sym

package standard library
go1.15rc1 Latest Latest
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 Go to latest Published: Jul 24, 2020 License: BSD-3-Clause Imports: 10 Imported by: 0

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Index

Constants

View Source 
const (
	SymVerABI0        = 0
	SymVerABIInternal = 1
	SymVerStatic      = 10 // Minimum version used by static (file-local) syms
)

Variables

View Source 
var AbiSymKindToSymKind = [...]SymKind{
	Sxxx,
	STEXT,
	SRODATA,
	SNOPTRDATA,
	SDATA,
	SBSS,
	SNOPTRBSS,
	STLSBSS,
	SDWARFINFO,
	SDWARFRANGE,
	SDWARFLOC,
	SDWARFLINES,
	SABIALIAS,
	SLIBFUZZER_EXTRA_COUNTER,
}

AbiSymKindToSymKind maps values read from object files (which are of type cmd/internal/objabi.SymKind) to values of type SymKind.

View Source 
var ReadOnly = []SymKind{
	STYPE,
	SSTRING,
	SGOSTRING,
	SGOFUNC,
	SGCBITS,
	SRODATA,
	SFUNCTAB,
}

ReadOnly are the symbol kinds that form read-only sections. In some cases, if they will require relocations, they are transformed into rel-ro sections using relROMap.

View Source 
var RelROMap = map[SymKind]SymKind{
	STYPE:     STYPERELRO,
	SSTRING:   SSTRINGRELRO,
	SGOSTRING: SGOSTRINGRELRO,
	SGOFUNC:   SGOFUNCRELRO,
	SGCBITS:   SGCBITSRELRO,
	SRODATA:   SRODATARELRO,
	SFUNCTAB:  SFUNCTABRELRO,
}

RelROMap describes the transformation of read-only symbols to rel-ro symbols.

Functions

func ABIToVersion added in go1.12 

func ABIToVersion(abi obj.ABI) int

func RelocName 

func RelocName(arch *sys.Arch, r objabi.RelocType) string

func VersionToABI added in go1.12 

func VersionToABI(v int) (obj.ABI, bool)

Types

type Attribute 

type Attribute int32

Attribute is a set of common symbol attributes. 

const (
	// AttrDuplicateOK marks a symbol that can be present in multiple object
	// files.
	AttrDuplicateOK Attribute = 1 << iota
	// AttrExternal marks function symbols loaded from host object files.
	AttrExternal
	// AttrNoSplit marks functions that cannot split the stack; the linker
	// cares because it checks that there are no call chains of nosplit
	// functions that require more than StackLimit bytes (see
	// lib.go:dostkcheck)
	AttrNoSplit
	// AttrReachable marks symbols that are transitively referenced from the
	// entry points. Unreachable symbols are not written to the output.
	AttrReachable
	// AttrCgoExportDynamic and AttrCgoExportStatic mark symbols referenced
	// by directives written by cgo (in response to //export directives in
	// the source).
	AttrCgoExportDynamic
	AttrCgoExportStatic
	// AttrSpecial marks symbols that do not have their address (i.e. Value)
	// computed by the usual mechanism of data.go:dodata() &
	// data.go:address().
	AttrSpecial
	// AttrStackCheck is used by dostkcheck to only check each NoSplit
	// function's stack usage once.
	AttrStackCheck
	// AttrNotInSymbolTable marks symbols that are not written to the symbol table.
	AttrNotInSymbolTable
	// AttrOnList marks symbols that are on some list (such as the list of
	// all text symbols, or one of the lists of data symbols) and is
	// consulted to avoid bugs where a symbol is put on a list twice.
	AttrOnList
	// AttrLocal marks symbols that are only visible within the module
	// (executable or shared library) being linked. Only relevant when
	// dynamically linking Go code.
	AttrLocal
	// AttrReflectMethod marks certain methods from the reflect package that
	// can be used to call arbitrary methods. If no symbol with this bit set
	// is marked as reachable, more dead code elimination can be done.
	AttrReflectMethod
	// AttrMakeTypelink Amarks types that should be added to the typelink
	// table. See typelinks.go:typelinks().
	AttrMakeTypelink
	// AttrShared marks symbols compiled with the -shared option.
	AttrShared
	// AttrVisibilityHidden symbols are ELF symbols with
	// visibility set to STV_HIDDEN. They become local symbols in
	// the final executable. Only relevant when internally linking
	// on an ELF platform.
	AttrVisibilityHidden
	// AttrSubSymbol mostly means that the symbol appears on the Sub list of some
	// other symbol.  Unfortunately, it's not 100% reliable; at least, it's not set
	// correctly for the .TOC. symbol in Link.dodata.  Usually the Outer field of the
	// symbol points to the symbol whose list it is on, but that it is not set for the
	// symbols added to .windynamic in initdynimport in pe.go.
	//
	// TODO(mwhudson): fix the inconsistencies noticed above.
	//
	// Sub lists are used when loading host objects (sections from the host object
	// become regular linker symbols and symbols go on the Sub list of their section)
	// and for constructing the global offset table when internally linking a dynamic
	// executable.
	//
	// TODO(mwhudson): perhaps a better name for this is AttrNonGoSymbol.
	AttrSubSymbol
	// AttrContainer is set on text symbols that are present as the .Outer for some
	// other symbol.
	AttrContainer
	// AttrTopFrame means that the function is an entry point and unwinders
	// should stop when they hit this function.
	AttrTopFrame
	// AttrReadOnly indicates whether the symbol's content (Symbol.P) is backed by
	// read-only memory.
	AttrReadOnly
)

func (*Attribute) CgoExport 

func (a *Attribute) CgoExport() bool

func (*Attribute) CgoExportDynamic 

func (a *Attribute) CgoExportDynamic() bool

func (*Attribute) CgoExportStatic 

func (a *Attribute) CgoExportStatic() bool

func (*Attribute) Container 

func (a *Attribute) Container() bool

func (*Attribute) DuplicateOK 

func (a *Attribute) DuplicateOK() bool

func (*Attribute) External 

func (a *Attribute) External() bool

func (*Attribute) Local 

func (a *Attribute) Local() bool
func (a *Attribute) MakeTypelink() bool

func (*Attribute) NoSplit 

func (a *Attribute) NoSplit() bool

func (*Attribute) NotInSymbolTable 

func (a *Attribute) NotInSymbolTable() bool

func (*Attribute) OnList 

func (a *Attribute) OnList() bool

func (*Attribute) Reachable 

func (a *Attribute) Reachable() bool

func (*Attribute) ReadOnly added in go1.13 

func (a *Attribute) ReadOnly() bool

func (*Attribute) ReflectMethod 

func (a *Attribute) ReflectMethod() bool

func (*Attribute) Set 

func (a *Attribute) Set(flag Attribute, value bool)

func (*Attribute) Shared 

func (a *Attribute) Shared() bool

func (*Attribute) Special 

func (a *Attribute) Special() bool

func (*Attribute) StackCheck 

func (a *Attribute) StackCheck() bool

func (*Attribute) SubSymbol 

func (a *Attribute) SubSymbol() bool

func (*Attribute) TopFrame added in go1.13 

func (a *Attribute) TopFrame() bool

func (*Attribute) VisibilityHidden 

func (a *Attribute) VisibilityHidden() bool

type AuxSymbol added in go1.12 

type AuxSymbol struct {
	// contains filtered or unexported fields
}

AuxSymbol contains less-frequently used sym.Symbol fields.

type CompilationUnit added in go1.14 

type CompilationUnit struct {
	Pkg            string        // The package name, eg ("fmt", or "runtime")
	Lib            *Library      // Our library
	Consts         *Symbol       // Package constants DIEs
	PCs            []dwarf.Range // PC ranges, relative to Textp[0]
	DWInfo         *dwarf.DWDie  // CU root DIE
	FuncDIEs       []*Symbol     // Function DIE subtrees
	AbsFnDIEs      []*Symbol     // Abstract function DIE subtrees
	RangeSyms      []*Symbol     // Symbols for debug_range
	Textp          []*Symbol     // Text symbols in this CU
	DWARFFileTable []string      // The file table used to generate the .debug_lines

	Consts2    LoaderSym   // Package constants DIEs (loader)
	FuncDIEs2  []LoaderSym // Function DIE subtrees (loader)
	AbsFnDIEs2 []LoaderSym // Abstract function DIE subtrees (loader)
	RangeSyms2 []LoaderSym // Symbols for debug_range (loader)
	Textp2     []LoaderSym // Text symbols in this CU (loader)
}

CompilationUnit is an abstraction used by DWARF to represent a chunk of debug-related data. We create a CompilationUnit per Object file in a library (so, one for all the Go code, one for each assembly file, etc.).

type Library 

type Library struct {
	Objref      string
	Srcref      string
	File        string
	Pkg         string
	Shlib       string
	Hash        string
	Fingerprint goobj2.FingerprintType
	Autolib     []goobj2.ImportedPkg
	Imports     []*Library
	Main        bool
	Safe        bool
	Units       []*CompilationUnit

	Textp2       []LoaderSym // text syms defined in this library
	DupTextSyms2 []LoaderSym // dupok text syms defined in this library
}

func (Library) String 

func (l Library) String() string

type LoaderSym added in go1.15 

type LoaderSym int

LoaderSym holds a loader.Sym value. We can't refer to this type from the sym package since loader imports sym.

type Pcdata 

type Pcdata struct {
	P []byte
}

type Reloc 

type Reloc struct {
	Off       int32            // offset to rewrite
	Siz       uint8            // number of bytes to rewrite, 1, 2, or 4
	Done      bool             // set to true when relocation is complete
	Type      objabi.RelocType // the relocation type
	Add       int64            // addend
	Sym       *Symbol          // symbol the relocation addresses
	*RelocExt                  // extra fields (see below), may be nil, call InitExt before use
}

Reloc is a relocation.

The typical Reloc rewrites part of a symbol at offset Off to address Sym. A Reloc is stored in a slice on the Symbol it rewrites.

Relocations are generated by the compiler as the type cmd/internal/obj.Reloc, which is encoded into the object file wire format and decoded by the linker into this type. A separate type is used to hold linker-specific state about the relocation.

Some relocations are created by cmd/link.

func (*Reloc) InitExt added in go1.13 

func (r *Reloc) InitExt()

type RelocByOff 

type RelocByOff []Reloc

RelocByOff implements sort.Interface for sorting relocations by offset.

func (RelocByOff) Len 

func (x RelocByOff) Len() int

func (RelocByOff) Less 

func (x RelocByOff) Less(i, j int) bool

func (RelocByOff) Swap 

func (x RelocByOff) Swap(i, j int)

type RelocExt added in go1.15 

type RelocExt struct {
	Xadd    int64        // addend passed to external linker
	Xsym    *Symbol      // symbol passed to external linker
	Variant RelocVariant // variation on Type, currently used only on PPC64 and S390X
}

relocExt contains extra fields in Reloc that are used only in certain cases.

type RelocVariant 

type RelocVariant uint8

RelocVariant is a linker-internal variation on a relocation. 

const (
	RV_NONE RelocVariant = iota
	RV_POWER_LO
	RV_POWER_HI
	RV_POWER_HA
	RV_POWER_DS

	// RV_390_DBL is a s390x-specific relocation variant that indicates that
	// the value to be placed into the relocatable field should first be
	// divided by 2.
	RV_390_DBL

	RV_CHECK_OVERFLOW RelocVariant = 1 << 7
	RV_TYPE_MASK      RelocVariant = RV_CHECK_OVERFLOW - 1
)

type Section 

type Section struct {
	Rwx     uint8
	Extnum  int16
	Align   int32
	Name    string
	Vaddr   uint64
	Length  uint64
	Seg     *Segment
	Elfsect interface{} // an *ld.ElfShdr
	Reloff  uint64
	Rellen  uint64
	Sym     *Symbol   // symbol for the section, if any
	Sym2    LoaderSym // symbol for the section, if any
	Index   uint16    // each section has a unique index, used internally
}

type Segment 

type Segment struct {
	Rwx      uint8  // permission as usual unix bits (5 = r-x etc)
	Vaddr    uint64 // virtual address
	Length   uint64 // length in memory
	Fileoff  uint64 // file offset
	Filelen  uint64 // length on disk
	Sections []*Section
}

type SymKind 

type SymKind uint8

A SymKind describes the kind of memory represented by a symbol. 

const (
	Sxxx SymKind = iota
	STEXT
	SELFRXSECT

	// Read-only sections.
	STYPE
	SSTRING
	SGOSTRING
	SGOFUNC
	SGCBITS
	SRODATA
	SFUNCTAB

	SELFROSECT
	SMACHOPLT

	// Read-only sections with relocations.
	//
	// Types STYPE-SFUNCTAB above are written to the .rodata section by default.
	// When linking a shared object, some conceptually "read only" types need to
	// be written to by relocations and putting them in a section called
	// ".rodata" interacts poorly with the system linkers. The GNU linkers
	// support this situation by arranging for sections of the name
	// ".data.rel.ro.XXX" to be mprotected read only by the dynamic linker after
	// relocations have applied, so when the Go linker is creating a shared
	// object it checks all objects of the above types and bumps any object that
	// has a relocation to it to the corresponding type below, which are then
	// written to sections with appropriate magic names.
	STYPERELRO
	SSTRINGRELRO
	SGOSTRINGRELRO
	SGOFUNCRELRO
	SGCBITSRELRO
	SRODATARELRO
	SFUNCTABRELRO

	// Part of .data.rel.ro if it exists, otherwise part of .rodata.
	STYPELINK
	SITABLINK
	SSYMTAB
	SPCLNTAB

	// Writable sections.
	SFirstWritable
	SBUILDINFO
	SELFSECT
	SMACHO
	SMACHOGOT
	SWINDOWS
	SELFGOT
	SNOPTRDATA
	SINITARR
	SDATA
	SXCOFFTOC
	SBSS
	SNOPTRBSS
	SLIBFUZZER_EXTRA_COUNTER
	STLSBSS
	SXREF
	SMACHOSYMSTR
	SMACHOSYMTAB
	SMACHOINDIRECTPLT
	SMACHOINDIRECTGOT
	SFILEPATH
	SCONST
	SDYNIMPORT
	SHOSTOBJ
	SUNDEFEXT // Undefined symbol for resolution by external linker

	// Sections for debugging information
	SDWARFSECT
	SDWARFINFO
	SDWARFRANGE
	SDWARFLOC
	SDWARFLINES

	// ABI aliases (these never appear in the output)
	SABIALIAS
)

Defined SymKind values.

TODO(rsc): Give idiomatic Go names.

func (SymKind) IsData added in go1.14 

func (t SymKind) IsData() bool

IsData returns true if the type is a data type.

func (SymKind) String 

func (i SymKind) String() string

type Symbol 

type Symbol struct {
	Name    string
	Type    SymKind
	Version int16
	Attr    Attribute
	Dynid   int32
	Align   int32
	Value   int64
	Size    int64
	Outer   *Symbol
	SymIdx  LoaderSym

	Sect *Section
	// P contains the raw symbol data.
	P []byte
	R []Reloc
	// contains filtered or unexported fields
}

Symbol is an entry in the symbol table.

func (*Symbol) AddAddr 

func (s *Symbol) AddAddr(arch *sys.Arch, t *Symbol) int64

func (*Symbol) AddAddrPlus 

func (s *Symbol) AddAddrPlus(arch *sys.Arch, t *Symbol, add int64) int64

func (*Symbol) AddAddrPlus4 

func (s *Symbol) AddAddrPlus4(t *Symbol, add int64) int64

func (*Symbol) AddBytes 

func (s *Symbol) AddBytes(bytes []byte) int64

func (*Symbol) AddCURelativeAddrPlus 

func (s *Symbol) AddCURelativeAddrPlus(arch *sys.Arch, t *Symbol, add int64) int64

func (*Symbol) AddPCRelPlus 

func (s *Symbol) AddPCRelPlus(arch *sys.Arch, t *Symbol, add int64) int64

func (*Symbol) AddRel 

func (s *Symbol) AddRel() *Reloc

func (*Symbol) AddSize 

func (s *Symbol) AddSize(arch *sys.Arch, t *Symbol) int64

func (*Symbol) AddUint 

func (s *Symbol) AddUint(arch *sys.Arch, v uint64) int64

func (*Symbol) AddUint16 

func (s *Symbol) AddUint16(arch *sys.Arch, v uint16) int64

func (*Symbol) AddUint32 

func (s *Symbol) AddUint32(arch *sys.Arch, v uint32) int64

func (*Symbol) AddUint64 

func (s *Symbol) AddUint64(arch *sys.Arch, v uint64) int64

func (*Symbol) AddUint8 

func (s *Symbol) AddUint8(v uint8) int64

func (*Symbol) AddUintXX 

func (s *Symbol) AddUintXX(arch *sys.Arch, v uint64, wid int) int64

func (*Symbol) Dynimplib 

func (s *Symbol) Dynimplib() string

func (*Symbol) Dynimpvers 

func (s *Symbol) Dynimpvers() string

func (*Symbol) ElfType 

func (s *Symbol) ElfType() elf.SymType

func (*Symbol) Extname 

func (s *Symbol) Extname() string

func (*Symbol) Got 

func (s *Symbol) Got() int32

func (*Symbol) Grow 

func (s *Symbol) Grow(siz int64)

func (*Symbol) IsFileLocal added in go1.12 

func (s *Symbol) IsFileLocal() bool

func (*Symbol) Len 

func (s *Symbol) Len() int64

func (*Symbol) Length added in go1.15 

func (s *Symbol) Length(dwarfContext interface{}) int64

func (*Symbol) Localentry 

func (s *Symbol) Localentry() uint8

func (*Symbol) Plt 

func (s *Symbol) Plt() int32

func (*Symbol) ResetDyninfo added in go1.11 

func (s *Symbol) ResetDyninfo()

func (*Symbol) SetAddr 

func (s *Symbol) SetAddr(arch *sys.Arch, off int64, t *Symbol) int64

func (*Symbol) SetAddrPlus 

func (s *Symbol) SetAddrPlus(arch *sys.Arch, off int64, t *Symbol, add int64) int64

func (*Symbol) SetDynimplib added in go1.11 

func (s *Symbol) SetDynimplib(lib string)

func (*Symbol) SetDynimpvers added in go1.11 

func (s *Symbol) SetDynimpvers(vers string)

func (*Symbol) SetElfType added in go1.12 

func (s *Symbol) SetElfType(val elf.SymType)

func (*Symbol) SetExtname added in go1.12 

func (s *Symbol) SetExtname(n string)

func (*Symbol) SetGot added in go1.12 

func (s *Symbol) SetGot(val int32)

func (*Symbol) SetLocalentry added in go1.12 

func (s *Symbol) SetLocalentry(val uint8)

func (*Symbol) SetPlt added in go1.12 

func (s *Symbol) SetPlt(val int32)

func (*Symbol) SetUint 

func (s *Symbol) SetUint(arch *sys.Arch, r int64, v uint64) int64

func (*Symbol) SetUint16 added in go1.12 

func (s *Symbol) SetUint16(arch *sys.Arch, r int64, v uint16) int64

func (*Symbol) SetUint32 

func (s *Symbol) SetUint32(arch *sys.Arch, r int64, v uint32) int64

func (*Symbol) SetUint8 

func (s *Symbol) SetUint8(arch *sys.Arch, r int64, v uint8) int64

func (*Symbol) String 

func (s *Symbol) String() string

type Symbols 

type Symbols struct {

	// Look up the symbol with the given name and version, creating the
	// symbol if it is not found.
	Lookup func(name string, v int) *Symbol

	// Look up the symbol with the given name and version, returning nil
	// if it is not found.
	ROLookup func(name string, v int) *Symbol
	// contains filtered or unexported fields
}

func NewSymbols 

func NewSymbols() *Symbols

func (*Symbols) IncVersion 

func (syms *Symbols) IncVersion() int

Allocate a new version (i.e. symbol namespace).

func (*Symbols) MaxVersion added in go1.15 

func (syms *Symbols) MaxVersion() int

returns the maximum version number

Source Files

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