link.go

     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/link/internal/loader"
    37  	"cmd/link/internal/sym"
    38  	"debug/elf"
    39  	"fmt"
    40  )
    41  
    42  type Shlib struct {
    43  	Path string
    44  	Hash []byte
    45  	Deps []string
    46  	File *elf.File
    47  }
    48  
    49  // Link holds the context for writing object code from a compiler
    50  // or for reading that input into the linker.
    51  type Link struct {
    52  	Target
    53  	ErrorReporter
    54  	ArchSyms
    55  
    56  	outSem chan int // limits the number of output writers
    57  	Out    *OutBuf
    58  
    59  	version int // current version number for static/file-local symbols
    60  
    61  	Debugvlog int
    62  	Bso       *bufio.Writer
    63  
    64  	Loaded bool // set after all inputs have been loaded as symbols
    65  
    66  	compressDWARF bool
    67  
    68  	Libdir       []string
    69  	Library      []*sym.Library
    70  	LibraryByPkg map[string]*sym.Library
    71  	Shlibs       []Shlib
    72  	Textp        []loader.Sym
    73  	Moduledata   loader.Sym
    74  
    75  	PackageFile  map[string]string
    76  	PackageShlib map[string]string
    77  
    78  	tramps []loader.Sym // trampolines
    79  
    80  	compUnits []*sym.CompilationUnit // DWARF compilation units
    81  	runtimeCU *sym.CompilationUnit   // One of the runtime CUs, the last one seen.
    82  
    83  	loader  *loader.Loader
    84  	cgodata []cgodata // cgo directives to load, three strings are args for loadcgo
    85  
    86  	datap  []loader.Sym
    87  	dynexp []loader.Sym
    88  
    89  	// Elf symtab variables.
    90  	numelfsym int // starts at 0, 1 is reserved
    91  
    92  	// These are symbols that created and written by the linker.
    93  	// Rather than creating a symbol, and writing all its data into the heap,
    94  	// you can create a symbol, and just a generation function will be called
    95  	// after the symbol's been created in the output mmap.
    96  	generatorSyms map[loader.Sym]generatorFunc
    97  }
    98  
    99  type cgodata struct {
   100  	file       string
   101  	pkg        string
   102  	directives [][]string
   103  }
   104  
   105  func (ctxt *Link) Logf(format string, args ...interface{}) {
   106  	fmt.Fprintf(ctxt.Bso, format, args...)
   107  	ctxt.Bso.Flush()
   108  }
   109  
   110  func addImports(ctxt *Link, l *sym.Library, pn string) {
   111  	pkg := objabi.PathToPrefix(l.Pkg)
   112  	for _, imp := range l.Autolib {
   113  		lib := addlib(ctxt, pkg, pn, imp.Pkg, imp.Fingerprint)
   114  		if lib != nil {
   115  			l.Imports = append(l.Imports, lib)
   116  		}
   117  	}
   118  	l.Autolib = nil
   119  }
   120  
   121  // Allocate a new version (i.e. symbol namespace).
   122  func (ctxt *Link) IncVersion() int {
   123  	ctxt.version++
   124  	return ctxt.version - 1
   125  }
   126  
   127  // returns the maximum version number
   128  func (ctxt *Link) MaxVersion() int {
   129  	return ctxt.version
   130  }
   131  
   132  // generatorFunc is a convenience type.
   133  // Some linker-created Symbols are large and shouldn't really live in the heap.
   134  // Such Symbols can define a generator function. Their bytes can be generated
   135  // directly in the output mmap.
   136  //
   137  // Relocations are applied prior to emitting generator Symbol contents.
   138  // Generator Symbols that require relocations can be written in two passes.
   139  // The first pass, at Symbol creation time, adds only relocations.
   140  // The second pass, at content generation time, adds the rest.
   141  // See generateFunctab for an example.
   142  //
   143  // Generator functions shouldn't grow the Symbol size.
   144  // Generator functions must be safe for concurrent use.
   145  //
   146  // Generator Symbols have their Data set to the mmapped area when the
   147  // generator is called.
   148  type generatorFunc func(*Link, loader.Sym)
   149  
   150  // createGeneratorSymbol is a convenience method for creating a generator
   151  // symbol.
   152  func (ctxt *Link) createGeneratorSymbol(name string, version int, t sym.SymKind, size int64, gen generatorFunc) loader.Sym {
   153  	ldr := ctxt.loader
   154  	s := ldr.LookupOrCreateSym(name, version)
   155  	ldr.SetIsGeneratedSym(s, true)
   156  	sb := ldr.MakeSymbolUpdater(s)
   157  	sb.SetType(t)
   158  	sb.SetSize(size)
   159  	ctxt.generatorSyms[s] = gen
   160  	return s
   161  }
   162
View as plain text