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."
