal(sb.symIdx) }
    76  func (sb *SymbolBuilder) Extname() string        { return sb.l.SymExtname(sb.symIdx) }
    77  func (sb *SymbolBuilder) CgoExportDynamic() bool { return sb.l.AttrCgoExportDynamic(sb.symIdx) }
    78  func (sb *SymbolBuilder) Dynimplib() string      { return sb.l.SymDynimplib(sb.symIdx) }
    79  func (sb *SymbolBuilder) Dynimpvers() string     { return sb.l.SymDynimpvers(sb.symIdx) }
    80  func (sb *SymbolBuilder) SubSym() Sym            { return sb.l.SubSym(sb.symIdx) }
    81  func (sb *SymbolBuilder) GoType() Sym            { return sb.l.SymGoType(sb.symIdx) }
    82  func (sb *SymbolBuilder) VisibilityHidden() bool { return sb.l.AttrVisibilityHidden(sb.symIdx) }
    83  func (sb *SymbolBuilder) Sect() *sym.Section     { return sb.l.SymSect(sb.symIdx) }
    84  
    85  // Setters for symbol properties.
    86  
    87  func (sb *SymbolBuilder) SetType(kind sym.SymKind)   { sb.kind = kind }
    88  func (sb *SymbolBuilder) SetSize(size int64)         { sb.size = size }
    89  func (sb *SymbolBuilder) SetData(data []byte)        { sb.data = data }
    90  func (sb *SymbolBuilder) SetOnList(v bool)           { sb.l.SetAttrOnList(sb.symIdx, v) }
    91  func (sb *SymbolBuilder) SetExternal(v bool)         { sb.l.SetAttrExternal(sb.symIdx, v) }
    92  func (sb *SymbolBuilder) SetValue(v int64)           { sb.l.SetSymValue(sb.symIdx, v) }
    93  func (sb *SymbolBuilder) SetAlign(align int32)       { sb.l.SetSymAlign(sb.symIdx, align) }
    94  func (sb *SymbolBuilder) SetLocalentry(value uint8)  { sb.l.SetSymLocalentry(sb.symIdx, value) }
    95  func (sb *SymbolBuilder) SetExtname(value string)    { sb.l.SetSymExtname(sb.symIdx, value) }
    96  func (sb *SymbolBuilder) SetDynimplib(value string)  { sb.l.SetSymDynimplib(sb.symIdx, value) }
    97  func (sb *SymbolBuilder) SetDynimpvers(value string) { sb.l.SetSymDynimpvers(sb.symIdx, value) }
    98  func (sb *SymbolBuilder) SetPlt(value int32)         { sb.l.SetPlt(sb.symIdx, value) }
    99  func (sb *SymbolBuilder) SetGot(value int32)         { sb.l.SetGot(sb.symIdx, value) }
   100  func (sb *SymbolBuilder) SetSpecial(value bool)      { sb.l.SetAttrSpecial(sb.symIdx, value) }
   101  func (sb *SymbolBuilder) SetLocal(value bool)        { sb.l.SetAttrLocal(sb.symIdx, value) }
   102  func (sb *SymbolBuilder) SetVisibilityHidden(value bool) {
   103  	sb.l.SetAttrVisibilityHidden(sb.symIdx, value)
   104  }
   105  func (sb *SymbolBuilder) SetNotInSymbolTable(value bool) {
   106  	sb.l.SetAttrNotInSymbolTable(sb.symIdx, value)
   107  }
   108  func (sb *SymbolBuilder) SetSect(sect *sym.Section) { sb.l.SetSymSect(sb.symIdx, sect) }
   109  
   110  func (sb *SymbolBuilder) AddBytes(data []byte) {
   111  	if sb.kind == 0 {
   112  		sb.kind = sym.SDATA
   113  	}
   114  	sb.data = append(sb.data, data...)
   115  	sb.size = int64(len(sb.data))
   116  }
   117  
   118  func (sb *SymbolBuilder) Relocs() Relocs {
   119  	return sb.l.Relocs(sb.symIdx)
   120  }
   121  
   122  // ResetRelocs removes all relocations on this symbol.
   123  func (sb *SymbolBuilder) ResetRelocs() {
   124  	sb.relocs = sb.relocs[:0]
   125  }
   126  
   127  // SetRelocType sets the type of the 'i'-th relocation on this sym to 't'
   128  func (sb *SymbolBuilder) SetRelocType(i int, t objabi.RelocType) {
   129  	sb.relocs[i].SetType(uint16(t))
   130  }
   131  
   132  // SetRelocSym sets the target sym of the 'i'-th relocation on this sym to 's'
   133  func (sb *SymbolBuilder) SetRelocSym(i int, tgt Sym) {
   134  	sb.relocs[i].SetSym(goobj.SymRef{PkgIdx: 0, SymIdx: uint32(tgt)})
   135  }
   136  
   137  // SetRelocAdd sets the addend of the 'i'-th relocation on this sym to 'a'
   138  func (sb *SymbolBuilder) SetRelocAdd(i int, a int64) {
   139  	sb.relocs[i].SetAdd(a)
   140  }
   141  
   142  // SetRelocAdd sets the size of the 'i'-th relocation on this sym to 'sz'
   143  func (sb *SymbolBuilder) SetRelocSiz(i int, sz uint8) {
   144  	sb.relocs[i].SetSiz(sz)
   145  }
   146  
   147  // Add n relocations, return a handle to the relocations.
   148  func (sb *SymbolBuilder) AddRelocs(n int) Relocs {
   149  	sb.relocs = append(sb.relocs, make([]goobj.Reloc, n)...)
   150  	return sb.l.Relocs(sb.symIdx)
   151  }
   152  
   153  // Add a relocation with given type, return its handle and index
   154  // (to set other fields).
   155  func (sb *SymbolBuilder) AddRel(typ objabi.RelocType) (Reloc, int) {
   156  	j := len(sb.relocs)
   157  	sb.relocs = append(sb.relocs, goobj.Reloc{})
   158  	sb.relocs[j].SetType(uint16(typ))
   159  	relocs := sb.Relocs()
   160  	return relocs.At(j), j
   161  }
   162  
   163  // SortRelocs Sort relocations by offset.
   164  func (sb *SymbolBuilder) SortRelocs() {
   165  	slices.SortFunc(sb.extSymPayload.relocs, func(a, b goobj.Reloc) int {
   166  		return cmp.Compare(a.Off(), b.Off())
   167  	})
   168  }
   169  
   170  func (sb *SymbolBuilder) Reachable() bool {
   171  	return sb.l.AttrReachable(sb.symIdx)
   172  }
   173  
   174  func (sb *SymbolBuilder) SetReachable(v bool) {
   175  	sb.l.SetAttrReachable(sb.symIdx, v)
   176  }
   177  
   178  func (sb *SymbolBuilder) ReadOnly() bool {
   179  	return sb.l.AttrReadOnly(sb.symIdx)
   180  }
   181  
   182  func (sb *SymbolBuilder) SetReadOnly(v bool) {
   183  	sb.l.SetAttrReadOnly(sb.symIdx, v)
   184  }
   185  
   186  func (sb *SymbolBuilder) DuplicateOK() bool {
   187  	return sb.l.AttrDuplicateOK(sb.symIdx)
   188  }
   189  
   190  func (sb *SymbolBuilder) SetDuplicateOK(v bool) {
   191  	sb.l.SetAttrDuplicateOK(sb.symIdx, v)
   192  }
   193  
   194  func (sb *SymbolBuilder) Outer() Sym {
   195  	return sb.l.OuterSym(sb.symIdx)
   196  }
   197  
   198  func (sb *SymbolBuilder) Sub() Sym {
   199  	return sb.l.SubSym(sb.symIdx)
   200  }
   201  
   202  func (sb *SymbolBuilder) SortSub() {
   203  	sb.l.SortSub(sb.symIdx)
   204  }
   205  
   206  func (sb *SymbolBuilder) AddInteriorSym(sub Sym) {
   207  	sb.l.AddInteriorSym(sb.symIdx, sub)
   208  }
   209  
   210  func (sb *SymbolBuilder) AddUint8(v uint8) int64 {
   211  	off := sb.size
   212  	if sb.kind == 0 {
   213  		sb.kind = sym.SDATA
   214  	}
   215  	sb.size++
   216  	sb.data = append(sb.data, v)
   217  	return off
   218  }
   219  
   220  func (sb *SymbolBuilder) AddUintXX(arch *sys.Arch, v uint64, wid int) int64 {
   221  	off := sb.size
   222  	sb.setUintXX(arch, off, v, int64(wid))
   223  	return off
   224  }
   225  
   226  func (sb *SymbolBuilder) setUintXX(arch *sys.Arch, off int64, v uint64, wid int64) int64 {
   227  	if sb.kind == 0 {
   228  		sb.kind = sym.SDATA
   229  	}
   230  	if sb.size < off+wid {
   231  		sb.size = off + wid
   232  		sb.Grow(sb.size)
   233  	}
   234  
   235  	switch wid {
   236  	case 1:
   237  		sb.data[off] = uint8(v)
   238  	case 2:
   239  		arch.ByteOrder.PutUint16(sb.data[off:], uint16(v))
   240  	case 4:
   241  		arch.ByteOrder.PutUint32(sb.data[off:], uint32(v))
   242  	case 8:
   243  		arch.ByteOrder.PutUint64(sb.data[off:], v)
   244  	}
   245  
   246  	return off + wid
   247  }
   248  
   249  func (sb *SymbolBuilder) AddUint16(arch *sys.Arch, v uint16) int64 {
   250  	return sb.AddUintXX(arch, uint64(v), 2)
   251  }
   252  
   253  func (sb *SymbolBuilder) AddUint32(arch *sys.Arch, v uint32) int64 {
   254  	return sb.AddUintXX(arch, uint64(v), 4)
   255  }
   256  
   257  func (sb *SymbolBuilder) AddUint64(arch *sys.Arch, v uint64) int64 {
   258  	return sb.AddUintXX(arch, v, 8)
   259  }
   260  
   261  func (sb *SymbolBuilder) AddUint(arch *sys.Arch, v uint64) int64 {
   262  	return sb.AddUintXX(arch, v, arch.PtrSize)
   263  }
   264  
   265  func (sb *SymbolBuilder) SetUint8(arch *sys.Arch, r int64, v uint8) int64 {
   266  	return sb.setUintXX(arch, r, uint64(v), 1)
   267  }
   268  
   269  func (sb *SymbolBuilder) SetUint16(arch *sys.Arch, r int64, v uint16) int64 {
   270  	return sb.setUintXX(arch, r, uint64(v), 2)
   271  }
   272  
   273  func (sb *SymbolBuilder) SetUint32(arch *sys.Arch, r int64, v uint32) int64 {
   274  	return sb.setUintXX(arch, r, uint64(v), 4)
   275  }
   276  
   277  func (sb *SymbolBuilder) SetUint(arch *sys.Arch, r int64, v uint64) int64 {
   278  	return sb.setUintXX(arch, r, v, int64(arch.PtrSize))
   279  }
   280  
   281  func (sb *SymbolBuilder) SetUintptr(arch *sys.Arch, r int64, v uintptr) int64 {
   282  	return sb.setUintXX(arch, r, uint64(v), int64(arch.PtrSize))
   283  }
   284  
   285  func (sb *SymbolBuilder) SetAddrPlus(arch *sys.Arch, off int64, tgt Sym, add int64) int64 {
   286  	if sb.Type() == 0 {
   287  		sb.SetType(sym.SDATA)
   288  	}
   289  	if off+int64(arch.PtrSize) > sb.size {
   290  		sb.size = off + int64(arch.PtrSize)
   291  		sb.Grow(sb.size)
   292  	}
   293  	r, _ := sb.AddRel(objabi.R_ADDR)
   294  	r.SetSym(tgt)
   295  	r.SetOff(int32(off))
   296  	r.SetSiz(uint8(arch.PtrSize))
   297  	r.SetAdd(add)
   298  	return off + int64(r.Siz())
   299  }
   300  
   301  func (sb *SymbolBuilder) SetAddr(arch *sys.Arch, off int64, tgt Sym) int64 {
   302  	return sb.SetAddrPlus(arch, off, tgt, 0)
   303  }
   304  
   305  func (sb *SymbolBuilder) AddStringAt(off int64, str string) int64 {
   306  	strLen := int64(len(str))
   307  	if off+strLen > int64(len(sb.data)) {
   308  		panic("attempt to write past end of buffer")
   309  	}
   310  	copy(sb.data[off:off+strLen], str)
   311  	return off + strLen
   312  }
   313  
   314  // AddCStringAt adds str plus a null terminating byte.
   315  func (sb *SymbolBuilder) AddCStringAt(off int64, str string) int64 {
   316  	strLen := int64(len(str))
   317  	if off+strLen+1 > int64(len(sb.data)) {
   318  		panic("attempt to write past end of buffer")
   319  	}
   320  	copy(sb.data[off:off+strLen], str)
   321  	sb.data[off+strLen] = 0
   322  	return off + strLen + 1
   323  }
   324  
   325  func (sb *SymbolBuilder) Addstring(str string) int64 {
   326  	if sb.kind == 0 {
   327  		sb.kind = sym.SNOPTRDATA
   328  	}
   329  	r := sb.size
   330  	sb.data = append(sb.data, str...)
   331  	sb.data = append(sb.data, 0)
   332  	sb.size = int64(len(sb.data))
   333  	return r
   334  }
   335  
   336  func (sb *SymbolBuilder) SetBytesAt(off int64, b []byte) int64 {
   337  	datLen := int64(len(b))
   338  	if off+datLen > int64(len(sb.data)) {
   339  		panic("attempt to write past end of buffer")
   340  	}
   341  	copy(sb.data[off:off+datLen], b)
   342  	return off + datLen
   343  }
   344  
   345  func (sb *SymbolBuilder) addSymRef(tgt Sym, add int64, typ objabi.RelocType, rsize int) int64 {
   346  	if sb.kind == 0 {
   347  		sb.kind = sym.SDATA
   348  	}
   349  	i := sb.size
   350  
   351  	sb.size += int64(rsize)
   352  	sb.Grow(sb.size)
   353  
   354  	r, _ := sb.AddRel(typ)
   355  	r.SetSym(tgt)
   356  	r.SetOff(int32(i))
   357  	r.SetSiz(uint8(rsize))
   358  	r.SetAdd(add)
   359  
   360  	return i + int64(rsize)
   361  }
   362  
   363  // Add a symbol reference (relocation) with given type, addend, and size
   364  // (the most generic form).
   365  func (sb *SymbolBuilder) AddSymRef(arch *sys.Arch, tgt Sym, add int64, typ objabi.RelocType, rsize int) int64 {
   366  	return sb.addSymRef(tgt, add, typ, rsize)
   367  }
   368  
   369  func (sb *SymbolBuilder) AddAddrPlus(arch *sys.Arch, tgt Sym, add int64) int64 {
   370  	return sb.addSymRef(tgt, add, objabi.R_ADDR, arch.PtrSize)
   371  }
   372  
   373  func (sb *SymbolBuilder) AddAddrPlus4(arch *sys.Arch, tgt Sym, add int64) int64 {
   374  	return sb.addSymRef(tgt, add, objabi.R_ADDR, 4)
   375  }
   376  
   377  func (sb *SymbolBuilder) AddAddr(arch *sys.Arch, tgt Sym) int64 {
   378  	return sb.AddAddrPlus(arch, tgt, 0)
   379  }
   380  
   381  func (sb *SymbolBuilder) AddPEImageRelativeAddrPlus(arch *sys.Arch, tgt Sym, add int64) int64 {
   382  	return sb.addSymRef(tgt, add, objabi.R_PEIMAGEOFF, 4)
   383  }
   384  
   385  func (sb *SymbolBuilder) AddPCRelPlus(arch *sys.Arch, tgt Sym, add int64) int64 {
   386  	return sb.addSymRef(tgt, add, objabi.R_PCREL, 4)
   387  }
   388  
   389  func (sb *SymbolBuilder) AddCURelativeAddrPlus(arch *sys.Arch, tgt Sym, add int64) int64 {
   390  	return sb.addSymRef(tgt, add, objabi.R_ADDRCUOFF, arch.PtrSize)
   391  }
   392  
   393  func (sb *SymbolBuilder) AddSize(arch *sys.Arch, tgt Sym) int64 {
   394  	return sb.addSymRef(tgt, 0, objabi.R_SIZE, arch.PtrSize)
   395  }
   396  
   397  // GenAddAddrPlusFunc returns a function to be called when capturing
   398  // a function symbol's address. In later stages of the link (when
   399  // address assignment is done) when doing internal linking and
   400  // targeting an executable, we can just emit the address of a function
   401  // directly instead of generating a relocation. Clients can call
   402  // this function (setting 'internalExec' based on build mode and target)
   403  // and then invoke the returned function in roughly the same way that
   404  // loader.*SymbolBuilder.AddAddrPlus would be used.
   405  func GenAddAddrPlusFunc(internalExec bool) func(s *SymbolBuilder, arch *sys.Arch, tgt Sym, add int64) int64 {
   406  	if internalExec {
   407  		return func(s *SymbolBuilder, arch *sys.Arch, tgt Sym, add int64) int64 {
   408  			if v := s.l.SymValue(tgt); v != 0 {
   409  				return s.AddUint(arch, uint64(v+add))
   410  			}
   411  			return s.AddAddrPlus(arch, tgt, add)
   412  		}
   413  	} else {
   414  		return (*SymbolBuilder).AddAddrPlus
   415  	}
   416  }
   417  
   418  func (sb *SymbolBuilder) MakeWritable() {
   419  	if sb.ReadOnly() {
   420  		sb.data = append([]byte(nil), sb.data...)
   421  		sb.l.SetAttrReadOnly(sb.symIdx, false)
   422  	}
   423  }
   424  
   425  func (sb *SymbolBuilder) AddUleb(v uint64) {
   426  	if v < 128 { // common case: 1 byte
   427  		sb.AddUint8(uint8(v))
   428  		return
   429  	}
   430  	for {
   431  		c := uint8(v & 0x7f)
   432  		v >>= 7
   433  		if v != 0 {
   434  			c |= 0x80
   435  		}
   436  		sb.AddUint8(c)
   437  		if c&0x80 == 0 {
   438  			break
   439  		}
   440  	}
   441  }
   442
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