Access to siginfo for the signal from debugger

[David Xu]

Kostik Belousov wrote:
> On Fri, Jul 02, 2010 at 10:13:57AM +0800, David Xu wrote:
>   
>> Kostik Belousov wrote:
>>     
>>> On Thu, Jul 01, 2010 at 05:05:26PM -0400, John Baldwin wrote:
>>>       
>>>> On Thursday 01 July 2010 09:42:17 am Kostik Belousov wrote:
>>>>         
>>>>> Hi,
>>>>> below is the patch that provides the debugger with access to siginfo
>>>>> of the signal that stopped the debuggee. This allows to see a lot more
>>>>> details for the cause of the process stop. E.g. you can see a fault
>>>>> address if process get SIGSEGV or SIGBUS, you can distinguish between
>>>>> breakpoint-generated SIGTRAP and non-breakpoint, whether the signal
>>>>> was send due to external event etc.
>>>>>
>>>>> The change to struct ptrace_lwpinfo is backward-compatible in the sense
>>>>> that programs that were compiled with old definition for the struct will
>>>>> work on new kernels.
>>>>>           
>>>> Nice!  Does gdb "just work" with these changes or does it need patching 
>>>> as well?
>>>>         
>>> It should "just work", and my testing seems to confirm this. gdb uses
>>> PT_LWPINFO to enumerate the thread ids, and I checked it on mt process.
>>>
>>> As I said, the change is ABI backward-compatible, i.e. you do not need
>>> even to recompile the old program for new kernel.
>>>
>>> Sure, gdb cannot show additional available information without
>>> modifications.
>>>       
>> Yes, you can add new fields to ptrace_lwpinfo without any problem.
>> To print new fields, you should change the function
>> fbsd_thread_signal_cmd in file
>> src/gnu/usr.bin/gdb/libgdb/fbsd-threads.c
>> after change, you just type 'thread signal' command in gdb to
>> show thread's signal info. The command is freebsd specific,
>> others may or may not have it.
>>     
>
> I did what you suggested. The drawback there is that "thread signal"
> only works for the threaded processes.
>   

I have tested it, it works fine. yes, it only works for threaded target.
The only problem is strerror(0) returns 'Unknown error', this is  a bit
strange.
 
---
Program received signal ?, Unknown signal.
[Switching to Thread 800c07700 (LWP 100165)]
0x00000008008bd1ac in sigwaitinfo () from /lib/libc.so.7
(gdb) thread signal
signal mask:
hup int quit ill trap abrt emt fpe bus segv sys pipe alrm term urg tstp 
cont chl
d ttin ttou io xcpu xfsz vtalrm prof winch info usr1 usr2 <snip>
signal pending:

si_signo 33
si_errno 0 (Unknown error: 0)
si_code TIMER si_pid 0 si_uid 0 si_status 0 si_addr 0x0
(gdb)
---

Thanks,