Add gops agent

vendor/github.com/google/gops/internal/objfile/plan9obj.go

@@ -0,0 +1,156 @@
+// Copyright 2014 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 Plan 9 a.out executables.
+
+package objfile
+
+import (
+	"debug/dwarf"
+	"debug/plan9obj"
+	"errors"
+	"fmt"
+	"os"
+	"sort"
+)
+
+var validSymType = map[rune]bool{
+	'T': true,
+	't': true,
+	'D': true,
+	'd': true,
+	'B': true,
+	'b': true,
+}
+
+type plan9File struct {
+	plan9 *plan9obj.File
+}
+
+func openPlan9(r *os.File) (rawFile, error) {
+	f, err := plan9obj.NewFile(r)
+	if err != nil {
+		return nil, err
+	}
+	return &plan9File{f}, nil
+}
+
+func (f *plan9File) symbols() ([]Sym, error) {
+	plan9Syms, err := f.plan9.Symbols()
+	if err != nil {
+		return nil, err
+	}
+
+	// Build sorted list of addresses of all symbols.
+	// We infer the size of a symbol by looking at where the next symbol begins.
+	var addrs []uint64
+	for _, s := range plan9Syms {
+		if !validSymType[s.Type] {
+			continue
+		}
+		addrs = append(addrs, s.Value)
+	}
+	sort.Sort(uint64s(addrs))
+
+	var syms []Sym
+
+	for _, s := range plan9Syms {
+		if !validSymType[s.Type] {
+			continue
+		}
+		sym := Sym{Addr: s.Value, Name: s.Name, Code: s.Type}
+		i := sort.Search(len(addrs), func(x int) bool { return addrs[x] > s.Value })
+		if i < len(addrs) {
+			sym.Size = int64(addrs[i] - s.Value)
+		}
+		syms = append(syms, sym)
+	}
+
+	return syms, nil
+}
+
+func (f *plan9File) pcln() (textStart uint64, symtab, pclntab []byte, err error) {
+	textStart = f.plan9.LoadAddress + f.plan9.HdrSize
+	if pclntab, err = loadPlan9Table(f.plan9, "runtime.pclntab", "runtime.epclntab"); err != nil {
+		// We didn't find the symbols, so look for the names used in 1.3 and earlier.
+		// TODO: Remove code looking for the old symbols when we no longer care about 1.3.
+		var err2 error
+		if pclntab, err2 = loadPlan9Table(f.plan9, "pclntab", "epclntab"); err2 != nil {
+			return 0, nil, nil, err
+		}
+	}
+	if symtab, err = loadPlan9Table(f.plan9, "runtime.symtab", "runtime.esymtab"); err != nil {
+		// Same as above.
+		var err2 error
+		if symtab, err2 = loadPlan9Table(f.plan9, "symtab", "esymtab"); err2 != nil {
+			return 0, nil, nil, err
+		}
+	}
+	return textStart, symtab, pclntab, nil
+}
+
+func (f *plan9File) text() (textStart uint64, text []byte, err error) {
+	sect := f.plan9.Section("text")
+	if sect == nil {
+		return 0, nil, fmt.Errorf("text section not found")
+	}
+	textStart = f.plan9.LoadAddress + f.plan9.HdrSize
+	text, err = sect.Data()
+	return
+}
+
+func findPlan9Symbol(f *plan9obj.File, name string) (*plan9obj.Sym, error) {
+	syms, err := f.Symbols()
+	if err != nil {
+		return nil, err
+	}
+	for _, s := range syms {
+		if s.Name != name {
+			continue
+		}
+		return &s, nil
+	}
+	return nil, fmt.Errorf("no %s symbol found", name)
+}
+
+func loadPlan9Table(f *plan9obj.File, sname, ename string) ([]byte, error) {
+	ssym, err := findPlan9Symbol(f, sname)
+	if err != nil {
+		return nil, err
+	}
+	esym, err := findPlan9Symbol(f, ename)
+	if err != nil {
+		return nil, err
+	}
+	sect := f.Section("text")
+	if sect == nil {
+		return nil, err
+	}
+	data, err := sect.Data()
+	if err != nil {
+		return nil, err
+	}
+	textStart := f.LoadAddress + f.HdrSize
+	return data[ssym.Value-textStart : esym.Value-textStart], nil
+}
+
+func (f *plan9File) goarch() string {
+	switch f.plan9.Magic {
+	case plan9obj.Magic386:
+		return "386"
+	case plan9obj.MagicAMD64:
+		return "amd64"
+	case plan9obj.MagicARM:
+		return "arm"
+	}
+	return ""
+}
+
+func (f *plan9File) loadAddress() (uint64, error) {
+	return 0, fmt.Errorf("unknown load address")
+}
+
+func (f *plan9File) dwarf() (*dwarf.Data, error) {
+	return nil, errors.New("no DWARF data in Plan 9 file")
+}