| From | Andi Kleen <> | Subject | [PATCH] [182/223] ARM: 6489/1: thumb2: fix incorrect optimisation in usracc | Date | Mon, 13 Dec 2010 00:48:07 +0100 (CET) |
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2.6.35-longterm review patch. If anyone has any objections, please let me know.
------------------ From: Will Deacon <will.deacon@arm.com>
commit 1142b71d85894dcff1466dd6c871ea3c89e0352c upstream.
Commit 8b592783 added a Thumb-2 variant of usracc which, when it is called with \rept=2, calls usraccoff once with an offset of 0 and secondly with a hard-coded offset of 4 in order to avoid incrementing the pointer again. If \inc != 4 then we will store the data to the wrong offset from \ptr. Luckily, the only caller that passes \rept=2 to this function is __clear_user so we haven't been actively corrupting user data.
This patch fixes usracc to pass \inc instead of #4 to usraccoff when it is called a second time.
Reported-by: Tony Thompson <tony.thompson@arm.com> Acked-by: Catalin Marinas <catalin.marinas@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de> Signed-off-by: Andi Kleen <ak@linux.intel.com>
--- arch/arm/include/asm/assembler.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
Index: linux/arch/arm/include/asm/assembler.h =================================================================== --- linux.orig/arch/arm/include/asm/assembler.h +++ linux/arch/arm/include/asm/assembler.h @@ -215,7 +215,7 @@ @ Slightly optimised to avoid incrementing the pointer twice usraccoff \instr, \reg, \ptr, \inc, 0, \cond, \abort .if \rept == 2 - usraccoff \instr, \reg, \ptr, \inc, 4, \cond, \abort + usraccoff \instr, \reg, \ptr, \inc, \inc, \cond, \abort .endif add\cond \ptr, #\rept * \inc
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