Paul Mackerras <pau...@samba.org> writes:
> On Thu, Sep 05, 2013 at 12:47:02PM +0530, Aneesh Kumar K.V wrote:
>
>> @@ -280,6 +280,13 @@ int __kprobes do_page_fault(struct pt_regs *regs,
>> unsigned long address,
>>
>> perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
>>
>> + /*
>> + * We want to do this outside mmap_sem, because reading code around nip
>> + * can result in fault, which will cause a deadlock when called with
>> + * mmap_sem held
>> + */
>> + store_update = store_updates_sp(regs);
>
> We should only call store_updates_sp() if user_mode(regs); that was
> the previous behaviour.
Updated to
diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
index 8726779..fad7af6 100644
--- a/arch/powerpc/mm/fault.c
+++ b/arch/powerpc/mm/fault.c
@@ -206,7 +206,7 @@ int __kprobes do_page_fault(struct pt_regs *regs, unsigned
long address,
int trap = TRAP(regs);
int is_exec = trap == 0x400;
int fault;
- int rc = 0;
+ int rc = 0, store_update = 0;
#if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE))
/*
@@ -280,6 +280,14 @@ int __kprobes do_page_fault(struct pt_regs *regs, unsigned
long address,
perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
+ /*
+ * We want to do this outside mmap_sem, because reading code around nip
+ * can result in fault, which will cause a deadlock when called with
+ * mmap_sem held
+ */
+ if (user_mode(regs))
+ store_update = store_updates_sp(regs);
+
/* When running in the kernel we expect faults to occur only to
* addresses in user space. All other faults represent errors in the
* kernel and should generate an OOPS. Unfortunately, in the case of an
@@ -345,8 +353,7 @@ retry:
* between the last mapped region and the stack will
* expand the stack rather than segfaulting.
*/
- if (address + 2048 < uregs->gpr[1]
- && (!user_mode(regs) || !store_updates_sp(regs)))
+ if (address + 2048 < uregs->gpr[1] && !store_update)
goto bad_area;
}
if (expand_stack(vma, address))
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