From a546498f3bf9aac311c66f965186373aee2ca0b0 Mon Sep 17 00:00:00 2001 From: Benjamin Herrenschmidt Date: Wed, 7 Mar 2012 16:48:45 +1100 Subject: 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 --- v2. Add the r12 clobber fix --- arch/powerpc/mm/fault.c | 11 +++++++++++ 1 file changed, 11 insertions(+) (limited to 'arch/powerpc/mm/fault.c') diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c index 2f0d1b0..7e89006 100644 --- a/arch/powerpc/mm/fault.c +++ b/arch/powerpc/mm/fault.c @@ -179,6 +179,10 @@ int __kprobes do_page_fault(struct pt_regs *regs, unsigned long address, } #endif + /* We restore the interrupt state now */ + if (!arch_irq_disabled_regs(regs)) + local_irq_enable(); + if (in_atomic() || mm == NULL) { if (!user_mode(regs)) return SIGSEGV; @@ -213,6 +217,13 @@ int __kprobes do_page_fault(struct pt_regs *regs, unsigned long address, goto bad_area_nosemaphore; down_read(&mm->mmap_sem); + } else { + /* + * The above down_read_trylock() might have succeeded in + * which case we'll have missed the might_sleep() from + * down_read(): + */ + might_sleep(); } vma = find_vma(mm, address); -- cgit v1.1