[PATCH 3/4] selftest/arm64/ptrace: add a test for orig_x0

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

The test creates two processes where one traces another one. The tracee
executes a system call, the tracer traps it, changes orig_x0, triggers a
signal and checks that the syscall is restarted with the setted
argument.

Test output:
$ ./ptrace_restart_syscall_test
1..3
ok 1 orig_x0: 0x3
ok 2 x0: 0x5
ok 3 The child exited with code 0.
# Totals: pass:3 fail:0 xfail:0 xpass:0 skip:0 error:0

Signed-off-by: Andrei Vagin <avagin@gmail.com>
---
tools/testing/selftests/arm64/ptrace/Makefile | 6 +
tools/testing/selftests/arm64/ptrace/lib.h | 36 ++++++
.../ptrace/ptrace_restart_syscall_test.c | 122 ++++++++++++++++++
3 files changed, 164 insertions(+)
create mode 100644 tools/testing/selftests/arm64/ptrace/Makefile
create mode 100644 tools/testing/selftests/arm64/ptrace/lib.h
create mode 100644 tools/testing/selftests/arm64/ptrace/ptrace_restart_syscall_test.c

diff --git a/tools/testing/selftests/arm64/ptrace/Makefile b/tools/testing/selftests/arm64/ptrace/Makefile
new file mode 100644
index 000000000000..1bc10e2d2ac8
--- /dev/null
+++ b/tools/testing/selftests/arm64/ptrace/Makefile
@@ -0,0 +1,6 @@
+# SPDX-License-Identifier: GPL-2.0
+
+CFLAGS += -g -I../../../../../usr/include/
+TEST_GEN_PROGS := ptrace_restart_syscall_test
+
+include ../../lib.mk
diff --git a/tools/testing/selftests/arm64/ptrace/lib.h b/tools/testing/selftests/arm64/ptrace/lib.h
new file mode 100644
index 000000000000..14f4737188a3
--- /dev/null
+++ b/tools/testing/selftests/arm64/ptrace/lib.h
@@ -0,0 +1,36 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#ifndef __PTRACE_TEST_LOG_H
+#define __PTRACE_TEST_LOG_H
+
+#define pr_p(func, fmt, ...) func("%s:%d: " fmt ": %m", \
+ __func__, __LINE__, ##__VA_ARGS__)
+
+#define pr_err(fmt, ...) \
+ ({ \
+ ksft_test_result_error(fmt "\n", ##__VA_ARGS__); \
+ -1; \
+ })
+
+#define pr_fail(fmt, ...) \
+ ({ \
+ ksft_test_result_fail(fmt "\n", ##__VA_ARGS__); \
+ -1; \
+ })
+
+#define pr_perror(fmt, ...) pr_p(pr_err, fmt, ##__VA_ARGS__)
+
+static inline int ptrace_and_wait(pid_t pid, int cmd, int sig)
+{
+ int status;
+
+ /* Stop on syscall-exit. */
+ if (ptrace(cmd, 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 (!WIFSTOPPED(status) || WSTOPSIG(status) != sig)
+ return pr_err("Unexpected status: %x", status);
+ return 0;
+}
+
+#endif
diff --git a/tools/testing/selftests/arm64/ptrace/ptrace_restart_syscall_test.c b/tools/testing/selftests/arm64/ptrace/ptrace_restart_syscall_test.c
new file mode 100644
index 000000000000..ce59657f41be
--- /dev/null
+++ b/tools/testing/selftests/arm64/ptrace/ptrace_restart_syscall_test.c
@@ -0,0 +1,122 @@
+// 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 <fcntl.h>
+
+#include <sys/types.h>
+#include <sys/ptrace.h>
+#include <sys/stat.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"
+
+static int child(int fd)
+{
+ char c;
+
+ if (read(fd, &c, 1) != 1)
+ return 1;
+
+ return 0;
+}
+
+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;
+ int p[2], fdzero;
+
+ ksft_set_plan(3);
+
+ if (pipe(p))
+ return pr_perror("Can't create a pipe");
+ fdzero = open("/dev/zero", O_RDONLY);
+ if (fdzero < 0)
+ return pr_perror("Can't open /dev/zero");
+
+ pid = fork();
+ if (pid == 0) {
+ kill(getpid(), SIGSTOP);
+ return child(p[0]);
+ }
+ if (pid < 0)
+ return 1;
+
+ if (ptrace(PTRACE_ATTACH, pid, 0, 0))
+ return pr_perror("Can't attach to the child %d", pid);
+ if (waitpid(pid, &status, 0) != pid)
+ return pr_perror("Can't wait for the child %d", pid);
+ /* 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;
+
+ /* Send a signal to interrupt the system call. */
+ kill(pid, SIGUSR1);
+
+ /* Stop on syscall-exit. */
+ if (ptrace_and_wait(pid, PTRACE_SYSCALL, SIGTRAP))
+ return 1;
+
+ if (ptrace(PTRACE_GETREGSET, pid, NT_PRSTATUS, &iov))
+ return pr_perror("Can't get child registers");
+ if (regs.orig_x0 != p[0])
+ return pr_fail("Unexpected x0: 0x%lx", regs.r.regs[0]);
+ ksft_test_result_pass("orig_x0: 0x%llx\n", regs.orig_x0);
+
+ /* Change orig_x0 that will be x0 for the restarted system call. */
+ regs.orig_x0 = fdzero;
+ if (ptrace(PTRACE_SETREGSET, pid, NT_PRSTATUS, &iov))
+ return pr_perror("Can't get child registers");
+
+ /* Trap the signal and skip it. */
+ if (ptrace_and_wait(pid, PTRACE_SYSCALL, SIGUSR1))
+ return 1;
+
+ /* Trap the restarted system call. */
+ if (ptrace_and_wait(pid, PTRACE_SYSCALL, SIGTRAP))
+ return 1;
+
+ /* Check that the syscall is started with the right first argument. */
+ if (ptrace(PTRACE_GETREGSET, pid, NT_PRSTATUS, &iov))
+ return pr_perror("Can't get child registers");
+ if (regs.r.regs[0] != fdzero)
+ return pr_fail("unexpected x0: %lx", regs.r.regs[0]);
+ ksft_test_result_pass("x0: 0x%llx\n", regs.r.regs[0]);
+
+ 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