From: Sergio Durigan Junior <sergiodj@redhat.com>
To: Pedro Alves <palves@redhat.com>
Cc: GDB Patches <gdb-patches@sourceware.org>
Subject: Re: [PATCH] Catch exception on solib_svr4_r_ldsomap
Date: Tue, 31 Mar 2015 23:39:00 -0000 [thread overview]
Message-ID: <878uecvirs.fsf@redhat.com> (raw)
In-Reply-To: <551A8546.4000208@redhat.com> (Pedro Alves's message of "Tue, 31 Mar 2015 12:30:14 +0100")
On Tuesday, March 31 2015, Pedro Alves wrote:
>>> So, gdb itself errors and stops processing the core?
>>
>> No, GDB does not "error and stop", but some testcases do that.
>
> Well, it clearly does do that. Hence your new patch. :-)
>
>>> I think I don't understand. :-) Can you please show an
>>> example session? Did GDB continue processing the core when
>>> it printed that error, or was it just a warning and it continued?
>>
>
> I meant "Did GDB stop processing the core", of course.
Sorry I misunderstood your question.
>> Sure, sorry for not sending the example session before! Here is the
>> pertinent part:
>>
>> (gdb) core /home/sergio/work/src/git/binutils-gdb/rhbz1085906-coredump-filter/build-64-3/gdb/testsuite/gdb.base/non-private-anon.gcore
>> [New LWP 28468]
>> Cannot access memory at address 0x355fc21148
>> Cannot access memory at address 0x355fc21140
>> (gdb) FAIL: gdb.base/coredump-filter.exp: loading and testing corefile for non-Private-Anonymous: load core
>> FAIL: gdb.base/coredump-filter.exp: loading and testing corefile
>> for non-Private-Anonymous: loading
>> /home/sergio/work/src/git/binutils-gdb/rhbz1085906-coredump-filter/build-64-3/gdb/testsuite/gdb.base/non-private-anon.gcore
>> spawn
>> /home/sergio/work/src/git/binutils-gdb/rhbz1085906-coredump-filter/build-64-3/gdb/testsuite/../../gdb/gdb
>> -nw -nx -data-directory
>> /home/sergio/work/src/git/binutils-gdb/rhbz1085906-coredump-filter/build-64-3/gdb/testsuite/../data-directory
>> ...
>>
>> GDB correctly loaded the corefile (despite the warnings), and the
>
> The error made the rest of core_open be skipped: if the core is still
> loaded, gdb is potentially in an inconsistent state at this point.
> I'd think we should completely discard the core/target if something
> errors out. And then if we can be tolerant to specific parts of
> loading a core failing, we should handle those before the error escapes
> out of core_open. We do something like that
> already (note core_close_cleanup and the TRY/CATCH'S), but it's clearly
> not complete. After:
>
> push_target (&core_ops);
> discard_cleanups (old_chain);
>
> ... several things can throw and let an exception escape.
Yeah, certainly we should be catching those before they escape. I will
see if I can take a look at more places to improve/fix later.
>> Right, so I took some time and found the right fix, I think. As we
>> agreed above, the fact that GDB is not printing the "Core was generated
>> by..." message is really strange, so I decided to investigate why it is
>> doing that.
>>
>> The answer is that we are forgetting to check for an exception on
>> solib_svr4_r_ldsomap. When loading the corefile, GDB calls this
>> function, which then calls read_memory_unsigned_integer, which throws an
>> error. This error is not being caught by the function, so it propagates
>> until the main loop catches it. The fix is obvious: we should catch
>> this regression and continue in the function. With it, GDB now
>> correctly prints the "Core was generated by..." message, and the patch
>> to adjust gdb_core_cmd is no longer needed.
>>
>> Regression-tested on Fedora 20 for x86_64, i686 and native-gdbserver.
>>
>> Does that make more sense now?
>>
>
> Yes, this is OK.
Thanks, pushed:
<https://sourceware.org/ml/gdb-cvs/2015-03/msg00274.html>
416f679e68468ea6dd7384213994ce74201f82e7
--
Sergio
GPG key ID: 0x65FC5E36
Please send encrypted e-mail if possible
http://sergiodj.net/
prev parent reply other threads:[~2015-03-31 23:39 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-25 0:06 [RFC/PATCH] Extend gdb_core_cmd to allow "Cannot access memory..." messages Sergio Durigan Junior
2015-03-27 10:06 ` Pedro Alves
2015-03-27 22:34 ` [PATCH] Catch exception on solib_svr4_r_ldsomap (was: Re: [RFC/PATCH] Extend gdb_core_cmd to allow "Cannot access memory..." messages) Sergio Durigan Junior
2015-03-31 11:30 ` [PATCH] Catch exception on solib_svr4_r_ldsomap Pedro Alves
2015-03-31 23:39 ` Sergio Durigan Junior [this message]
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