tools/testing/selftests/x86/ptrace_syscall.c

// SPDX-License-Identifier: GPL-2.0
#define _GNU_SOURCE

#include <sys/ptrace.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/syscall.h>
#include <sys/user.h>
#include <unistd.h>
#include <errno.h>
#include <stddef.h>
#include <stdio.h>
#include <err.h>
#include <string.h>
#include <asm/ptrace-abi.h>
#include <sys/auxv.h>

/* Bitness-agnostic defines for user_regs_struct fields. */
#ifdef __x86_64__
# define user_syscall_nr	orig_rax
# define user_arg0		rdi
# define user_arg1		rsi
# define user_arg2		rdx
# define user_arg3		r10
# define user_arg4		r8
# define user_arg5		r9
# define user_ip		rip
# define user_ax		rax
#else
# define user_syscall_nr	orig_eax
# define user_arg0		ebx
# define user_arg1		ecx
# define user_arg2		edx
# define user_arg3		esi
# define user_arg4		edi
# define user_arg5		ebp
# define user_ip		eip
# define user_ax		eax
#endif

static int nerrs = 0;

struct syscall_args32 {
	uint32_t nr, arg0, arg1, arg2, arg3, arg4, arg5;
};

#ifdef __i386__
extern void sys32_helper(struct syscall_args32 *, void *);
extern void int80_and_ret(void);
#endif

/*
 * Helper to invoke int80 with controlled regs and capture the final regs.
 */
static void do_full_int80(struct syscall_args32 *args)
{
#ifdef __x86_64__
	register unsigned long bp asm("bp") = args->arg5;
	asm volatile ("int $0x80"
		      : "+a" (args->nr),
			"+b" (args->arg0), "+c" (args->arg1), "+d" (args->arg2),
			"+S" (args->arg3), "+D" (args->arg4), "+r" (bp)
			: : "r8", "r9", "r10", "r11");
	args->arg5 = bp;
#else
	sys32_helper(args, int80_and_ret);
#endif
}

#ifdef __i386__
static void (*vsyscall32)(void);

/*
 * Nasty helper to invoke AT_SYSINFO (i.e. __kernel_vsyscall) with
 * controlled regs and capture the final regs.  This is so nasty that it
 * crashes my copy of gdb :)
 */
static void do_full_vsyscall32(struct syscall_args32 *args)
{
	sys32_helper(args, vsyscall32);
}
#endif

static siginfo_t wait_trap(pid_t chld)
{
	siginfo_t si;
	if (waitid(P_PID, chld, &si, WEXITED|WSTOPPED) != 0)
		err(1, "waitid");
	if (si.si_pid != chld)
		errx(1, "got unexpected pid in event\n");
	if (si.si_code != CLD_TRAPPED)
		errx(1, "got unexpected event type %d\n", si.si_code);
	return si;
}

static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *),
		       int flags)
{
	struct sigaction sa;
	memset(&sa, 0, sizeof(sa));
	sa.sa_sigaction = handler;
	sa.sa_flags = SA_SIGINFO | flags;
	sigemptyset(&sa.sa_mask);
	if (sigaction(sig, &sa, 0))
		err(1, "sigaction");
}

static void setsigign(int sig, int flags)
{
	struct sigaction sa;
	memset(&sa, 0, sizeof(sa));
	sa.sa_sigaction = (void *)SIG_IGN;
	sa.sa_flags = flags;
	sigemptyset(&sa.sa_mask);
	if (sigaction(sig, &sa, 0))
		err(1, "sigaction");
}

static void clearhandler(int sig)
{
	struct sigaction sa;
	memset(&sa, 0, sizeof(sa));
	sa.sa_handler = SIG_DFL;
	sigemptyset(&sa.sa_mask);
	if (sigaction(sig, &sa, 0))
		err(1, "sigaction");
}

#ifdef __x86_64__
# define REG_BP REG_RBP
#else
# define REG_BP REG_EBP
#endif

static void empty_handler(int sig, siginfo_t *si, void *ctx_void)
{
}

static void test_sys32_regs(void (*do_syscall)(struct syscall_args32 *))
{
	struct syscall_args32 args = {
		.nr = 224,	/* gettid */
		.arg0 = 10, .arg1 = 11, .arg2 = 12,
		.arg3 = 13, .arg4 = 14, .arg5 = 15,
	};

	do_syscall(&args);

	if (args.nr != getpid() ||
	    args.arg0 != 10 || args.arg1 != 11 || args.arg2 != 12 ||
	    args.arg3 != 13 || args.arg4 != 14 || args.arg5 != 15) {
		printf("[FAIL]\tgetpid() failed to preserve regs\n");
		nerrs++;
	} else {
		printf("[OK]\tgetpid() preserves regs\n");
	}

	sethandler(SIGUSR1, empty_handler, 0);

	args.nr = 37;	/* kill */
	args.arg0 = getpid();
	args.arg1 = SIGUSR1;
	do_syscall(&args);
	if (args.nr != 0 ||
	    args.arg0 != getpid() || args.arg1 != SIGUSR1 || args.arg2 != 12 ||
	    args.arg3 != 13 || args.arg4 != 14 || args.arg5 != 15) {
		printf("[FAIL]\tkill(getpid(), SIGUSR1) failed to preserve regs\n");
		nerrs++;
	} else {
		printf("[OK]\tkill(getpid(), SIGUSR1) preserves regs\n");
	}
	clearhandler(SIGUSR1);
}

static void test_ptrace_syscall_restart(void)
{
	printf("[RUN]\tptrace-induced syscall restart\n");
	pid_t chld = fork();
	if (chld < 0)
		err(1, "fork");

	if (chld == 0) {
		if (ptrace(PTRACE_TRACEME, 0, 0, 0) != 0)
			err(1, "PTRACE_TRACEME");

		pid_t pid = getpid(), tid = syscall(SYS_gettid);

		printf("\tChild will make one syscall\n");
		syscall(SYS_tgkill, pid, tid, SIGSTOP);

		syscall(SYS_gettid, 10, 11, 12, 13, 14, 15);
		_exit(0);
	}

	int status;

	/* Wait for SIGSTOP. */
	if (waitpid(chld, &status, 0) != chld || !WIFSTOPPED(status))
		err(1, "waitpid");

	struct user_regs_struct regs;

	printf("[RUN]\tSYSEMU\n");
	if (ptrace(PTRACE_SYSEMU, chld, 0, 0) != 0)
		err(1, "PTRACE_SYSEMU");
	wait_trap(chld);

	if (ptrace(PTRACE_GETREGS, chld, 0, &regs) != 0)
		err(1, "PTRACE_GETREGS");

	if (regs.user_syscall_nr != SYS_gettid ||
	    regs.user_arg0 != 10 || regs.user_arg1 != 11 ||
	    regs.user_arg2 != 12 || regs.user_arg3 != 13 ||
	    regs.user_arg4 != 14 || regs.user_arg5 != 15) {
		printf("[FAIL]\tInitial args are wrong (nr=%lu, args=%lu %lu %lu %lu %lu %lu)\n", (unsigned long)regs.user_syscall_nr, (unsigned long)regs.user_arg0, (unsigned long)regs.user_arg1, (unsigned long)regs.user_arg2, (unsigned long)regs.user_arg3, (unsigned long)regs.user_arg4, (unsigned long)regs.user_arg5);
		nerrs++;
	} else {
		printf("[OK]\tInitial nr and args are correct\n");
	}

	printf("[RUN]\tRestart the syscall (ip = 0x%lx)\n",
	       (unsigned long)regs.user_ip);

	/*
	 * This does exactly what it appears to do if syscall is int80 or
	 * SYSCALL64.  For SYSCALL32 or SYSENTER, though, this is highly
	 * magical.  It needs to work so that ptrace and syscall restart
	 * work as expected.
	 */
	regs.user_ax = regs.user_syscall_nr;
	regs.user_ip -= 2;
	if (ptrace(PTRACE_SETREGS, chld, 0, &regs) != 0)
		err(1, "PTRACE_SETREGS");

	if (ptrace(PTRACE_SYSEMU, chld, 0, 0) != 0)
		err(1, "PTRACE_SYSEMU");
	wait_trap(chld);

	if (ptrace(PTRACE_GETREGS, chld, 0, &regs) != 0)
		err(1, "PTRACE_GETREGS");

	if (regs.user_syscall_nr != SYS_gettid ||
	    regs.user_arg0 != 10 || regs.user_arg1 != 11 ||
	    regs.user_arg2 != 12 || regs.user_arg3 != 13 ||
	    regs.user_arg4 != 14 || regs.user_arg5 != 15) {
		printf("[FAIL]\tRestart nr or args are wrong (nr=%lu, args=%lu %lu %lu %lu %lu %lu)\n", (unsigned long)regs.user_syscall_nr, (unsigned long)regs.user_arg0, (unsigned long)regs.user_arg1, (unsigned long)regs.user_arg2, (unsigned long)regs.user_arg3, (unsigned long)regs.user_arg4, (unsigned long)regs.user_arg5);
		nerrs++;
	} else {
		printf("[OK]\tRestarted nr and args are correct\n");
	}

	printf("[RUN]\tChange nr and args and restart the syscall (ip = 0x%lx)\n",
	       (unsigned long)regs.user_ip);

	regs.user_ax = SYS_getpid;
	regs.user_arg0 = 20;
	regs.user_arg1 = 21;
	regs.user_arg2 = 22;
	regs.user_arg3 = 23;
	regs.user_arg4 = 24;
	regs.user_arg5 = 25;
	regs.user_ip -= 2;

	if (ptrace(PTRACE_SETREGS, chld, 0, &regs) != 0)
		err(1, "PTRACE_SETREGS");

	if (ptrace(PTRACE_SYSEMU, chld, 0, 0) != 0)
		err(1, "PTRACE_SYSEMU");
	wait_trap(chld);

	if (ptrace(PTRACE_GETREGS, chld, 0, &regs) != 0)
		err(1, "PTRACE_GETREGS");

	if (regs.user_syscall_nr != SYS_getpid ||
	    regs.user_arg0 != 20 || regs.user_arg1 != 21 || regs.user_arg2 != 22 ||
	    regs.user_arg3 != 23 || regs.user_arg4 != 24 || regs.user_arg5 != 25) {
		printf("[FAIL]\tRestart nr or args are wrong (nr=%lu, args=%lu %lu %lu %lu %lu %lu)\n", (unsigned long)regs.user_syscall_nr, (unsigned long)regs.user_arg0, (unsigned long)regs.user_arg1, (unsigned long)regs.user_arg2, (unsigned long)regs.user_arg3, (unsigned long)regs.user_arg4, (unsigned long)regs.user_arg5);
		nerrs++;
	} else {
		printf("[OK]\tReplacement nr and args are correct\n");
	}

	if (ptrace(PTRACE_CONT, chld, 0, 0) != 0)
		err(1, "PTRACE_CONT");
	if (waitpid(chld, &status, 0) != chld)
		err(1, "waitpid");
	if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
		printf("[FAIL]\tChild failed\n");
		nerrs++;
	} else {
		printf("[OK]\tChild exited cleanly\n");
	}
}

static void test_restart_under_ptrace(void)
{
	printf("[RUN]\tkernel syscall restart under ptrace\n");
	pid_t chld = fork();
	if (chld < 0)
		err(1, "fork");

	if (chld == 0) {
		if (ptrace(PTRACE_TRACEME, 0, 0, 0) != 0)
			err(1, "PTRACE_TRACEME");

		pid_t pid = getpid(), tid = syscall(SYS_gettid);

		printf("\tChild will take a nap until signaled\n");
		setsigign(SIGUSR1, SA_RESTART);
		syscall(SYS_tgkill, pid, tid, SIGSTOP);

		syscall(SYS_pause, 0, 0, 0, 0, 0, 0);
		_exit(0);
	}

	int status;

	/* Wait for SIGSTOP. */
	if (waitpid(chld, &status, 0) != chld || !WIFSTOPPED(status))
		err(1, "waitpid");

	struct user_regs_struct regs;

	printf("[RUN]\tSYSCALL\n");
	if (ptrace(PTRACE_SYSCALL, chld, 0, 0) != 0)
		err(1, "PTRACE_SYSCALL");
	wait_trap(chld);

	/* We should be stopped at pause(2) entry. */

	if (ptrace(PTRACE_GETREGS, chld, 0, &regs) != 0)
		err(1, "PTRACE_GETREGS");

	if (regs.user_syscall_nr != SYS_pause ||
	    regs.user_arg0 != 0 || regs.user_arg1 != 0 ||
	    regs.user_arg2 != 0 || regs.user_arg3 != 0 ||
	    regs.user_arg4 != 0 || regs.user_arg5 != 0) {
		printf("[FAIL]\tInitial args are wrong (nr=%lu, args=%lu %lu %lu %lu %lu %lu)\n", (unsigned long)regs.user_syscall_nr, (unsigned long)regs.user_arg0, (unsigned long)regs.user_arg1, (unsigned long)regs.user_arg2, (unsigned long)regs.user_arg3, (unsigned long)regs.user_arg4, (unsigned long)regs.user_arg5);
		nerrs++;
	} else {
		printf("[OK]\tInitial nr and args are correct\n");
	}

	/* Interrupt it. */
	kill(chld, SIGUSR1);

	/* Advance.  We should be stopped at exit. */
	printf("[RUN]\tSYSCALL\n");
	if (ptrace(PTRACE_SYSCALL, chld, 0, 0) != 0)
		err(1, "PTRACE_SYSCALL");
	wait_trap(chld);

	if (ptrace(PTRACE_GETREGS, chld, 0, &regs) != 0)
		err(1, "PTRACE_GETREGS");

	if (regs.user_syscall_nr != SYS_pause ||
	    regs.user_arg0 != 0 || regs.user_arg1 != 0 ||
	    regs.user_arg2 != 0 || regs.user_arg3 != 0 ||
	    regs.user_arg4 != 0 || regs.user_arg5 != 0) {
		printf("[FAIL]\tArgs after SIGUSR1 are wrong (nr=%lu, args=%lu %lu %lu %lu %lu %lu)\n", (unsigned long)regs.user_syscall_nr, (unsigned long)regs.user_arg0, (unsigned long)regs.user_arg1, (unsigned long)regs.user_arg2, (unsigned long)regs.user_arg3, (unsigned long)regs.user_arg4, (unsigned long)regs.user_arg5);
		nerrs++;
	} else {
		printf("[OK]\tArgs after SIGUSR1 are correct (ax = %ld)\n",
		       (long)regs.user_ax);
	}

	/* Poke the regs back in.  This must not break anything. */
	if (ptrace(PTRACE_SETREGS, chld, 0, &regs) != 0)
		err(1, "PTRACE_SETREGS");

	/* Catch the (ignored) SIGUSR1. */
	if (ptrace(PTRACE_CONT, chld, 0, 0) != 0)
		err(1, "PTRACE_CONT");
	if (waitpid(chld, &status, 0) != chld)
		err(1, "waitpid");
	if (!WIFSTOPPED(status)) {
		printf("[FAIL]\tChild was stopped for SIGUSR1 (status = 0x%x)\n", status);
		nerrs++;
	} else {
		printf("[OK]\tChild got SIGUSR1\n");
	}

	/* The next event should be pause(2) again. */
	printf("[RUN]\tStep again\n");
	if (ptrace(PTRACE_SYSCALL, chld, 0, 0) != 0)
		err(1, "PTRACE_SYSCALL");
	wait_trap(chld);

	/* We should be stopped at pause(2) entry. */

	if (ptrace(PTRACE_GETREGS, chld, 0, &regs) != 0)
		err(1, "PTRACE_GETREGS");

	if (regs.user_syscall_nr != SYS_pause ||
	    regs.user_arg0 != 0 || regs.user_arg1 != 0 ||
	    regs.user_arg2 != 0 || regs.user_arg3 != 0 ||
	    regs.user_arg4 != 0 || regs.user_arg5 != 0) {
		printf("[FAIL]\tpause did not restart (nr=%lu, args=%lu %lu %lu %lu %lu %lu)\n", (unsigned long)regs.user_syscall_nr, (unsigned long)regs.user_arg0, (unsigned long)regs.user_arg1, (unsigned long)regs.user_arg2, (unsigned long)regs.user_arg3, (unsigned long)regs.user_arg4, (unsigned long)regs.user_arg5);
		nerrs++;
	} else {
		printf("[OK]\tpause(2) restarted correctly\n");
	}

	/* Kill it. */
	kill(chld, SIGKILL);
	if (waitpid(chld, &status, 0) != chld)
		err(1, "waitpid");
}

int main()
{
	printf("[RUN]\tCheck int80 return regs\n");
	test_sys32_regs(do_full_int80);

#if defined(__i386__) && (!defined(__GLIBC__) || __GLIBC__ > 2 || __GLIBC_MINOR__ >= 16)
	vsyscall32 = (void *)getauxval(AT_SYSINFO);
	if (vsyscall32) {
		printf("[RUN]\tCheck AT_SYSINFO return regs\n");
		test_sys32_regs(do_full_vsyscall32);
	} else {
		printf("[SKIP]\tAT_SYSINFO is not available\n");
	}
#endif

	test_ptrace_syscall_restart();

	test_restart_under_ptrace();

	return 0;
}