[Linux-ia64] correct seg fault address on ia-64??

Pereira, D LailaX E
2001-11-14T16:03:57Z

Hi ,

In the following program, I was trying to obtain the address where a
segmentation fault is caused.
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <signal.h>
#include <sys/mman.h>

int *x;
int page_size;

void segv_handler( int sig, siginfo_t *sip,struct sigcontext *scp){

void *vadr=sip->si_addr;
unsigned long *pc;
unsigned long instr;
int readwrite;

if (sig=SIGSEGV){
printf("\nSegv handler ..\n");
}
printf("vaddr : %x \n",vadr);

readwrite=(((*(unsigned long*)scp->sc_ip)>>21)&1);
printf("Read or write %d\n",readwrite);
exit(1);
}

int main(){
int s;
struct sigaction sa;
int temp;

page_size=getpagesize();
printf("Pagesize : %d ,PID=%d\n",page_size,(int)getpid());
fflush(stdout);

/*SEGV handler setup*/
sa.sa_handler=(void*)&segv_handler;
sigemptyset(&sa.sa_mask);
sigaddset(&sa.sa_mask,SIGIO);
sigaddset(&sa.sa_mask,SIGALRM);

sa.sa_flags=SA_SIGINFO;

if (sigaction(SIGSEGV,&sa,NULL)){
printf(" Error assigning signal!\n");
}

x=(int*)malloc(2*page_size);

/* Align to a multiple of page_size, assumed to be a power of two */
x = (int *)((long)(((int) (long)x + page_size-1) & ~(page_size-1)));
printf("Address: %x\n",x );
//x[0]E6;

s=mprotect(x,page_size,PROT_NONE); //make it none access
printf("Page protection : NONE : try reading the page\n ");
printf("segv should arise now ...\n");
//read the page ... segv?
temp=x[0];
return 0;
}

When I run the program on a ia-64 machine (linux OS) , then I get the
following output:
Pagesize : 16384 ,PID(513
Address: 4000
Page protection : NONE : try reading the page
segv should arise now ...

Segv handler ..
vaddr : 4000
Read or write 0

.............
However , when I ran the program thru gdb, I got the following:
Reading symbols from a.out...done.
(gdb) run ex3.c
......
Pagesize : 16384 ,PID(471
Address: 4000
Page protection : NONE : try reading the page
segv should arise now ...

Program received signal SIGSEGV, Segmentation fault.
0x40000000000010e0 in main ()
(gdb) where
#0 0x40000000000010e0 in main ()
#1 0x20000000000906b0 in __libc_start_main (
main=0x40000000000013e8 <_fini+408>, argc=2,
ubp_av=0x80000fffffffb848,
init=0x40000000000013b8 <_fini+360>,
fini=0x200000000003db30 <_dl_debug_mask>,
rtld_fini=0x20000000002581c8 <_dl_get_origin+632>,
stack_end=0x80000fffffffb840) at ../sysdeps/generic/libc-start.c:129
#2 0x40000000000010b0 in main ()
(gdb)....

So thru, gdb the seg fault address is "0x40000000000010e0" , is my
interpretation right ??
Why is that when I run the program on itanium , I get the address as "4000"
and thru gdb as " 0x40000000000010e0". What is wrong?? Please let me know.

d'laila