linux/tools/testing/selftests/sigaltstack/sas.c

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/*
* Stas Sergeev <stsp@users.sourceforge.net>
*
* test sigaltstack(SS_ONSTACK | SS_AUTODISARM)
* If that succeeds, then swapcontext() can be used inside sighandler safely.
*
*/
#define _GNU_SOURCE
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/mman.h>
#include <ucontext.h>
#include <alloca.h>
#include <string.h>
#include <assert.h>
#include <errno.h>
#ifndef SS_AUTODISARM
signals/sigaltstack: Change SS_AUTODISARM to (1U << 31) Using bit 4 divides the space of available bits strangely. Use bit 31 instead so that we have a better chance of keeping flag and mode bits separate in the long run. Signed-off-by: Andy Lutomirski <luto@kernel.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Aleksa Sarai <cyphar@cyphar.com> Cc: Amanieu d'Antras <amanieu@gmail.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: Eric W. Biederman <ebiederm@xmission.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Heinrich Schuchardt <xypron.glpk@gmx.de> Cc: Jason Low <jason.low2@hp.com> Cc: Josh Triplett <josh@joshtriplett.org> Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Palmer Dabbelt <palmer@dabbelt.com> Cc: Paul Moore <pmoore@redhat.com> Cc: Pavel Emelyanov <xemul@parallels.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Richard Weinberger <richard@nod.at> Cc: Sasha Levin <sasha.levin@oracle.com> Cc: Shuah Khan <shuahkh@osg.samsung.com> Cc: Stas Sergeev <stsp@list.ru> Cc: Tejun Heo <tj@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vladimir Davydov <vdavydov@parallels.com> Cc: linux-api@vger.kernel.org Link: http://lkml.kernel.org/r/bb996508a600af14b406810c3d58fe0e0d0afe0d.1462296606.git.luto@kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-05-04 01:31:52 +08:00
#define SS_AUTODISARM (1U << 31)
#endif
static void *sstack, *ustack;
static ucontext_t uc, sc;
static const char *msg = "[OK]\tStack preserved";
static const char *msg2 = "[FAIL]\tStack corrupted";
struct stk_data {
char msg[128];
int flag;
};
void my_usr1(int sig, siginfo_t *si, void *u)
{
char *aa;
int err;
stack_t stk;
struct stk_data *p;
register unsigned long sp asm("sp");
if (sp < (unsigned long)sstack ||
sp >= (unsigned long)sstack + SIGSTKSZ) {
printf("[FAIL]\tSP is not on sigaltstack\n");
exit(EXIT_FAILURE);
}
/* put some data on stack. other sighandler will try to overwrite it */
aa = alloca(1024);
assert(aa);
p = (struct stk_data *)(aa + 512);
strcpy(p->msg, msg);
p->flag = 1;
printf("[RUN]\tsignal USR1\n");
err = sigaltstack(NULL, &stk);
if (err) {
perror("[FAIL]\tsigaltstack()");
exit(EXIT_FAILURE);
}
if (stk.ss_flags != SS_DISABLE)
printf("[FAIL]\tss_flags=%x, should be SS_DISABLE\n",
stk.ss_flags);
else
printf("[OK]\tsigaltstack is disabled in sighandler\n");
swapcontext(&sc, &uc);
printf("%s\n", p->msg);
if (!p->flag) {
printf("[RUN]\tAborting\n");
exit(EXIT_FAILURE);
}
}
void my_usr2(int sig, siginfo_t *si, void *u)
{
char *aa;
struct stk_data *p;
printf("[RUN]\tsignal USR2\n");
aa = alloca(1024);
/* dont run valgrind on this */
/* try to find the data stored by previous sighandler */
p = memmem(aa, 1024, msg, strlen(msg));
if (p) {
printf("[FAIL]\tsigaltstack re-used\n");
/* corrupt the data */
strcpy(p->msg, msg2);
/* tell other sighandler that his data is corrupted */
p->flag = 0;
}
}
static void switch_fn(void)
{
printf("[RUN]\tswitched to user ctx\n");
raise(SIGUSR2);
setcontext(&sc);
}
int main(void)
{
struct sigaction act;
stack_t stk;
int err;
sigemptyset(&act.sa_mask);
act.sa_flags = SA_ONSTACK | SA_SIGINFO;
act.sa_sigaction = my_usr1;
sigaction(SIGUSR1, &act, NULL);
act.sa_sigaction = my_usr2;
sigaction(SIGUSR2, &act, NULL);
sstack = mmap(NULL, SIGSTKSZ, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS | MAP_STACK, -1, 0);
if (sstack == MAP_FAILED) {
perror("mmap()");
return EXIT_FAILURE;
}
err = sigaltstack(NULL, &stk);
if (err) {
perror("[FAIL]\tsigaltstack()");
exit(EXIT_FAILURE);
}
if (stk.ss_flags == SS_DISABLE) {
printf("[OK]\tInitial sigaltstack state was SS_DISABLE\n");
} else {
printf("[FAIL]\tInitial sigaltstack state was %x; "
"should have been SS_DISABLE\n", stk.ss_flags);
return EXIT_FAILURE;
}
stk.ss_sp = sstack;
stk.ss_size = SIGSTKSZ;
stk.ss_flags = SS_ONSTACK | SS_AUTODISARM;
err = sigaltstack(&stk, NULL);
if (err) {
if (errno == EINVAL) {
printf("[NOTE]\tThe running kernel doesn't support SS_AUTODISARM\n");
/*
* If test cases for the !SS_AUTODISARM variant were
* added, we could still run them. We don't have any
* test cases like that yet, so just exit and report
* success.
*/
return 0;
} else {
perror("[FAIL]\tsigaltstack(SS_ONSTACK | SS_AUTODISARM)");
return EXIT_FAILURE;
}
}
ustack = mmap(NULL, SIGSTKSZ, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS | MAP_STACK, -1, 0);
if (ustack == MAP_FAILED) {
perror("mmap()");
return EXIT_FAILURE;
}
getcontext(&uc);
uc.uc_link = NULL;
uc.uc_stack.ss_sp = ustack;
uc.uc_stack.ss_size = SIGSTKSZ;
makecontext(&uc, switch_fn, 0);
raise(SIGUSR1);
err = sigaltstack(NULL, &stk);
if (err) {
perror("[FAIL]\tsigaltstack()");
exit(EXIT_FAILURE);
}
if (stk.ss_flags != SS_AUTODISARM) {
printf("[FAIL]\tss_flags=%x, should be SS_AUTODISARM\n",
stk.ss_flags);
exit(EXIT_FAILURE);
}
printf("[OK]\tsigaltstack is still SS_AUTODISARM after signal\n");
printf("[OK]\tTest passed\n");
return 0;
}