Source file src/cmd/link/internal/ld/link.go
Documentation: cmd/link/internal/ld
1 // Derived from Inferno utils/6l/l.h and related files. 2 // https://bitbucket.org/inferno-os/inferno-os/src/master/utils/6l/l.h 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 "bufio" 35 "cmd/internal/objabi" 36 "cmd/internal/sys" 37 "cmd/link/internal/loader" 38 "cmd/link/internal/sym" 39 "debug/elf" 40 "fmt" 41 ) 42 43 type Shlib struct { 44 Path string 45 Hash []byte 46 Deps []string 47 File *elf.File 48 } 49 50 // Link holds the context for writing object code from a compiler 51 // or for reading that input into the linker. 52 type Link struct { 53 Target 54 ErrorReporter 55 ArchSyms 56 57 outSem chan int // limits the number of output writers 58 Out *OutBuf 59 60 version int // current version number for static/file-local symbols 61 62 Debugvlog int 63 Bso *bufio.Writer 64 65 Loaded bool // set after all inputs have been loaded as symbols 66 67 compressDWARF bool 68 69 Libdir []string 70 Library []*sym.Library 71 LibraryByPkg map[string]*sym.Library 72 Shlibs []Shlib 73 Textp []loader.Sym 74 Moduledata loader.Sym 75 76 PackageFile map[string]string 77 PackageShlib map[string]string 78 79 tramps []loader.Sym // trampolines 80 81 compUnits []*sym.CompilationUnit // DWARF compilation units 82 runtimeCU *sym.CompilationUnit // One of the runtime CUs, the last one seen. 83 84 loader *loader.Loader 85 cgodata []cgodata // cgo directives to load, three strings are args for loadcgo 86 87 cgo_export_static map[string]bool 88 cgo_export_dynamic map[string]bool 89 90 datap []loader.Sym 91 dynexp []loader.Sym 92 93 // Elf symtab variables. 94 numelfsym int // starts at 0, 1 is reserved 95 96 // These are symbols that created and written by the linker. 97 // Rather than creating a symbol, and writing all its data into the heap, 98 // you can create a symbol, and just a generation function will be called 99 // after the symbol's been created in the output mmap. 100 generatorSyms map[loader.Sym]generatorFunc 101 } 102 103 type cgodata struct { 104 file string 105 pkg string 106 directives [][]string 107 } 108 109 // The smallest possible offset from the hardware stack pointer to a local 110 // variable on the stack. Architectures that use a link register save its value 111 // on the stack in the function prologue and so always have a pointer between 112 // the hardware stack pointer and the local variable area. 113 func (ctxt *Link) FixedFrameSize() int64 { 114 switch ctxt.Arch.Family { 115 case sys.AMD64, sys.I386: 116 return 0 117 case sys.PPC64: 118 // PIC code on ppc64le requires 32 bytes of stack, and it's easier to 119 // just use that much stack always on ppc64x. 120 return int64(4 * ctxt.Arch.PtrSize) 121 default: 122 return int64(ctxt.Arch.PtrSize) 123 } 124 } 125 126 func (ctxt *Link) Logf(format string, args ...interface{}) { 127 fmt.Fprintf(ctxt.Bso, format, args...) 128 ctxt.Bso.Flush() 129 } 130 131 func addImports(ctxt *Link, l *sym.Library, pn string) { 132 pkg := objabi.PathToPrefix(l.Pkg) 133 for _, imp := range l.Autolib { 134 lib := addlib(ctxt, pkg, pn, imp.Pkg, imp.Fingerprint) 135 if lib != nil { 136 l.Imports = append(l.Imports, lib) 137 } 138 } 139 l.Autolib = nil 140 } 141 142 // Allocate a new version (i.e. symbol namespace). 143 func (ctxt *Link) IncVersion() int { 144 ctxt.version++ 145 return ctxt.version - 1 146 } 147 148 // returns the maximum version number 149 func (ctxt *Link) MaxVersion() int { 150 return ctxt.version 151 } 152 153 // generatorFunc is a convenience type. 154 // Linker created symbols that are large, and shouldn't really live in the 155 // heap can define a generator function, and their bytes can be generated 156 // directly in the output mmap. 157 // 158 // Generator symbols shouldn't grow the symbol size, and might be called in 159 // parallel in the future. 160 // 161 // Generator Symbols have their Data set to the mmapped area when the 162 // generator is called. 163 type generatorFunc func(*Link, loader.Sym) 164 165 // createGeneratorSymbol is a convenience method for creating a generator 166 // symbol. 167 func (ctxt *Link) createGeneratorSymbol(name string, version int, t sym.SymKind, size int64, gen generatorFunc) loader.Sym { 168 ldr := ctxt.loader 169 s := ldr.LookupOrCreateSym(name, version) 170 ldr.SetIsGeneratedSym(s, true) 171 sb := ldr.MakeSymbolUpdater(s) 172 sb.SetType(t) 173 sb.SetSize(size) 174 ctxt.generatorSyms[s] = gen 175 return s 176 } 177