[PATCH 4/4] selftest/arm64/ptrace: add a test for orig_x7

Andrei Vagin
2021-03-22T22:54:03Z

In system calls, x7 is used to indicate whether a tracee has been
stopped on syscall-enter or syscall-exit and the origin value of x7 is
saved in orig_x7.

Test output:
$ ./ptrace_syscall_test
1..4
ok 1 x7: 0
ok 2 x7: 1
ok 3 x7: 686920776f726c64
ok 4 The child exited with code 0.
# Totals: pass:4 fail:0 xfail:0 xpass:0 skip:0 error:0

Signed-off-by: Andrei Vagin <avagin@gmail.com>
---
tools/testing/selftests/arm64/ptrace/Makefile | 2 +-
.../arm64/ptrace/ptrace_syscall_test.c | 158 ++++++++++++++++++
2 files changed, 159 insertions(+), 1 deletion(-)
create mode 100644 tools/testing/selftests/arm64/ptrace/ptrace_syscall_test.c

diff --git a/tools/testing/selftests/arm64/ptrace/Makefile b/tools/testing/selftests/arm64/ptrace/Makefile
index 1bc10e2d2ac8..ea02c1a63806 100644
--- a/tools/testing/selftests/arm64/ptrace/Makefile
+++ b/tools/testing/selftests/arm64/ptrace/Makefile
@@ -1,6 +1,6 @@
# SPDX-License-Identifier: GPL-2.0

CFLAGS += -g -I../../../../../usr/include/
-TEST_GEN_PROGS := ptrace_restart_syscall_test
+TEST_GEN_PROGS := ptrace_restart_syscall_test ptrace_syscall_test

include ../../lib.mk
diff --git a/tools/testing/selftests/arm64/ptrace/ptrace_syscall_test.c b/tools/testing/selftests/arm64/ptrace/ptrace_syscall_test.c
new file mode 100644
index 000000000000..ad55b44ae9f5
--- /dev/null
+++ b/tools/testing/selftests/arm64/ptrace/ptrace_syscall_test.c
@@ -0,0 +1,158 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <errno.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include <sys/types.h>
+#include <sys/ptrace.h>
+#include <sys/user.h>
+#include <sys/wait.h>
+#include <sys/uio.h>
+#include <linux/elf.h>
+#include <linux/unistd.h>
+
+#include "../../kselftest.h"
+#include "lib.h"
+
+#define X7_TEST_VAL 0x686920776f726c64UL
+
+static long test_syscall(long *x7)
+{
+ register long x0 __asm__("x0") = 0;
+ register long *x1 __asm__("x1") = x7;
+ register long x8 __asm__("x8") = 0x555;
+
+ __asm__ (
+ "ldr x7, [x1, 0]\n"
+ "svc 0\n"
+ "str x7, [x1, 0]\n"
+ : "=r"(x0)
+ : "r"(x0), "r"(x1), "r"(x8)
+ :
+ );
+ return x0;
+}
+
+static int child(void)
+{
+ long val = X7_TEST_VAL;
+
+ if (test_syscall(&val)) {
+ ksft_print_msg("The test syscall failed\n");
+ return 1;
+ }
+ if (val != X7_TEST_VAL) {
+ ksft_print_msg("Unexpected x7: %lx\n", val);
+ return 1;
+ }
+
+ if (test_syscall(&val)) {
+ ksft_print_msg("The test syscall failed\n");
+ return 1;
+ }
+ if (val != ~X7_TEST_VAL) {
+ ksft_print_msg("Unexpected x7: %lx\n", val);
+ return 1;
+ }
+
+ return 0;
+}
+
+#ifndef PTRACE_SYSEMU
+#define PTRACE_SYSEMU 31
+#endif
+
+int main(int argc, void **argv)
+{
+ union {
+ struct user_regs_struct r;
+ struct {
+ char __regs[272];
+ unsigned long long orig_x0;
+ unsigned long long orig_x7;
+ };
+ } regs = {};
+ struct iovec iov = {
+ .iov_base = &regs,
+ .iov_len = sizeof(regs),
+ };
+ int status;
+ pid_t pid;
+
+ ksft_set_plan(4);
+
+ pid = fork();
+ if (pid == 0) {
+ kill(getpid(), SIGSTOP);
+ _exit(child());
+ }
+ if (pid < 0)
+ return 1;
+
+ if (ptrace_and_wait(pid, PTRACE_ATTACH, SIGSTOP))
+ return 1;
+ /* skip SIGSTOP */
+ if (ptrace_and_wait(pid, PTRACE_CONT, SIGSTOP))
+ return 1;
+
+ /* Resume the child to the next system call. */
+ if (ptrace_and_wait(pid, PTRACE_SYSCALL, SIGTRAP))
+ return 1;
+
+ /* Check that x7 is 0 on syscall-enter. */
+ if (ptrace(PTRACE_GETREGSET, pid, NT_PRSTATUS, &iov))
+ return pr_perror("Can't get child registers");
+ if (regs.orig_x7 != X7_TEST_VAL)
+ return pr_fail("Unexpected orig_x7: %lx", regs.orig_x7);
+ if (regs.r.regs[7] != 0)
+ return pr_fail("Unexpected x7: %lx", regs.r.regs[7]);
+ ksft_test_result_pass("x7: %llx\n", regs.r.regs[7]);
+
+ if (ptrace_and_wait(pid, PTRACE_SYSCALL, SIGTRAP))
+ return 1;
+
+ /* Check that x7 is 1 on syscall-exit. */
+ if (ptrace(PTRACE_GETREGSET, pid, NT_PRSTATUS, &iov))
+ return pr_perror("Can't get child registers");
+ if (regs.r.regs[7] != 1)
+ return pr_fail("Unexpected x7: %lx", regs.r.regs[7]);
+ ksft_test_result_pass("x7: %llx\n", regs.r.regs[7]);
+
+ /* Check that the child will not see a new value of x7. */
+ regs.r.regs[0] = 0;
+ regs.r.regs[7] = ~X7_TEST_VAL;
+ if (ptrace(PTRACE_SETREGSET, pid, NT_PRSTATUS, &iov))
+ return pr_perror("Can't set child registers");
+
+ /* Resume the child to the next system call. */
+ if (ptrace_and_wait(pid, PTRACE_SYSEMU, SIGTRAP))
+ return 1;
+
+ /* Check that orig_x7 contains the actual value of x7. */
+ if (ptrace(PTRACE_GETREGSET, pid, NT_PRSTATUS, &iov))
+ return pr_perror("Can't get child registers");
+ if (regs.orig_x7 != X7_TEST_VAL)
+ return pr_fail("Unexpected orig_x7: %lx", regs.orig_x7);
+ ksft_test_result_pass("x7: %llx\n", regs.orig_x7);
+
+ /* Check that the child will see a new value of x7. */
+ regs.r.regs[0] = 0;
+ regs.orig_x7 = ~X7_TEST_VAL;
+ if (ptrace(PTRACE_SETREGSET, pid, NT_PRSTATUS, &iov))
+ return pr_perror("Can't set child registers");
+
+ if (ptrace(PTRACE_CONT, pid, 0, 0))
+ return pr_perror("Can't resume the child %d", pid);
+ if (waitpid(pid, &status, 0) != pid)
+ return pr_perror("Can't wait for the child %d", pid);
+ if (status != 0)
+ return pr_fail("Child exited with code %d.", status);
+
+ ksft_test_result_pass("The child exited with code 0.\n");
+ ksft_exit_pass();
+ return 0;
+}
+
--
2.29.2