/
linux_core.go
481 lines (434 loc) · 13.5 KB
/
linux_core.go
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package core
import (
"bytes"
"debug/elf"
"encoding/binary"
"fmt"
"io"
"os"
"strings"
"github.com/undoio/delve/pkg/elfwriter"
"github.com/undoio/delve/pkg/proc"
"github.com/undoio/delve/pkg/proc/amd64util"
"github.com/undoio/delve/pkg/proc/linutil"
)
// Copied from golang.org/x/sys/unix.Timeval since it's not available on all
// systems.
type linuxCoreTimeval struct {
Sec int64
Usec int64
}
// NT_FILE is file mapping information, e.g. program text mappings. Desc is a LinuxNTFile.
const _NT_FILE elf.NType = 0x46494c45 // "FILE".
// NT_X86_XSTATE is other registers, including AVX and such.
const _NT_X86_XSTATE elf.NType = 0x202 // Note type for notes containing X86 XSAVE area.
// NT_AUXV is the note type for notes containing a copy of the Auxv array
const _NT_AUXV elf.NType = 0x6
// NT_FPREGSET is the note type for floating point registers.
const _NT_FPREGSET elf.NType = 0x2
// Fetch architecture using exeELF.Machine from core file
// Refer http://man7.org/linux/man-pages/man5/elf.5.html
const (
_EM_AARCH64 = 183
_EM_X86_64 = 62
_ARM_FP_HEADER_START = 512
)
const elfErrorBadMagicNumber = "bad magic number"
func linuxThreadsFromNotes(p *process, notes []*note, machineType elf.Machine) proc.Thread {
var currentThread proc.Thread
var lastThreadAMD *linuxAMD64Thread
var lastThreadARM *linuxARM64Thread
for _, note := range notes {
switch note.Type {
case elf.NT_PRSTATUS:
if machineType == _EM_X86_64 {
t := note.Desc.(*linuxPrStatusAMD64)
lastThreadAMD = &linuxAMD64Thread{linutil.AMD64Registers{Regs: &t.Reg}, t}
p.Threads[int(t.Pid)] = &thread{lastThreadAMD, p, proc.CommonThread{}}
if currentThread == nil {
currentThread = p.Threads[int(t.Pid)]
}
} else if machineType == _EM_AARCH64 {
t := note.Desc.(*linuxPrStatusARM64)
lastThreadARM = &linuxARM64Thread{linutil.ARM64Registers{Regs: &t.Reg}, t}
p.Threads[int(t.Pid)] = &thread{lastThreadARM, p, proc.CommonThread{}}
if currentThread == nil {
currentThread = p.Threads[int(t.Pid)]
}
}
case _NT_FPREGSET:
if machineType == _EM_AARCH64 {
if lastThreadARM != nil {
lastThreadARM.regs.Fpregs = note.Desc.(*linutil.ARM64PtraceFpRegs).Decode()
}
}
case _NT_X86_XSTATE:
if machineType == _EM_X86_64 {
if lastThreadAMD != nil {
lastThreadAMD.regs.Fpregs = note.Desc.(*amd64util.AMD64Xstate).Decode()
}
}
case elf.NT_PRPSINFO:
p.pid = int(note.Desc.(*linuxPrPsInfo).Pid)
}
}
return currentThread
}
// readLinuxOrPlatformIndependentCore reads a core file from corePath
// corresponding to the executable at exePath. For details on the Linux ELF
// core format, see:
// http://www.gabriel.urdhr.fr/2015/05/29/core-file/,
// http://uhlo.blogspot.fr/2012/05/brief-look-into-core-dumps.html,
// elf_core_dump in http://lxr.free-electrons.com/source/fs/binfmt_elf.c,
// and, if absolutely desperate, readelf.c from the binutils source.
func readLinuxOrPlatformIndependentCore(corePath, exePath string) (*process, proc.Thread, error) {
coreFile, err := elf.Open(corePath)
if err != nil {
if _, isfmterr := err.(*elf.FormatError); isfmterr && (strings.Contains(err.Error(), elfErrorBadMagicNumber) || strings.Contains(err.Error(), " at offset 0x0: too short")) {
// Go >=1.11 and <1.11 produce different errors when reading a non-elf file.
return nil, nil, ErrUnrecognizedFormat
}
return nil, nil, err
}
if coreFile.Type != elf.ET_CORE {
return nil, nil, fmt.Errorf("%v is not a core file", coreFile)
}
machineType := coreFile.Machine
notes, platformIndependentDelveCore, err := readNotes(coreFile, machineType)
if err != nil {
return nil, nil, err
}
exe, err := os.Open(exePath)
if err != nil {
return nil, nil, err
}
exeELF, err := elf.NewFile(exe)
if err != nil {
if !platformIndependentDelveCore {
return nil, nil, err
}
} else {
if exeELF.Machine != machineType {
return nil, nil, fmt.Errorf("architecture mismatch between core file (%#x) and executable file (%#x)", machineType, exeELF.Machine)
}
if exeELF.Type != elf.ET_EXEC && exeELF.Type != elf.ET_DYN {
return nil, nil, fmt.Errorf("%v is not an exe file", exeELF)
}
}
memory := buildMemory(coreFile, exeELF, exe, notes)
// TODO support 386
var bi *proc.BinaryInfo
if platformIndependentDelveCore {
goos, goarch, err := platformFromNotes(notes)
if err != nil {
return nil, nil, err
}
bi = proc.NewBinaryInfo(goos, goarch)
} else {
switch machineType {
case _EM_X86_64:
bi = proc.NewBinaryInfo("linux", "amd64")
case _EM_AARCH64:
bi = proc.NewBinaryInfo("linux", "arm64")
default:
return nil, nil, fmt.Errorf("unsupported machine type")
}
}
entryPoint := findEntryPoint(notes, bi.Arch.PtrSize())
p := &process{
mem: memory,
Threads: map[int]*thread{},
entryPoint: entryPoint,
bi: bi,
breakpoints: proc.NewBreakpointMap(),
}
if platformIndependentDelveCore {
currentThread, err := threadsFromDelveNotes(p, notes)
return p, currentThread, err
}
currentThread := linuxThreadsFromNotes(p, notes, machineType)
return p, currentThread, nil
}
type linuxAMD64Thread struct {
regs linutil.AMD64Registers
t *linuxPrStatusAMD64
}
type linuxARM64Thread struct {
regs linutil.ARM64Registers
t *linuxPrStatusARM64
}
func (t *linuxAMD64Thread) registers() (proc.Registers, error) {
var r linutil.AMD64Registers
r.Regs = t.regs.Regs
r.Fpregs = t.regs.Fpregs
return &r, nil
}
func (t *linuxARM64Thread) registers() (proc.Registers, error) {
var r linutil.ARM64Registers
r.Regs = t.regs.Regs
r.Fpregs = t.regs.Fpregs
return &r, nil
}
func (t *linuxAMD64Thread) pid() int {
return int(t.t.Pid)
}
func (t *linuxARM64Thread) pid() int {
return int(t.t.Pid)
}
// Note is a note from the PT_NOTE prog.
// Relevant types:
// - NT_FILE: File mapping information, e.g. program text mappings. Desc is a LinuxNTFile.
// - NT_PRPSINFO: Information about a process, including PID and signal. Desc is a LinuxPrPsInfo.
// - NT_PRSTATUS: Information about a thread, including base registers, state, etc. Desc is a LinuxPrStatus.
// - NT_FPREGSET (Not implemented): x87 floating point registers.
// - NT_X86_XSTATE: Other registers, including AVX and such.
type note struct {
Type elf.NType
Name string
Desc interface{} // Decoded Desc from the
}
// readNotes reads all the notes from the notes prog in core.
func readNotes(core *elf.File, machineType elf.Machine) ([]*note, bool, error) {
var notesProg *elf.Prog
for _, prog := range core.Progs {
if prog.Type == elf.PT_NOTE {
notesProg = prog
break
}
}
r := notesProg.Open()
hasDelveThread := false
hasDelveHeader := false
hasElfPrStatus := false
notes := []*note{}
for {
note, err := readNote(r, machineType)
if err == io.EOF {
break
}
if err != nil {
return nil, false, err
}
switch note.Type {
case elfwriter.DelveHeaderNoteType:
hasDelveHeader = true
case elfwriter.DelveThreadNodeType:
hasDelveThread = true
case elf.NT_PRSTATUS:
hasElfPrStatus = true
}
notes = append(notes, note)
}
return notes, hasDelveThread && hasDelveHeader && !hasElfPrStatus, nil
}
// readNote reads a single note from r, decoding the descriptor if possible.
func readNote(r io.ReadSeeker, machineType elf.Machine) (*note, error) {
// Notes are laid out as described in the SysV ABI:
// http://www.sco.com/developers/gabi/latest/ch5.pheader.html#note_section
note := ¬e{}
hdr := &elfNotesHdr{}
err := binary.Read(r, binary.LittleEndian, hdr)
if err != nil {
return nil, err // don't wrap so readNotes sees EOF.
}
note.Type = elf.NType(hdr.Type)
name := make([]byte, hdr.Namesz)
if _, err := r.Read(name); err != nil {
return nil, fmt.Errorf("reading name: %v", err)
}
note.Name = string(name)
if err := skipPadding(r, 4); err != nil {
return nil, fmt.Errorf("aligning after name: %v", err)
}
desc := make([]byte, hdr.Descsz)
if _, err := r.Read(desc); err != nil {
return nil, fmt.Errorf("reading desc: %v", err)
}
descReader := bytes.NewReader(desc)
switch note.Type {
case elf.NT_PRSTATUS:
if machineType == _EM_X86_64 {
note.Desc = &linuxPrStatusAMD64{}
} else if machineType == _EM_AARCH64 {
note.Desc = &linuxPrStatusARM64{}
} else {
return nil, fmt.Errorf("unsupported machine type")
}
if err := binary.Read(descReader, binary.LittleEndian, note.Desc); err != nil {
return nil, fmt.Errorf("reading NT_PRSTATUS: %v", err)
}
case elf.NT_PRPSINFO:
note.Desc = &linuxPrPsInfo{}
if err := binary.Read(descReader, binary.LittleEndian, note.Desc); err != nil {
return nil, fmt.Errorf("reading NT_PRPSINFO: %v", err)
}
case _NT_FILE:
// No good documentation reference, but the structure is
// simply a header, including entry count, followed by that
// many entries, and then the file name of each entry,
// null-delimited. Not reading the names here.
data := &linuxNTFile{}
if err := binary.Read(descReader, binary.LittleEndian, &data.linuxNTFileHdr); err != nil {
return nil, fmt.Errorf("reading NT_FILE header: %v", err)
}
for i := 0; i < int(data.Count); i++ {
entry := &linuxNTFileEntry{}
if err := binary.Read(descReader, binary.LittleEndian, entry); err != nil {
return nil, fmt.Errorf("reading NT_FILE entry %v: %v", i, err)
}
data.entries = append(data.entries, entry)
}
note.Desc = data
case _NT_X86_XSTATE:
if machineType == _EM_X86_64 {
var fpregs amd64util.AMD64Xstate
if err := amd64util.AMD64XstateRead(desc, true, &fpregs); err != nil {
return nil, err
}
note.Desc = &fpregs
}
case _NT_AUXV, elfwriter.DelveHeaderNoteType, elfwriter.DelveThreadNodeType:
note.Desc = desc
case _NT_FPREGSET:
if machineType == _EM_AARCH64 {
fpregs := &linutil.ARM64PtraceFpRegs{}
rdr := bytes.NewReader(desc[:_ARM_FP_HEADER_START])
if err := binary.Read(rdr, binary.LittleEndian, fpregs.Byte()); err != nil {
return nil, err
}
note.Desc = fpregs
}
}
if err := skipPadding(r, 4); err != nil {
return nil, fmt.Errorf("aligning after desc: %v", err)
}
return note, nil
}
// skipPadding moves r to the next multiple of pad.
func skipPadding(r io.ReadSeeker, pad int64) error {
pos, err := r.Seek(0, os.SEEK_CUR)
if err != nil {
return err
}
if pos%pad == 0 {
return nil
}
if _, err := r.Seek(pad-(pos%pad), os.SEEK_CUR); err != nil {
return err
}
return nil
}
func buildMemory(core, exeELF *elf.File, exe io.ReaderAt, notes []*note) proc.MemoryReader {
memory := &splicedMemory{}
// For now, assume all file mappings are to the exe.
for _, note := range notes {
if note.Type == _NT_FILE {
fileNote := note.Desc.(*linuxNTFile)
for _, entry := range fileNote.entries {
r := &offsetReaderAt{
reader: exe,
offset: entry.Start - (entry.FileOfs * fileNote.PageSize),
}
memory.Add(r, entry.Start, entry.End-entry.Start)
}
}
}
// Load memory segments from exe and then from the core file,
// allowing the corefile to overwrite previously loaded segments
for _, elfFile := range []*elf.File{exeELF, core} {
if elfFile == nil {
continue
}
for _, prog := range elfFile.Progs {
if prog.Type == elf.PT_LOAD {
if prog.Filesz == 0 {
continue
}
r := &offsetReaderAt{
reader: prog.ReaderAt,
offset: prog.Vaddr,
}
memory.Add(r, prog.Vaddr, prog.Filesz)
}
}
}
return memory
}
func findEntryPoint(notes []*note, ptrSize int) uint64 {
for _, note := range notes {
if note.Type == _NT_AUXV {
return linutil.EntryPointFromAuxv(note.Desc.([]byte), ptrSize)
}
}
return 0
}
// LinuxPrPsInfo has various structures from the ELF spec and the Linux kernel.
// AMD64 specific primarily because of unix.PtraceRegs, but also
// because some of the fields are word sized.
// See http://lxr.free-electrons.com/source/include/uapi/linux/elfcore.h
type linuxPrPsInfo struct {
State uint8
Sname int8
Zomb uint8
Nice int8
_ [4]uint8
Flag uint64
Uid, Gid uint32
Pid, Ppid, Pgrp, Sid int32
Fname [16]uint8
Args [80]uint8
}
// LinuxPrStatusAMD64 is a copy of the prstatus kernel struct.
type linuxPrStatusAMD64 struct {
Siginfo linuxSiginfo
Cursig uint16
_ [2]uint8
Sigpend uint64
Sighold uint64
Pid, Ppid, Pgrp, Sid int32
Utime, Stime, CUtime, CStime linuxCoreTimeval
Reg linutil.AMD64PtraceRegs
Fpvalid int32
}
// LinuxPrStatusARM64 is a copy of the prstatus kernel struct.
type linuxPrStatusARM64 struct {
Siginfo linuxSiginfo
Cursig uint16
_ [2]uint8
Sigpend uint64
Sighold uint64
Pid, Ppid, Pgrp, Sid int32
Utime, Stime, CUtime, CStime linuxCoreTimeval
Reg linutil.ARM64PtraceRegs
Fpvalid int32
}
// LinuxSiginfo is a copy of the
// siginfo kernel struct.
type linuxSiginfo struct {
Signo int32
Code int32
Errno int32
}
// LinuxNTFile contains information on mapped files.
type linuxNTFile struct {
linuxNTFileHdr
entries []*linuxNTFileEntry
}
// LinuxNTFileHdr is a header struct for NTFile.
type linuxNTFileHdr struct {
Count uint64
PageSize uint64
}
// LinuxNTFileEntry is an entry of an NT_FILE note.
type linuxNTFileEntry struct {
Start uint64
End uint64
FileOfs uint64
}
// elfNotesHdr is the ELF Notes header.
// Same size on 64 and 32-bit machines.
type elfNotesHdr struct {
Namesz uint32
Descsz uint32
Type uint32
}