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Commit 96477b4c authored by Ville Syrjälä's avatar Ville Syrjälä Committed by H. Peter Anvin
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x86-32: Add support for 64bit get_user() 

Implement __get_user_8() for x86-32. It will return the
64-bit result in edx:eax register pair, and ecx is used
to pass in the address and return the error value.

For consistency, change the register assignment for all
other __get_user_x() variants, so that address is passed in
ecx/rcx, the error value is returned in ecx/rcx, and eax/rax
contains the actual value.

[ hpa: I modified the patch so that it does NOT change the calling
  conventions for the existing callsites, this also means that the code
  is completely unchanged for 64 bits.

  Instead, continue to use eax for address input/error output and use
  the ecx:edx register pair for the output. ]

This is a partial refresh of a patch [1] by Jamie Lokier from
2004. Only the minimal changes to implement 64bit get_user()
were picked from the original patch.

[1] http://article.gmane.org/gmane.linux.kernel/198823



Originally-by: default avatarJamie Lokier <jamie@shareable.org>
Signed-off-by: default avatarVille Syrjälä <ville.syrjala@linux.intel.com>
Link:
http://lkml.kernel.org/r/1355312043-11467-1-git-send-email-ville.syrjala@linux.intel.com


Signed-off-by: default avatarH. Peter Anvin <hpa@linux.intel.com>
parent 07f4207a

arch/x86/include/asm/uaccess.h

+15 −4
Original line number Diff line number Diff line
@@ -151,8 +151,15 @@ extern int __get_user_bad(void); 
 * On error, the variable @x is set to zero.

 */

#ifdef CONFIG_X86_32

#define __get_user_8(__ret_gu, __val_gu, ptr)				\

		__get_user_x(X, __ret_gu, __val_gu, ptr)

#define __get_user_8(ret, x, ptr)		      \

do {						      \

	register unsigned long long __xx asm("%edx"); \

	asm volatile("call __get_user_8"	      \

		     : "=a" (ret), "=r" (__xx)	      \

		     : "0" (ptr));		      \

	(x) = __xx;				      \

} while (0)



#else

#define __get_user_8(__ret_gu, __val_gu, ptr)				\

		__get_user_x(8, __ret_gu, __val_gu, ptr)
@@ -162,6 +169,7 @@ extern int __get_user_bad(void); 
({									\

	int __ret_gu;							\

	unsigned long __val_gu;						\

	unsigned long long __val_gu8;					\

	__chk_user_ptr(ptr);						\

	might_fault();							\

	switch (sizeof(*(ptr))) {					\
@@ -175,12 +183,15 @@ extern int __get_user_bad(void); 
		__get_user_x(4, __ret_gu, __val_gu, ptr);		\

		break;							\

	case 8:								\

		__get_user_8(__ret_gu, __val_gu, ptr);			\

		__get_user_8(__ret_gu, __val_gu8, ptr);			\

		break;							\

	default:							\

		__get_user_x(X, __ret_gu, __val_gu, ptr);		\

		break;							\

	}								\

	if (sizeof(*(ptr)) == 8)					\

		(x) = (__typeof__(*(ptr)))__val_gu8;			\

	else								\

		(x) = (__typeof__(*(ptr)))__val_gu;			\

	__ret_gu;							\

})

arch/x86/kernel/i386_ksyms_32.c

+1 −0
Original line number Diff line number Diff line
@@ -26,6 +26,7 @@ EXPORT_SYMBOL(csum_partial_copy_generic); 
EXPORT_SYMBOL(__get_user_1);

EXPORT_SYMBOL(__get_user_2);

EXPORT_SYMBOL(__get_user_4);

EXPORT_SYMBOL(__get_user_8);



EXPORT_SYMBOL(__put_user_1);

EXPORT_SYMBOL(__put_user_2);

arch/x86/lib/getuser.S

+32 −5
Original line number Diff line number Diff line
@@ -15,11 +15,10 @@ 
 * __get_user_X

 *

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

 *		The register is modified, but all changes are undone

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

 *

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

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

 *		%ecx contains the high half for 32-bit __get_user_8

 *

 *

 * These functions should not modify any other registers,
@@ -79,9 +78,9 @@ ENTRY(__get_user_4) 
	CFI_ENDPROC

ENDPROC(__get_user_4)



#ifdef CONFIG_X86_64

ENTRY(__get_user_8)

	CFI_STARTPROC

#ifdef CONFIG_X86_64

	add $7,%_ASM_AX

	jc bad_get_user

	GET_THREAD_INFO(%_ASM_DX)
@@ -92,9 +91,22 @@ ENTRY(__get_user_8) 
	xor %eax,%eax

	ASM_CLAC

	ret

#else

	add $7,%_ASM_AX

	jc bad_get_user_8

	GET_THREAD_INFO(%_ASM_DX)

	cmp TI_addr_limit(%_ASM_DX),%_ASM_AX

	jae bad_get_user_8

	ASM_STAC

4:	mov -7(%_ASM_AX),%edx

5:	mov -3(%_ASM_AX),%ecx

	xor %eax,%eax

	ASM_CLAC

	ret

#endif

	CFI_ENDPROC

ENDPROC(__get_user_8)

#endif





bad_get_user:

	CFI_STARTPROC
@@ -105,9 +117,24 @@ bad_get_user: 
	CFI_ENDPROC

END(bad_get_user)



#ifdef CONFIG_X86_32

bad_get_user_8:

	CFI_STARTPROC

	xor %edx,%edx

	xor %ecx,%ecx

	mov $(-EFAULT),%_ASM_AX

	ASM_CLAC

	ret

	CFI_ENDPROC

END(bad_get_user_8)

#endif



	_ASM_EXTABLE(1b,bad_get_user)

	_ASM_EXTABLE(2b,bad_get_user)

	_ASM_EXTABLE(3b,bad_get_user)

#ifdef CONFIG_X86_64

	_ASM_EXTABLE(4b,bad_get_user)

#else

	_ASM_EXTABLE(4b,bad_get_user_8)

	_ASM_EXTABLE(5b,bad_get_user_8)

#endif