1 files changed, 263 insertions, 0 deletions
diff --git a/src/cmd/go/internal/version/exe.go b/src/cmd/go/internal/version/exe.go
new file mode 100644
index 0000000..0e7deef
--- /dev/null
+++ b/src/cmd/go/internal/version/exe.go
@@ -0,0 +1,263 @@
+// Copyright 2019 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 version
+
+import (
+	"bytes"
+	"debug/elf"
+	"debug/macho"
+	"debug/pe"
+	"fmt"
+	"internal/xcoff"
+	"io"
+	"os"
+)
+
+// An exe is a generic interface to an OS executable (ELF, Mach-O, PE, XCOFF).
+type exe interface {
+	// Close closes the underlying file.
+	Close() error
+
+	// ReadData reads and returns up to size byte starting at virtual address addr.
+	ReadData(addr, size uint64) ([]byte, error)
+
+	// DataStart returns the writable data segment start address.
+	DataStart() uint64
+}
+
+// openExe opens file and returns it as an exe.
+func openExe(file string) (exe, error) {
+	f, err := os.Open(file)
+	if err != nil {
+		return nil, err
+	}
+	data := make([]byte, 16)
+	if _, err := io.ReadFull(f, data); err != nil {
+		return nil, err
+	}
+	f.Seek(0, 0)
+	if bytes.HasPrefix(data, []byte("\x7FELF")) {
+		e, err := elf.NewFile(f)
+		if err != nil {
+			f.Close()
+			return nil, err
+		}
+		return &elfExe{f, e}, nil
+	}
+	if bytes.HasPrefix(data, []byte("MZ")) {
+		e, err := pe.NewFile(f)
+		if err != nil {
+			f.Close()
+			return nil, err
+		}
+		return &peExe{f, e}, nil
+	}
+	if bytes.HasPrefix(data, []byte("\xFE\xED\xFA")) || bytes.HasPrefix(data[1:], []byte("\xFA\xED\xFE")) {
+		e, err := macho.NewFile(f)
+		if err != nil {
+			f.Close()
+			return nil, err
+		}
+		return &machoExe{f, e}, nil
+	}
+	if bytes.HasPrefix(data, []byte{0x01, 0xDF}) || bytes.HasPrefix(data, []byte{0x01, 0xF7}) {
+		e, err := xcoff.NewFile(f)
+		if err != nil {
+			f.Close()
+			return nil, err
+		}
+		return &xcoffExe{f, e}, nil
+
+	}
+	return nil, fmt.Errorf("unrecognized executable format")
+}
+
+// elfExe is the ELF implementation of the exe interface.
+type elfExe struct {
+	os *os.File
+	f  *elf.File
+}
+
+func (x *elfExe) Close() error {
+	return x.os.Close()
+}
+
+func (x *elfExe) ReadData(addr, size uint64) ([]byte, error) {
+	for _, prog := range x.f.Progs {
+		if prog.Vaddr <= addr && addr <= prog.Vaddr+prog.Filesz-1 {
+			n := prog.Vaddr + prog.Filesz - addr
+			if n > size {
+				n = size
+			}
+			data := make([]byte, n)
+			_, err := prog.ReadAt(data, int64(addr-prog.Vaddr))
+			if err != nil {
+				return nil, err
+			}
+			return data, nil
+		}
+	}
+	return nil, fmt.Errorf("address not mapped")
+}
+
+func (x *elfExe) DataStart() uint64 {
+	for _, s := range x.f.Sections {
+		if s.Name == ".go.buildinfo" {
+			return s.Addr
+		}
+	}
+	for _, p := range x.f.Progs {
+		if p.Type == elf.PT_LOAD && p.Flags&(elf.PF_X|elf.PF_W) == elf.PF_W {
+			return p.Vaddr
+		}
+	}
+	return 0
+}
+
+// peExe is the PE (Windows Portable Executable) implementation of the exe interface.
+type peExe struct {
+	os *os.File
+	f  *pe.File
+}
+
+func (x *peExe) Close() error {
+	return x.os.Close()
+}
+
+func (x *peExe) imageBase() uint64 {
+	switch oh := x.f.OptionalHeader.(type) {
+	case *pe.OptionalHeader32:
+		return uint64(oh.ImageBase)
+	case *pe.OptionalHeader64:
+		return oh.ImageBase
+	}
+	return 0
+}
+
+func (x *peExe) ReadData(addr, size uint64) ([]byte, error) {
+	addr -= x.imageBase()
+	for _, sect := range x.f.Sections {
+		if uint64(sect.VirtualAddress) <= addr && addr <= uint64(sect.VirtualAddress+sect.Size-1) {
+			n := uint64(sect.VirtualAddress+sect.Size) - addr
+			if n > size {
+				n = size
+			}
+			data := make([]byte, n)
+			_, err := sect.ReadAt(data, int64(addr-uint64(sect.VirtualAddress)))
+			if err != nil {
+				return nil, err
+			}
+			return data, nil
+		}
+	}
+	return nil, fmt.Errorf("address not mapped")
+}
+
+func (x *peExe) DataStart() uint64 {
+	// Assume data is first writable section.
+	const (
+		IMAGE_SCN_CNT_CODE               = 0x00000020
+		IMAGE_SCN_CNT_INITIALIZED_DATA   = 0x00000040
+		IMAGE_SCN_CNT_UNINITIALIZED_DATA = 0x00000080
+		IMAGE_SCN_MEM_EXECUTE            = 0x20000000
+		IMAGE_SCN_MEM_READ               = 0x40000000
+		IMAGE_SCN_MEM_WRITE              = 0x80000000
+		IMAGE_SCN_MEM_DISCARDABLE        = 0x2000000
+		IMAGE_SCN_LNK_NRELOC_OVFL        = 0x1000000
+		IMAGE_SCN_ALIGN_32BYTES          = 0x600000
+	)
+	for _, sect := range x.f.Sections {
+		if sect.VirtualAddress != 0 && sect.Size != 0 &&
+			sect.Characteristics&^IMAGE_SCN_ALIGN_32BYTES == IMAGE_SCN_CNT_INITIALIZED_DATA|IMAGE_SCN_MEM_READ|IMAGE_SCN_MEM_WRITE {
+			return uint64(sect.VirtualAddress) + x.imageBase()
+		}
+	}
+	return 0
+}
+
+// machoExe is the Mach-O (Apple macOS/iOS) implementation of the exe interface.
+type machoExe struct {
+	os *os.File
+	f  *macho.File
+}
+
+func (x *machoExe) Close() error {
+	return x.os.Close()
+}
+
+func (x *machoExe) ReadData(addr, size uint64) ([]byte, error) {
+	for _, load := range x.f.Loads {
+		seg, ok := load.(*macho.Segment)
+		if !ok {
+			continue
+		}
+		if seg.Addr <= addr && addr <= seg.Addr+seg.Filesz-1 {
+			if seg.Name == "__PAGEZERO" {
+				continue
+			}
+			n := seg.Addr + seg.Filesz - addr
+			if n > size {
+				n = size
+			}
+			data := make([]byte, n)
+			_, err := seg.ReadAt(data, int64(addr-seg.Addr))
+			if err != nil {
+				return nil, err
+			}
+			return data, nil
+		}
+	}
+	return nil, fmt.Errorf("address not mapped")
+}
+
+func (x *machoExe) DataStart() uint64 {
+	// Look for section named "__go_buildinfo".
+	for _, sec := range x.f.Sections {
+		if sec.Name == "__go_buildinfo" {
+			return sec.Addr
+		}
+	}
+	// Try the first non-empty writable segment.
+	const RW = 3
+	for _, load := range x.f.Loads {
+		seg, ok := load.(*macho.Segment)
+		if ok && seg.Addr != 0 && seg.Filesz != 0 && seg.Prot == RW && seg.Maxprot == RW {
+			return seg.Addr
+		}
+	}
+	return 0
+}
+
+// xcoffExe is the XCOFF (AIX eXtended COFF) implementation of the exe interface.
+type xcoffExe struct {
+	os *os.File
+	f  *xcoff.File
+}
+
+func (x *xcoffExe) Close() error {
+	return x.os.Close()
+}
+
+func (x *xcoffExe) ReadData(addr, size uint64) ([]byte, error) {
+	for _, sect := range x.f.Sections {
+		if uint64(sect.VirtualAddress) <= addr && addr <= uint64(sect.VirtualAddress+sect.Size-1) {
+			n := uint64(sect.VirtualAddress+sect.Size) - addr
+			if n > size {
+				n = size
+			}
+			data := make([]byte, n)
+			_, err := sect.ReadAt(data, int64(addr-uint64(sect.VirtualAddress)))
+			if err != nil {
+				return nil, err
+			}
+			return data, nil
+		}
+	}
+	return nil, fmt.Errorf("address not mapped")
+}
+
+func (x *xcoffExe) DataStart() uint64 {
+	return x.f.SectionByType(xcoff.STYP_DATA).VirtualAddress
+}