77 lines
1.8 KiB
C
77 lines
1.8 KiB
C
#define _GNU_SOURCE
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#include <assert.h>
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#include <errno.h>
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#include <sched.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <sys/mman.h>
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#include <sys/wait.h>
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#include <unistd.h>
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// Based on a test by Steven Stewart-Gallus, see 342040
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int fork_routine(void *arg)
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{
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write(1, "fork_routine\n", 13);
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_Exit(EXIT_SUCCESS);
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}
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int main(void)
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{
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long page_size = sysconf(_SC_PAGE_SIZE);
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assert(page_size != -1);
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/* We need an extra page for signals */
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long stack_size = sysconf(_SC_THREAD_STACK_MIN) + page_size;
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assert(stack_size != -1);
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size_t stack_and_guard_size = page_size + stack_size + page_size;
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void *child_stack = mmap(
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NULL, stack_and_guard_size, PROT_READ | PROT_WRITE,
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MAP_PRIVATE | MAP_ANONYMOUS | MAP_GROWSDOWN, -1, 0);
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if (NULL == child_stack) {
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perror("mmap");
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return EXIT_FAILURE;
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}
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/* Guard pages are shared between the stacks */
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if (-1 == mprotect((char *)child_stack, page_size, PROT_NONE)) {
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perror("mprotect");
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return EXIT_FAILURE;
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}
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if (-1 == mprotect((char *)child_stack + page_size + stack_size,
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page_size, PROT_NONE)) {
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perror("mprotect");
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return EXIT_FAILURE;
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}
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void *stack_start = (char *)child_stack + page_size + stack_size;
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if (0)
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printf("stack_start %p page_size %d stack_size %d\n",
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stack_start, (int)page_size, (int)stack_size);
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write(1, "parent before clone\n", 20);
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pid_t child =
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clone(fork_routine, stack_start,
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SIGCHLD | CLONE_VFORK | CLONE_VM, NULL);
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write(1, "parent after clone\n", 19);
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if (-1 == child) {
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perror("clone");
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return EXIT_FAILURE;
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}
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for (;;) {
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int xx;
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switch (waitpid(child, &xx, 0)) {
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case -1:
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switch (errno) {
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case EINTR:
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continue;
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default:
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perror("waitpid");
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return EXIT_FAILURE;
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}
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default:
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return EXIT_SUCCESS;
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}
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}
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}
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