4 files changed, 218 insertions, 0 deletions
diff --git a/tools/testing/selftests/sigaltstack/.gitignore b/tools/testing/selftests/sigaltstack/.gitignore
new file mode 100644
index 000000000..50a19a888
--- /dev/null
+++ b/tools/testing/selftests/sigaltstack/.gitignore
@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0-only
+sas
diff --git a/tools/testing/selftests/sigaltstack/Makefile b/tools/testing/selftests/sigaltstack/Makefile
new file mode 100644
index 000000000..3e96d5d47
--- /dev/null
+++ b/tools/testing/selftests/sigaltstack/Makefile
@@ -0,0 +1,6 @@
+# SPDX-License-Identifier: GPL-2.0-only
+CFLAGS = -Wall
+TEST_GEN_PROGS = sas
+
+include ../lib.mk
+
diff --git a/tools/testing/selftests/sigaltstack/current_stack_pointer.h b/tools/testing/selftests/sigaltstack/current_stack_pointer.h
new file mode 100644
index 000000000..ea9bdf3a9
--- /dev/null
+++ b/tools/testing/selftests/sigaltstack/current_stack_pointer.h
@@ -0,0 +1,23 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#if __alpha__
+register unsigned long sp asm("$30");
+#elif __arm__ || __aarch64__ || __csky__ || __m68k__ || __mips__ || __riscv
+register unsigned long sp asm("sp");
+#elif __i386__
+register unsigned long sp asm("esp");
+#elif __loongarch64
+register unsigned long sp asm("$sp");
+#elif __ppc__
+register unsigned long sp asm("r1");
+#elif __s390x__
+register unsigned long sp asm("%15");
+#elif __sh__
+register unsigned long sp asm("r15");
+#elif __x86_64__
+register unsigned long sp asm("rsp");
+#elif __XTENSA__
+register unsigned long sp asm("a1");
+#else
+#error "implement current_stack_pointer equivalent"
+#endif
diff --git a/tools/testing/selftests/sigaltstack/sas.c b/tools/testing/selftests/sigaltstack/sas.c
new file mode 100644
index 000000000..41646c223
--- /dev/null
+++ b/tools/testing/selftests/sigaltstack/sas.c
@@ -0,0 +1,187 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * 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>
+
+#include "../kselftest.h"
+#include "current_stack_pointer.h"
+
+#ifndef SS_AUTODISARM
+#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;
+
+	if (sp < (unsigned long)sstack ||
+			sp >= (unsigned long)sstack + SIGSTKSZ) {
+		ksft_exit_fail_msg("SP is not on sigaltstack\n");
+	}
+	/* 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;
+	ksft_print_msg("[RUN]\tsignal USR1\n");
+	err = sigaltstack(NULL, &stk);
+	if (err) {
+		ksft_exit_fail_msg("sigaltstack() - %s\n", strerror(errno));
+		exit(EXIT_FAILURE);
+	}
+	if (stk.ss_flags != SS_DISABLE)
+		ksft_test_result_fail("tss_flags=%x, should be SS_DISABLE\n",
+				stk.ss_flags);
+	else
+		ksft_test_result_pass(
+				"sigaltstack is disabled in sighandler\n");
+	swapcontext(&sc, &uc);
+	ksft_print_msg("%s\n", p->msg);
+	if (!p->flag) {
+		ksft_exit_fail_msg("[RUN]\tAborting\n");
+		exit(EXIT_FAILURE);
+	}
+}
+
+void my_usr2(int sig, siginfo_t *si, void *u)
+{
+	char *aa;
+	struct stk_data *p;
+
+	ksft_print_msg("[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) {
+		ksft_test_result_fail("sigaltstack 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)
+{
+	ksft_print_msg("[RUN]\tswitched to user ctx\n");
+	raise(SIGUSR2);
+	setcontext(&sc);
+}
+
+int main(void)
+{
+	struct sigaction act;
+	stack_t stk;
+	int err;
+
+	ksft_print_header();
+	ksft_set_plan(3);
+
+	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) {
+		ksft_exit_fail_msg("mmap() - %s\n", strerror(errno));
+		return EXIT_FAILURE;
+	}
+
+	err = sigaltstack(NULL, &stk);
+	if (err) {
+		ksft_exit_fail_msg("sigaltstack() - %s\n", strerror(errno));
+		exit(EXIT_FAILURE);
+	}
+	if (stk.ss_flags == SS_DISABLE) {
+		ksft_test_result_pass(
+				"Initial sigaltstack state was SS_DISABLE\n");
+	} else {
+		ksft_exit_fail_msg("Initial 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) {
+			ksft_test_result_skip(
+				"[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 {
+			ksft_exit_fail_msg(
+				"sigaltstack(SS_ONSTACK | SS_AUTODISARM)  %s\n",
+					strerror(errno));
+			return EXIT_FAILURE;
+		}
+	}
+
+	ustack = mmap(NULL, SIGSTKSZ, PROT_READ | PROT_WRITE,
+		      MAP_PRIVATE | MAP_ANONYMOUS | MAP_STACK, -1, 0);
+	if (ustack == MAP_FAILED) {
+		ksft_exit_fail_msg("mmap() - %s\n", strerror(errno));
+		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) {
+		ksft_exit_fail_msg("sigaltstack() - %s\n", strerror(errno));
+		exit(EXIT_FAILURE);
+	}
+	if (stk.ss_flags != SS_AUTODISARM) {
+		ksft_exit_fail_msg("ss_flags=%x, should be SS_AUTODISARM\n",
+				stk.ss_flags);
+		exit(EXIT_FAILURE);
+	}
+	ksft_test_result_pass(
+			"sigaltstack is still SS_AUTODISARM after signal\n");
+
+	ksft_exit_pass();
+	return 0;
+}