siginfo and core files

siginfo and core files

[jmf list]

Hello,

Is it possible to access the si_addr and si_signo siginfo fields from
a core dump in GDB? When debugging a live process I access these
values via the $_siginfo convenience var. I am not sure if both of
these values are normally stored in a core dump, or if they are
accessible via GDB.

I noticed that the signal number is printed to the console when I load
a core file, so I started reading the GDB source around the string
"Program terminated with signal" and found that the signal number is
read from the core file via gdb/corelow.c::core_open and
bfd/corefile.c::bfd_core_fail_failing_signal. It isn't apparent to me
that any of the other siginfo is stored or read, however.

I would like to access these values via the GDB Python API for both
live processes and core files. As it stands, I could potentially parse
'info target' to determine the target type, and respectively use
"$_siginfo" to get both si_signo and si_addr if my script is running
on a live process, or use "target core <corefile>" to get just the
signal number (and let the tool degrade gracefully for lack of
si_addr) if my script is running on a core file. That solution is a
bit of a kludge though, and I would like to access si_addr in the core
file if possible.

I am running GDB 7.4 in FC16 on x86_64 for this analysis.

Thanks. Any help would be appreciated,
J

Re: siginfo and core files

[Pedro Alves]

On 05/25/2012 02:53 PM, jmf list wrote:

> Is it possible to access the si_addr and si_signo siginfo fields from
> a core dump in GDB?

> When debugging a live process I access these

> values via the $_siginfo convenience var. I am not sure if both of
> these values are normally stored in a core dump, or if they are
> accessible via GDB.


I don't think the whole siginfo object is stored on core files.

See /usr/include/linux/elfcore.h .  The elf_prstatus and elf_prpsinfo
structures is what is put in the core.   We can retrieve some info, but
unfortunately, it doesn't look like si_addr is anywhere to be found.

-- 
Pedro Alves