none/tests/linux/clonev.c

   1 #define _GNU_SOURCE
   2 #include <assert.h>
   3 #include <errno.h>
   4 #include <sched.h>
   5 #include <stdio.h>
   6 #include <stdlib.h>
   7 #include <sys/mman.h>
   8 #include <sys/wait.h>
   9 #include <unistd.h>
  10 // Based on a test by Steven Stewart-Gallus, see 342040
  11 int fork_routine(void *arg)
  12 {
  13         write(1, "fork_routine\n", 13);
  14         _Exit(EXIT_SUCCESS);
  15 }
  16
  17 int main(void)
  18 {
  19         long page_size = sysconf(_SC_PAGE_SIZE);
  20         assert(page_size != -1);
  21
  22         /* We need an extra page for signals */
  23         long stack_size = sysconf(_SC_THREAD_STACK_MIN) + page_size;
  24         assert(stack_size != -1);
  25
  26         size_t stack_and_guard_size = page_size + stack_size + page_size;
  27         void *child_stack = mmap(
  28             NULL, stack_and_guard_size, PROT_READ | PROT_WRITE,
  29             MAP_PRIVATE | MAP_ANONYMOUS | MAP_GROWSDOWN, -1, 0);
  30         if (NULL == child_stack) {
  31                 perror("mmap");
  32                 return EXIT_FAILURE;
  33         }
  34
  35         /* Guard pages are shared between the stacks */
  36         if (-1 == mprotect((char *)child_stack, page_size, PROT_NONE)) {
  37                 perror("mprotect");
  38                 return EXIT_FAILURE;
  39         }
  40
  41         if (-1 == mprotect((char *)child_stack + page_size + stack_size,
  42                            page_size, PROT_NONE)) {
  43                 perror("mprotect");
  44                 return EXIT_FAILURE;
  45         }
  46
  47         void *stack_start = (char *)child_stack + page_size + stack_size;
  48         if (0)
  49            printf("stack_start %p page_size %d stack_size %d\n",
  50                   stack_start, (int)page_size, (int)stack_size);
  51         write(1, "parent before clone\n", 20);
  52         pid_t child =
  53             clone(fork_routine, stack_start,
  54                   SIGCHLD | CLONE_VFORK | CLONE_VM, NULL);
  55         write(1, "parent after clone\n", 19);
  56         if (-1 == child) {
  57                 perror("clone");
  58                 return EXIT_FAILURE;
  59         }
  60
  61         for (;;) {
  62                 int xx;
  63                 switch (waitpid(child, &xx, 0)) {
  64                 case -1:
  65                         switch (errno) {
  66                         case EINTR:
  67                                 continue;
  68                         default:
  69                                 perror("waitpid");
  70                                 return EXIT_FAILURE;
  71                         }
  72
  73                 default:
  74                         return EXIT_SUCCESS;
  75                 }
  76         }
  77 }