Check whether PTRACE_SET_SYSCALL_INFO semantics implemented in the kernel matches userspace expectations.

Signed-off-by: Dmitry V. Levin ldv@strace.io --- tools/testing/selftests/ptrace/Makefile | 2 +- .../selftests/ptrace/set_syscall_info.c | 441 ++++++++++++++++++ 2 files changed, 442 insertions(+), 1 deletion(-) create mode 100644 tools/testing/selftests/ptrace/set_syscall_info.c

diff --git a/tools/testing/selftests/ptrace/Makefile b/tools/testing/selftests/ptrace/Makefile index 1c631740a730..c5e0b76ba6ac 100644 --- a/tools/testing/selftests/ptrace/Makefile +++ b/tools/testing/selftests/ptrace/Makefile @@ -1,6 +1,6 @@ # SPDX-License-Identifier: GPL-2.0-only CFLAGS += -std=c99 -pthread -Wall $(KHDR_INCLUDES)

-TEST_GEN_PROGS := get_syscall_info peeksiginfo vmaccess get_set_sud +TEST_GEN_PROGS := get_syscall_info set_syscall_info peeksiginfo vmaccess get_set_sud

include ../lib.mk diff --git a/tools/testing/selftests/ptrace/set_syscall_info.c b/tools/testing/selftests/ptrace/set_syscall_info.c new file mode 100644 index 000000000000..c977991e0c4a --- /dev/null +++ b/tools/testing/selftests/ptrace/set_syscall_info.c @@ -0,0 +1,441 @@ +// 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> + +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(pid); \ + TH_LOG("wait #%d: " fmt, \ + ptrace_stop, ##__VA_ARGS__); \ + } while (0) + +struct si_entry { + int nr; + __kernel_ulong_t args[6]; +}; +struct si_exit { + unsigned int is_error; + int rval; +}; + +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, + { + (__kernel_ulong_t) ".", + dummy[1], dummy[2], + dummy[3], dummy[4], dummy[5] + } + }, { + -1, + { + (__kernel_ulong_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, + { + (__kernel_ulong_t) "", + dummy[1], dummy[2], + dummy[3], dummy[4], dummy[5] + } + }, { + __NR_chdir, + { + (__kernel_ulong_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, + { + splice_in[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; + unsigned int ptrace_stop; + + pid_t pid = fork(); + + ASSERT_LE(0, pid) { + TH_LOG("fork: %m"); + } + + if (pid == 0) { + /* get the pid before PTRACE_TRACEME */ + pid = getpid(); + ASSERT_EQ(0, sys_ptrace(PTRACE_TRACEME, 0, 0, 0)) { + TH_LOG("PTRACE_TRACEME: %m"); + } + ASSERT_EQ(0, kill(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(pid, wait(&status)) { + /* cannot happen */ + LOG_KILL_TRACEE("wait: %m"); + } + if (WIFEXITED(status)) { + 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)) { + 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, 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, + pid, size, + (uintptr_t) &info))) { + LOG_KILL_TRACEE("PTRACE_GET_SYSCALL_INFO: %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]; + + ASSERT_EQ(expected_entry_size, rc) { + LOG_KILL_TRACEE("entry stop mismatch"); + } + ASSERT_EQ(PTRACE_SYSCALL_INFO_ENTRY, info.op) { + LOG_KILL_TRACEE("entry stop mismatch"); + } + ASSERT_TRUE(info.arch) { + LOG_KILL_TRACEE("entry stop mismatch"); + } + ASSERT_TRUE(info.instruction_pointer) { + LOG_KILL_TRACEE("entry stop mismatch"); + } + ASSERT_TRUE(info.stack_pointer) { + LOG_KILL_TRACEE("entry stop mismatch"); + } + ASSERT_EQ(exp_entry->nr, info.entry.nr) { + LOG_KILL_TRACEE("syscall nr mismatch"); + } + for (i = 0; i < ARRAY_SIZE(exp_entry->args); ++i) { + ASSERT_EQ(exp_entry->args[i], info.entry.args[i]) { + LOG_KILL_TRACEE("syscall arg #%u mismatch", i); + } + } + 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, + pid, size, + (uintptr_t) &info)) { + LOG_KILL_TRACEE("PTRACE_SET_SYSCALL_INFO: %m"); + } + } 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]; + + ASSERT_EQ(expected_exit_size, rc) { + LOG_KILL_TRACEE("exit stop mismatch"); + } + ASSERT_EQ(PTRACE_SYSCALL_INFO_EXIT, info.op) { + LOG_KILL_TRACEE("exit stop mismatch"); + } + ASSERT_TRUE(info.arch) { + LOG_KILL_TRACEE("exit stop mismatch"); + } + ASSERT_TRUE(info.instruction_pointer) { + LOG_KILL_TRACEE("exit stop mismatch"); + } + ASSERT_TRUE(info.stack_pointer) { + LOG_KILL_TRACEE("exit stop mismatch"); + } + ASSERT_EQ(exp_exit->is_error, info.exit.is_error) { + LOG_KILL_TRACEE("exit stop mismatch"); + } + ASSERT_EQ(exp_exit->rval, info.exit.rval) { + LOG_KILL_TRACEE("exit stop mismatch"); + } + info.exit.is_error = set_exit->is_error; + info.exit.rval = set_exit->rval; + ASSERT_EQ(0, sys_ptrace(PTRACE_SET_SYSCALL_INFO, + pid, size, + (uintptr_t) &info)) { + LOG_KILL_TRACEE("PTRACE_SET_SYSCALL_INFO: %m"); + } + } + break; + + default: + LOG_KILL_TRACEE("unexpected stop signal %u", + WSTOPSIG(status)); + abort(); + } + + ASSERT_EQ(0, sys_ptrace(PTRACE_SYSCALL, pid, 0, 0)) { + LOG_KILL_TRACEE("PTRACE_SYSCALL: %m"); + } + } + + ASSERT_EQ(ptrace_stop, ARRAY_SIZE(si) * 2); +} + +TEST_HARNESS_MAIN