mirror of
https://github.com/moby/moby.git
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63 lines
1.6 KiB
C
63 lines
1.6 KiB
C
#define _GNU_SOURCE
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#include <errno.h>
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#include <sched.h>
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#include <signal.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.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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#define STACK_SIZE (1024 * 1024) /* Stack size for cloned child */
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struct clone_args {
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char **argv;
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};
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// child_exec is the func that will be executed as the result of clone
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static int child_exec(void *stuff)
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{
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struct clone_args *args = (struct clone_args *)stuff;
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if (execvp(args->argv[0], args->argv) != 0) {
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fprintf(stderr, "failed to execvp argments %s\n",
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strerror(errno));
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exit(-1);
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}
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// we should never reach here!
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exit(EXIT_FAILURE);
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}
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int main(int argc, char **argv)
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{
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struct clone_args args;
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args.argv = &argv[1];
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int clone_flags = CLONE_NEWUSER | SIGCHLD;
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// allocate stack for child
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char *stack; /* Start of stack buffer */
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char *child_stack; /* End of stack buffer */
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stack =
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mmap(NULL, STACK_SIZE, PROT_READ | PROT_WRITE,
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MAP_SHARED | MAP_ANON | MAP_STACK, -1, 0);
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if (stack == MAP_FAILED) {
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fprintf(stderr, "mmap failed: %s\n", strerror(errno));
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exit(EXIT_FAILURE);
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}
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child_stack = stack + STACK_SIZE; /* Assume stack grows downward */
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// the result of this call is that our child_exec will be run in another
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// process returning its pid
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pid_t pid = clone(child_exec, child_stack, clone_flags, &args);
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if (pid < 0) {
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fprintf(stderr, "clone failed: %s\n", strerror(errno));
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exit(EXIT_FAILURE);
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}
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// lets wait on our child process here before we, the parent, exits
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if (waitpid(pid, NULL, 0) == -1) {
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fprintf(stderr, "failed to wait pid %d\n", pid);
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exit(EXIT_FAILURE);
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}
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exit(EXIT_SUCCESS);
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}
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