Patch "x86: Add 1/2/4/8 byte optimization to 64bit __copy_{from,to}_user_inatomic" has been added to the 3.10-stable tree

PATCH [email protected] 1 participant 1 message Oct 18, 2015

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2015-10-18 00:51 UTC #0 lore raw

This is a note to let you know that I've just added the patch titled

    x86: Add 1/2/4/8 byte optimization to 64bit __copy_{from,to}_user_inatomic

to the 3.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:

     x86-add-1-2-4-8-byte-optimization-to-64bit-__copy_-from-to-_user_inatomic.patch

and it can be found in the queue-3.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

Quoted 1 line

From ff47ab4ff3cddfa7bc1b25b990e24abe2ae474ff Mon Sep 17 00:00:00 2001

From: Andi Kleen <[email protected]>
Date: Fri, 16 Aug 2013 14:17:19 -0700
Subject: x86: Add 1/2/4/8 byte optimization to 64bit __copy_{from,to}_user_inatomic

From: Andi Kleen <[email protected]>

commit ff47ab4ff3cddfa7bc1b25b990e24abe2ae474ff upstream.

The 64bit __copy_{from,to}_user_inatomic always called copy_from_user_generic, but skipped the special optimizations for 1/2/4/8 byte accesses.

This especially hurts the futex call, which accesses the 4 byte futex user value with a complicated fast string operation in a function call, instead of a single movl.

Use __copy_{from,to}_user for _inatomic instead to get the same optimizations. The only problem was the might_fault() in those functions. So move that to new wrapper and call __copy_{f,t}_user_nocheck() from *_inatomic directly.

32bit already did this correctly by duplicating the code.

Signed-off-by Andi Kleen <[email protected]>

Link http://lkml.kernel.org/r/[email protected] open here

Signed-off-by H. Peter Anvin <[email protected]>

Cc Thomas Gleixner <[email protected]>

Signed-off-by Greg Kroah-Hartman <[email protected]>

---
 arch/x86/include/asm/uaccess_64.h |   24 ++++++++++++++++++------
 1 file changed, 18 insertions(+), 6 deletions(-)

arch/x86/include/asm/uaccess_64.h +18 -6

@@ -77,11 +77,10 @@ int copy_to_user(void __user *dst, const
 }
 
 static __always_inline __must_check
-int __copy_from_user(void *dst, const void __user *src, unsigned size)
+int __copy_from_user_nocheck(void *dst, const void __user *src, unsigned size)
 {
 	int ret = 0;
 
-	might_fault();
 	if (!__builtin_constant_p(size))
 		return copy_user_generic(dst, (__force void *)src, size);
 	switch (size) {

@@ -121,11 +120,17 @@ int __copy_from_user(void *dst, const vo
 }
 
 static __always_inline __must_check
-int __copy_to_user(void __user *dst, const void *src, unsigned size)
+int __copy_from_user(void *dst, const void __user *src, unsigned size)
+{
+	might_fault();
+	return __copy_from_user_nocheck(dst, src, size);
+}
+
+static __always_inline __must_check
+int __copy_to_user_nocheck(void __user *dst, const void *src, unsigned size)
 {
 	int ret = 0;
 
-	might_fault();
 	if (!__builtin_constant_p(size))
 		return copy_user_generic((__force void *)dst, src, size);
 	switch (size) {

@@ -165,6 +170,13 @@ int __copy_to_user(void __user *dst, con
 }
 
 static __always_inline __must_check
+int __copy_to_user(void __user *dst, const void *src, unsigned size)
+{
+	might_fault();
+	return __copy_to_user_nocheck(dst, src, size);
+}
+
+static __always_inline __must_check
 int __copy_in_user(void __user *dst, const void __user *src, unsigned size)
 {
 	int ret = 0;

@@ -220,13 +232,13 @@ int __copy_in_user(void __user *dst, con
 static __must_check __always_inline int
 __copy_from_user_inatomic(void *dst, const void __user *src, unsigned size)
 {
-	return copy_user_generic(dst, (__force const void *)src, size);
+	return __copy_from_user_nocheck(dst, (__force const void *)src, size);
 }
 
 static __must_check __always_inline int
 __copy_to_user_inatomic(void __user *dst, const void *src, unsigned size)
 {
-	return copy_user_generic((__force void *)dst, src, size);
+	return __copy_to_user_nocheck((__force void *)dst, src, size);
 }
 
 extern long __copy_user_nocache(void *dst, const void __user *src,

Patches currently in stable-queue which might be from [email protected] are

queue-3.10/x86-apic-serialize-lvtt-and-tsc_deadline-writes.patch queue-3.10/x86-add-1-2-4-8-byte-optimization-to-64bit-__copy_-from-to-_user_inatomic.patch