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Date: Tue, 25 Jan 2011 10:52:49 +0100
From: Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>
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Subject: Re: [Xenomai-help] NULL pointer access on bfin when linking with
 xenomai and pthread
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To: xenoka09@domain.hid
Cc: xenomai@xenomai.org

Kolja Waschk wrote:
>> Some Xenomai code is executed before the main function is called. What I
>> do not understand is why gdb does not stop at the place of the segfault?
> 
> One step further.  After issuing "sharedlibrary" the syms are read. The backtrace then is
> 
> #0  0x01666f10 in pthread_sighandler_rt (signo=28, si=0x13bd374, uc=0x13bd3f4)
>      at libpthread/linuxthreads.old/signals.c:127
> #1  <signal handler called>
> #2  0x0160cf1e in __syscall_rt_sigaction (signum=<value optimized out>, act=0x13bd580, oldact=0x13bd4f4, size=8)
>      at libc/sysdeps/linux/common/__syscall_rt_sigaction.c:17
> #3  0x0162f482 in __libc_sigaction (sig=28, act=0x13bd638, oact=0xb8995c) at libc/signal/sigaction.c:58
> #4  0x01666fba in *___GI_sigaction (sig=28, act=0x13bd6e8, oact=0xb8995c) at libpthread/linuxthreads.old/signals.c:163
> #5  0x00b71c9a in xeno_sigshadow_install () at ../../../../xenomai-2.5.5.2/src/skins/common/sigshadow.c:70
> #6  0x01665f66 in __pthread_once (once_control=0xb89958, init_routine=@0x1545bc4: 0xb71c64 <xeno_sigshadow_install>)
>      at libpthread/linuxthreads.old/mutex.c:315
> #7  0x016c4132 in __wrap_pthread_setschedparam (thread=1024, policy=0, param=0x13bf9c8)
>      at ../../../../xenomai-2.5.5.2/src/skins/posix/thread.c:71
> #8  0x016c376a in __init_posix_interface () at ../../../../xenomai-2.5.5.2/src/skins/posix/init.c:90
> #9  0x016c8234 in __do_global_ctors_aux ()
>     from /opt/uClinux-2010R1-RC5_tools-RC4/blackfin-linux-dist/staging/usr/lib/libpthread_rt.so.1
> #10 0x016c2cb6 in _init () from /opt/uClinux-2010R1-RC5_tools-RC4/blackfin-linux-dist/staging/usr/lib/libpthread_rt.so.1
> #11 0x019c41b6 in _dl_get_ready_to_run (tpnt=0xb8836c, load_addr=<value optimized out>, auxvt=0x13bfda0, envp=0x13bfe6c,
>      argv=0x13bfe64, dl_boot_progmap=0x13bff40, dl_boot_got_pointer=21056480) at ldso/ldso/ldso.c:836
> #12 0x019c44a4 in ?? ()
>     from /opt/uClinux-2010R1-RC5_tools-RC4/bfin-linux-uclibc/bfin-linux-uclibc/runtime/lib/ld-uClibc.so.0
> #13 0x019c0cb0 in _dl_boot () at ./ldso/ldso/bfin/dl-inlines.h:31
> Cannot access memory at address 0x16ffc78

First, you should print the stack pointer, and cat /proc/$pid/map while
the process is stopped inside gdb, to see if you would not have a stack
overflow.

If not, recompile xenomai with --enable-debug, try and put a breakpoint
on the function xeno_sigshadow_handler.  If you hit the breakpoint, try
and execute the function step by step, looking whether a pointer could
be invalid.

-- 
                                                                Gilles.