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>

diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index ed1718f..5971c85 100644 (file)
--- 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