powerpc: Call do_page_fault() with interrupts off

We currently turn interrupts back to their previous state before
calling do_page_fault(). This can be annoying when debugging as
a bad fault will potentially have lost some processor state before
getting into the debugger.

We also end up calling some generic code with interrupts enabled
such as notify_page_fault() with interrupts enabled, which could
be unexpected.

This changes our code to behave more like other architectures,
and make the assembly entry code call into do_page_faults() with
interrupts disabled. They are conditionally re-enabled from
within do_page_fault() in the same spot x86 does it.

While there, add the might_sleep() test in the case of a successful
trylock of the mmap semaphore, again like x86.

Also fix a bug in the existing assembly where r12 (_MSR) could get
clobbered by C calls (the DTL accounting in the exception common
macro and DISABLE_INTS) in some cases.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
---

v2. Add the r12 clobber fix

1 files changed, 2 insertions, 2 deletions

diff --git a/arch/powerpc/kernel/head_8xx.S b/arch/powerpc/kernel/head_8xx.S
index b68cb173ba2c..b2a5860accfb 100644
--- a/arch/powerpc/kernel/head_8xx.S
+++ b/arch/powerpc/kernel/head_8xx.S
@@ -220,7 +220,7 @@ DataAccess:
         mfspr   r4,SPRN_DAR
         li      r10,0x00f0
         mtspr   SPRN_DAR,r10    /* Tag DAR, to be used in DTLB Error */
-        EXC_XFER_EE_LITE(0x300, handle_page_fault)
+        EXC_XFER_LITE(0x300, handle_page_fault)
 
 /* Instruction access exception.
  * This is "never generated" by the MPC8xx.  We jump to it for other
@@ -231,7 +231,7 @@ InstructionAccess:
         EXCEPTION_PROLOG
         mr      r4,r12
         mr      r5,r9
-        EXC_XFER_EE_LITE(0x400, handle_page_fault)
+        EXC_XFER_LITE(0x400, handle_page_fault)
 
 /* External interrupt */
         EXCEPTION(0x500, HardwareInterrupt, do_IRQ, EXC_XFER_LITE)