ppc64: fix missing to check all bits of _TIF_USER_WORK_MASK in preempt

In entry_64.S version of ret_from_except_lite, you'll notice that
in the !preempt case, after we've checked MSR_PR we test for any
TIF flag in _TIF_USER_WORK_MASK to decide whether to go to do_work
or not. However, in the preempt case, we do a convoluted trick to
test SIGPENDING only if PR was set and always test NEED_RESCHED ...
but we forget to test any other bit of _TIF_USER_WORK_MASK !!! So
that means that with preempt, we completely fail to test for things
like single step, syscall tracing, etc...

This should be fixed as the following path:

 - Test PR. If not set, go to resume_kernel, else continue.

 - If go resume_kernel, to do that original do_work.

 - If else, then always test for _TIF_USER_WORK_MASK to decide to do
that original user_work, else restore directly.

Signed-off-by: Tiejun Chen <tiejun.chen@windriver.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 40 insertions, 57 deletions

diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index ed1718feb9d9..5971c85df136 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -558,27 +558,54 @@ _GLOBAL(ret_from_except_lite)
         mtmsrd  r10,1             /* Update machine state */
 #endif /* CONFIG_PPC_BOOK3E */
 
-#ifdef CONFIG_PREEMPT
         clrrdi  r9,r1,THREAD_SHIFT      /* current_thread_info() */
-        li      r0,_TIF_NEED_RESCHED    /* bits to check */
         ld      r3,_MSR(r1)
         ld      r4,TI_FLAGS(r9)
-        /* Move MSR_PR bit in r3 to _TIF_SIGPENDING position in r0 */
-        rlwimi  r0,r3,32+TIF_SIGPENDING-MSR_PR_LG,_TIF_SIGPENDING
-        and.    r0,r4,r0        /* check NEED_RESCHED and maybe SIGPENDING */
-        bne     do_work
-
-#else /* !CONFIG_PREEMPT */
-        ld      r3,_MSR(r1)     /* Returning to user mode? */
         andi.   r3,r3,MSR_PR
-        beq     restore         /* if not, just restore regs and return */
+        beq     resume_kernel
 
         /* Check current_thread_info()->flags */
+        andi.   r0,r4,_TIF_USER_WORK_MASK
+        beq     restore
+
+        andi.   r0,r4,_TIF_NEED_RESCHED
+        beq     1f
+        bl      .restore_interrupts
+        bl      .schedule
+        b       .ret_from_except_lite
+
+1:      bl      .save_nvgprs
+        bl      .restore_interrupts
+        addi    r3,r1,STACK_FRAME_OVERHEAD
+        bl      .do_notify_resume
+        b       .ret_from_except
+
+resume_kernel:
+#ifdef CONFIG_PREEMPT
+        /* Check if we need to preempt */
+        andi.   r0,r4,_TIF_NEED_RESCHED
+        beq+    restore
+        /* Check that preempt_count() == 0 and interrupts are enabled */
+        lwz     r8,TI_PREEMPT(r9)
+        cmpwi   cr1,r8,0
+        ld      r0,SOFTE(r1)
+        cmpdi   r0,0
+        crandc  eq,cr1*4+eq,eq
+        bne     restore
+
+        /*
+         * Here we are preempting the current task. We want to make
+         * sure we are soft-disabled first
+         */
+        SOFT_DISABLE_INTS(r3,r4)
+1:      bl      .preempt_schedule_irq
+
+        /* Re-test flags and eventually loop */
         clrrdi  r9,r1,THREAD_SHIFT
         ld      r4,TI_FLAGS(r9)
-        andi.   r0,r4,_TIF_USER_WORK_MASK
-        bne     do_work
-#endif /* !CONFIG_PREEMPT */
+        andi.   r0,r4,_TIF_NEED_RESCHED
+        bne     1b
+#endif /* CONFIG_PREEMPT */
 
         .globl  fast_exc_return_irq
 fast_exc_return_irq:
@@ -759,50 +786,6 @@ restore_check_irq_replay:
 #endif /* CONFIG_PPC_BOOK3E */
 1:      b       .ret_from_except /* What else to do here ? */
  
-
-
-3:
-do_work:
-#ifdef CONFIG_PREEMPT
-        andi.   r0,r3,MSR_PR    /* Returning to user mode? */
-        bne     user_work
-        /* Check that preempt_count() == 0 and interrupts are enabled */
-        lwz     r8,TI_PREEMPT(r9)
-        cmpwi   cr1,r8,0
-        ld      r0,SOFTE(r1)
-        cmpdi   r0,0
-        crandc  eq,cr1*4+eq,eq
-        bne     restore
-
-        /*
-         * Here we are preempting the current task. We want to make
-         * sure we are soft-disabled first
-         */
-        SOFT_DISABLE_INTS(r3,r4)
-1:      bl      .preempt_schedule_irq
-
-        /* Re-test flags and eventually loop */
-        clrrdi  r9,r1,THREAD_SHIFT
-        ld      r4,TI_FLAGS(r9)
-        andi.   r0,r4,_TIF_NEED_RESCHED
-        bne     1b
-        b       restore
-
-user_work:
-#endif /* CONFIG_PREEMPT */
-
-        andi.   r0,r4,_TIF_NEED_RESCHED
-        beq     1f
-        bl      .restore_interrupts
-        bl      .schedule
-        b       .ret_from_except_lite
-
-1:      bl      .save_nvgprs
-        bl      .restore_interrupts
-        addi    r3,r1,STACK_FRAME_OVERHEAD
-        bl      .do_notify_resume
-        b       .ret_from_except
-
 unrecov_restore:
         addi    r3,r1,STACK_FRAME_OVERHEAD
         bl      .unrecoverable_exception