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