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// SPDX-License-Identifier: GPL-2.0-only
#define _GNU_SOURCE
#include <signal.h>
#include <stdio.h>
#include <stdbool.h>
#include <string.h>
#include <err.h>
#include <errno.h>
#include <limits.h>
#include <sys/mman.h>
#include <sys/auxv.h>
#include <sys/prctl.h>
#include <sys/resource.h>
#include <setjmp.h>
/* sigaltstack()-enforced minimum stack */
#define ENFORCED_MINSIGSTKSZ 2048
#ifndef AT_MINSIGSTKSZ
# define AT_MINSIGSTKSZ 51
#endif
static int nerrs;
static bool sigalrm_expected;
static unsigned long at_minstack_size;
static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *),
int flags)
{
struct sigaction sa;
memset(&sa, 0, sizeof(sa));
sa.sa_sigaction = handler;
sa.sa_flags = SA_SIGINFO | flags;
sigemptyset(&sa.sa_mask);
if (sigaction(sig, &sa, 0))
err(1, "sigaction");
}
static void clearhandler(int sig)
{
struct sigaction sa;
memset(&sa, 0, sizeof(sa));
sa.sa_handler = SIG_DFL;
sigemptyset(&sa.sa_mask);
if (sigaction(sig, &sa, 0))
err(1, "sigaction");
}
static int setup_altstack(void *start, unsigned long size)
{
stack_t ss;
memset(&ss, 0, sizeof(ss));
ss.ss_size = size;
ss.ss_sp = start;
return sigaltstack(&ss, NULL);
}
static jmp_buf jmpbuf;
static void sigsegv(int sig, siginfo_t *info, void *ctx_void)
{
if (sigalrm_expected) {
printf("[FAIL]\tWrong signal delivered: SIGSEGV (expected SIGALRM).");
nerrs++;
} else {
printf("[OK]\tSIGSEGV signal delivered.\n");
}
siglongjmp(jmpbuf, 1);
}
static void sigalrm(int sig, siginfo_t *info, void *ctx_void)
{
if (!sigalrm_expected) {
printf("[FAIL]\tWrong signal delivered: SIGALRM (expected SIGSEGV).");
nerrs++;
} else {
printf("[OK]\tSIGALRM signal delivered.\n");
}
}
static void test_sigaltstack(void *altstack, unsigned long size)
{
if (setup_altstack(altstack, size))
err(1, "sigaltstack()");
sigalrm_expected = (size > at_minstack_size) ? true : false;
sethandler(SIGSEGV, sigsegv, 0);
sethandler(SIGALRM, sigalrm, SA_ONSTACK);
if (!sigsetjmp(jmpbuf, 1)) {
printf("[RUN]\tTest an alternate signal stack of %ssufficient size.\n",
sigalrm_expected ? "" : "in");
printf("\tRaise SIGALRM. %s is expected to be delivered.\n",
sigalrm_expected ? "It" : "SIGSEGV");
raise(SIGALRM);
}
clearhandler(SIGALRM);
clearhandler(SIGSEGV);
}
int main(void)
{
void *altstack;
at_minstack_size = getauxval(AT_MINSIGSTKSZ);
altstack = mmap(NULL, at_minstack_size + SIGSTKSZ, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS | MAP_STACK, -1, 0);
if (altstack == MAP_FAILED)
err(1, "mmap()");
if ((ENFORCED_MINSIGSTKSZ + 1) < at_minstack_size)
test_sigaltstack(altstack, ENFORCED_MINSIGSTKSZ + 1);
test_sigaltstack(altstack, at_minstack_size + SIGSTKSZ);
return nerrs == 0 ? 0 : 1;
}
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