Add gops agent

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

@@ -0,0 +1,208 @@
+// 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 PE executables (Microsoft Windows).
+
+package objfile
+
+import (
+	"debug/dwarf"
+	"debug/pe"
+	"fmt"
+	"os"
+	"sort"
+)
+
+type peFile struct {
+	pe *pe.File
+}
+
+func openPE(r *os.File) (rawFile, error) {
+	f, err := pe.NewFile(r)
+	if err != nil {
+		return nil, err
+	}
+	switch f.OptionalHeader.(type) {
+	case *pe.OptionalHeader32, *pe.OptionalHeader64:
+		// ok
+	default:
+		return nil, fmt.Errorf("unrecognized PE format")
+	}
+	return &peFile{f}, nil
+}
+
+func (f *peFile) symbols() ([]Sym, error) {
+	// 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
+
+	var imageBase uint64
+	switch oh := f.pe.OptionalHeader.(type) {
+	case *pe.OptionalHeader32:
+		imageBase = uint64(oh.ImageBase)
+	case *pe.OptionalHeader64:
+		imageBase = oh.ImageBase
+	}
+
+	var syms []Sym
+	for _, s := range f.pe.Symbols {
+		const (
+			N_UNDEF = 0  // An undefined (extern) symbol
+			N_ABS   = -1 // An absolute symbol (e_value is a constant, not an address)
+			N_DEBUG = -2 // A debugging symbol
+		)
+		sym := Sym{Name: s.Name, Addr: uint64(s.Value), Code: '?'}
+		switch s.SectionNumber {
+		case N_UNDEF:
+			sym.Code = 'U'
+		case N_ABS:
+			sym.Code = 'C'
+		case N_DEBUG:
+			sym.Code = '?'
+		default:
+			if s.SectionNumber < 0 || len(f.pe.Sections) < int(s.SectionNumber) {
+				return nil, fmt.Errorf("invalid section number in symbol table")
+			}
+			sect := f.pe.Sections[s.SectionNumber-1]
+			const (
+				text  = 0x20
+				data  = 0x40
+				bss   = 0x80
+				permW = 0x80000000
+			)
+			ch := sect.Characteristics
+			switch {
+			case ch&text != 0:
+				sym.Code = 'T'
+			case ch&data != 0:
+				if ch&permW == 0 {
+					sym.Code = 'R'
+				} else {
+					sym.Code = 'D'
+				}
+			case ch&bss != 0:
+				sym.Code = 'B'
+			}
+			sym.Addr += imageBase + uint64(sect.VirtualAddress)
+		}
+		syms = append(syms, sym)
+		addrs = append(addrs, sym.Addr)
+	}
+
+	sort.Sort(uint64s(addrs))
+	for i := range syms {
+		j := sort.Search(len(addrs), func(x int) bool { return addrs[x] > syms[i].Addr })
+		if j < len(addrs) {
+			syms[i].Size = int64(addrs[j] - syms[i].Addr)
+		}
+	}
+
+	return syms, nil
+}
+
+func (f *peFile) pcln() (textStart uint64, symtab, pclntab []byte, err error) {
+	var imageBase uint64
+	switch oh := f.pe.OptionalHeader.(type) {
+	case *pe.OptionalHeader32:
+		imageBase = uint64(oh.ImageBase)
+	case *pe.OptionalHeader64:
+		imageBase = oh.ImageBase
+	default:
+		return 0, nil, nil, fmt.Errorf("pe file format not recognized")
+	}
+	if sect := f.pe.Section(".text"); sect != nil {
+		textStart = imageBase + uint64(sect.VirtualAddress)
+	}
+	if pclntab, err = loadPETable(f.pe, "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 = loadPETable(f.pe, "pclntab", "epclntab"); err2 != nil {
+			return 0, nil, nil, err
+		}
+	}
+	if symtab, err = loadPETable(f.pe, "runtime.symtab", "runtime.esymtab"); err != nil {
+		// Same as above.
+		var err2 error
+		if symtab, err2 = loadPETable(f.pe, "symtab", "esymtab"); err2 != nil {
+			return 0, nil, nil, err
+		}
+	}
+	return textStart, symtab, pclntab, nil
+}
+
+func (f *peFile) text() (textStart uint64, text []byte, err error) {
+	var imageBase uint64
+	switch oh := f.pe.OptionalHeader.(type) {
+	case *pe.OptionalHeader32:
+		imageBase = uint64(oh.ImageBase)
+	case *pe.OptionalHeader64:
+		imageBase = oh.ImageBase
+	default:
+		return 0, nil, fmt.Errorf("pe file format not recognized")
+	}
+	sect := f.pe.Section(".text")
+	if sect == nil {
+		return 0, nil, fmt.Errorf("text section not found")
+	}
+	textStart = imageBase + uint64(sect.VirtualAddress)
+	text, err = sect.Data()
+	return
+}
+
+func findPESymbol(f *pe.File, name string) (*pe.Symbol, error) {
+	for _, s := range f.Symbols {
+		if s.Name != name {
+			continue
+		}
+		if s.SectionNumber <= 0 {
+			return nil, fmt.Errorf("symbol %s: invalid section number %d", name, s.SectionNumber)
+		}
+		if len(f.Sections) < int(s.SectionNumber) {
+			return nil, fmt.Errorf("symbol %s: section number %d is larger than max %d", name, s.SectionNumber, len(f.Sections))
+		}
+		return s, nil
+	}
+	return nil, fmt.Errorf("no %s symbol found", name)
+}
+
+func loadPETable(f *pe.File, sname, ename string) ([]byte, error) {
+	ssym, err := findPESymbol(f, sname)
+	if err != nil {
+		return nil, err
+	}
+	esym, err := findPESymbol(f, ename)
+	if err != nil {
+		return nil, err
+	}
+	if ssym.SectionNumber != esym.SectionNumber {
+		return nil, fmt.Errorf("%s and %s symbols must be in the same section", sname, ename)
+	}
+	sect := f.Sections[ssym.SectionNumber-1]
+	data, err := sect.Data()
+	if err != nil {
+		return nil, err
+	}
+	return data[ssym.Value:esym.Value], nil
+}
+
+func (f *peFile) goarch() string {
+	// Not sure how to get the info we want from PE header.
+	// Look in symbol table for telltale rt0 symbol.
+	if _, err := findPESymbol(f.pe, "_rt0_386_windows"); err == nil {
+		return "386"
+	}
+	if _, err := findPESymbol(f.pe, "_rt0_amd64_windows"); err == nil {
+		return "amd64"
+	}
+	return ""
+}
+
+func (f *peFile) loadAddress() (uint64, error) {
+	return 0, fmt.Errorf("unknown load address")
+}
+
+func (f *peFile) dwarf() (*dwarf.Data, error) {
+	return f.pe.DWARF()
+}