[Bug backtrace/14646] New: [x32] backtrace doesn't work before main

[Bug backtrace/14646] New: [x32] backtrace doesn't work before main

[hjl.tools at gmail dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=14646

             Bug #: 14646
           Summary: [x32] backtrace doesn't work before main
           Product: gdb
           Version: HEAD
            Status: NEW
          Severity: normal
          Priority: P2
         Component: backtrace
        AssignedTo: unassigned@sourceware.org
        ReportedBy: hjl.tools@gmail.com
    Classification: Unclassified


On Linux/x32 with glibc compiled with GCC 4.7.2, I
got

[hjl@gnu-tools-1 tmp]$ cat x.c
int
main ()
{
  return 0;
}
[hjl@gnu-tools-1 tmp]$ gcc -mx32 -g x.c 
[hjl@gnu-tools-1 tmp]$ gdb a.out 
GNU gdb (GDB) 7.5.50.20120925-cvs
Copyright (C) 2012 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-unknown-linux-gnu".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
Reading symbols from /tmp/a.out...done.
(gdb) b __init_misc
Function "__init_misc" not defined.
Make breakpoint pending on future shared library load? (y or [n]) y

Breakpoint 1 (__init_misc) pending.
(gdb) r
Starting program: /tmp/a.out 

Breakpoint 1, 0xf7b1cbc0 in __init_misc () from /libx32/libc.so.6
(gdb) bt
#0  0xf7b1cbc0 in __init_misc () from /libx32/libc.so.6
#1  0xf7a45b96 in _init () from /libx32/libc.so.6
#2  0x00000004 in ?? ()
Backtrace stopped: previous frame inner to this frame (corrupt stack?)
(gdb) 

Linux/x86-64 works much better:
[hjl@gnu-tools-1 tmp]$ gcc -g x.c -o 64
[hjl@gnu-tools-1 tmp]$ gdb 64
GNU gdb (GDB) 7.5.50.20120925-cvs
Copyright (C) 2012 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-unknown-linux-gnu".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
Reading symbols from /tmp/64...done.
(gdb) b __init_misc
Function "__init_misc" not defined.
Make breakpoint pending on future shared library load? (y or [n]) y

Breakpoint 1 (__init_misc) pending.
(gdb) r
Starting program: /tmp/64 

Breakpoint 1, 0x00000035978f1540 in __init_misc () from /lib64/libc.so.6
(gdb) bt
#0  0x00000035978f1540 in __init_misc () from /lib64/libc.so.6
#1  0x0000003597821519 in _init () from /lib64/libc.so.6
#2  0x000000359740f850 in call_init.part.0 () from /lib64/ld-linux-x86-64.so.2
#3  0x000000359740f950 in _dl_init_internal () from /lib64/ld-linux-x86-64.so.2
#4  0x000000359740152a in _dl_start_user () from /lib64/ld-linux-x86-64.so.2
#5  0x0000000000000001 in ?? ()
#6  0x00007fffffffe386 in ?? ()
#7  0x0000000000000000 in ?? ()
(gdb)

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[Bug backtrace/14646] [x32] backtrace doesn't work before main

[hjl.tools at gmail dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=14646

--- Comment #1 from H.J. Lu <hjl.tools at gmail dot com> 2012-09-29 23:25:39 UTC ---
hjl/x32/gdb_7_4-branch git branch at

http://sourceware.org/git/?p=gdb.git;a=summary

works fine.

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[Bug backtrace/14646] [x32] backtrace doesn't work before main

[hjl.tools at gmail dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=14646

--- Comment #2 from H.J. Lu <hjl.tools at gmail dot com> 2012-09-30 21:16:04 UTC ---
amd64_x32_init_abi has

  tdep->sp_regnum_from_eax = AMD64_RSP_REGNUM;
  tdep->pc_regnum_from_eax = AMD64_RIP_REGNUM;

But unwind frame info is based on the real RSP/RIP
registers.  Pseudo sp/pc registers don't work with
frame related codes:

[hjl@gnu-tools-1 gdb]$ egrep "pc_regnum|sp_regnum" *fram*.c 
dwarf2-frame.c:  if (regnum == gdbarch_pc_regnum (gdbarch))
dwarf2-frame.c:  else if (regnum == gdbarch_sp_regnum (gdbarch))
dwarf2-frame.c:          == gdbarch_sp_regnum (gdbarch)))
dwarf2-frame-tailcall.c:  if (regnum == gdbarch_pc_regnum (this_gdbarch))
dwarf2-frame-tailcall.c:  else if (cache->prev_sp_p && regnum ==
gdbarch_sp_regnum (this_gdbarch))
dwarf2-frame-tailcall.c:      int sp_regnum;
dwarf2-frame-tailcall.c:      sp_regnum = gdbarch_sp_regnum (prev_gdbarch);
dwarf2-frame-tailcall.c:      if (sp_regnum == -1)
dwarf2-frame-tailcall.c:      prev_sp = frame_unwind_register_unsigned
(this_frame, sp_regnum);
frame.c:      && gdbarch_pc_regnum (gdbarch) >= 0
frame.c:                      gdbarch_pc_regnum (gdbarch),
frame.c:                      gdbarch_pc_regnum (gdbarch),
frame.c:     the gdbarch_sp_regnum register is meaningful.  */
frame.c:  if (gdbarch_sp_regnum (gdbarch) >= 0)
frame.c:                    gdbarch_sp_regnum (gdbarch));
[hjl@gnu-tools-1 gdb]$ 

It is to print

(gdb) p $sp
$1 = (void *) 0xffffd028

instead of

(gdb) p $sp
$1 = 4294955048

But it breaks frame unwind.

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[Bug backtrace/14646] [x32] backtrace doesn't work before main

[jan.kratochvil at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=14646

Jan Kratochvil <jan.kratochvil at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jan.kratochvil at redhat
                   |                            |dot com

--- Comment #3 from Jan Kratochvil <jan.kratochvil at redhat dot com> 2012-10-01 16:13:27 UTC ---
Not taking this bug but it would be good to have a -nostdlib testcase for this
regression as it should be compatible with common x86_64 OSes.

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[Bug backtrace/14646] [x32] backtrace doesn't work

[hjl.tools at gmail dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=14646

H.J. Lu <hjl.tools at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[x32] backtrace doesn't     |[x32] backtrace doesn't
                   |work before main            |work

--- Comment #4 from H.J. Lu <hjl.tools at gmail dot com> 2012-10-01 16:31:07 UTC ---
(In reply to comment #3)
> Not taking this bug but it would be good to have a -nostdlib testcase for this
> regression as it should be compatible with common x86_64 OSes.

How should a -nostdlib testcase work? I believe such testcase only works
in x32 environment.

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[Bug backtrace/14646] [x32] backtrace doesn't work

[jan.kratochvil at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=14646

--- Comment #5 from Jan Kratochvil <jan.kratochvil at redhat dot com> 2012-10-01 16:55:45 UTC ---
While normal GDB testfiles run only on the native arch I believe x32 testfiles
could have an exception to run (also) with x86_64 testsuite run target.

Fedora 16 x86_64
gcc -o x32 x32.c -Wall -g -nostdlib -mx32
gdb ./x32
----------------------------
int f (void) {
  volatile int i = 4, j = 2;
  return i * 10 + j; }
int _start (void) {
  f ();
  return 0; }
----------------------------
gcc -dumpmachine
x86_64-unknown-linux-gnu
----------------------------
GNU gdb (GDB) 7.5.50.20120930-cvs
This GDB was configured as "x86_64-unknown-linux-gnu".
(gdb) b _start
Breakpoint 1 at 0x4000c1: file x32.c, line 5.
(gdb) r
Starting program: /home/jkratoch/t/x32 

Breakpoint 1, _start () at x32.c:5
5      f ();
(gdb) s
f () at x32.c:2
2      volatile int i = 4, j = 2;
(gdb) fini
Run till exit from #0  f () at x32.c:2
_start () at x32.c:6
6      return 0; }
Value returned is $1 = 42
(gdb) _

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[Bug backtrace/14646] [x32] backtrace doesn't work

[hjl.tools at gmail dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=14646

--- Comment #6 from H.J. Lu <hjl.tools at gmail dot com> 2012-10-01 17:14:35 UTC ---
(In reply to comment #5)
> While normal GDB testfiles run only on the native arch I believe x32 testfiles
> could have an exception to run (also) with x86_64 testsuite run target.
> 
> Fedora 16 x86_64
> gcc -o x32 x32.c -Wall -g -nostdlib -mx32

How did you enable x32 support in your kernel?
My request to enable x32 in Fedora 18 kernel
was rejected.

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[Bug backtrace/14646] [x32] backtrace doesn't work

[jan.kratochvil at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=14646

--- Comment #7 from Jan Kratochvil <jan.kratochvil at redhat dot com> 2012-10-01 17:20:15 UTC ---
Sorry I do not know more:
$ grep -i x32 /boot/config-3.4.11-1.fc16.x86_64 
# CONFIG_X86_X32 is not set

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[Bug backtrace/14646] [x32] backtrace doesn't work

[hjl.tools at gmail dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=14646

--- Comment #8 from H.J. Lu <hjl.tools at gmail dot com> 2012-10-01 17:33:35 UTC ---
(In reply to comment #7)
> Sorry I do not know more:
> $ grep -i x32 /boot/config-3.4.11-1.fc16.x86_64 
> # CONFIG_X86_X32 is not set

This is very odd. Does your GCC really support -mx32?
What does "file x32" say?

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[Bug backtrace/14646] [x32] backtrace doesn't work

[jan.kratochvil at redhat dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=14646

--- Comment #9 from Jan Kratochvil <jan.kratochvil at redhat dot com> 2012-10-01 17:59:26 UTC ---
OK, you are right; GCC has built it as x32 but the kernel executes it as
x86_64:

$ file x32
x32: ELF 32-bit LSB executable, x86-64, version 1 (SYSV), statically linked,
not stripped

(gdb) disas
Dump of assembler code for function f:
=> 0x00400094 <+0>:    push   %rbp
[...]
(gdb) p/x $sp
$1 = 0xffffce20
(gdb) stepi
0x00400095    1    int f (void) {
(gdb) p/x $sp
$2 = 0xffffce18

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[Bug backtrace/14646] [x32] backtrace doesn't work

[hjl.tools at gmail dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=14646

--- Comment #10 from H.J. Lu <hjl.tools at gmail dot com> 2012-10-01 18:42:07 UTC ---
(In reply to comment #9)
> OK, you are right; GCC has built it as x32 but the kernel executes it as
> x86_64:
> 
> $ file x32
> x32: ELF 32-bit LSB executable, x86-64, version 1 (SYSV), statically linked,
> not stripped
> 

Your kernel has partial x32 support.  I don't think we should
count on it.  It is better to run x32 tests in x32 environment.

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[Bug backtrace/14646] [x32] backtrace doesn't work

[cvs-commit at gcc dot gnu.org]

http://sourceware.org/bugzilla/show_bug.cgi?id=14646

--- Comment #11 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> 2012-10-15 20:37:44 UTC ---
CVSROOT:    /cvs/src
Module name:    src
Changes by:    hjl@sourceware.org    2012-10-15 20:37:39

Modified files:
    gdb            : ChangeLog amd64-tdep.c i386-tdep.c i386-tdep.h 

Log message:
    Remove sp_regnum_from_eax and pc_regnum_from_eax

    PR backtrace/14646
    PR gdb/14647
    * i386-tdep.h (gdbarch_tdep): Remove sp_regnum_from_eax and
    pc_regnum_from_eax.
    * i386-tdep.c (i386_gdbarch_init): Don't use sp_regnum_from_eax
    nor pc_regnum_from_eax.
    * amd64-tdep.c (amd64_x32_init_abi): Don't set sp_regnum_from_eax
    nor pc_regnum_from_eax.

Patches:
http://sourceware.org/cgi-bin/cvsweb.cgi/src/gdb/ChangeLog.diff?cvsroot=src&r1=1.14736&r2=1.14737
http://sourceware.org/cgi-bin/cvsweb.cgi/src/gdb/amd64-tdep.c.diff?cvsroot=src&r1=1.112&r2=1.113
http://sourceware.org/cgi-bin/cvsweb.cgi/src/gdb/i386-tdep.c.diff?cvsroot=src&r1=1.357&r2=1.358
http://sourceware.org/cgi-bin/cvsweb.cgi/src/gdb/i386-tdep.h.diff?cvsroot=src&r1=1.80&r2=1.81

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[Bug backtrace/14646] [x32] backtrace doesn't work

[cvs-commit at gcc dot gnu.org]

http://sourceware.org/bugzilla/show_bug.cgi?id=14646

--- Comment #12 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> 2012-11-10 00:50:53 UTC ---
CVSROOT:    /cvs/src
Module name:    src
Branch:     gdb_7_5-branch
Changes by:    hjl@sourceware.org    2012-11-10 00:50:46

Modified files:
    gdb            : ChangeLog amd64-tdep.c i386-tdep.c i386-tdep.h 

Log message:
    Remove sp_regnum_from_eax and pc_regnum_from_eax

    PR backtrace/14646
    PR gdb/14647
    * i386-tdep.h (gdbarch_tdep): Remove sp_regnum_from_eax and
    pc_regnum_from_eax.
    * i386-tdep.c (i386_gdbarch_init): Don't use sp_regnum_from_eax
    nor pc_regnum_from_eax.
    * amd64-tdep.c (amd64_x32_init_abi): Don't set sp_regnum_from_eax
    nor pc_regnum_from_eax.

Patches:
http://sourceware.org/cgi-bin/cvsweb.cgi/src/gdb/ChangeLog.diff?cvsroot=src&only_with_tag=gdb_7_5-branch&r1=1.14469.2.37&r2=1.14469.2.38
http://sourceware.org/cgi-bin/cvsweb.cgi/src/gdb/amd64-tdep.c.diff?cvsroot=src&only_with_tag=gdb_7_5-branch&r1=1.109&r2=1.109.2.1
http://sourceware.org/cgi-bin/cvsweb.cgi/src/gdb/i386-tdep.c.diff?cvsroot=src&only_with_tag=gdb_7_5-branch&r1=1.355&r2=1.355.2.1
http://sourceware.org/cgi-bin/cvsweb.cgi/src/gdb/i386-tdep.h.diff?cvsroot=src&only_with_tag=gdb_7_5-branch&r1=1.80&r2=1.80.2.1

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[Bug backtrace/14646] [x32] backtrace doesn't work

[hjl.tools at gmail dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=14646

H.J. Lu <hjl.tools at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED
   Target Milestone|---                         |7.5

--- Comment #13 from H.J. Lu <hjl.tools at gmail dot com> 2012-11-10 00:52:07 UTC ---
Fixed on 7.5 branch.

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