--- /dev/null
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (c) 2018-2025 Dmitry V. Levin <ldv@strace.io>
+ * All rights reserved.
+ *
+ * Check whether PTRACE_SET_SYSCALL_INFO semantics implemented in the kernel
+ * matches userspace expectations.
+ */
+
+#include "../kselftest_harness.h"
+#include <err.h>
+#include <fcntl.h>
+#include <signal.h>
+#include <asm/unistd.h>
+#include <linux/types.h>
+#include <linux/ptrace.h>
+
+#if defined(_MIPS_SIM) && _MIPS_SIM == _MIPS_SIM_NABI32
+/*
+ * MIPS N32 is the only architecture where __kernel_ulong_t
+ * does not match the bitness of syscall arguments.
+ */
+typedef unsigned long long kernel_ulong_t;
+#else
+typedef __kernel_ulong_t kernel_ulong_t;
+#endif
+
+struct si_entry {
+ int nr;
+ kernel_ulong_t args[6];
+};
+struct si_exit {
+ unsigned int is_error;
+ int rval;
+};
+
+static unsigned int ptrace_stop;
+static pid_t tracee_pid;
+
+static int
+kill_tracee(pid_t pid)
+{
+ if (!pid)
+ return 0;
+
+ int saved_errno = errno;
+
+ int rc = kill(pid, SIGKILL);
+
+ errno = saved_errno;
+ return rc;
+}
+
+static long
+sys_ptrace(int request, pid_t pid, unsigned long addr, unsigned long data)
+{
+ return syscall(__NR_ptrace, request, pid, addr, data);
+}
+
+#define LOG_KILL_TRACEE(fmt, ...) \
+ do { \
+ kill_tracee(tracee_pid); \
+ TH_LOG("wait #%d: " fmt, \
+ ptrace_stop, ##__VA_ARGS__); \
+ } while (0)
+
+static void
+check_psi_entry(struct __test_metadata *_metadata,
+ const struct ptrace_syscall_info *info,
+ const struct si_entry *exp_entry,
+ const char *text)
+{
+ unsigned int i;
+ int exp_nr = exp_entry->nr;
+#if defined __s390__ || defined __s390x__
+ /* s390 is the only architecture that has 16-bit syscall numbers */
+ exp_nr &= 0xffff;
+#endif
+
+ ASSERT_EQ(PTRACE_SYSCALL_INFO_ENTRY, info->op) {
+ LOG_KILL_TRACEE("%s: entry stop mismatch", text);
+ }
+ ASSERT_TRUE(info->arch) {
+ LOG_KILL_TRACEE("%s: entry stop mismatch", text);
+ }
+ ASSERT_TRUE(info->instruction_pointer) {
+ LOG_KILL_TRACEE("%s: entry stop mismatch", text);
+ }
+ ASSERT_TRUE(info->stack_pointer) {
+ LOG_KILL_TRACEE("%s: entry stop mismatch", text);
+ }
+ ASSERT_EQ(exp_nr, info->entry.nr) {
+ LOG_KILL_TRACEE("%s: syscall nr mismatch", text);
+ }
+ for (i = 0; i < ARRAY_SIZE(exp_entry->args); ++i) {
+ ASSERT_EQ(exp_entry->args[i], info->entry.args[i]) {
+ LOG_KILL_TRACEE("%s: syscall arg #%u mismatch",
+ text, i);
+ }
+ }
+}
+
+static void
+check_psi_exit(struct __test_metadata *_metadata,
+ const struct ptrace_syscall_info *info,
+ const struct si_exit *exp_exit,
+ const char *text)
+{
+ ASSERT_EQ(PTRACE_SYSCALL_INFO_EXIT, info->op) {
+ LOG_KILL_TRACEE("%s: exit stop mismatch", text);
+ }
+ ASSERT_TRUE(info->arch) {
+ LOG_KILL_TRACEE("%s: exit stop mismatch", text);
+ }
+ ASSERT_TRUE(info->instruction_pointer) {
+ LOG_KILL_TRACEE("%s: exit stop mismatch", text);
+ }
+ ASSERT_TRUE(info->stack_pointer) {
+ LOG_KILL_TRACEE("%s: exit stop mismatch", text);
+ }
+ ASSERT_EQ(exp_exit->is_error, info->exit.is_error) {
+ LOG_KILL_TRACEE("%s: exit stop mismatch", text);
+ }
+ ASSERT_EQ(exp_exit->rval, info->exit.rval) {
+ LOG_KILL_TRACEE("%s: exit stop mismatch", text);
+ }
+}
+
+TEST(set_syscall_info)
+{
+ const pid_t tracer_pid = getpid();
+ const kernel_ulong_t dummy[] = {
+ (kernel_ulong_t) 0xdad0bef0bad0fed0ULL,
+ (kernel_ulong_t) 0xdad1bef1bad1fed1ULL,
+ (kernel_ulong_t) 0xdad2bef2bad2fed2ULL,
+ (kernel_ulong_t) 0xdad3bef3bad3fed3ULL,
+ (kernel_ulong_t) 0xdad4bef4bad4fed4ULL,
+ (kernel_ulong_t) 0xdad5bef5bad5fed5ULL,
+ };
+ int splice_in[2], splice_out[2];
+
+ ASSERT_EQ(0, pipe(splice_in));
+ ASSERT_EQ(0, pipe(splice_out));
+ ASSERT_EQ(sizeof(dummy), write(splice_in[1], dummy, sizeof(dummy)));
+
+ const struct {
+ struct si_entry entry[2];
+ struct si_exit exit[2];
+ } si[] = {
+ /* change scno, keep non-error rval */
+ {
+ {
+ {
+ __NR_gettid,
+ {
+ dummy[0], dummy[1], dummy[2],
+ dummy[3], dummy[4], dummy[5]
+ }
+ }, {
+ __NR_getppid,
+ {
+ dummy[0], dummy[1], dummy[2],
+ dummy[3], dummy[4], dummy[5]
+ }
+ }
+ }, {
+ { 0, tracer_pid }, { 0, tracer_pid }
+ }
+ },
+
+ /* set scno to -1, keep error rval */
+ {
+ {
+ {
+ __NR_chdir,
+ {
+ (uintptr_t) ".",
+ dummy[1], dummy[2],
+ dummy[3], dummy[4], dummy[5]
+ }
+ }, {
+ -1,
+ {
+ (uintptr_t) ".",
+ dummy[1], dummy[2],
+ dummy[3], dummy[4], dummy[5]
+ }
+ }
+ }, {
+ { 1, -ENOSYS }, { 1, -ENOSYS }
+ }
+ },
+
+ /* keep scno, change non-error rval */
+ {
+ {
+ {
+ __NR_getppid,
+ {
+ dummy[0], dummy[1], dummy[2],
+ dummy[3], dummy[4], dummy[5]
+ }
+ }, {
+ __NR_getppid,
+ {
+ dummy[0], dummy[1], dummy[2],
+ dummy[3], dummy[4], dummy[5]
+ }
+ }
+ }, {
+ { 0, tracer_pid }, { 0, tracer_pid + 1 }
+ }
+ },
+
+ /* change arg1, keep non-error rval */
+ {
+ {
+ {
+ __NR_chdir,
+ {
+ (uintptr_t) "",
+ dummy[1], dummy[2],
+ dummy[3], dummy[4], dummy[5]
+ }
+ }, {
+ __NR_chdir,
+ {
+ (uintptr_t) ".",
+ dummy[1], dummy[2],
+ dummy[3], dummy[4], dummy[5]
+ }
+ }
+ }, {
+ { 0, 0 }, { 0, 0 }
+ }
+ },
+
+ /* set scno to -1, change error rval to non-error */
+ {
+ {
+ {
+ __NR_gettid,
+ {
+ dummy[0], dummy[1], dummy[2],
+ dummy[3], dummy[4], dummy[5]
+ }
+ }, {
+ -1,
+ {
+ dummy[0], dummy[1], dummy[2],
+ dummy[3], dummy[4], dummy[5]
+ }
+ }
+ }, {
+ { 1, -ENOSYS }, { 0, tracer_pid }
+ }
+ },
+
+ /* change scno, change non-error rval to error */
+ {
+ {
+ {
+ __NR_chdir,
+ {
+ dummy[0], dummy[1], dummy[2],
+ dummy[3], dummy[4], dummy[5]
+ }
+ }, {
+ __NR_getppid,
+ {
+ dummy[0], dummy[1], dummy[2],
+ dummy[3], dummy[4], dummy[5]
+ }
+ }
+ }, {
+ { 0, tracer_pid }, { 1, -EISDIR }
+ }
+ },
+
+ /* change scno and all args, change non-error rval */
+ {
+ {
+ {
+ __NR_gettid,
+ {
+ dummy[0], dummy[1], dummy[2],
+ dummy[3], dummy[4], dummy[5]
+ }
+ }, {
+ __NR_splice,
+ {
+ splice_in[0], 0, splice_out[1], 0,
+ sizeof(dummy), SPLICE_F_NONBLOCK
+ }
+ }
+ }, {
+ { 0, sizeof(dummy) }, { 0, sizeof(dummy) + 1 }
+ }
+ },
+
+ /* change arg1, no exit stop */
+ {
+ {
+ {
+ __NR_exit_group,
+ {
+ dummy[0], dummy[1], dummy[2],
+ dummy[3], dummy[4], dummy[5]
+ }
+ }, {
+ __NR_exit_group,
+ {
+ 0, dummy[1], dummy[2],
+ dummy[3], dummy[4], dummy[5]
+ }
+ }
+ }, {
+ { 0, 0 }, { 0, 0 }
+ }
+ },
+ };
+
+ long rc;
+ unsigned int i;
+
+ tracee_pid = fork();
+
+ ASSERT_LE(0, tracee_pid) {
+ TH_LOG("fork: %m");
+ }
+
+ if (tracee_pid == 0) {
+ /* get the pid before PTRACE_TRACEME */
+ tracee_pid = getpid();
+ ASSERT_EQ(0, sys_ptrace(PTRACE_TRACEME, 0, 0, 0)) {
+ TH_LOG("PTRACE_TRACEME: %m");
+ }
+ ASSERT_EQ(0, kill(tracee_pid, SIGSTOP)) {
+ /* cannot happen */
+ TH_LOG("kill SIGSTOP: %m");
+ }
+ for (i = 0; i < ARRAY_SIZE(si); ++i) {
+ rc = syscall(si[i].entry[0].nr,
+ si[i].entry[0].args[0],
+ si[i].entry[0].args[1],
+ si[i].entry[0].args[2],
+ si[i].entry[0].args[3],
+ si[i].entry[0].args[4],
+ si[i].entry[0].args[5]);
+ if (si[i].exit[1].is_error) {
+ if (rc != -1 || errno != -si[i].exit[1].rval)
+ break;
+ } else {
+ if (rc != si[i].exit[1].rval)
+ break;
+ }
+ }
+ /*
+ * Something went wrong, but in this state tracee
+ * cannot reliably issue syscalls, so just crash.
+ */
+ *(volatile unsigned char *) (uintptr_t) i = 42;
+ /* unreachable */
+ _exit(i + 1);
+ }
+
+ for (ptrace_stop = 0; ; ++ptrace_stop) {
+ struct ptrace_syscall_info info = {
+ .op = 0xff /* invalid PTRACE_SYSCALL_INFO_* op */
+ };
+ const size_t size = sizeof(info);
+ const int expected_entry_size =
+ (void *) &info.entry.args[6] - (void *) &info;
+ const int expected_exit_size =
+ (void *) (&info.exit.is_error + 1) -
+ (void *) &info;
+ int status;
+
+ ASSERT_EQ(tracee_pid, wait(&status)) {
+ /* cannot happen */
+ LOG_KILL_TRACEE("wait: %m");
+ }
+ if (WIFEXITED(status)) {
+ tracee_pid = 0; /* the tracee is no more */
+ ASSERT_EQ(0, WEXITSTATUS(status)) {
+ LOG_KILL_TRACEE("unexpected exit status %u",
+ WEXITSTATUS(status));
+ }
+ break;
+ }
+ ASSERT_FALSE(WIFSIGNALED(status)) {
+ tracee_pid = 0; /* the tracee is no more */
+ LOG_KILL_TRACEE("unexpected signal %u",
+ WTERMSIG(status));
+ }
+ ASSERT_TRUE(WIFSTOPPED(status)) {
+ /* cannot happen */
+ LOG_KILL_TRACEE("unexpected wait status %#x", status);
+ }
+
+ ASSERT_LT(ptrace_stop, ARRAY_SIZE(si) * 2) {
+ LOG_KILL_TRACEE("ptrace stop overflow");
+ }
+
+ switch (WSTOPSIG(status)) {
+ case SIGSTOP:
+ ASSERT_EQ(0, ptrace_stop) {
+ LOG_KILL_TRACEE("unexpected signal stop");
+ }
+ ASSERT_EQ(0, sys_ptrace(PTRACE_SETOPTIONS, tracee_pid,
+ 0, PTRACE_O_TRACESYSGOOD)) {
+ LOG_KILL_TRACEE("PTRACE_SETOPTIONS: %m");
+ }
+ break;
+
+ case SIGTRAP | 0x80:
+ ASSERT_LT(0, ptrace_stop) {
+ LOG_KILL_TRACEE("unexpected syscall stop");
+ }
+ ASSERT_LT(0, (rc = sys_ptrace(PTRACE_GET_SYSCALL_INFO,
+ tracee_pid, size,
+ (uintptr_t) &info))) {
+ LOG_KILL_TRACEE("PTRACE_GET_SYSCALL_INFO #1: %m");
+ }
+ if (ptrace_stop & 1) {
+ /* entering syscall */
+ const struct si_entry *exp_entry =
+ &si[ptrace_stop / 2].entry[0];
+ const struct si_entry *set_entry =
+ &si[ptrace_stop / 2].entry[1];
+
+ /* check ptrace_syscall_info before the changes */
+ ASSERT_EQ(expected_entry_size, rc) {
+ LOG_KILL_TRACEE("PTRACE_GET_SYSCALL_INFO #1"
+ ": entry stop mismatch");
+ }
+ check_psi_entry(_metadata, &info, exp_entry,
+ "PTRACE_GET_SYSCALL_INFO #1");
+
+ /* apply the changes */
+ info.entry.nr = set_entry->nr;
+ for (i = 0; i < ARRAY_SIZE(set_entry->args); ++i)
+ info.entry.args[i] = set_entry->args[i];
+ ASSERT_EQ(0, sys_ptrace(PTRACE_SET_SYSCALL_INFO,
+ tracee_pid, size,
+ (uintptr_t) &info)) {
+ LOG_KILL_TRACEE("PTRACE_SET_SYSCALL_INFO: %m");
+ }
+
+ /* check ptrace_syscall_info after the changes */
+ memset(&info, 0, sizeof(info));
+ info.op = 0xff;
+ ASSERT_LT(0, (rc = sys_ptrace(PTRACE_GET_SYSCALL_INFO,
+ tracee_pid, size,
+ (uintptr_t) &info))) {
+ LOG_KILL_TRACEE("PTRACE_GET_SYSCALL_INFO: %m");
+ }
+ ASSERT_EQ(expected_entry_size, rc) {
+ LOG_KILL_TRACEE("PTRACE_GET_SYSCALL_INFO #2"
+ ": entry stop mismatch");
+ }
+ check_psi_entry(_metadata, &info, set_entry,
+ "PTRACE_GET_SYSCALL_INFO #2");
+ } else {
+ /* exiting syscall */
+ const struct si_exit *exp_exit =
+ &si[ptrace_stop / 2 - 1].exit[0];
+ const struct si_exit *set_exit =
+ &si[ptrace_stop / 2 - 1].exit[1];
+
+ /* check ptrace_syscall_info before the changes */
+ ASSERT_EQ(expected_exit_size, rc) {
+ LOG_KILL_TRACEE("PTRACE_GET_SYSCALL_INFO #1"
+ ": exit stop mismatch");
+ }
+ check_psi_exit(_metadata, &info, exp_exit,
+ "PTRACE_GET_SYSCALL_INFO #1");
+
+ /* apply the changes */
+ info.exit.is_error = set_exit->is_error;
+ info.exit.rval = set_exit->rval;
+ ASSERT_EQ(0, sys_ptrace(PTRACE_SET_SYSCALL_INFO,
+ tracee_pid, size,
+ (uintptr_t) &info)) {
+ LOG_KILL_TRACEE("PTRACE_SET_SYSCALL_INFO: %m");
+ }
+
+ /* check ptrace_syscall_info after the changes */
+ memset(&info, 0, sizeof(info));
+ info.op = 0xff;
+ ASSERT_LT(0, (rc = sys_ptrace(PTRACE_GET_SYSCALL_INFO,
+ tracee_pid, size,
+ (uintptr_t) &info))) {
+ LOG_KILL_TRACEE("PTRACE_GET_SYSCALL_INFO #2: %m");
+ }
+ ASSERT_EQ(expected_exit_size, rc) {
+ LOG_KILL_TRACEE("PTRACE_GET_SYSCALL_INFO #2"
+ ": exit stop mismatch");
+ }
+ check_psi_exit(_metadata, &info, set_exit,
+ "PTRACE_GET_SYSCALL_INFO #2");
+ }
+ break;
+
+ default:
+ LOG_KILL_TRACEE("unexpected stop signal %u",
+ WSTOPSIG(status));
+ abort();
+ }
+
+ ASSERT_EQ(0, sys_ptrace(PTRACE_SYSCALL, tracee_pid, 0, 0)) {
+ LOG_KILL_TRACEE("PTRACE_SYSCALL: %m");
+ }
+ }
+
+ ASSERT_EQ(ptrace_stop, ARRAY_SIZE(si) * 2);
+}
+
+TEST_HARNESS_MAIN
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