linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
* [PATCH] x86_32: add support for 64 bit __get_user()
@ 2016-03-09 17:22 Benjamin LaHaise
  2016-03-09 17:36 ` H. Peter Anvin
                   ` (3 more replies)
  0 siblings, 4 replies; 14+ messages in thread
From: Benjamin LaHaise @ 2016-03-09 17:22 UTC (permalink / raw)
  To: Ingo Molnar, Russell King
  Cc: Thomas Gleixner, H. Peter Anvin, x86, linux-kernel

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>

diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
index a4a30e4..2d0607a 100644
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -333,7 +333,23 @@ 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, addr, err, errret)			\
+	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" (err), "=A"(x)				\
+		     : "m" (__m(addr)), "m" __m(((u32 *)(addr)) + 1),	\
+		       "i" (errret), "0" (err))
+
 #define __get_user_asm_ex_u64(x, ptr)			(x) = __get_user_bad()
 #else
 #define __get_user_asm_u64(x, ptr, retval, errret) \
@@ -420,11 +436,20 @@ do {									\
 #define __get_user_nocheck(x, ptr, size)				\
 ({									\
 	int __gu_err;							\
-	unsigned long __gu_val;						\
-	__uaccess_begin();						\
-	__get_user_size(__gu_val, (ptr), (size), __gu_err, -EFAULT);	\
-	__uaccess_end();						\
-	(x) = (__force __typeof__(*(ptr)))__gu_val;			\
+	if (size == 8) {						\
+		unsigned long __gu_val[2];				\
+		__gu_err = 0;						\
+		__uaccess_begin();					\
+		__get_user_asm_u64(__gu_val, ptr, __gu_err, -EFAULT);	\
+		__uaccess_end();					\
+		(x) = *(__force __typeof__((ptr)))__gu_val;		\
+	} else {							\
+		unsigned long __gu_val;					\
+		__uaccess_begin();					\
+		__get_user_size(__gu_val, (ptr), (size), __gu_err, -EFAULT); \
+		__uaccess_end();					\
+		(x) = (__force __typeof__(*(ptr)))__gu_val;		\
+	}								\
 	__builtin_expect(__gu_err, 0);					\
 })
 
-- 
"Thought is the essence of where you are now."

^ permalink raw reply related	[flat|nested] 14+ messages in thread

end of thread, other threads:[~2016-03-14 16:39 UTC | newest]

Thread overview: 14+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2016-03-09 17:22 [PATCH] x86_32: add support for 64 bit __get_user() Benjamin LaHaise
2016-03-09 17:36 ` H. Peter Anvin
2016-03-09 17:50   ` Benjamin LaHaise
2016-03-09 18:22     ` H. Peter Anvin
2016-03-09 18:27       ` Benjamin LaHaise
2016-03-09 19:30       ` [PATCH] x86_32: add support for 64 bit __get_user() v2 Benjamin LaHaise
2016-03-09 19:41         ` kbuild test robot
2016-03-09 20:05         ` [PATCH] x86_32: add support for 64 bit __get_user() v3 Benjamin LaHaise
2016-03-14 15:37           ` Benjamin LaHaise
2016-03-14 16:39             ` Ingo Molnar
2016-03-09 20:24         ` [PATCH] x86_32: add support for 64 bit __get_user() v2 kbuild test robot
2016-03-09 18:17 ` [PATCH] x86_32: add support for 64 bit __get_user() kbuild test robot
2016-03-09 18:22 ` kbuild test robot
2016-03-09 18:23 ` kbuild test robot

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).