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Commit 70ffdb93 authored by David Hildenbrand's avatar David Hildenbrand Committed by Ingo Molnar
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mm/fault, arch: Use pagefault_disable() to check for disabled pagefaults in the handler 



Introduce faulthandler_disabled() and use it to check for irq context and
disabled pagefaults (via pagefault_disable()) in the pagefault handlers.

Please note that we keep the in_atomic() checks in place - to detect
whether in irq context (in which case preemption is always properly
disabled).

In contrast, preempt_disable() should never be used to disable pagefaults.
With !CONFIG_PREEMPT_COUNT, preempt_disable() doesn't modify the preempt
counter, and therefore the result of in_atomic() differs.
We validate that condition by using might_fault() checks when calling
might_sleep().

Therefore, add a comment to faulthandler_disabled(), describing why this
is needed.

faulthandler_disabled() and pagefault_disable() are defined in
linux/uaccess.h, so let's properly add that include to all relevant files.

This patch is based on a patch from Thomas Gleixner.

Reviewed-and-tested-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarDavid Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: David.Laight@ACULAB.COM
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: airlied@linux.ie
Cc: akpm@linux-foundation.org
Cc: benh@kernel.crashing.org
Cc: bigeasy@linutronix.de
Cc: borntraeger@de.ibm.com
Cc: daniel.vetter@intel.com
Cc: heiko.carstens@de.ibm.com
Cc: herbert@gondor.apana.org.au
Cc: hocko@suse.cz
Cc: hughd@google.com
Cc: mst@redhat.com
Cc: paulus@samba.org
Cc: ralf@linux-mips.org
Cc: schwidefsky@de.ibm.com
Cc: yang.shi@windriver.com
Link: http://lkml.kernel.org/r/1431359540-32227-7-git-send-email-dahi@linux.vnet.ibm.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent ce01948e

arch/alpha/mm/fault.c

+2 −3
Original line number Diff line number Diff line
@@ -23,8 +23,7 @@ 
#include <linux/smp.h>

#include <linux/interrupt.h>

#include <linux/module.h>



#include <asm/uaccess.h>

#include <linux/uaccess.h>



extern void die_if_kernel(char *,struct pt_regs *,long, unsigned long *);
@@ -107,7 +106,7 @@ do_page_fault(unsigned long address, unsigned long mmcsr, 


	/* If we're in an interrupt context, or have no user context,

	   we must not take the fault.  */

	if (!mm || in_atomic())

	if (!mm || faulthandler_disabled())

		goto no_context;



#ifdef CONFIG_ALPHA_LARGE_VMALLOC

arch/arc/mm/fault.c

+1 −1
Original line number Diff line number Diff line
@@ -86,7 +86,7 @@ void do_page_fault(unsigned long address, struct pt_regs *regs) 
	 * If we're in an interrupt or have no user

	 * context, we must not take the fault..

	 */

	if (in_atomic() || !mm)

	if (faulthandler_disabled() || !mm)

		goto no_context;



	if (user_mode(regs))

arch/arm/mm/fault.c

+1 −1
Original line number Diff line number Diff line
@@ -276,7 +276,7 @@ do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs) 
	 * If we're in an interrupt or have no user

	 * context, we must not take the fault..

	 */

	if (in_atomic() || !mm)

	if (faulthandler_disabled() || !mm)

		goto no_context;



	if (user_mode(regs))

arch/arm64/mm/fault.c

+1 −1
Original line number Diff line number Diff line
@@ -211,7 +211,7 @@ static int __kprobes do_page_fault(unsigned long addr, unsigned int esr, 
	 * If we're in an interrupt or have no user context, we must not take

	 * the fault.

	 */

	if (in_atomic() || !mm)

	if (faulthandler_disabled() || !mm)

		goto no_context;



	if (user_mode(regs))

arch/avr32/mm/fault.c

+2 −2
Original line number Diff line number Diff line
@@ -14,11 +14,11 @@ 
#include <linux/pagemap.h>

#include <linux/kdebug.h>

#include <linux/kprobes.h>

#include <linux/uaccess.h>



#include <asm/mmu_context.h>

#include <asm/sysreg.h>

#include <asm/tlb.h>

#include <asm/uaccess.h>



#ifdef CONFIG_KPROBES

static inline int notify_page_fault(struct pt_regs *regs, int trap)
@@ -81,7 +81,7 @@ asmlinkage void do_page_fault(unsigned long ecr, struct pt_regs *regs) 
	 * If we're in an interrupt or have no user context, we must

	 * not take the fault...

	 */

	if (in_atomic() || !mm || regs->sr & SYSREG_BIT(GM))

	if (faulthandler_disabled() || !mm || regs->sr & SYSREG_BIT(GM))

		goto no_context;



	local_irq_enable();