* Debugging 64-bit programs using 32-bit GDB
@ 2013-07-09 10:02 Nikita Karetnikov
2013-07-24 14:33 ` Pedro Alves
0 siblings, 1 reply; 6+ messages in thread
From: Nikita Karetnikov @ 2013-07-09 10:02 UTC (permalink / raw)
To: gdb
[-- Attachment #1: Type: text/plain, Size: 412 bytes --]
Is it possible to debug a 64-bit executable ('bin/guile' [1]) using
32-bit GDB? (I use GNU/Linux.)
I've tried to configure GDB 7.6 with '--enable-64-bit-bfd' (see [2]),
but it still shows "mips-tdep.c:709: internal-error: bad register
size".
[1] http://www.fdn.fr/~lcourtes/tmp/guile-static-stripped-2.0.9-mips64el-linux-gnuabi64.tar.xz
[2] http://www.linux-mips.org/archives/linux-mips/2010-10/msg00336.html
[-- Attachment #2: Type: application/pgp-signature, Size: 835 bytes --]
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Debugging 64-bit programs using 32-bit GDB
2013-07-09 10:02 Debugging 64-bit programs using 32-bit GDB Nikita Karetnikov
@ 2013-07-24 14:33 ` Pedro Alves
2013-07-24 16:09 ` Doug Evans
2013-07-24 21:21 ` Maciej W. Rozycki
0 siblings, 2 replies; 6+ messages in thread
From: Pedro Alves @ 2013-07-24 14:33 UTC (permalink / raw)
To: Nikita Karetnikov; +Cc: gdb
On 07/09/2013 11:06 AM, Nikita Karetnikov wrote:
> Is it possible to debug a 64-bit executable ('bin/guile' [1]) using
> 32-bit GDB? (I use GNU/Linux.)
I don't think so. The ptrace registers interfaces allow retrieving
the right register sets (at least the modern interfaces), but
things like breakpoints, etc. won't work, as the 32-bit GDB won't
be able to handle the inferior's 64-bit addresses (due to how ptrace
works). Last I checked, Power had extra ptrace interfaces for that.
Don't know about MIPS.
(you can however connect a 32-bit GDB to a 64-bit GDBserver, and use
that to debug a 64-bit program, though that's more trouble
than just using a 64-bit GDB.).
>
> I've tried to configure GDB 7.6 with '--enable-64-bit-bfd' (see [2]),
> but it still shows "mips-tdep.c:709: internal-error: bad register
> size".
The x86_64 port catches the case early and bails out (amd64_linux_read_description):
if (sizeof (void *) == 4 && is_64bit && !is_x32)
error (_("Can't debug 64-bit process with 32-bit GDB"));
It'd be obviously better if MIPS native target did the same, instead
of tripping on assertions.
> [1] http://www.fdn.fr/~lcourtes/tmp/guile-static-stripped-2.0.9-mips64el-linux-gnuabi64.tar.xz
> [2] http://www.linux-mips.org/archives/linux-mips/2010-10/msg00336.html
--
Pedro Alves
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Debugging 64-bit programs using 32-bit GDB
2013-07-24 14:33 ` Pedro Alves
@ 2013-07-24 16:09 ` Doug Evans
2013-07-24 16:25 ` Pedro Alves
2013-07-24 21:21 ` Maciej W. Rozycki
1 sibling, 1 reply; 6+ messages in thread
From: Doug Evans @ 2013-07-24 16:09 UTC (permalink / raw)
To: Pedro Alves; +Cc: Nikita Karetnikov, gdb
On Wed, Jul 24, 2013 at 7:33 AM, Pedro Alves <palves@redhat.com> wrote:
> On 07/09/2013 11:06 AM, Nikita Karetnikov wrote:
>> Is it possible to debug a 64-bit executable ('bin/guile' [1]) using
>> 32-bit GDB? (I use GNU/Linux.)
>
> I don't think so. The ptrace registers interfaces allow retrieving
> the right register sets (at least the modern interfaces), but
> things like breakpoints, etc. won't work, as the 32-bit GDB won't
> be able to handle the inferior's 64-bit addresses (due to how ptrace
> works). Last I checked, Power had extra ptrace interfaces for that.
> Don't know about MIPS.
>
> (you can however connect a 32-bit GDB to a 64-bit GDBserver, and use
> that to debug a 64-bit program, though that's more trouble
> than just using a 64-bit GDB.).
>
>>
>> I've tried to configure GDB 7.6 with '--enable-64-bit-bfd' (see [2]),
>> but it still shows "mips-tdep.c:709: internal-error: bad register
>> size".
>
> The x86_64 port catches the case early and bails out (amd64_linux_read_description):
>
> if (sizeof (void *) == 4 && is_64bit && !is_x32)
> error (_("Can't debug 64-bit process with 32-bit GDB"));
[filed for reference sake]
Alas basic 32-bit linux builds of gdb don't compile amd64-linux-nat.c.
It would be really nice to print a better error message than the
following for 32-bit gdb debugging 64-bit executable:
"/tmp/hello.x64": not in executable format: File format not recognized
It's a not uncommon failure mode.
Hmmm, amd64-linux-nat.c is not compiled even if I do
--enable-targets=all --enable-64-bit-bfd.
When does the above error get triggered?
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Debugging 64-bit programs using 32-bit GDB
2013-07-24 16:09 ` Doug Evans
@ 2013-07-24 16:25 ` Pedro Alves
2013-07-24 17:14 ` Pedro Alves
0 siblings, 1 reply; 6+ messages in thread
From: Pedro Alves @ 2013-07-24 16:25 UTC (permalink / raw)
To: Doug Evans; +Cc: Nikita Karetnikov, gdb
On 07/24/2013 05:09 PM, Doug Evans wrote:
> On Wed, Jul 24, 2013 at 7:33 AM, Pedro Alves <palves@redhat.com> wrote:
>> On 07/09/2013 11:06 AM, Nikita Karetnikov wrote:
>>> Is it possible to debug a 64-bit executable ('bin/guile' [1]) using
>>> 32-bit GDB? (I use GNU/Linux.)
>>
>> I don't think so. The ptrace registers interfaces allow retrieving
>> the right register sets (at least the modern interfaces), but
>> things like breakpoints, etc. won't work, as the 32-bit GDB won't
>> be able to handle the inferior's 64-bit addresses (due to how ptrace
>> works). Last I checked, Power had extra ptrace interfaces for that.
>> Don't know about MIPS.
>>
>> (you can however connect a 32-bit GDB to a 64-bit GDBserver, and use
>> that to debug a 64-bit program, though that's more trouble
>> than just using a 64-bit GDB.).
>>
>>>
>>> I've tried to configure GDB 7.6 with '--enable-64-bit-bfd' (see [2]),
>>> but it still shows "mips-tdep.c:709: internal-error: bad register
>>> size".
>>
>> The x86_64 port catches the case early and bails out (amd64_linux_read_description):
>>
>> if (sizeof (void *) == 4 && is_64bit && !is_x32)
>> error (_("Can't debug 64-bit process with 32-bit GDB"));
>
> [filed for reference sake]
>
> Alas basic 32-bit linux builds of gdb don't compile amd64-linux-nat.c.
> It would be really nice to print a better error message than the
> following for 32-bit gdb debugging 64-bit executable:
>
> "/tmp/hello.x64": not in executable format: File format not recognized
>
> It's a not uncommon failure mode.
Agree, but not sure how much clearer can it get. Maybe:
"/tmp/hello.x64": not in recognized executable file format.
?
I'd just suggest building 32-bit GDB with 64-bit support. Even if
it can't debug 64-bit programs natively, it can remote debug
them, and debug 64-bit cores, in addition to getting rid of that
failure mode.
> Hmmm, amd64-linux-nat.c is not compiled even if I do
> --enable-targets=all --enable-64-bit-bfd.
Oh, you're right, of course. Guess I was thinking of gdbserver,
where linux-x86.c is shared between 32-bit and 64-bit, and it has
the similar handling:
if (sizeof (void *) == 4)
{
if (is_elf64 > 0)
error (_("Can't debug 64-bit process with 32-bit GDBserver"));
#ifndef __x86_64__
else if (machine == EM_X86_64)
error (_("Can't debug x86-64 process with 32-bit GDBserver"));
#endif
}
Two weeks vacation can swap out a lot of context. :-)
> When does the above error get triggered?
Looks like it doesn't.
--
Pedro Alves
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Debugging 64-bit programs using 32-bit GDB
2013-07-24 16:25 ` Pedro Alves
@ 2013-07-24 17:14 ` Pedro Alves
0 siblings, 0 replies; 6+ messages in thread
From: Pedro Alves @ 2013-07-24 17:14 UTC (permalink / raw)
To: Doug Evans; +Cc: Nikita Karetnikov, gdb
On 07/24/2013 05:24 PM, Pedro Alves wrote:
>> When does the above error get triggered?
>
> Looks like it doesn't.
I realized I might have replied to the wrong question.
I was saying that for 32-bit x86 GDB, that error isn't
triggered, because the code isn't reached.
That error in amd64-linux-nat.c is triggered when you try
to debug a 64-bit process with an x32 (not 32-bit x86) GDB.
--
Pedro Alves
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Debugging 64-bit programs using 32-bit GDB
2013-07-24 14:33 ` Pedro Alves
2013-07-24 16:09 ` Doug Evans
@ 2013-07-24 21:21 ` Maciej W. Rozycki
1 sibling, 0 replies; 6+ messages in thread
From: Maciej W. Rozycki @ 2013-07-24 21:21 UTC (permalink / raw)
To: Pedro Alves; +Cc: Nikita Karetnikov, gdb
On Wed, 24 Jul 2013, Pedro Alves wrote:
> > Is it possible to debug a 64-bit executable ('bin/guile' [1]) using
> > 32-bit GDB? (I use GNU/Linux.)
>
> I don't think so. The ptrace registers interfaces allow retrieving
> the right register sets (at least the modern interfaces), but
> things like breakpoints, etc. won't work, as the 32-bit GDB won't
> be able to handle the inferior's 64-bit addresses (due to how ptrace
> works). Last I checked, Power had extra ptrace interfaces for that.
> Don't know about MIPS.
This is apparently supported -- <asm/ptrace.h> on MIPS/Linux has this:
/* Calls to trace a 64bit program from a 32bit program. */
#define PTRACE_PEEKTEXT_3264 0xc0
#define PTRACE_PEEKDATA_3264 0xc1
#define PTRACE_POKETEXT_3264 0xc2
#define PTRACE_POKEDATA_3264 0xc3
#define PTRACE_GET_THREAD_AREA_3264 0xc4
and arch/mips/kernel/ptrace32.c in the kernel tree has corresponding code.
So it looks like we could support it.
Maciej
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2013-07-24 21:21 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2013-07-09 10:02 Debugging 64-bit programs using 32-bit GDB Nikita Karetnikov
2013-07-24 14:33 ` Pedro Alves
2013-07-24 16:09 ` Doug Evans
2013-07-24 16:25 ` Pedro Alves
2013-07-24 17:14 ` Pedro Alves
2013-07-24 21:21 ` Maciej W. Rozycki
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox