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Commit 4cd41569 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge branch 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 

Pull x86/asm changes from Ingo Molnar:
 "Misc optimizations"

* 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86: Slightly tweak the access_ok() C variant for better code
  x86: Replace assembly access_ok() with a C variant
  x86-64, copy_user: Use leal to produce 32-bit results
  x86-64, copy_user: Remove zero byte check before copy user buffer.
parents 1a7dbbcc a740576a

arch/x86/include/asm/uaccess.h

+20 −12
Original line number Diff line number Diff line
@@ -40,22 +40,30 @@ 
/*

 * Test whether a block of memory is a valid user space address.

 * Returns 0 if the range is valid, nonzero otherwise.

 *

 * This is equivalent to the following test:

 * (u33)addr + (u33)size > (u33)current->addr_limit.seg (u65 for x86_64)

 *

 * This needs 33-bit (65-bit for x86_64) arithmetic. We have a carry...

 */

static inline bool __chk_range_not_ok(unsigned long addr, unsigned long size, unsigned long limit)

{

	/*

	 * If we have used "sizeof()" for the size,

	 * we know it won't overflow the limit (but

	 * it might overflow the 'addr', so it's

	 * important to subtract the size from the

	 * limit, not add it to the address).

	 */

	if (__builtin_constant_p(size))

		return addr > limit - size;



	/* Arbitrary sizes? Be careful about overflow */

	addr += size;

	if (addr < size)

		return true;

	return addr > limit;

}



#define __range_not_ok(addr, size, limit)				\

({									\

	unsigned long flag, roksum;					\

	__chk_user_ptr(addr);						\

	asm("add %3,%1 ; sbb %0,%0 ; cmp %1,%4 ; sbb $0,%0"		\

	    : "=&r" (flag), "=r" (roksum)				\

	    : "1" (addr), "g" ((long)(size)),				\

	      "rm" (limit));						\

	flag;								\

	__chk_range_not_ok((unsigned long __force)(addr), size, limit); \

})



/**
@@ -78,7 +86,7 @@ 
 * this function, memory access functions may still return -EFAULT.

 */

#define access_ok(type, addr, size) \

	(likely(__range_not_ok(addr, size, user_addr_max()) == 0))

	likely(!__range_not_ok(addr, size, user_addr_max()))



/*

 * The exception table consists of pairs of addresses relative to the

arch/x86/lib/copy_user_64.S

+4 −8
Original line number Diff line number Diff line
@@ -186,7 +186,7 @@ ENTRY(copy_user_generic_unrolled) 
30:	shll $6,%ecx

	addl %ecx,%edx

	jmp 60f

40:	lea (%rdx,%rcx,8),%rdx

40:	leal (%rdx,%rcx,8),%edx

	jmp 60f

50:	movl %ecx,%edx

60:	jmp copy_user_handle_tail /* ecx is zerorest also */
@@ -236,8 +236,6 @@ ENDPROC(copy_user_generic_unrolled) 
ENTRY(copy_user_generic_string)

	CFI_STARTPROC

	ASM_STAC

	andl %edx,%edx

	jz 4f

	cmpl $8,%edx

	jb 2f		/* less than 8 bytes, go to byte copy loop */

	ALIGN_DESTINATION
@@ -249,12 +247,12 @@ ENTRY(copy_user_generic_string) 
2:	movl %edx,%ecx

3:	rep

	movsb

4:	xorl %eax,%eax

	xorl %eax,%eax

	ASM_CLAC

	ret



	.section .fixup,"ax"

11:	lea (%rdx,%rcx,8),%rcx

11:	leal (%rdx,%rcx,8),%ecx

12:	movl %ecx,%edx		/* ecx is zerorest also */

	jmp copy_user_handle_tail

	.previous
@@ -279,12 +277,10 @@ ENDPROC(copy_user_generic_string) 
ENTRY(copy_user_enhanced_fast_string)

	CFI_STARTPROC

	ASM_STAC

	andl %edx,%edx

	jz 2f

	movl %edx,%ecx

1:	rep

	movsb

2:	xorl %eax,%eax

	xorl %eax,%eax

	ASM_CLAC

	ret