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debug/plan9obj, cmd/addr2line: on Plan 9 use a.out header

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size instead of abusing text symbol

cmd/addr2line needs to know the virtual address of the start
of the text segment (load address plus header size). For
this, it used the text symbol added by the linker. This is
wrong on amd64. Header size is 40 bytes, not 32 like on 386
and arm. Function alignment is 16 bytes causing text to be
at 0x200030.

debug/plan9obj now exports both the load address and the
header size; cmd/addr2line uses this new information and
doesn't rely on text anymore.

LGTM=0intro
R=0intro, gobot, ality
CC=ality, golang-codereviews, jas, mischief
https://golang.org/cl/106460044
This commit is contained in:
Aram Hăvărneanu 2014-07-09 12:33:13 +02:00
parent fa113cf767
commit 0a2083edd7
2 changed files with 16 additions and 17 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
src/cmd/addr2line/main.go
View File

@ -237,10 +237,6 @@ func loadPlan9Table(f *plan9obj.File, sname, ename string) ([]byte, error) {
if err != nil {
return nil, err
}
text, err := findPlan9Symbol(f, "text")
if err != nil {
return nil, err
}
sect := f.Section("text")
if sect == nil {
return nil, err
@ -249,5 +245,5 @@ func loadPlan9Table(f *plan9obj.File, sname, ename string) ([]byte, error) {
if err != nil {
return nil, err
}
return data[ssym.Value-text.Value : esym.Value-text.Value], nil
return data[ssym.Value-(f.LoadAddress+f.HdrSize) : esym.Value-(f.LoadAddress+f.HdrSize)], nil
}

27
src/pkg/debug/plan9obj/file.go
View File

@ -15,10 +15,12 @@ import (
// A FileHeader represents a Plan 9 a.out file header.
type FileHeader struct {
Magic uint32
Bss uint32
Entry uint64
PtrSize int
Magic uint32
Bss uint32
Entry uint64
PtrSize int
LoadAddress uint64
HdrSize uint64
}
// A File represents an open Plan 9 a.out file.
@ -148,20 +150,21 @@ func NewFile(r io.ReaderAt) (*File, error) {
}
f := &File{FileHeader: FileHeader{
Magic: ph.Magic,
Bss: ph.Bss,
Entry: uint64(ph.Entry),
PtrSize: 4,
Magic: ph.Magic,
Bss: ph.Bss,
Entry: uint64(ph.Entry),
PtrSize: 4,
LoadAddress: 0x1000,
HdrSize: 4 * 8,
}}
hdrSize := 4 * 8
if ph.Magic&Magic64 != 0 {
if err := binary.Read(sr, binary.BigEndian, &f.Entry); err != nil {
return nil, err
}
f.PtrSize = 8
hdrSize += 8
f.LoadAddress = 0x200000
f.HdrSize += 8
}
var sects = []struct {
@ -177,7 +180,7 @@ func NewFile(r io.ReaderAt) (*File, error) {
f.Sections = make([]*Section, 5)
off := uint32(hdrSize)
off := uint32(f.HdrSize)
for i, sect := range sects {
s := new(Section)