Attachment 682451 Details for Bug 896737 – example test code for clone(2) with TLS segfault

example test code for clone(2) with TLS segfault

test.c (text/plain), 1.67 KB, created by Eric Paris on 2013-01-18 14:27:41 UTC

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Creator: Eric Paris

Created: 2013-01-18 14:27:41 UTC

Size: 1.67 KB

patch

obsolete

>#define _GNU_SOURCE
>#include <sched.h>
>#include <signal.h>
>#include <stdlib.h>
>#include <stdio.h>
>#include <string.h>
>#include <unistd.h>
>#include <pthread.h>
>
>#include <sys/mman.h>
>#include <sys/syscall.h>
>#include <sys/types.h>
>#include <sys/wait.h>
>
>#include <linux/unistd.h>
>#include <asm/ldt.h>
>
>#define MMAP_PROT	(PROT_EXEC|PROT_READ|PROT_WRITE)
>#define MMAP_FLAGS	(MAP_PRIVATE|MAP_ANONYMOUS|MAP_GROWSDOWN|MAP_STACK)
>#define CLONE_FLAGS	(CLONE_NEWNS|CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWPID|CLONE_NEWNET|SIGCHLD)
>
>static __thread char *cache = NULL;
>
>static int clone_fn(void *v __attribute__((unused)))
>{
>	printf("clone: %s\n", cache);
>	return 0;
>}
>
>static void *pthread_fn(void *v __attribute__((unused)))
>{
>	printf("pthread: %s\n", cache);
>	return NULL;
>}
>
>static void clear(void)
>{
>	free(cache);
>	cache = NULL;
>}
>
>int main(void)
>{
>	pid_t fork_child, clone_child;
>	pthread_t pthread_child;
>	struct user_desc tls;
>	void *clone_stack, *pthread_ret;
>	int status;
>
>	status = pthread_atfork(NULL, NULL, clear);
>	if (status < 0)
>		return status;
>
>	cache = strdup("CACHED STRING");
>
>	printf("parent: %s\n", cache);
>
>	fork_child = fork();
>	if (fork_child == 0)
>		return printf("fork: cache=%s\n", cache);
>
>	wait(&status);
>
>	status = pthread_create(&pthread_child, NULL, pthread_fn, NULL);
>	if (status < 0)
>		return status;
>	status = pthread_join(pthread_child, &pthread_ret);
>	if (status < 0)
>		return status;
>
>	clone_stack = mmap(NULL, 4096*4, MMAP_PROT, MMAP_FLAGS, -1, 0);
>	if (clone_stack == MAP_FAILED)
>		return -1;
>	clone_stack += 4096*4;
>
>	clone_child = clone(clone_fn, clone_stack, CLONE_FLAGS|CLONE_SETTLS, NULL, &tls, NULL);
>	if (clone_child < 0)
>		return clone_child;
>
>	wait(&status);
>
>	return status;
>}

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Attachments on bug 896737: 682451