Filippo,
That really helps! Now a minor variation of the program does not throw a full
backtrace and stops short after showing the c library call. Again on x86 host
machine it correctly shows a deep backtrace.
Attached is the file. I am calling "func1()" which crashes inside snprintf
library call implementation.
ARMv7a# ./crash_test
Trying to construct invalid buffer!
SIGSEGV Handler!
Got Backtrace Size=3
0x000087bc
0x0000887c
0xb6f02420
ARMv7a #
I think we need to add unwind-tables or -finstrument-functions for uClibc as
well. I am using buildroot for the toolchain. Any ideas?
/Thanks
-----Original Message-----
From: Filippo ARCIDIACONO [mailto:filippo.arcidiac...@st.com]
Sent: Thursday, September 12, 2013 10:14 AM
To: Rajendra Dendukuri
Cc: SHREYAS JOSHI; uclibc@uclibc.org
Subject: Re: backtrace() not working on ARMv7a
On 9/12/2013 2:49 PM, Rajendra Dendukuri wrote:
> Thanks Shreyas for the tip. But it is not working even with "-fexceptions" or
> "-fasynchronous-unwind-tables" options.
>
> Forum,
> Anyone faced this issue before?
Yes. I got the same behavior using your test.
Doing some googling , see
http://stackoverflow.com/questions/9229702/gcc-return-address-of-calling-function-in-arm-architecture
on ARM arch the gcc __builtin_return_address() function does not work
beyond the current function|||| (only __builtin_return_address(0) works),
this explain because we don't obtain a full backtrace.
Using -finstrument-function compiler option (see gcc documentation at
http://gcc.gnu.org/onlinedocs/gcc-4.7.3/gcc/Code-Gen-Options.html#Code-Gen-Options)
I got a full backtrace:
root@arcidiaf:/home/filippo# gcc -o crash_test -O0 -fexceptions
-finstrument-functions crash_tst.c
root@arcidiaf:/home/filippo# ./crash_test
Trying to access NULL pointer!
SIGSEGV Handler!
Got Backtrace Size=6
0x00008854
0x0000894c
0x76ef1c24
0x000089b4
0x00008b18
0x76f3c7bc
||
>
> /Thanks
>
> From: SHREYAS JOSHI [mailto:dexterous.m...@yahoo.com]
> Sent: Thursday, September 12, 2013 2:33 AM
> To: Rajendra Dendukuri; uclibc@uclibc.org
> Subject: Re: backtrace() not working on ARMv7a
>
> Try -fexceptions.
>
> For further details, check the following link.
>
> http://www.tune2wizard.com/backtrace/
>
>
> Thanks & regards,
> Shreyas Joshi
>
>
> ________________________________
> From: Rajendra Dendukuri <rajen...@broadcom.com<mailto:rajen...@broadcom.com>>
> To: "uclibc@uclibc.org<mailto:uclibc@uclibc.org>"
> <uclibc@uclibc.org<mailto:uclibc@uclibc.org>>
> Sent: Wednesday, September 11, 2013 10:01 PM
> Subject: backtrace() not working on ARMv7a
>
> Hi uclibc list,
>
> I am trying to generate a call stack trace using backtrace() API which is
> part of libubacktrace. The idea is to catch a SIGSEGV signal and call
> backtrace() to print all the address values and compare the obtained
> addresses from objdump -D of executable. Attached is a simplified version of
> the application. Following is the output seen on ARMv7a platform with
> buildroot cross-toolchain (gcc- 4.6.3, uClibc-0.9.33.2, binutis-2.21.1).
>
> To compile the application:
> ${CROSS_COMPILE}gcc -o crash_test -O0 -funwind-tables -rdynamic crash_test.c
>
> ARMv7a# ./crash_test
> Trying to access NULL pointer!
> SIGSEGV Handler!
> Got Backtrace Size=2
> 0x00008724
> 0x000087c4
> ARMv7a#
>
> The above function call trace is only that of the signal hander
> (print_back_trace, sigsegv_handler) and does not show the entire call stack
> for the function where program crashed (print_back_trace, sigsegv_handler,
> func2, main).
>
> On x86 host same program shows a deeper function call trace right up to the
> main function and even beyond:
> x86-RHEL5-host$./crash_test
> Trying to access NULL pointer!
> SIGSEGV Handler!
> Got Backtrace Size=7
> 0x00400939
> 0x004009ab
> 0x30930302f0
> 0x004009d3
> 0x00400a7b
> 0x309301d994
> 0x00400889
> x86-RHEL5-host$
>
> Can someone please comment on what is going wrong. Any special flags that
> need to be used while compiling/linking the program.
>
> /Thanks
>
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>
>
#include <termios.h>
#include <unistd.h>
#include <stdlib.h>
#include <pthread.h>
#include <signal.h>
#include <stdio.h>
#include <string.h>
void print_back_trace() {
void *array[32];
int index, size;
size = backtrace (array, 32);
printf("Got Backtrace Size=%d\n", size);
for (index = 0; index < size; index++)
{
printf ("0x%08lx\n", (unsigned long) array[index]);
}
}
static void sigsegv_handler (int sig, siginfo_t * info, void *v)
{
printf("SIGSEGV Handler!\n");
print_back_trace();
exit (0);
}
void func2() {
int val;
unsigned int *ptr;
ptr = 0;
printf("Trying to access NULL pointer!\n");
val = *ptr;
printf ("Read 0x%x from %p\n", val, ptr);
}
void func1() {
int val;
char buf[256];
val = 100;
printf("\nTrying to construct invalid buffer!\n");
snprintf(buf, sizeof (buf), "%s", val);
printf("The content of buf: %s\n", buf);
}
int main()
{
struct sigaction sig_act;
int rc;
sig_act.sa_sigaction = sigsegv_handler;
rc = sigaction (SIGSEGV, &sig_act, 0);
func1();
return 0;
}
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