On Wed, 2 May 2007 07:26:13 +0400 "Dan Kruchinin" <[email protected]> wrote:
> Hi.
>
> I don't know why, but when I'm dereferencing PAGE_OFFSET(0xC0000000 on
> x86) address from user space on rc7-mm2 I don't receive SIGSEGV signal
> and there is no any core dump.
> btw: on poor rc-7 all is ok.
>
> test_code:
> ---
> #include <stdio.h>
> #include <stdlib.h>
> #include <errno.h>
> #include <unistd.h>
> #include <sys/wait.h>
> #include <sys/time.h>
> #include <sys/resource.h>
> #include <sys/types.h>
>
> #define PAGE_OFFSET 0xC0000000
>
> static void _error(const char *msg)
> {
> int errcode = errno;
>
> fprintf(stderr, "ERROR:\n--> %s [%s]\n", msg, strerror(errcode));
> exit(EXIT_FAILURE);
> }
>
> int main(void)
> {
> int pid;
> struct rlimit rl;
> int status;
>
> printf("Trying to cause ELF core dump...\n");
>
> rl.rlim_cur = rl.rlim_max = 0x10000000;
>
> if(setrlimit(RLIMIT_CORE, &rl) < 0)
> _error("setrlim error!");
> if((pid = fork()) < 0)
> _error("fork error!");
> else if(pid == 0) {
> *((long*) PAGE_OFFSET ) = 0; /* trying to dereference kernel start address */
> _exit(EXIT_SUCCESS);
> }
>
> if(waitpid(pid, &status, 0) < 0)
> _error("waitpid error!");
> if(WCOREDUMP(status))
> printf("All is ok. We receive SIGSEGV and core dump has occured.\n");
> else
> printf("All is bad. We don't receive SIGSEGV and core dump hasn't
> occured. (WHY?!)\n"); /* here I just get SIGCHLD, this means that
> child process have made it's work success... */
>
> exit(EXIT_SUCCESS);
> }
> ---
>
> [asgard@midgard]$ uname -a
> Linux midgard 2.6.21-rc7-mm2 #5 SMP Wed May 2 04:15:09 MSD 2007 i686 GNU/Linux
>
> [asgard@midgard]$ ./a.out
> Trying to cause ELF core dump...
> All is bad. We don't receive SIGSEGV and core dump hasn't occured. (WHY?!)
>
> ---
>
> [asgard@midgard]$ uname -a
> Linux midgard 2.6.21-rc7 #5 SMP Wed May 2 02:11:50 MSD 2007 i686 GNU/Linux
>
> [asgard@midgard]$ ./a.out
> Trying to cause ELF core dump...
> All is ok. We receive SIGSEGV and core dump has occured.
>
Thanks for the report. I can reproduce it.
Bisection shows that x86_64-mm-paravirt-initial-pagetable.patch caused
this.
I didn't check whether the patch actually permits us to read kernel
memory. Probably it does. Probably we'd prefer that it didn't ;)
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
