/*
* 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>
#ifndef SS_AUTODISARM
#define SS_AUTODISARM (1 << 4)
#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=%i, 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;
}
stk.ss_sp = sstack;
stk.ss_size = SIGSTKSZ;
stk.ss_flags = SS_ONSTACK | SS_AUTODISARM;
err = sigaltstack(&stk, NULL);
if (err) {
perror("[FAIL]\tsigaltstack(SS_ONSTACK | SS_AUTODISARM)");
stk.ss_flags = SS_ONSTACK;
}
err = sigaltstack(&stk, NULL);
if (err) {
perror("[FAIL]\tsigaltstack(SS_ONSTACK)");
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 != 0) {
printf("[FAIL]\tss_flags=%i, should be 0\n",
stk.ss_flags);
exit(EXIT_FAILURE);
}
printf("[OK]\tsigaltstack is enabled after signal\n");
printf("[OK]\tTest passed\n");
return 0;
}
