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, 10 insertions, 0 deletions

diff --git a/arch/powerpc/include/asm/hw_irq.h b/arch/powerpc/include/asm/hw_irq.h
index bb712c9488b3..531ba00fcbab 100644
--- a/arch/powerpc/include/asm/hw_irq.h
+++ b/arch/powerpc/include/asm/hw_irq.h
@@ -79,6 +79,11 @@ static inline bool arch_irqs_disabled(void)
 		get_paca()->hard_enabled = 0;	\
 	} while(0)
 
+static inline bool arch_irq_disabled_regs(struct pt_regs *regs)
+{
+	return !regs->softe;
+}
+
 #else /* CONFIG_PPC64 */
 
 #define SET_MSR_EE(x)	mtmsr(x)
@@ -139,6 +144,11 @@ static inline bool arch_irqs_disabled(void)
 
 #define hard_irq_disable()		arch_local_irq_disable()
 
+static inline bool arch_irq_disabled_regs(struct pt_regs *regs)
+{
+	return !(regs->msr & MSR_EE);
+}
+
 #endif /* CONFIG_PPC64 */
 
 #define ARCH_IRQ_INIT_FLAGS	IRQ_NOREQUEST