From mboxrd@z Thu Jan 1 00:00:00 1970 From: will.deacon@arm.com (Will Deacon) Date: Thu, 15 Oct 2015 14:02:47 +0100 Subject: [PATCH] ARM: SWP emulation: Restore original *data when failed In-Reply-To: <561F6F3B.6030607@arm.com> References: <1444791077-26020-1-git-send-email-shengjiu.wang@freescale.com> <20151015082417.GX32532@n2100.arm.linux.org.uk> <20151015083629.GA32630@shlinux2> <20151015085700.GY32532@n2100.arm.linux.org.uk> <561F6F3B.6030607@arm.com> Message-ID: <20151015130247.GB29301@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Thu, Oct 15, 2015 at 10:17:47AM +0100, Vladimir Murzin wrote: > We might need the same change for arm64 counterpart (see > arch/arm64/kernel/armv8_deprecated.c). Something like below? Will >>From 63c3e83073cfac2e011adf0ed6f335275cc977a7 Mon Sep 17 00:00:00 2001 From: Will Deacon Date: Thu, 15 Oct 2015 13:55:53 +0100 Subject: [PATCH] arm64: compat: fix stxr failure case in SWP emulation If the STXR instruction fails in the SWP emulation code, we leave *data overwritten with the loaded value, therefore corrupting the data written by a subsequent, successful attempt. This patch re-jigs the code so that we only write back to *data once we know that the update has happened. Reported-by: Shengjiu Wang Reported-by: Vladimir Murzin Signed-off-by: Will Deacon --- arch/arm64/kernel/armv8_deprecated.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/arch/arm64/kernel/armv8_deprecated.c b/arch/arm64/kernel/armv8_deprecated.c index bcee7abac68e..6039d1eb5912 100644 --- a/arch/arm64/kernel/armv8_deprecated.c +++ b/arch/arm64/kernel/armv8_deprecated.c @@ -284,12 +284,12 @@ static void register_insn_emulation_sysctl(struct ctl_table *table) __asm__ __volatile__( \ ALTERNATIVE("nop", SET_PSTATE_PAN(0), ARM64_HAS_PAN, \ CONFIG_ARM64_PAN) \ - " mov %w2, %w1\n" \ - "0: ldxr"B" %w1, [%3]\n" \ - "1: stxr"B" %w0, %w2, [%3]\n" \ + "0: ldxr"B" %w2, [%3]\n" \ + "1: stxr"B" %w0, %w1, [%3]\n" \ " cbz %w0, 2f\n" \ " mov %w0, %w4\n" \ "2:\n" \ + " mov %w1, %w2\n" \ " .pushsection .fixup,\"ax\"\n" \ " .align 2\n" \ "3: mov %w0, %w5\n" \ -- 2.1.4