Add gops agent

vendor/github.com/google/gops/internal/objfile/elf.go

@@ -0,0 +1,124 @@
+// Copyright 2013 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.
+
+// Parsing of ELF executables (Linux, FreeBSD, and so on).
+
+package objfile
+
+import (
+	"debug/dwarf"
+	"debug/elf"
+	"encoding/binary"
+	"fmt"
+	"os"
+)
+
+type elfFile struct {
+	elf *elf.File
+}
+
+func openElf(r *os.File) (rawFile, error) {
+	f, err := elf.NewFile(r)
+	if err != nil {
+		return nil, err
+	}
+	return &elfFile{f}, nil
+}
+
+func (f *elfFile) symbols() ([]Sym, error) {
+	elfSyms, err := f.elf.Symbols()
+	if err != nil {
+		return nil, err
+	}
+
+	var syms []Sym
+	for _, s := range elfSyms {
+		sym := Sym{Addr: s.Value, Name: s.Name, Size: int64(s.Size), Code: '?'}
+		switch s.Section {
+		case elf.SHN_UNDEF:
+			sym.Code = 'U'
+		case elf.SHN_COMMON:
+			sym.Code = 'B'
+		default:
+			i := int(s.Section)
+			if i < 0 || i >= len(f.elf.Sections) {
+				break
+			}
+			sect := f.elf.Sections[i]
+			switch sect.Flags & (elf.SHF_WRITE | elf.SHF_ALLOC | elf.SHF_EXECINSTR) {
+			case elf.SHF_ALLOC | elf.SHF_EXECINSTR:
+				sym.Code = 'T'
+			case elf.SHF_ALLOC:
+				sym.Code = 'R'
+			case elf.SHF_ALLOC | elf.SHF_WRITE:
+				sym.Code = 'D'
+			}
+		}
+		if elf.ST_BIND(s.Info) == elf.STB_LOCAL {
+			sym.Code += 'a' - 'A'
+		}
+		syms = append(syms, sym)
+	}
+
+	return syms, nil
+}
+
+func (f *elfFile) pcln() (textStart uint64, symtab, pclntab []byte, err error) {
+	if sect := f.elf.Section(".text"); sect != nil {
+		textStart = sect.Addr
+	}
+	if sect := f.elf.Section(".gosymtab"); sect != nil {
+		if symtab, err = sect.Data(); err != nil {
+			return 0, nil, nil, err
+		}
+	}
+	if sect := f.elf.Section(".gopclntab"); sect != nil {
+		if pclntab, err = sect.Data(); err != nil {
+			return 0, nil, nil, err
+		}
+	}
+	return textStart, symtab, pclntab, nil
+}
+
+func (f *elfFile) text() (textStart uint64, text []byte, err error) {
+	sect := f.elf.Section(".text")
+	if sect == nil {
+		return 0, nil, fmt.Errorf("text section not found")
+	}
+	textStart = sect.Addr
+	text, err = sect.Data()
+	return
+}
+
+func (f *elfFile) goarch() string {
+	switch f.elf.Machine {
+	case elf.EM_386:
+		return "386"
+	case elf.EM_X86_64:
+		return "amd64"
+	case elf.EM_ARM:
+		return "arm"
+	case elf.EM_PPC64:
+		if f.elf.ByteOrder == binary.LittleEndian {
+			return "ppc64le"
+		}
+		return "ppc64"
+	case elf.EM_S390:
+		return "s390x"
+	}
+	return ""
+}
+
+func (f *elfFile) loadAddress() (uint64, error) {
+	for _, p := range f.elf.Progs {
+		if p.Type == elf.PT_LOAD {
+			return p.Vaddr, nil
+		}
+	}
+	return 0, fmt.Errorf("unknown load address")
+}
+
+func (f *elfFile) dwarf() (*dwarf.Data, error) {
+	return f.elf.DWARF()
+}