1 files changed, 370 insertions, 0 deletions
diff --git a/tools/testing/selftests/arm64/pauth/pac.c b/tools/testing/selftests/arm64/pauth/pac.c
new file mode 100644
index 000000000..b743daa77
--- /dev/null
+++ b/tools/testing/selftests/arm64/pauth/pac.c
@@ -0,0 +1,370 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2020 ARM Limited
+
+#define _GNU_SOURCE
+
+#include <sys/auxv.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <signal.h>
+#include <setjmp.h>
+#include <sched.h>
+
+#include "../../kselftest_harness.h"
+#include "helper.h"
+
+#define PAC_COLLISION_ATTEMPTS 10
+/*
+ * The kernel sets TBID by default. So bits 55 and above should remain
+ * untouched no matter what.
+ * The VA space size is 48 bits. Bigger is opt-in.
+ */
+#define PAC_MASK (~0xff80ffffffffffff)
+#define ARBITRARY_VALUE (0x1234)
+#define ASSERT_PAUTH_ENABLED() \
+do { \
+	unsigned long hwcaps = getauxval(AT_HWCAP); \
+	/* data key instructions are not in NOP space. This prevents a SIGILL */ \
+	if (!(hwcaps & HWCAP_PACA))					\
+		SKIP(return, "PAUTH not enabled"); \
+} while (0)
+#define ASSERT_GENERIC_PAUTH_ENABLED() \
+do { \
+	unsigned long hwcaps = getauxval(AT_HWCAP); \
+	/* generic key instructions are not in NOP space. This prevents a SIGILL */ \
+	if (!(hwcaps & HWCAP_PACG)) \
+		SKIP(return, "Generic PAUTH not enabled");	\
+} while (0)
+
+void sign_specific(struct signatures *sign, size_t val)
+{
+	sign->keyia = keyia_sign(val);
+	sign->keyib = keyib_sign(val);
+	sign->keyda = keyda_sign(val);
+	sign->keydb = keydb_sign(val);
+}
+
+void sign_all(struct signatures *sign, size_t val)
+{
+	sign->keyia = keyia_sign(val);
+	sign->keyib = keyib_sign(val);
+	sign->keyda = keyda_sign(val);
+	sign->keydb = keydb_sign(val);
+	sign->keyg  = keyg_sign(val);
+}
+
+int n_same(struct signatures *old, struct signatures *new, int nkeys)
+{
+	int res = 0;
+
+	res += old->keyia == new->keyia;
+	res += old->keyib == new->keyib;
+	res += old->keyda == new->keyda;
+	res += old->keydb == new->keydb;
+	if (nkeys == NKEYS)
+		res += old->keyg == new->keyg;
+
+	return res;
+}
+
+int n_same_single_set(struct signatures *sign, int nkeys)
+{
+	size_t vals[nkeys];
+	int same = 0;
+
+	vals[0] = sign->keyia & PAC_MASK;
+	vals[1] = sign->keyib & PAC_MASK;
+	vals[2] = sign->keyda & PAC_MASK;
+	vals[3] = sign->keydb & PAC_MASK;
+
+	if (nkeys >= 4)
+		vals[4] = sign->keyg & PAC_MASK;
+
+	for (int i = 0; i < nkeys - 1; i++) {
+		for (int j = i + 1; j < nkeys; j++) {
+			if (vals[i] == vals[j])
+				same += 1;
+		}
+	}
+	return same;
+}
+
+int exec_sign_all(struct signatures *signed_vals, size_t val)
+{
+	int new_stdin[2];
+	int new_stdout[2];
+	int status;
+	int i;
+	ssize_t ret;
+	pid_t pid;
+	cpu_set_t mask;
+
+	ret = pipe(new_stdin);
+	if (ret == -1) {
+		perror("pipe returned error");
+		return -1;
+	}
+
+	ret = pipe(new_stdout);
+	if (ret == -1) {
+		perror("pipe returned error");
+		return -1;
+	}
+
+	/*
+	 * pin this process and all its children to a single CPU, so it can also
+	 * guarantee a context switch with its child
+	 */
+	sched_getaffinity(0, sizeof(mask), &mask);
+
+	for (i = 0; i < sizeof(cpu_set_t); i++)
+		if (CPU_ISSET(i, &mask))
+			break;
+
+	CPU_ZERO(&mask);
+	CPU_SET(i, &mask);
+	sched_setaffinity(0, sizeof(mask), &mask);
+
+	pid = fork();
+	// child
+	if (pid == 0) {
+		dup2(new_stdin[0], STDIN_FILENO);
+		if (ret == -1) {
+			perror("dup2 returned error");
+			exit(1);
+		}
+
+		dup2(new_stdout[1], STDOUT_FILENO);
+		if (ret == -1) {
+			perror("dup2 returned error");
+			exit(1);
+		}
+
+		close(new_stdin[0]);
+		close(new_stdin[1]);
+		close(new_stdout[0]);
+		close(new_stdout[1]);
+
+		ret = execl("exec_target", "exec_target", (char *)NULL);
+		if (ret == -1) {
+			perror("exec returned error");
+			exit(1);
+		}
+	}
+
+	close(new_stdin[0]);
+	close(new_stdout[1]);
+
+	ret = write(new_stdin[1], &val, sizeof(size_t));
+	if (ret == -1) {
+		perror("write returned error");
+		return -1;
+	}
+
+	/*
+	 * wait for the worker to finish, so that read() reads all data
+	 * will also context switch with worker so that this function can be used
+	 * for context switch tests
+	 */
+	waitpid(pid, &status, 0);
+	if (WIFEXITED(status) == 0) {
+		fprintf(stderr, "worker exited unexpectedly\n");
+		return -1;
+	}
+	if (WEXITSTATUS(status) != 0) {
+		fprintf(stderr, "worker exited with error\n");
+		return -1;
+	}
+
+	ret = read(new_stdout[0], signed_vals, sizeof(struct signatures));
+	if (ret == -1) {
+		perror("read returned error");
+		return -1;
+	}
+
+	return 0;
+}
+
+sigjmp_buf jmpbuf;
+void pac_signal_handler(int signum, siginfo_t *si, void *uc)
+{
+	if (signum == SIGSEGV || signum == SIGILL)
+		siglongjmp(jmpbuf, 1);
+}
+
+/* check that a corrupted PAC results in SIGSEGV or SIGILL */
+TEST(corrupt_pac)
+{
+	struct sigaction sa;
+
+	ASSERT_PAUTH_ENABLED();
+	if (sigsetjmp(jmpbuf, 1) == 0) {
+		sa.sa_sigaction = pac_signal_handler;
+		sa.sa_flags = SA_SIGINFO | SA_RESETHAND;
+		sigemptyset(&sa.sa_mask);
+
+		sigaction(SIGSEGV, &sa, NULL);
+		sigaction(SIGILL, &sa, NULL);
+
+		pac_corruptor();
+		ASSERT_TRUE(0) TH_LOG("SIGSEGV/SIGILL signal did not occur");
+	}
+}
+
+/*
+ * There are no separate pac* and aut* controls so checking only the pac*
+ * instructions is sufficient
+ */
+TEST(pac_instructions_not_nop)
+{
+	size_t keyia = 0;
+	size_t keyib = 0;
+	size_t keyda = 0;
+	size_t keydb = 0;
+
+	ASSERT_PAUTH_ENABLED();
+
+	for (int i = 0; i < PAC_COLLISION_ATTEMPTS; i++) {
+		keyia |= keyia_sign(i) & PAC_MASK;
+		keyib |= keyib_sign(i) & PAC_MASK;
+		keyda |= keyda_sign(i) & PAC_MASK;
+		keydb |= keydb_sign(i) & PAC_MASK;
+	}
+
+	ASSERT_NE(0, keyia) TH_LOG("keyia instructions did nothing");
+	ASSERT_NE(0, keyib) TH_LOG("keyib instructions did nothing");
+	ASSERT_NE(0, keyda) TH_LOG("keyda instructions did nothing");
+	ASSERT_NE(0, keydb) TH_LOG("keydb instructions did nothing");
+}
+
+TEST(pac_instructions_not_nop_generic)
+{
+	size_t keyg = 0;
+
+	ASSERT_GENERIC_PAUTH_ENABLED();
+
+	for (int i = 0; i < PAC_COLLISION_ATTEMPTS; i++)
+		keyg |= keyg_sign(i) & PAC_MASK;
+
+	ASSERT_NE(0, keyg)  TH_LOG("keyg instructions did nothing");
+}
+
+TEST(single_thread_different_keys)
+{
+	int same = 10;
+	int nkeys = NKEYS;
+	int tmp;
+	struct signatures signed_vals;
+	unsigned long hwcaps = getauxval(AT_HWCAP);
+
+	/* generic and data key instructions are not in NOP space. This prevents a SIGILL */
+	ASSERT_PAUTH_ENABLED();
+	if (!(hwcaps & HWCAP_PACG)) {
+		TH_LOG("WARNING: Generic PAUTH not enabled. Skipping generic key checks");
+		nkeys = NKEYS - 1;
+	}
+
+	/*
+	 * In Linux the PAC field can be up to 7 bits wide. Even if keys are
+	 * different, there is about 5% chance for PACs to collide with
+	 * different addresses. This chance rapidly increases with fewer bits
+	 * allocated for the PAC (e.g. wider address). A comparison of the keys
+	 * directly will be more reliable.
+	 * All signed values need to be different at least once out of n
+	 * attempts to be certain that the keys are different
+	 */
+	for (int i = 0; i < PAC_COLLISION_ATTEMPTS; i++) {
+		if (nkeys == NKEYS)
+			sign_all(&signed_vals, i);
+		else
+			sign_specific(&signed_vals, i);
+
+		tmp = n_same_single_set(&signed_vals, nkeys);
+		if (tmp < same)
+			same = tmp;
+	}
+
+	ASSERT_EQ(0, same) TH_LOG("%d keys clashed every time", same);
+}
+
+/*
+ * fork() does not change keys. Only exec() does so call a worker program.
+ * Its only job is to sign a value and report back the resutls
+ */
+TEST(exec_changed_keys)
+{
+	struct signatures new_keys;
+	struct signatures old_keys;
+	int ret;
+	int same = 10;
+	int nkeys = NKEYS;
+	unsigned long hwcaps = getauxval(AT_HWCAP);
+
+	/* generic and data key instructions are not in NOP space. This prevents a SIGILL */
+	ASSERT_PAUTH_ENABLED();
+	if (!(hwcaps & HWCAP_PACG)) {
+		TH_LOG("WARNING: Generic PAUTH not enabled. Skipping generic key checks");
+		nkeys = NKEYS - 1;
+	}
+
+	for (int i = 0; i < PAC_COLLISION_ATTEMPTS; i++) {
+		ret = exec_sign_all(&new_keys, i);
+		ASSERT_EQ(0, ret) TH_LOG("failed to run worker");
+
+		if (nkeys == NKEYS)
+			sign_all(&old_keys, i);
+		else
+			sign_specific(&old_keys, i);
+
+		ret = n_same(&old_keys, &new_keys, nkeys);
+		if (ret < same)
+			same = ret;
+	}
+
+	ASSERT_EQ(0, same) TH_LOG("exec() did not change %d keys", same);
+}
+
+TEST(context_switch_keep_keys)
+{
+	int ret;
+	struct signatures trash;
+	struct signatures before;
+	struct signatures after;
+
+	ASSERT_PAUTH_ENABLED();
+
+	sign_specific(&before, ARBITRARY_VALUE);
+
+	/* will context switch with a process with different keys at least once */
+	ret = exec_sign_all(&trash, ARBITRARY_VALUE);
+	ASSERT_EQ(0, ret) TH_LOG("failed to run worker");
+
+	sign_specific(&after, ARBITRARY_VALUE);
+
+	ASSERT_EQ(before.keyia, after.keyia) TH_LOG("keyia changed after context switching");
+	ASSERT_EQ(before.keyib, after.keyib) TH_LOG("keyib changed after context switching");
+	ASSERT_EQ(before.keyda, after.keyda) TH_LOG("keyda changed after context switching");
+	ASSERT_EQ(before.keydb, after.keydb) TH_LOG("keydb changed after context switching");
+}
+
+TEST(context_switch_keep_keys_generic)
+{
+	int ret;
+	struct signatures trash;
+	size_t before;
+	size_t after;
+
+	ASSERT_GENERIC_PAUTH_ENABLED();
+
+	before = keyg_sign(ARBITRARY_VALUE);
+
+	/* will context switch with a process with different keys at least once */
+	ret = exec_sign_all(&trash, ARBITRARY_VALUE);
+	ASSERT_EQ(0, ret) TH_LOG("failed to run worker");
+
+	after = keyg_sign(ARBITRARY_VALUE);
+
+	ASSERT_EQ(before, after) TH_LOG("keyg changed after context switching");
+}
+
+TEST_HARNESS_MAIN