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  	// For every symbol defined in the shared library, record its address
    48  	// in the original shared library address space.
    49  	symAddr map[string]uint64
    50  	// For relocations in the shared library, map from the address
    51  	// (in the shared library address space) at which that
    52  	// relocation applies to the target symbol.  We only keep
    53  	// track of a single kind of relocation: a standard absolute
    54  	// address relocation with no addend. These were R_ADDR
    55  	// relocations when the shared library was built.
    56  	relocTarget map[uint64]string
    57  }
    58  
    59  // A relocation that applies to part of the shared library.
    60  type shlibReloc struct {
    61  	// Address (in the shared library address space) the relocation applies to.
    62  	addr uint64
    63  	// Target symbol name.
    64  	target string
    65  }
    66  
    67  type shlibRelocs []shlibReloc
    68  
    69  func (s shlibRelocs) Len() int           { return len(s) }
    70  func (s shlibRelocs) Swap(i, j int)      { s[i], s[j] = s[j], s[i] }
    71  func (s shlibRelocs) Less(i, j int) bool { return s[i].addr < s[j].addr }
    72  
    73  // Link holds the context for writing object code from a compiler
    74  // or for reading that input into the linker.
    75  type Link struct {
    76  	Target
    77  	ErrorReporter
    78  	ArchSyms
    79  
    80  	outSem chan int // limits the number of output writers
    81  	Out    *OutBuf
    82  
    83  	version int // current version number for static/file-local symbols
    84  
    85  	Debugvlog int
    86  	Bso       *bufio.Writer
    87  
    88  	Loaded bool // set after all inputs have been loaded as symbols
    89  
    90  	compressDWARF bool
    91  
    92  	Libdir       []string
    93  	Library      []*sym.Library
    94  	LibraryByPkg map[string]*sym.Library
    95  	Shlibs       []Shlib
    96  	Textp        []loader.Sym
    97  	Moduledata   loader.Sym
    98  
    99  	moduledataTypeDescOffset int64
   100  	moduledataItabOffset     int64
   101  	moduledataItabSizeOffset int64
   102  
   103  	PackageFile  map[string]string
   104  	PackageShlib map[string]string
   105  
   106  	tramps           []loader.Sym      // trampolines
   107  	dwarfTrampolines []dwarfTrampoline // trampolines with statically addressable targets
   108  
   109  	compUnits []*sym.CompilationUnit // DWARF compilation units
   110  	runtimeCU *sym.CompilationUnit   // One of the runtime CUs, the last one seen.
   111  
   112  	loader  *loader.Loader
   113  	cgodata []cgodata // cgo directives to load, three strings are args for loadcgo
   114  
   115  	datap  []loader.Sym
   116  	dynexp []loader.Sym
   117  
   118  	// Elf symtab variables.
   119  	numelfsym int // starts at 0, 1 is reserved
   120  
   121  	// These are symbols that created and written by the linker.
   122  	// Rather than creating a symbol, and writing all its data into the heap,
   123  	// you can create a symbol, and just a generation function will be called
   124  	// after the symbol's been created in the output mmap.
   125  	generatorSyms map[loader.Sym]generatorFunc
   126  }
   127  
   128  type cgodata struct {
   129  	file       string
   130  	pkg        string
   131  	directives [][]string
   132  }
   133  
   134  func (ctxt *Link) Logf(format string, args ...any) {
   135  	fmt.Fprintf(ctxt.Bso, format, args...)
   136  	ctxt.Bso.Flush()
   137  }
   138  
   139  func addImports(ctxt *Link, l *sym.Library, pn string) {
   140  	pkg := objabi.PathToPrefix(l.Pkg)
   141  	for _, imp := range l.Autolib {
   142  		lib := addlib(ctxt, pkg, pn, imp.Pkg, imp.Fingerprint)
   143  		if lib != nil {
   144  			l.Imports = append(l.Imports, lib)
   145  		}
   146  	}
   147  	l.Autolib = nil
   148  }
   149  
   150  // Allocate a new version (i.e. symbol namespace).
   151  func (ctxt *Link) IncVersion() int {
   152  	ctxt.version++
   153  	return ctxt.version - 1
   154  }
   155  
   156  // returns the maximum version number
   157  func (ctxt *Link) MaxVersion() int {
   158  	return ctxt.version
   159  }
   160  
   161  // generatorFunc is a convenience type.
   162  // Some linker-created Symbols are large and shouldn't really live in the heap.
   163  // Such Symbols can define a generator function. Their bytes can be generated
   164  // directly in the output mmap.
   165  //
   166  // Relocations are applied prior to emitting generator Symbol contents.
   167  // Generator Symbols that require relocations can be written in two passes.
   168  // The first pass, at Symbol creation time, adds only relocations.
   169  // The second pass, at content generation time, adds the rest.
   170  // See generateFunctab for an example.
   171  //
   172  // Generator functions shouldn't grow the Symbol size.
   173  // Generator functions must be safe for concurrent use.
   174  //
   175  // Generator Symbols have their Data set to the mmapped area when the
   176  // generator is called.
   177  type generatorFunc func(*Link, loader.Sym)
   178  
   179  // createGeneratorSymbol is a convenience method for creating a generator
   180  // symbol.
   181  func (ctxt *Link) createGeneratorSymbol(name string, version int, t sym.SymKind, size int64, gen generatorFunc) loader.Sym {
   182  	ldr := ctxt.loader
   183  	s := ldr.LookupOrCreateSym(name, version)
   184  	ldr.SetIsGeneratedSym(s, true)
   185  	sb := ldr.MakeSymbolUpdater(s)
   186  	sb.SetType(t)
   187  	sb.SetSize(size)
   188  	ctxt.generatorSyms[s] = gen
   189  	return s
   190  }
   191
View as plain text