Messages in this thread Patch in this message | | | Date | Wed, 9 Mar 2016 15:05:56 -0500 | From | Benjamin LaHaise <> | Subject | [PATCH] x86_32: add support for 64 bit __get_user() v3 |
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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 .
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 <bcrl@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."
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