parisc/entry: fix trace test in syscall exit path

commit 8779e05 ("parisc: Fix ptrace check on syscall return")
fixed testing of TI_FLAGS. This uncovered a bug in the test mask.
syscall_restore_rfi is only used when the kernel needs to exit to
usespace with single or block stepping and the recovery counter
enabled. The test however used _TIF_SYSCALL_TRACE_MASK, which
includes a lot of bits that shouldn't be tested here.

Fix this by using TIF_SINGLESTEP and TIF_BLOCKSTEP directly.

I encountered this bug by enabling syscall tracepoints. Both in qemu and
on real hardware. As soon as i enabled the tracepoint (sys_exit_read,
but i guess it doesn't really matter which one), i got random page
faults in userspace almost immediately.

Signed-off-by: Sven Schnelle <[email protected]>
Signed-off-by: Helge Deller <[email protected]>

Author: Sven Schnelle

arch/parisc/kernel/entry.S

@@ -1805,7 +1805,7 @@ syscall_restore:
 
 	/* Are we being ptraced? */
 	LDREG	TASK_TI_FLAGS(%r1),%r19
-	ldi	_TIF_SYSCALL_TRACE_MASK,%r2
+	ldi	_TIF_SINGLESTEP|_TIF_BLOCKSTEP,%r2
 	and,COND(=)	%r19,%r2,%r0
 	b,n	syscall_restore_rfi