powerpc: Fix various syscall/signal/swapcontext bugs

A careful reading of the recent changes to the system call entry/exit
paths revealed several problems, plus some things that could be
simplified and improved:

* 32-bit wasn't testing the _TIF_NOERROR bit in the syscall fast exit
  path, so it was only doing anything with it once it saw some other
  bit being set.  In other words, the noerror behaviour would apply to
  the next system call where we had to reschedule or deliver a signal,
  which is not necessarily the current system call.

* 32-bit wasn't doing the call to ptrace_notify in the syscall exit
  path when the _TIF_SINGLESTEP bit was set.

* _TIF_RESTOREALL was in both _TIF_USER_WORK_MASK and
  _TIF_PERSYSCALL_MASK, which is odd since _TIF_RESTOREALL is only set
  by system calls.  I took it out of _TIF_USER_WORK_MASK.

* On 64-bit, _TIF_RESTOREALL wasn't causing the non-volatile registers
  to be restored (unless perhaps a signal was delivered or the syscall
  was traced or single-stepped).  Thus the non-volatile registers
  weren't restored on exit from a signal handler.  We probably got
  away with it mostly because signal handlers written in C wouldn't
  alter the non-volatile registers.

* On 32-bit I simplified the code and made it more like 64-bit by
  making the syscall exit path jump to ret_from_except to handle
  preemption and signal delivery.

* 32-bit was calling do_signal unnecessarily when _TIF_RESTOREALL was
  set - but I think because of that 32-bit was actually restoring the
  non-volatile registers on exit from a signal handler.

* I changed the order of enabling interrupts and saving the
  non-volatile registers before calling do_syscall_trace_leave; now we
  enable interrupts first.

Signed-off-by: Paul Mackerras <paulus@samba.org>

1 files changed, 2 insertions, 6 deletions

diff --git a/include/asm-powerpc/thread_info.h b/include/asm-powerpc/thread_info.h
index 237fc2b7297..ffc7462d77b 100644
--- a/include/asm-powerpc/thread_info.h
+++ b/include/asm-powerpc/thread_info.h
@@ -37,7 +37,6 @@ struct thread_info {
 	int		preempt_count;		/* 0 => preemptable,
 						   <0 => BUG */
 	struct restart_block restart_block;
-	void __user *nvgprs_frame;
 	/* low level flags - has atomic operations done on it */
 	unsigned long	flags ____cacheline_aligned_in_smp;
 };
@@ -120,7 +119,6 @@ static inline struct thread_info *current_thread_info(void)
 #define TIF_MEMDIE		10
 #define TIF_SECCOMP		11	/* secure computing */
 #define TIF_RESTOREALL		12	/* Restore all regs (implies NOERROR) */
-#define TIF_SAVE_NVGPRS		13	/* Save r14-r31 in signal frame */
 #define TIF_NOERROR		14	/* Force successful syscall return */
 #define TIF_RESTORE_SIGMASK	15	/* Restore signal mask in do_signal */
 
@@ -137,15 +135,13 @@ static inline struct thread_info *current_thread_info(void)
 #define _TIF_SINGLESTEP		(1<<TIF_SINGLESTEP)
 #define _TIF_SECCOMP		(1<<TIF_SECCOMP)
 #define _TIF_RESTOREALL		(1<<TIF_RESTOREALL)
-#define _TIF_SAVE_NVGPRS	(1<<TIF_SAVE_NVGPRS)
 #define _TIF_NOERROR		(1<<TIF_NOERROR)
 #define _TIF_RESTORE_SIGMASK	(1<<TIF_RESTORE_SIGMASK)
 #define _TIF_SYSCALL_T_OR_A	(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT|_TIF_SECCOMP)
 
 #define _TIF_USER_WORK_MASK	(_TIF_NOTIFY_RESUME | _TIF_SIGPENDING | \
-				 _TIF_NEED_RESCHED | _TIF_RESTOREALL | \
-				 _TIF_RESTORE_SIGMASK)
-#define _TIF_PERSYSCALL_MASK	(_TIF_RESTOREALL|_TIF_NOERROR|_TIF_SAVE_NVGPRS)
+				 _TIF_NEED_RESCHED | _TIF_RESTORE_SIGMASK)
+#define _TIF_PERSYSCALL_MASK	(_TIF_RESTOREALL|_TIF_NOERROR)
 
 #endif /* __KERNEL__ */