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Date: Mon, 20 Jan 2014 14:52:58 +0100
From: Ingo Molnar <mingo@...nel.org>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org, "H. Peter Anvin" <hpa@...or.com>,
Thomas Gleixner <tglx@...utronix.de>,
Andrew Morton <akpm@...ux-foundation.org>
Subject: [GIT PULL] x86/asm changes for v3.14
Linus,
Please pull the latest x86-asm-for-linus git tree from:
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86-asm-for-linus
# HEAD: a740576a4abf933de8f50787f24f24456cebd761 x86: Slightly tweak the access_ok() C variant for better code
Misc optimizations.
Thanks,
Ingo
------------------>
Fenghua Yu (1):
x86-64, copy_user: Remove zero byte check before copy user buffer.
H. Peter Anvin (2):
x86-64, copy_user: Use leal to produce 32-bit results
x86: Slightly tweak the access_ok() C variant for better code
Linus Torvalds (1):
x86: Replace assembly access_ok() with a C variant
arch/x86/include/asm/uaccess.h | 32 ++++++++++++++++++++------------
arch/x86/lib/copy_user_64.S | 12 ++++--------
2 files changed, 24 insertions(+), 20 deletions(-)
diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
index 8ec57c0..6f1bb74 100644
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -40,22 +40,30 @@
/*
* Test whether a block of memory is a valid user space address.
* Returns 0 if the range is valid, nonzero otherwise.
- *
- * This is equivalent to the following test:
- * (u33)addr + (u33)size > (u33)current->addr_limit.seg (u65 for x86_64)
- *
- * This needs 33-bit (65-bit for x86_64) arithmetic. We have a carry...
*/
+static inline bool __chk_range_not_ok(unsigned long addr, unsigned long size, unsigned long limit)
+{
+ /*
+ * If we have used "sizeof()" for the size,
+ * we know it won't overflow the limit (but
+ * it might overflow the 'addr', so it's
+ * important to subtract the size from the
+ * limit, not add it to the address).
+ */
+ if (__builtin_constant_p(size))
+ return addr > limit - size;
+
+ /* Arbitrary sizes? Be careful about overflow */
+ addr += size;
+ if (addr < size)
+ return true;
+ return addr > limit;
+}
#define __range_not_ok(addr, size, limit) \
({ \
- unsigned long flag, roksum; \
__chk_user_ptr(addr); \
- asm("add %3,%1 ; sbb %0,%0 ; cmp %1,%4 ; sbb $0,%0" \
- : "=&r" (flag), "=r" (roksum) \
- : "1" (addr), "g" ((long)(size)), \
- "rm" (limit)); \
- flag; \
+ __chk_range_not_ok((unsigned long __force)(addr), size, limit); \
})
/**
@@ -78,7 +86,7 @@
* this function, memory access functions may still return -EFAULT.
*/
#define access_ok(type, addr, size) \
- (likely(__range_not_ok(addr, size, user_addr_max()) == 0))
+ likely(!__range_not_ok(addr, size, user_addr_max()))
/*
* The exception table consists of pairs of addresses relative to the
diff --git a/arch/x86/lib/copy_user_64.S b/arch/x86/lib/copy_user_64.S
index a30ca15..dee945d 100644
--- a/arch/x86/lib/copy_user_64.S
+++ b/arch/x86/lib/copy_user_64.S
@@ -186,7 +186,7 @@ ENTRY(copy_user_generic_unrolled)
30: shll $6,%ecx
addl %ecx,%edx
jmp 60f
-40: lea (%rdx,%rcx,8),%rdx
+40: leal (%rdx,%rcx,8),%edx
jmp 60f
50: movl %ecx,%edx
60: jmp copy_user_handle_tail /* ecx is zerorest also */
@@ -236,8 +236,6 @@ ENDPROC(copy_user_generic_unrolled)
ENTRY(copy_user_generic_string)
CFI_STARTPROC
ASM_STAC
- andl %edx,%edx
- jz 4f
cmpl $8,%edx
jb 2f /* less than 8 bytes, go to byte copy loop */
ALIGN_DESTINATION
@@ -249,12 +247,12 @@ ENTRY(copy_user_generic_string)
2: movl %edx,%ecx
3: rep
movsb
-4: xorl %eax,%eax
+ xorl %eax,%eax
ASM_CLAC
ret
.section .fixup,"ax"
-11: lea (%rdx,%rcx,8),%rcx
+11: leal (%rdx,%rcx,8),%ecx
12: movl %ecx,%edx /* ecx is zerorest also */
jmp copy_user_handle_tail
.previous
@@ -279,12 +277,10 @@ ENDPROC(copy_user_generic_string)
ENTRY(copy_user_enhanced_fast_string)
CFI_STARTPROC
ASM_STAC
- andl %edx,%edx
- jz 2f
movl %edx,%ecx
1: rep
movsb
-2: xorl %eax,%eax
+ xorl %eax,%eax
ASM_CLAC
ret
--
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