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

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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: Benjamin 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: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Benjamin LaHaise 2016-03-09 15:05:56 -05:00 committed by Ingo Molnar
parent 1886297ce0
commit b2f680380d
1 changed files with 21 additions and 2 deletions
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23
arch/x86/include/asm/uaccess.h
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@ -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(); \