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awilliam
GitHub Repository: awilliam/linux-vfio
 Path: blob/master/arch/x86/lib/getuser.S
10817 views
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/*

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 * __get_user functions.

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 *

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 * (C) Copyright 1998 Linus Torvalds

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 * (C) Copyright 2005 Andi Kleen

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 * (C) Copyright 2008 Glauber Costa

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 *

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 * These functions have a non-standard call interface

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 * to make them more efficient, especially as they

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 * return an error value in addition to the "real"

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 * return value.

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 */

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/*

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 * __get_user_X

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 *

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 * Inputs:	%[r|e]ax contains the address.

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 *		The register is modified, but all changes are undone

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 *		before returning because the C code doesn't know about it.

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 *

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 * Outputs:	%[r|e]ax is error code (0 or -EFAULT)

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 *		%[r|e]dx contains zero-extended value

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 *

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 *

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 * These functions should not modify any other registers,

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 * as they get called from within inline assembly.

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 */

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#include <linux/linkage.h>

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#include <asm/dwarf2.h>

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#include <asm/page_types.h>

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#include <asm/errno.h>

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#include <asm/asm-offsets.h>

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#include <asm/thread_info.h>

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#include <asm/asm.h>

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	.text

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ENTRY(__get_user_1)

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	CFI_STARTPROC

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	GET_THREAD_INFO(%_ASM_DX)

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	cmp TI_addr_limit(%_ASM_DX),%_ASM_AX

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	jae bad_get_user

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1:	movzb (%_ASM_AX),%edx

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	xor %eax,%eax

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	ret

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	CFI_ENDPROC

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ENDPROC(__get_user_1)

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ENTRY(__get_user_2)

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	CFI_STARTPROC

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	add $1,%_ASM_AX

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	jc bad_get_user

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	GET_THREAD_INFO(%_ASM_DX)

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	cmp TI_addr_limit(%_ASM_DX),%_ASM_AX

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	jae bad_get_user

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2:	movzwl -1(%_ASM_AX),%edx

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	xor %eax,%eax

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	ret

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	CFI_ENDPROC

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ENDPROC(__get_user_2)

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ENTRY(__get_user_4)

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	CFI_STARTPROC

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	add $3,%_ASM_AX

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	jc bad_get_user

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	GET_THREAD_INFO(%_ASM_DX)

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	cmp TI_addr_limit(%_ASM_DX),%_ASM_AX

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	jae bad_get_user

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3:	mov -3(%_ASM_AX),%edx

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	xor %eax,%eax

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	ret

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	CFI_ENDPROC

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ENDPROC(__get_user_4)

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#ifdef CONFIG_X86_64

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ENTRY(__get_user_8)

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	CFI_STARTPROC

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	add $7,%_ASM_AX

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	jc bad_get_user

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	GET_THREAD_INFO(%_ASM_DX)

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	cmp TI_addr_limit(%_ASM_DX),%_ASM_AX

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	jae	bad_get_user

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4:	movq -7(%_ASM_AX),%_ASM_DX

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	xor %eax,%eax

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	ret

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	CFI_ENDPROC

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ENDPROC(__get_user_8)

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#endif

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bad_get_user:

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	CFI_STARTPROC

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	xor %edx,%edx

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	mov $(-EFAULT),%_ASM_AX

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	ret

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	CFI_ENDPROC

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END(bad_get_user)

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.section __ex_table,"a"

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	_ASM_PTR 1b,bad_get_user

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	_ASM_PTR 2b,bad_get_user

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	_ASM_PTR 3b,bad_get_user

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#ifdef CONFIG_X86_64

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	_ASM_PTR 4b,bad_get_user

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#endif

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