Re: x86_64 frame pointer via thread context

[Petr Vandrovec <vandrove@vc.cvut.cz>]

Dave Jiang wrote:
> Petr Vandrovec wrote:
> 
>> Dave Jiang wrote:
>>
>>> Andi Kleen wrote:
>>>
>>>> Dave Jiang <djiang@mvista.com> writes:
>>>>
>>>>> Am I doing something wrong, or is this intended to be this way on
>>>>> x86_64, or is something incorrect in the kernel? This method works
>>>>> fine on i386. Thanks for any help!
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> I just tested your program on SLES9 with updated kernel and RBP
>>>> looks correct to me. Probably something is wrong with your user space
>>>> includes or your compiler.
>>>>
>>>> -Andi
>>>
>>>
>>>
>>>
>>> I revised the app a little so that it would allow the threads to 
>>> start, thus should prevent rBP w/ all 0's showing up. Below are some 
>>> of results that I've gotten from various different distros and 
>>> platforms. As you can see, the f's shows up on most of them, 
>>> including Suse 9.2. The only one showed up looking ok is the 
>>> Mandrake/Mandriva distro. I'm not sure how different SLES9 is from 
>>> Suse9.2....
>>
>>
>>
>> Replace call to sleep() with busy loop.  Glibc's sleep() uses %ebp for
>> its own data, so when you interrupt sleep(), you get rbp=(unsigned 
>> int)-1,
>> as rbp really contains 0x0000.0000.ffff.ffff when nanosleep() syscall
>> is issued.
>>                                 Petr
>>
> 
>  From what I understand, when you signal a thread, the signal handler 
> executes in the thread context and not the main process context. So 
> therefore the rbp would be the thread's copy and not the one that 
> sleep() just modified. So whatever sleep does to the main process 
> context, there shouldn't be any effect on the thread context.... Also, 
> what can I call to allow the threads to run? sleep() allows me to run 
> the other threads. Busy wait does not.....

I do not understand.  You call sleep() from both threads you spawn
(as well from main), so both threads are always interrupted in the
sleep(2).  Load your process to the debugger...

#0  tb_sig_handler (sig=33, info=0x407ff2f0, ucontext=0x407ff1c0) at ttest1.c:26
#1  <signal handler called>
#2  0x00002aaaaad81335 in nanosleep () from /lib/libc.so.6
#3  0x00002aaaaad811a5 in sleep () from /lib/libc.so.6
#4  0x0000000000400871 in test_thread1 (arg=0x0) at ttest1.c:40
#5  0x00002aaaaabc6b55 in start_thread () from /lib/libpthread.so.0
#6  0x00002aaaaada87f0 in clone () from /lib/libc.so.6

							Petr