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x86: Add an inlined __copy_from_user_nmi() variant

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Add a inlined __ variant of copy_from_user_nmi. The inlined variant allows
the user to:

 - batch the access_ok() check for multiple accesses

 - avoid having a pagefault_disable/enable() on every access if the
   caller already ensures disabled page faults due to its context.

 - get all the optimizations in copy_*_user() for small constant sized
   transfers

It is just a define to __copy_from_user_inatomic().

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1445551641-13379-1-git-send-email-andi@firstfloor.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Andi Kleen 2015-10-22 15:07:20 -07:00 committed by Ingo Molnar
parent 8c2accc8ca
commit 10013ebb5d
1 changed files with 9 additions and 0 deletions
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9
arch/x86/include/asm/uaccess.h
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@ -745,5 +745,14 @@ copy_to_user(void __user *to, const void *from, unsigned long n)
#undef __copy_from_user_overflow
#undef __copy_to_user_overflow
/*
* We rely on the nested NMI work to allow atomic faults from the NMI path; the
* nested NMI paths are careful to preserve CR2.
*
* Caller must use pagefault_enable/disable, or run in interrupt context,
* and also do a uaccess_ok() check
*/
#define __copy_from_user_nmi __copy_from_user_inatomic
#endif /* _ASM_X86_UACCESS_H */