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
#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);
func2();
return 0;
}
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