155 lines
3.5 KiB
C
155 lines
3.5 KiB
C
#include <stdio.h>
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#include <stdlib.h>
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#include <signal.h>
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#include <setjmp.h>
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#include <unistd.h>
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#include <fcntl.h>
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#include <sys/stat.h>
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#include <sys/mman.h>
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#include <sys/wait.h>
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#include <errno.h>
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#include <string.h>
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/* - Checks if mapping of already closed file survives fork()
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- Checks if mapping the same region of the same file twice
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is done correctly.
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*/
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sigset_t unblock_sigsegv;
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jmp_buf r;
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static const char *msg;
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static const char *what;
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/* filler for file */
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char const line[] = "y1 y1 y1 y1 y1 y1 y1 y1 y1 y1 y1 y1 y1 y1 y1 y1 y1";
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void
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perror_exit (const char *str)
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{
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printf ("%s: %s\n", str, strerror (errno));
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fflush (stdout);
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exit (1);
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}
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void
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sigsegv (int unused)
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{
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sigprocmask (SIG_UNBLOCK, &unblock_sigsegv, 0);
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if (msg)
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{
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char buf[132];
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sprintf (buf, "%s %s\n", what, msg);
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write (1, buf, strlen (buf));
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msg = NULL;
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}
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longjmp (r, 1);
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}
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int
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main(int argc, char **argv)
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{
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int fd, status;
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struct stat statbuf;
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volatile char c, *buf1, *buf2;
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pid_t pid;
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/* Create data file */
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if ((fd = open("y.txt", O_RDWR | O_CREAT | O_TRUNC, 0644)) == -1)
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perror_exit ("Can't create data file");
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write (fd, line, sizeof(line) - 1);
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close (fd);
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/* Open data file */
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if ((fd = open("y.txt", O_RDONLY)) == -1)
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perror_exit ("Can't open data file");
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if (fstat(fd, &statbuf) < 0)
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perror_exit ("fstat failed");
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if (!statbuf.st_size)
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perror_exit ("filesize is 0");
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if ((buf1 = mmap(NULL, statbuf.st_size, PROT_READ, MAP_SHARED, fd, 0))
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== MAP_FAILED)
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perror_exit ("mmap 1 failed");
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close(fd);
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/* Open data file a second time */
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if ((fd = open("y.txt", O_RDONLY)) == -1)
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perror_exit ("Can't open data file in second run");
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if ((buf2 = mmap(NULL, statbuf.st_size, PROT_READ, MAP_SHARED, fd, 0))
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== MAP_FAILED)
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perror_exit ("mmap 2 failed");
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close(fd);
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sigemptyset (&unblock_sigsegv);
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sigaddset (&unblock_sigsegv, SIGSEGV);
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signal (SIGSEGV, sigsegv);
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if (setjmp (r))
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perror_exit ("SEGV in fork");
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if ((pid = fork()))
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{
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// write (1, "continuing in parent\n", strlen ("continuing in parent\n"));
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what = "parent";
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}
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else
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{
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// write (1, "continuing in child\n", strlen ("continuing in child\n"));
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what = "child";
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}
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if (pid == -1)
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perror_exit ("fork failed");
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if (setjmp (r))
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perror_exit (pid ? "SEGV in parent" : "SEGV in child");
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msg = "testing buf1";
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c = buf1[0];
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msg = "testing buf2";
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c = buf2[0];
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if (setjmp (r))
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perror_exit (pid ? "SEGV in parent's munmap" : "SEGV in child's munmap");
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if (munmap((void *) buf1, statbuf.st_size))
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perror_exit (pid ? "munmap failed in parent" : "munmap failed in child");
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if (setjmp (r) == 0)
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{
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msg = "testing buf1 after unmap";
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c = buf1[0];
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perror_exit (pid ? "no SEGV in parent after munmap" : "no SEGV in child after munmap");
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}
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if (setjmp (r))
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perror_exit (pid ? "SEGV in parent after munmap" : "SEGV in child after munmap");
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msg = "testing buf2 again";
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c = buf2[0];
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if (setjmp (r))
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perror_exit (pid ? "SEGV in parent's munmap" : "SEGV in child's munmap");
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if (munmap((void *) buf2, statbuf.st_size))
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perror_exit (pid ? "munmap failed in parent" : "munmap failed in child");
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if (pid)
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{
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waitpid (pid, &status, 0);
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unlink ("y.txt");
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if (!WIFEXITED (status) || WEXITSTATUS (status))
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{
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printf ("forked process exited with status %p\n", (char *) status);
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return 1;
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}
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}
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return 0;
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}
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