Commit 0e197515 authored by Ian Lance Taylor's avatar Ian Lance Taylor

debug/elf: support DWARF that needs relocs for 386

It's not clear how widespread this issue is, but we do have a
test case generated by a development version of clang.

I don't know whether this should go into 1.3 or not; happy to
hear arguments either way.

LGTM=rsc
R=golang-codereviews, bradfitz, rsc
CC=golang-codereviews
https://golang.org/cl/96680045
parent 68bbf9d4
......@@ -522,13 +522,17 @@ func (f *File) applyRelocations(dst []byte, rels []byte) error {
if f.Class == ELFCLASS64 && f.Machine == EM_X86_64 {
return f.applyRelocationsAMD64(dst, rels)
}
if f.Class == ELFCLASS32 && f.Machine == EM_386 {
return f.applyRelocations386(dst, rels)
}
return errors.New("not implemented")
}
func (f *File) applyRelocationsAMD64(dst []byte, rels []byte) error {
if len(rels)%Sym64Size != 0 {
return errors.New("length of relocation section is not a multiple of Sym64Size")
// 24 is the size of Rela64.
if len(rels)%24 != 0 {
return errors.New("length of relocation section is not a multiple of 24")
}
symbols, _, err := f.getSymbols(SHT_SYMTAB)
......@@ -570,6 +574,43 @@ func (f *File) applyRelocationsAMD64(dst []byte, rels []byte) error {
return nil
}
func (f *File) applyRelocations386(dst []byte, rels []byte) error {
// 8 is the size of Rel32.
if len(rels)%8 != 0 {
return errors.New("length of relocation section is not a multiple of 8")
}
symbols, _, err := f.getSymbols(SHT_SYMTAB)
if err != nil {
return err
}
b := bytes.NewReader(rels)
var rel Rel32
for b.Len() > 0 {
binary.Read(b, f.ByteOrder, &rel)
symNo := rel.Info >> 8
t := R_386(rel.Info & 0xff)
if symNo == 0 || symNo > uint32(len(symbols)) {
continue
}
sym := &symbols[symNo-1]
if t == R_386_32 {
if rel.Off+4 >= uint32(len(dst)) {
continue
}
val := f.ByteOrder.Uint32(dst[rel.Off : rel.Off+4])
val += uint32(sym.Value)
f.ByteOrder.PutUint32(dst[rel.Off:rel.Off+4], val)
}
}
return nil
}
func (f *File) DWARF() (*dwarf.Data, error) {
// There are many other DWARF sections, but these
// are the required ones, and the debug/dwarf package
......@@ -603,6 +644,19 @@ func (f *File) DWARF() (*dwarf.Data, error) {
}
}
// When using clang we need to process relocations even for 386.
rel := f.Section(".rel.debug_info")
if rel != nil && rel.Type == SHT_REL && f.Machine == EM_386 {
data, err := rel.Data()
if err != nil {
return nil, err
}
err = f.applyRelocations(dat[1], data)
if err != nil {
return nil, err
}
}
abbrev, info, str := dat[0], dat[1], dat[2]
d, err := dwarf.New(abbrev, nil, nil, info, nil, nil, nil, str)
if err != nil {
......
......@@ -260,6 +260,12 @@ var relocationTests = []relocationTest{
{0, &dwarf.Entry{Offset: 0xb, Tag: dwarf.TagCompileUnit, Children: true, Field: []dwarf.Field{{Attr: dwarf.AttrProducer, Val: "GNU C 4.2.4 (Ubuntu 4.2.4-1ubuntu4)"}, {Attr: dwarf.AttrLanguage, Val: int64(1)}, {Attr: dwarf.AttrName, Val: "go-relocation-test-gcc424.c"}, {Attr: dwarf.AttrCompDir, Val: "/tmp"}, {Attr: dwarf.AttrLowpc, Val: uint64(0x0)}, {Attr: dwarf.AttrHighpc, Val: uint64(0x6)}, {Attr: dwarf.AttrStmtList, Val: int64(0)}}}},
},
},
{
"testdata/go-relocation-test-clang-x86.obj",
[]relocationTestEntry{
{0, &dwarf.Entry{Offset: 0xb, Tag: dwarf.TagCompileUnit, Children: true, Field: []dwarf.Field{{Attr: dwarf.AttrProducer, Val: "clang version google3-trunk (trunk r209387)"}, {Attr: dwarf.AttrLanguage, Val: int64(12)}, {Attr: dwarf.AttrName, Val: "go-relocation-test-clang.c"}, {Attr: dwarf.AttrStmtList, Val: int64(0)}, {Attr: dwarf.AttrCompDir, Val: "/tmp"}}}},
},
},
{
"testdata/gcc-amd64-openbsd-debug-with-rela.obj",
[]relocationTestEntry{
......
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