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Commit 40361343 authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Ingo Molnar
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selftests/x86: Add a test for syscall restart under ptrace 



This catches a regression from the compat syscall rework.  The
32-bit variant of this test currently fails.  The issue is that, for
a 32-bit tracer and a 32-bit tracee, GETREGS+SETREGS with no changes
should be a no-op.  It currently isn't a no-op if RAX indicates
signal restart, because the high bits get cleared and the kernel
loses track of the restart state.

Reported-by: default avatarRobert O'Callahan <robert@ocallahan.org>
Signed-off-by: default avatarAndy Lutomirski <luto@kernel.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Shuah Khan <shuahkh@osg.samsung.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/c4040b40b5b4a37ed31375a69b683f753ec6788a.1455142412.git.luto@kernel.org


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent adcfd23e

tools/testing/selftests/x86/ptrace_syscall.c

+126 −0
Original line number Diff line number Diff line
@@ -103,6 +103,17 @@ static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *), 
		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;
@@ -277,6 +288,119 @@ static void test_ptrace_syscall_restart(void) 
	}

}



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");



		printf("\tChild will take a nap until signaled\n");

		setsigign(SIGUSR1, SA_RESTART);

		raise(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");
@@ -290,5 +414,7 @@ int main() 


	test_ptrace_syscall_restart();



	test_restart_under_ptrace();



	return 0;

}