1 files changed, 109 insertions, 0 deletions
diff --git a/src/runtime/pprof/elf.go b/src/runtime/pprof/elf.go
new file mode 100644
index 0000000..a8b5ea6
--- /dev/null
+++ b/src/runtime/pprof/elf.go
@@ -0,0 +1,109 @@
+// 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 pprof
+
+import (
+	"encoding/binary"
+	"errors"
+	"fmt"
+	"os"
+)
+
+var (
+	errBadELF    = errors.New("malformed ELF binary")
+	errNoBuildID = errors.New("no NT_GNU_BUILD_ID found in ELF binary")
+)
+
+// elfBuildID returns the GNU build ID of the named ELF binary,
+// without introducing a dependency on debug/elf and its dependencies.
+func elfBuildID(file string) (string, error) {
+	buf := make([]byte, 256)
+	f, err := os.Open(file)
+	if err != nil {
+		return "", err
+	}
+	defer f.Close()
+
+	if _, err := f.ReadAt(buf[:64], 0); err != nil {
+		return "", err
+	}
+
+	// ELF file begins with \x7F E L F.
+	if buf[0] != 0x7F || buf[1] != 'E' || buf[2] != 'L' || buf[3] != 'F' {
+		return "", errBadELF
+	}
+
+	var byteOrder binary.ByteOrder
+	switch buf[5] {
+	default:
+		return "", errBadELF
+	case 1: // little-endian
+		byteOrder = binary.LittleEndian
+	case 2: // big-endian
+		byteOrder = binary.BigEndian
+	}
+
+	var shnum int
+	var shoff, shentsize int64
+	switch buf[4] {
+	default:
+		return "", errBadELF
+	case 1: // 32-bit file header
+		shoff = int64(byteOrder.Uint32(buf[32:]))
+		shentsize = int64(byteOrder.Uint16(buf[46:]))
+		if shentsize != 40 {
+			return "", errBadELF
+		}
+		shnum = int(byteOrder.Uint16(buf[48:]))
+	case 2: // 64-bit file header
+		shoff = int64(byteOrder.Uint64(buf[40:]))
+		shentsize = int64(byteOrder.Uint16(buf[58:]))
+		if shentsize != 64 {
+			return "", errBadELF
+		}
+		shnum = int(byteOrder.Uint16(buf[60:]))
+	}
+
+	for i := 0; i < shnum; i++ {
+		if _, err := f.ReadAt(buf[:shentsize], shoff+int64(i)*shentsize); err != nil {
+			return "", err
+		}
+		if typ := byteOrder.Uint32(buf[4:]); typ != 7 { // SHT_NOTE
+			continue
+		}
+		var off, size int64
+		if shentsize == 40 {
+			// 32-bit section header
+			off = int64(byteOrder.Uint32(buf[16:]))
+			size = int64(byteOrder.Uint32(buf[20:]))
+		} else {
+			// 64-bit section header
+			off = int64(byteOrder.Uint64(buf[24:]))
+			size = int64(byteOrder.Uint64(buf[32:]))
+		}
+		size += off
+		for off < size {
+			if _, err := f.ReadAt(buf[:16], off); err != nil { // room for header + name GNU\x00
+				return "", err
+			}
+			nameSize := int(byteOrder.Uint32(buf[0:]))
+			descSize := int(byteOrder.Uint32(buf[4:]))
+			noteType := int(byteOrder.Uint32(buf[8:]))
+			descOff := off + int64(12+(nameSize+3)&^3)
+			off = descOff + int64((descSize+3)&^3)
+			if nameSize != 4 || noteType != 3 || buf[12] != 'G' || buf[13] != 'N' || buf[14] != 'U' || buf[15] != '\x00' { // want name GNU\x00 type 3 (NT_GNU_BUILD_ID)
+				continue
+			}
+			if descSize > len(buf) {
+				return "", errBadELF
+			}
+			if _, err := f.ReadAt(buf[:descSize], descOff); err != nil {
+				return "", err
+			}
+			return fmt.Sprintf("%x", buf[:descSize]), nil
+		}
+	}
+	return "", errNoBuildID
+}