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

n0ano
2001-11-14T16:42:56Z

D'Laila-

Remember that longs and pointers are 64 bits. The `%x' format
to `printf' says to print out a 32-bit integer so you wind up
truncating the upper 32-bits of the address. Just change your
format to `%lx' and you should print out the right address.

On Wed, Nov 14, 2001 at 08:03:57AM -0800, Pereira, D LailaX E wrote:
>
> 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
> _______________________________________________
> Linux-IA64 mailing list
> Linux-IA64@linuxia64.org
> http://lists.linuxia64.org/lists/listinfo/linux-ia64

--
Don Dugger
"Censeo Toto nos in Kansa esse decisse." - D. Gale
n0ano@indstorage.com
Ph: 303/652-0870x117