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Commit b2f68038 authored by Benjamin LaHaise's avatar Benjamin LaHaise Committed by Ingo Molnar
Browse files

x86/mm/32: Add support for 64-bit __get_user() on 32-bit kernels 

The existing __get_user() implementation does not support fetching
64-bit values on 32-bit x86.  Implement this in a way that does not
generate any incorrect warnings as cautioned by Russell King.

Test code available at:

  http://www.kvack.org/~bcrl/x86_32-get_user.tar

 .

Signed-off-by: default avatarBenjamin LaHaise <bcrl@kvack.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 1886297c

arch/x86/include/asm/uaccess.h

+21 −2
Original line number Diff line number Diff line
@@ -333,7 +333,26 @@ do { \ 
} while (0)



#ifdef CONFIG_X86_32

#define __get_user_asm_u64(x, ptr, retval, errret)	(x) = __get_user_bad()

#define __get_user_asm_u64(x, ptr, retval, errret)			\

({									\

	__typeof__(ptr) __ptr = (ptr);					\

	asm volatile(ASM_STAC "\n"					\

		     "1:	movl %2,%%eax\n"			\

		     "2:	movl %3,%%edx\n"			\

		     "3: " ASM_CLAC "\n"				\

		     ".section .fixup,\"ax\"\n"				\

		     "4:	mov %4,%0\n"				\

		     "	xorl %%eax,%%eax\n"				\

		     "	xorl %%edx,%%edx\n"				\

		     "	jmp 3b\n"					\

		     ".previous\n"					\

		     _ASM_EXTABLE(1b, 4b)				\

		     _ASM_EXTABLE(2b, 4b)				\

		     : "=r" (retval), "=A"(x)				\

		     : "m" (__m(__ptr)), "m" __m(((u32 *)(__ptr)) + 1),	\

		       "i" (errret), "0" (retval));			\

})



#define __get_user_asm_ex_u64(x, ptr)			(x) = __get_user_bad()

#else

#define __get_user_asm_u64(x, ptr, retval, errret) \
@@ -420,7 +439,7 @@ do { \ 
#define __get_user_nocheck(x, ptr, size)				\

({									\

	int __gu_err;							\

	unsigned long __gu_val;						\

	__inttype(*(ptr)) __gu_val;					\

	__uaccess_begin();						\

	__get_user_size(__gu_val, (ptr), (size), __gu_err, -EFAULT);	\

	__uaccess_end();						\