From 4f5c94211f9fba74661aa22e95cdeb2f4ffa0511 Mon Sep 17 00:00:00 2001 From: Michael Stapelberg Date: Thu, 8 Feb 2018 10:00:00 +0100 Subject: [PATCH] Reproducible BUILD_PATH_PREFIX_MAP Make builds reproducible by honoring BUILD_PATH_PREFIX_MAP Upstream has rejected the patch in this form and promised to implement an alternative they are happy with instead. That hasn't happened yet though. Bug: https://github.com/golang/go/issues/22491, https://github.com/golang/go/issues/16860 Forwarded: https://golang.org/cl/73291 (rejected upstream though) --- src/cmd/go/internal/work/gc.go | 5 +- src/cmd/link/internal/ld/buildpathprefix.go | 56 +++++++++++++++++++++ src/cmd/link/internal/ld/dwarf.go | 4 +- src/cmd/link/internal/ld/pcln.go | 4 +- 4 files changed, 64 insertions(+), 5 deletions(-) create mode 100644 src/cmd/link/internal/ld/buildpathprefix.go diff --git a/src/cmd/go/internal/work/gc.go b/src/cmd/go/internal/work/gc.go index 3d09f69f..91965dff 100644 --- a/src/cmd/go/internal/work/gc.go +++ b/src/cmd/go/internal/work/gc.go @@ -560,7 +560,10 @@ func (gcToolchain) ld(b *Builder, root *Action, out, importcfg, mainpkg string) dir, out = filepath.Split(out) } - return b.run(root, dir, root.Package.ImportPath, nil, cfg.BuildToolexec, base.Tool("link"), "-o", out, "-importcfg", importcfg, ldflags, mainpkg) + // Apply the rewrite of $WORK to /tmp/go-build also to DWARF file tables: + env := []string{"BUILD_PATH_PREFIX_MAP=/tmp/go-build=" + b.WorkDir + ":" + os.Getenv("BUILD_PATH_PREFIX_MAP")} + + return b.run(root, dir, root.Package.ImportPath, env, cfg.BuildToolexec, base.Tool("link"), "-o", out, "-importcfg", importcfg, ldflags, mainpkg) } func (gcToolchain) ldShared(b *Builder, root *Action, toplevelactions []*Action, out, importcfg string, allactions []*Action) error { diff --git a/src/cmd/link/internal/ld/buildpathprefix.go b/src/cmd/link/internal/ld/buildpathprefix.go new file mode 100644 index 00000000..8cda8a5f --- /dev/null +++ b/src/cmd/link/internal/ld/buildpathprefix.go @@ -0,0 +1,56 @@ +// Copyright 2010 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package ld + +import ( + "log" + "os" + "strings" + "sync" +) + +func decode(s string) string { + s = strings.Replace(s, "%.", ":", -1) + s = strings.Replace(s, "%+", "=", -1) + s = strings.Replace(s, "%#", "%", -1) + return s +} + +type prefixMapEntry struct { + target string + source string +} + +var ( + buildPathPrefixMap []prefixMapEntry + buildPathPrefixMapOnce sync.Once +) + +// See https://reproducible-builds.org/specs/build-path-prefix-map/ +func applyBuildPathPrefixMap(dir string) string { + // Parse the BUILD_PATH_PREFIX_MAP only once; this function gets called for + // every compiled file. + buildPathPrefixMapOnce.Do(func() { + for _, item := range strings.Split(os.Getenv("BUILD_PATH_PREFIX_MAP"), ":") { + if strings.TrimSpace(item) == "" { + continue + } + parts := strings.Split(item, "=") + if got, want := len(parts), 2; got != want { + log.Fatalf("parsing BUILD_PATH_PREFIX_MAP: incorrect number of = separators in item %q: got %d, want %d", item, got-1, want-1) + } + buildPathPrefixMap = append(buildPathPrefixMap, prefixMapEntry{ + target: decode(parts[0]), + source: decode(parts[1]), + }) + } + }) + for _, e := range buildPathPrefixMap { + if strings.HasPrefix(dir, e.source) { + return e.target + strings.TrimPrefix(dir, e.source) + } + } + return dir +} diff --git a/src/cmd/link/internal/ld/dwarf.go b/src/cmd/link/internal/ld/dwarf.go index a150306d..b4d60502 100644 --- a/src/cmd/link/internal/ld/dwarf.go +++ b/src/cmd/link/internal/ld/dwarf.go @@ -1173,7 +1173,7 @@ func writelines(ctxt *Link, unit *compilationUnit, ls *sym.Symbol) { } // File indexes are 1-based. fileNums[int(f.Value)] = len(fileNums) + 1 - Addstring(ls, f.Name) + Addstring(ls, applyBuildPathPrefixMap(f.Name)) ls.AddUint8(0) ls.AddUint8(0) ls.AddUint8(0) @@ -1752,7 +1752,7 @@ func dwarfGenerateDebugInfo(ctxt *Link) { unit.dwinfo = newdie(ctxt, &dwroot, dwarf.DW_ABRV_COMPUNIT, unit.lib.Pkg, 0) newattr(unit.dwinfo, dwarf.DW_AT_language, dwarf.DW_CLS_CONSTANT, int64(dwarf.DW_LANG_Go), 0) // OS X linker requires compilation dir or absolute path in comp unit name to output debug info. - compDir := getCompilationDir() + compDir := applyBuildPathPrefixMap(getCompilationDir()) // TODO: Make this be the actual compilation directory, not // the linker directory. If we move CU construction into the // compiler, this should happen naturally. diff --git a/src/cmd/link/internal/ld/pcln.go b/src/cmd/link/internal/ld/pcln.go index e4db8346..554db4eb 100644 --- a/src/cmd/link/internal/ld/pcln.go +++ b/src/cmd/link/internal/ld/pcln.go @@ -302,7 +302,7 @@ func (ctxt *Link) pclntab() { off = int32(ftab.SetAddr(ctxt.Arch, int64(off), s)) // name int32 - nameoff := nameToOffset(s.Name) + nameoff := nameToOffset(applyBuildPathPrefixMap(s.Name)) off = int32(ftab.SetUint32(ctxt.Arch, int64(off), uint32(nameoff))) // args int32 @@ -449,7 +449,7 @@ func (ctxt *Link) pclntab() { ftab.SetUint32(ctxt.Arch, int64(start), uint32(len(ctxt.Filesyms)+1)) for i := len(ctxt.Filesyms) - 1; i >= 0; i-- { s := ctxt.Filesyms[i] - ftab.SetUint32(ctxt.Arch, int64(start)+s.Value*4, uint32(ftabaddstring(ctxt, ftab, s.Name))) + ftab.SetUint32(ctxt.Arch, int64(start)+s.Value*4, uint32(ftabaddstring(ctxt, ftab, applyBuildPathPrefixMap(s.Name)))) } ftab.Size = int64(len(ftab.P))