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Date: Wed, 2 May 2007 07:26:13 +0400 From: "Dan Kruchinin" <dubalom@...il.com> To: linux-kernel@...r.kernel.org Subject: [RFC BUG?] dereference PAGE_OFFSET address (rc7-mm2) 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@...gard]$ uname -a Linux midgard 2.6.21-rc7-mm2 #5 SMP Wed May 2 04:15:09 MSD 2007 i686 GNU/Linux [asgard@...gard]$ ./a.out Trying to cause ELF core dump... All is bad. We don't receive SIGSEGV and core dump hasn't occured. (WHY?!) --- [asgard@...gard]$ uname -a Linux midgard 2.6.21-rc7 #5 SMP Wed May 2 02:11:50 MSD 2007 i686 GNU/Linux [asgard@...gard]$ ./a.out Trying to cause ELF core dump... All is ok. We receive SIGSEGV and core dump has occured. With best regards. Dan Kruchinin. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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