Merge branch 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86/asm changes from Ingo Molnar: "Misc optimizations" * 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: x86: Slightly tweak the access_ok() C variant for better code x86: Replace assembly access_ok() with a C variant x86-64, copy_user: Use leal to produce 32-bit results x86-64, copy_user: Remove zero byte check before copy user buffer.
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commit
4cd4156994
2 changed files with 24 additions and 20 deletions
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@ -40,22 +40,30 @@
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/*
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* Test whether a block of memory is a valid user space address.
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* Returns 0 if the range is valid, nonzero otherwise.
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*
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* This is equivalent to the following test:
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* (u33)addr + (u33)size > (u33)current->addr_limit.seg (u65 for x86_64)
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*
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* This needs 33-bit (65-bit for x86_64) arithmetic. We have a carry...
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*/
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static inline bool __chk_range_not_ok(unsigned long addr, unsigned long size, unsigned long limit)
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{
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/*
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* If we have used "sizeof()" for the size,
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* we know it won't overflow the limit (but
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* it might overflow the 'addr', so it's
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* important to subtract the size from the
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* limit, not add it to the address).
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*/
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if (__builtin_constant_p(size))
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return addr > limit - size;
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/* Arbitrary sizes? Be careful about overflow */
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addr += size;
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if (addr < size)
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return true;
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return addr > limit;
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}
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#define __range_not_ok(addr, size, limit) \
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({ \
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unsigned long flag, roksum; \
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__chk_user_ptr(addr); \
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asm("add %3,%1 ; sbb %0,%0 ; cmp %1,%4 ; sbb $0,%0" \
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: "=&r" (flag), "=r" (roksum) \
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: "1" (addr), "g" ((long)(size)), \
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"rm" (limit)); \
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flag; \
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__chk_range_not_ok((unsigned long __force)(addr), size, limit); \
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})
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/**
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@ -78,7 +86,7 @@
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* this function, memory access functions may still return -EFAULT.
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*/
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#define access_ok(type, addr, size) \
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(likely(__range_not_ok(addr, size, user_addr_max()) == 0))
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likely(!__range_not_ok(addr, size, user_addr_max()))
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/*
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* The exception table consists of pairs of addresses relative to the
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@ -186,7 +186,7 @@ ENTRY(copy_user_generic_unrolled)
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30: shll $6,%ecx
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addl %ecx,%edx
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jmp 60f
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40: lea (%rdx,%rcx,8),%rdx
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40: leal (%rdx,%rcx,8),%edx
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jmp 60f
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50: movl %ecx,%edx
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60: jmp copy_user_handle_tail /* ecx is zerorest also */
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@ -236,8 +236,6 @@ ENDPROC(copy_user_generic_unrolled)
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ENTRY(copy_user_generic_string)
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CFI_STARTPROC
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ASM_STAC
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andl %edx,%edx
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jz 4f
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cmpl $8,%edx
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jb 2f /* less than 8 bytes, go to byte copy loop */
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ALIGN_DESTINATION
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@ -249,12 +247,12 @@ ENTRY(copy_user_generic_string)
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2: movl %edx,%ecx
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3: rep
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movsb
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4: xorl %eax,%eax
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xorl %eax,%eax
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ASM_CLAC
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ret
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.section .fixup,"ax"
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11: lea (%rdx,%rcx,8),%rcx
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11: leal (%rdx,%rcx,8),%ecx
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12: movl %ecx,%edx /* ecx is zerorest also */
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jmp copy_user_handle_tail
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.previous
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@ -279,12 +277,10 @@ ENDPROC(copy_user_generic_string)
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ENTRY(copy_user_enhanced_fast_string)
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CFI_STARTPROC
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ASM_STAC
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andl %edx,%edx
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jz 2f
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movl %edx,%ecx
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1: rep
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movsb
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2: xorl %eax,%eax
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xorl %eax,%eax
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ASM_CLAC
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ret
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