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: Robert O'Callahan <robert@ocallahan.org>
Signed-off-by: Andy 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: Ingo Molnar <mingo@kernel.org>

diff --git a/tools/testing/selftests/x86/ptrace_syscall.c b/tools/testing/selftests/x86/ptrace_syscall.c
index c6a0acc0a63290a3060ce651d6f3d811876e594a..421456784bc64d7c2ad5b14753194bcf89905d1d 100644 (file)
--- a/tools/testing/selftests/x86/ptrace_syscall.c
+++ b/tools/testing/selftests/x86/ptrace_syscall.c
@@ -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;
 }