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Source file src/cmd/link/internal/ld/ar.go

Documentation: cmd/link/internal/ld

  // Inferno utils/include/ar.h
  // https://bitbucket.org/inferno-os/inferno-os/src/default/utils/include/ar.h
  //
  //	Copyright © 1994-1999 Lucent Technologies Inc.  All rights reserved.
  //	Portions Copyright © 1995-1997 C H Forsyth (forsyth@terzarima.net)
  //	Portions Copyright © 1997-1999 Vita Nuova Limited
  //	Portions Copyright © 2000-2007 Vita Nuova Holdings Limited (www.vitanuova.com)
  //	Portions Copyright © 2004,2006 Bruce Ellis
  //	Portions Copyright © 2005-2007 C H Forsyth (forsyth@terzarima.net)
  //	Revisions Copyright © 2000-2007 Lucent Technologies Inc. and others
  //	Portions Copyright © 2009 The Go Authors. All rights reserved.
  //
  // Permission is hereby granted, free of charge, to any person obtaining a copy
  // of this software and associated documentation files (the "Software"), to deal
  // in the Software without restriction, including without limitation the rights
  // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  // copies of the Software, and to permit persons to whom the Software is
  // furnished to do so, subject to the following conditions:
  //
  // The above copyright notice and this permission notice shall be included in
  // all copies or substantial portions of the Software.
  //
  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
  // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  // THE SOFTWARE.
  
  package ld
  
  import (
  	"cmd/internal/bio"
  	"cmd/internal/objabi"
  	"encoding/binary"
  	"fmt"
  	"io"
  	"os"
  )
  
  const (
  	SARMAG  = 8
  	SAR_HDR = 16 + 44
  )
  
  const (
  	ARMAG = "!<arch>\n"
  )
  
  type ArHdr struct {
  	name string
  	date string
  	uid  string
  	gid  string
  	mode string
  	size string
  	fmag string
  }
  
  // hostArchive reads an archive file holding host objects and links in
  // required objects. The general format is the same as a Go archive
  // file, but it has an armap listing symbols and the objects that
  // define them. This is used for the compiler support library
  // libgcc.a.
  func hostArchive(ctxt *Link, name string) {
  	f, err := bio.Open(name)
  	if err != nil {
  		if os.IsNotExist(err) {
  			// It's OK if we don't have a libgcc file at all.
  			if ctxt.Debugvlog != 0 {
  				ctxt.Logf("skipping libgcc file: %v\n", err)
  			}
  			return
  		}
  		Exitf("cannot open file %s: %v", name, err)
  	}
  	defer f.Close()
  
  	var magbuf [len(ARMAG)]byte
  	if _, err := io.ReadFull(f, magbuf[:]); err != nil {
  		Exitf("file %s too short", name)
  	}
  
  	var arhdr ArHdr
  	l := nextar(f, f.Offset(), &arhdr)
  	if l <= 0 {
  		Exitf("%s missing armap", name)
  	}
  
  	var armap archiveMap
  	if arhdr.name == "/" || arhdr.name == "/SYM64/" {
  		armap = readArmap(name, f, arhdr)
  	} else {
  		Exitf("%s missing armap", name)
  	}
  
  	loaded := make(map[uint64]bool)
  	any := true
  	for any {
  		var load []uint64
  		for _, s := range ctxt.Syms.Allsym {
  			for _, r := range s.R {
  				if r.Sym != nil && r.Sym.Type&SMASK == SXREF {
  					if off := armap[r.Sym.Name]; off != 0 && !loaded[off] {
  						load = append(load, off)
  						loaded[off] = true
  					}
  				}
  			}
  		}
  
  		for _, off := range load {
  			l := nextar(f, int64(off), &arhdr)
  			if l <= 0 {
  				Exitf("%s missing archive entry at offset %d", name, off)
  			}
  			pname := fmt.Sprintf("%s(%s)", name, arhdr.name)
  			l = atolwhex(arhdr.size)
  
  			libgcc := Library{Pkg: "libgcc"}
  			h := ldobj(ctxt, f, &libgcc, l, pname, name, ArchiveObj)
  			f.Seek(h.off, 0)
  			h.ld(ctxt, f, h.pkg, h.length, h.pn)
  		}
  
  		any = len(load) > 0
  	}
  }
  
  // archiveMap is an archive symbol map: a mapping from symbol name to
  // offset within the archive file.
  type archiveMap map[string]uint64
  
  // readArmap reads the archive symbol map.
  func readArmap(filename string, f *bio.Reader, arhdr ArHdr) archiveMap {
  	is64 := arhdr.name == "/SYM64/"
  	wordSize := 4
  	if is64 {
  		wordSize = 8
  	}
  
  	contents := make([]byte, atolwhex(arhdr.size))
  	if _, err := io.ReadFull(f, contents); err != nil {
  		Exitf("short read from %s", filename)
  	}
  
  	var c uint64
  	if is64 {
  		c = binary.BigEndian.Uint64(contents)
  	} else {
  		c = uint64(binary.BigEndian.Uint32(contents))
  	}
  	contents = contents[wordSize:]
  
  	ret := make(archiveMap)
  
  	names := contents[c*uint64(wordSize):]
  	for i := uint64(0); i < c; i++ {
  		n := 0
  		for names[n] != 0 {
  			n++
  		}
  		name := string(names[:n])
  		names = names[n+1:]
  
  		// For Mach-O and PE/386 files we strip a leading
  		// underscore from the symbol name.
  		if objabi.GOOS == "darwin" || (objabi.GOOS == "windows" && objabi.GOARCH == "386") {
  			if name[0] == '_' && len(name) > 1 {
  				name = name[1:]
  			}
  		}
  
  		var off uint64
  		if is64 {
  			off = binary.BigEndian.Uint64(contents)
  		} else {
  			off = uint64(binary.BigEndian.Uint32(contents))
  		}
  		contents = contents[wordSize:]
  
  		ret[name] = off
  	}
  
  	return ret
  }
  

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