Any more comments/feedback on this? Can this be merged for 4.6?
-ben
On Wed, Mar 09, 2016 at 03:05:56PM -0500, Benjamin LaHaise wrote:
> 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 .
>
> v2: use __inttype() as suggested by H. Peter Anvin, which cleans the
> code up nicely, and fix things to work on x86_64 as well.
>
> v3: fix undefined behaviour on 32 bit x86 caused by multiple expansion
> of ptr in the 64 bit case.
>
> Signed-off-by: Benjamin LaHaise <b...@kvack.org>
>
> diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
> index a4a30e4..8743552 100644
> --- a/arch/x86/include/asm/uaccess.h
> +++ b/arch/x86/include/asm/uaccess.h
> @@ -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(); \
>
> --
> "Thought is the essence of where you are now."
--
"Thought is the essence of where you are now."
