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cmd/go: split out cmd/go/internal/buildid
This is one CL in a long sequence of changes to break up the go command from one package into a plausible group of packages. This sequence is concerned only with moving code, not changing or cleaning up code. There will still be more cleanup after this sequence. The entire sequence will be submitted together: it is not a goal for the tree to build at every step. For #18653. Change-Id: I20dbc352c3df3c83a75811dd8e78c580a46b2202 Reviewed-on: https://go-review.googlesource.com/36195 Reviewed-by: David Crawshaw <[email protected]>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,201 @@ | ||
| // Copyright 2017 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 buildid | ||
|
|
||
| import ( | ||
| "bytes" | ||
| "cmd/go/internal/cfg" | ||
| "fmt" | ||
| "io" | ||
| "os" | ||
| "strconv" | ||
| "strings" | ||
| ) | ||
|
|
||
| var ( | ||
| errBuildIDToolchain = fmt.Errorf("build ID only supported in gc toolchain") | ||
| errBuildIDMalformed = fmt.Errorf("malformed object file") | ||
| errBuildIDUnknown = fmt.Errorf("lost build ID") | ||
| ) | ||
|
|
||
| var ( | ||
| bangArch = []byte("!<arch>") | ||
| pkgdef = []byte("__.PKGDEF") | ||
| goobject = []byte("go object ") | ||
| buildid = []byte("build id ") | ||
| ) | ||
|
|
||
| // ReadBuildID reads the build ID from an archive or binary. | ||
| // It only supports the gc toolchain. | ||
| // Other toolchain maintainers should adjust this function. | ||
| func ReadBuildID(name, target string) (id string, err error) { | ||
| if cfg.BuildToolchainName != "gc" { | ||
| return "", errBuildIDToolchain | ||
| } | ||
|
|
||
| // For commands, read build ID directly from binary. | ||
| if name == "main" { | ||
| return ReadBuildIDFromBinary(target) | ||
| } | ||
|
|
||
| // Otherwise, we expect to have an archive (.a) file, | ||
| // and we can read the build ID from the Go export data. | ||
| if !strings.HasSuffix(target, ".a") { | ||
| return "", &os.PathError{Op: "parse", Path: target, Err: errBuildIDUnknown} | ||
| } | ||
|
|
||
| // Read just enough of the target to fetch the build ID. | ||
| // The archive is expected to look like: | ||
| // | ||
| // !<arch> | ||
| // __.PKGDEF 0 0 0 644 7955 ` | ||
| // go object darwin amd64 devel X:none | ||
| // build id "b41e5c45250e25c9fd5e9f9a1de7857ea0d41224" | ||
| // | ||
| // The variable-sized strings are GOOS, GOARCH, and the experiment list (X:none). | ||
| // Reading the first 1024 bytes should be plenty. | ||
| f, err := os.Open(target) | ||
| if err != nil { | ||
| return "", err | ||
| } | ||
| data := make([]byte, 1024) | ||
| n, err := io.ReadFull(f, data) | ||
| f.Close() | ||
|
|
||
| if err != nil && n == 0 { | ||
| return "", err | ||
| } | ||
|
|
||
| bad := func() (string, error) { | ||
| return "", &os.PathError{Op: "parse", Path: target, Err: errBuildIDMalformed} | ||
| } | ||
|
|
||
| // Archive header. | ||
| for i := 0; ; i++ { // returns during i==3 | ||
| j := bytes.IndexByte(data, '\n') | ||
| if j < 0 { | ||
| return bad() | ||
| } | ||
| line := data[:j] | ||
| data = data[j+1:] | ||
| switch i { | ||
| case 0: | ||
| if !bytes.Equal(line, bangArch) { | ||
| return bad() | ||
| } | ||
| case 1: | ||
| if !bytes.HasPrefix(line, pkgdef) { | ||
| return bad() | ||
| } | ||
| case 2: | ||
| if !bytes.HasPrefix(line, goobject) { | ||
| return bad() | ||
| } | ||
| case 3: | ||
| if !bytes.HasPrefix(line, buildid) { | ||
| // Found the object header, just doesn't have a build id line. | ||
| // Treat as successful, with empty build id. | ||
| return "", nil | ||
| } | ||
| id, err := strconv.Unquote(string(line[len(buildid):])) | ||
| if err != nil { | ||
| return bad() | ||
| } | ||
| return id, nil | ||
| } | ||
| } | ||
| } | ||
|
|
||
| var ( | ||
| goBuildPrefix = []byte("\xff Go build ID: \"") | ||
| goBuildEnd = []byte("\"\n \xff") | ||
|
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||
| elfPrefix = []byte("\x7fELF") | ||
|
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| machoPrefixes = [][]byte{ | ||
| {0xfe, 0xed, 0xfa, 0xce}, | ||
| {0xfe, 0xed, 0xfa, 0xcf}, | ||
| {0xce, 0xfa, 0xed, 0xfe}, | ||
| {0xcf, 0xfa, 0xed, 0xfe}, | ||
| } | ||
| ) | ||
|
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| var BuildIDReadSize = 32 * 1024 // changed for testing | ||
|
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||
| // ReadBuildIDFromBinary reads the build ID from a binary. | ||
| // | ||
| // ELF binaries store the build ID in a proper PT_NOTE section. | ||
| // | ||
| // Other binary formats are not so flexible. For those, the linker | ||
| // stores the build ID as non-instruction bytes at the very beginning | ||
| // of the text segment, which should appear near the beginning | ||
| // of the file. This is clumsy but fairly portable. Custom locations | ||
| // can be added for other binary types as needed, like we did for ELF. | ||
| func ReadBuildIDFromBinary(filename string) (id string, err error) { | ||
| if filename == "" { | ||
| return "", &os.PathError{Op: "parse", Path: filename, Err: errBuildIDUnknown} | ||
| } | ||
|
|
||
| // Read the first 32 kB of the binary file. | ||
| // That should be enough to find the build ID. | ||
| // In ELF files, the build ID is in the leading headers, | ||
| // which are typically less than 4 kB, not to mention 32 kB. | ||
| // In Mach-O files, there's no limit, so we have to parse the file. | ||
| // On other systems, we're trying to read enough that | ||
| // we get the beginning of the text segment in the read. | ||
| // The offset where the text segment begins in a hello | ||
| // world compiled for each different object format today: | ||
| // | ||
| // Plan 9: 0x20 | ||
| // Windows: 0x600 | ||
| // | ||
| f, err := os.Open(filename) | ||
| if err != nil { | ||
| return "", err | ||
| } | ||
| defer f.Close() | ||
|
|
||
| data := make([]byte, BuildIDReadSize) | ||
| _, err = io.ReadFull(f, data) | ||
| if err == io.ErrUnexpectedEOF { | ||
| err = nil | ||
| } | ||
| if err != nil { | ||
| return "", err | ||
| } | ||
|
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||
| if bytes.HasPrefix(data, elfPrefix) { | ||
| return readELFGoBuildID(filename, f, data) | ||
| } | ||
| for _, m := range machoPrefixes { | ||
| if bytes.HasPrefix(data, m) { | ||
| return readMachoGoBuildID(filename, f, data) | ||
| } | ||
| } | ||
|
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||
| return readRawGoBuildID(filename, data) | ||
| } | ||
|
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||
| // readRawGoBuildID finds the raw build ID stored in text segment data. | ||
| func readRawGoBuildID(filename string, data []byte) (id string, err error) { | ||
| i := bytes.Index(data, goBuildPrefix) | ||
| if i < 0 { | ||
| // Missing. Treat as successful but build ID empty. | ||
| return "", nil | ||
| } | ||
|
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||
| j := bytes.Index(data[i+len(goBuildPrefix):], goBuildEnd) | ||
| if j < 0 { | ||
| return "", &os.PathError{Op: "parse", Path: filename, Err: errBuildIDMalformed} | ||
| } | ||
|
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||
| quoted := data[i+len(goBuildPrefix)-1 : i+len(goBuildPrefix)+j+1] | ||
| id, err = strconv.Unquote(string(quoted)) | ||
| if err != nil { | ||
| return "", &os.PathError{Op: "parse", Path: filename, Err: errBuildIDMalformed} | ||
| } | ||
|
|
||
| return id, nil | ||
| } |
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