Commit 29edd8b0 authored by Jiri Olsa's avatar Jiri Olsa Committed by Masami Hiramatsu (Google)
Browse files

selftests/x86: Add return uprobe shadow stack test 

Adding return uprobe test for shadow stack and making sure it's
working properly. Borrowed some of the code from bpf selftests.

Link: https://lore.kernel.org/all/20240611112158.40795-5-jolsa@kernel.org/



Acked-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Signed-off-by: default avatarJiri Olsa <jolsa@kernel.org>
Signed-off-by: default avatarMasami Hiramatsu (Google) <mhiramat@kernel.org>
parent ff474a78

tools/testing/selftests/x86/test_shadow_stack.c

+145 −0
Original line number Diff line number Diff line
@@ -34,6 +34,7 @@ 
#include <sys/ptrace.h>

#include <sys/signal.h>

#include <linux/elf.h>

#include <linux/perf_event.h>



/*

 * Define the ABI defines if needed, so people can run the tests
@@ -734,6 +735,144 @@ int test_32bit(void) 
	return !segv_triggered;

}



static int parse_uint_from_file(const char *file, const char *fmt)

{

	int err, ret;

	FILE *f;



	f = fopen(file, "re");

	if (!f) {

		err = -errno;

		printf("failed to open '%s': %d\n", file, err);

		return err;

	}

	err = fscanf(f, fmt, &ret);

	if (err != 1) {

		err = err == EOF ? -EIO : -errno;

		printf("failed to parse '%s': %d\n", file, err);

		fclose(f);

		return err;

	}

	fclose(f);

	return ret;

}



static int determine_uprobe_perf_type(void)

{

	const char *file = "/sys/bus/event_source/devices/uprobe/type";



	return parse_uint_from_file(file, "%d\n");

}



static int determine_uprobe_retprobe_bit(void)

{

	const char *file = "/sys/bus/event_source/devices/uprobe/format/retprobe";



	return parse_uint_from_file(file, "config:%d\n");

}



static ssize_t get_uprobe_offset(const void *addr)

{

	size_t start, end, base;

	char buf[256];

	bool found = false;

	FILE *f;



	f = fopen("/proc/self/maps", "r");

	if (!f)

		return -errno;



	while (fscanf(f, "%zx-%zx %s %zx %*[^\n]\n", &start, &end, buf, &base) == 4) {

		if (buf[2] == 'x' && (uintptr_t)addr >= start && (uintptr_t)addr < end) {

			found = true;

			break;

		}

	}



	fclose(f);



	if (!found)

		return -ESRCH;



	return (uintptr_t)addr - start + base;

}



static __attribute__((noinline)) void uretprobe_trigger(void)

{

	asm volatile ("");

}



/*

 * This test setups return uprobe, which is sensitive to shadow stack

 * (crashes without extra fix). After executing the uretprobe we fail

 * the test if we receive SIGSEGV, no crash means we're good.

 *

 * Helper functions above borrowed from bpf selftests.

 */

static int test_uretprobe(void)

{

	const size_t attr_sz = sizeof(struct perf_event_attr);

	const char *file = "/proc/self/exe";

	int bit, fd = 0, type, err = 1;

	struct perf_event_attr attr;

	struct sigaction sa = {};

	ssize_t offset;



	type = determine_uprobe_perf_type();

	if (type < 0) {

		if (type == -ENOENT)

			printf("[SKIP]\tUretprobe test, uprobes are not available\n");

		return 0;

	}



	offset = get_uprobe_offset(uretprobe_trigger);

	if (offset < 0)

		return 1;



	bit = determine_uprobe_retprobe_bit();

	if (bit < 0)

		return 1;



	sa.sa_sigaction = segv_gp_handler;

	sa.sa_flags = SA_SIGINFO;

	if (sigaction(SIGSEGV, &sa, NULL))

		return 1;



	/* Setup return uprobe through perf event interface. */

	memset(&attr, 0, attr_sz);

	attr.size = attr_sz;

	attr.type = type;

	attr.config = 1 << bit;

	attr.config1 = (__u64) (unsigned long) file;

	attr.config2 = offset;



	fd = syscall(__NR_perf_event_open, &attr, 0 /* pid */, -1 /* cpu */,

		     -1 /* group_fd */, PERF_FLAG_FD_CLOEXEC);

	if (fd < 0)

		goto out;



	if (sigsetjmp(jmp_buffer, 1))

		goto out;



	ARCH_PRCTL(ARCH_SHSTK_ENABLE, ARCH_SHSTK_SHSTK);



	/*

	 * This either segfaults and goes through sigsetjmp above

	 * or succeeds and we're good.

	 */

	uretprobe_trigger();



	printf("[OK]\tUretprobe test\n");

	err = 0;



out:

	ARCH_PRCTL(ARCH_SHSTK_DISABLE, ARCH_SHSTK_SHSTK);

	signal(SIGSEGV, SIG_DFL);

	if (fd)

		close(fd);

	return err;

}



void segv_handler_ptrace(int signum, siginfo_t *si, void *uc)

{

	/* The SSP adjustment caused a segfault. */
@@ -926,6 +1065,12 @@ int main(int argc, char *argv[]) 
		goto out;

	}



	if (test_uretprobe()) {

		ret = 1;

		printf("[FAIL]\turetprobe test\n");

		goto out;

	}



	return ret;



out: