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Commit edf10162 authored by Glauber Costa's avatar Glauber Costa Committed by Ingo Molnar
Browse files

x86: don't clobber r8 nor use rcx. 



There's really no reason to clobber r8 or pass the address in rcx.
We can safely use only two registers (which we already have to touch anyway)
to do the job.

Signed-off-by: default avatarGlauber Costa <gcosta@redhat.com>
Signed-off-by: default avatarH. Peter Anvin <hpa@zytor.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent f8dd0d3c

arch/x86/lib/getuser_64.S

+21 −21
Original line number Original line Diff line number Diff line
@@ -36,10 +36,10 @@ 
	.text

	.text

ENTRY(__get_user_1)

ENTRY(__get_user_1)

	CFI_STARTPROC

	CFI_STARTPROC

	GET_THREAD_INFO(%r8)

	GET_THREAD_INFO(%rdx)

	cmpq threadinfo_addr_limit(%r8),%rcx

	cmpq threadinfo_addr_limit(%rdx),%rax

	jae bad_get_user

	jae bad_get_user

1:	movzb (%rcx),%edx

1:	movzb (%rax),%edx

	xorl %eax,%eax

	xorl %eax,%eax

	ret

	ret

	CFI_ENDPROC

	CFI_ENDPROC
@@ -47,48 +47,48 @@ ENDPROC(__get_user_1) 




ENTRY(__get_user_2)

ENTRY(__get_user_2)

	CFI_STARTPROC

	CFI_STARTPROC

	GET_THREAD_INFO(%r8)

	GET_THREAD_INFO(%rdx)

	addq $1,%rcx

	addq $1,%rax

	jc 20f

	jc 20f

	cmpq threadinfo_addr_limit(%r8),%rcx

	cmpq threadinfo_addr_limit(%rdx),%rax

	jae 20f

	jae 20f

	decq   %rcx

	decq   %rax

2:	movzwl (%rcx),%edx

2:	movzwl (%rax),%edx

	xorl %eax,%eax

	xorl %eax,%eax

	ret

	ret

20:	decq    %rcx

20:	decq    %rax

	jmp	bad_get_user

	jmp	bad_get_user

	CFI_ENDPROC

	CFI_ENDPROC

ENDPROC(__get_user_2)

ENDPROC(__get_user_2)





ENTRY(__get_user_4)

ENTRY(__get_user_4)

	CFI_STARTPROC

	CFI_STARTPROC

	GET_THREAD_INFO(%r8)

	GET_THREAD_INFO(%rdx)

	addq $3,%rcx

	addq $3,%rax

	jc 30f

	jc 30f

	cmpq threadinfo_addr_limit(%r8),%rcx

	cmpq threadinfo_addr_limit(%rdx),%rax

	jae 30f

	jae 30f

	subq $3,%rcx

	subq $3,%rax

3:	movl (%rcx),%edx

3:	movl (%rax),%edx

	xorl %eax,%eax

	xorl %eax,%eax

	ret

	ret

30:	subq $3,%rcx

30:	subq $3,%rax

	jmp bad_get_user

	jmp bad_get_user

	CFI_ENDPROC

	CFI_ENDPROC

ENDPROC(__get_user_4)

ENDPROC(__get_user_4)





ENTRY(__get_user_8)

ENTRY(__get_user_8)

	CFI_STARTPROC

	CFI_STARTPROC

	GET_THREAD_INFO(%r8)

	GET_THREAD_INFO(%rdx)

	addq $7,%rcx

	addq $7,%rax

	jc 40f

	jc 40f

	cmpq threadinfo_addr_limit(%r8),%rcx

	cmpq threadinfo_addr_limit(%rdx),%rax

	jae	40f

	jae	40f

	subq	$7,%rcx

	subq	$7,%rax

4:	movq (%rcx),%rdx

4:	movq (%rax),%rdx

	xorl %eax,%eax

	xorl %eax,%eax

	ret

	ret

40:	subq $7,%rcx

40:	subq $7,%rax

	jmp bad_get_user

	jmp bad_get_user

	CFI_ENDPROC

	CFI_ENDPROC

ENDPROC(__get_user_8)

ENDPROC(__get_user_8)

include/asm-x86/uaccess_64.h

+1 −2
Original line number Original line Diff line number Diff line
@@ -90,8 +90,7 @@ extern int fixup_exception(struct pt_regs *regs); 
#define __get_user_x(size, ret, x, ptr)		      \

#define __get_user_x(size, ret, x, ptr)		      \

	asm volatile("call __get_user_" #size	      \

	asm volatile("call __get_user_" #size	      \

		     : "=a" (ret),"=d" (x)	      \

		     : "=a" (ret),"=d" (x)	      \

		     : "c" (ptr)		      \

		     : "0" (ptr))		      \

		     : "r8")





/* Careful: we have to cast the result to the type of the pointer

/* Careful: we have to cast the result to the type of the pointer

 * for sign reasons */

 * for sign reasons */