This is a note to let you know that I've just added the patch titled
[Variant 1/Spectre-v1] arm64: Implement array_index_mask_nospec()
to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...
The filename of the patch is: arm64-implement-array_index_mask_nospec.patch and it can be found in the queue-4.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.
From foo@baz Wed Feb 14 14:44:54 CET 2018
From: Robin Murphy robin.murphy@arm.com Date: Mon, 5 Feb 2018 15:34:17 +0000 Subject: [Variant 1/Spectre-v1] arm64: Implement array_index_mask_nospec()
From: Robin Murphy robin.murphy@arm.com
Commit 022620eed3d0 upstream.
Provide an optimised, assembly implementation of array_index_mask_nospec() for arm64 so that the compiler is not in a position to transform the code in ways which affect its ability to inhibit speculation (e.g. by introducing conditional branches).
This is similar to the sequence used by x86, modulo architectural differences in the carry/borrow flags.
Reviewed-by: Mark Rutland mark.rutland@arm.com Signed-off-by: Robin Murphy robin.murphy@arm.com Signed-off-by: Will Deacon will.deacon@arm.com Signed-off-by: Catalin Marinas catalin.marinas@arm.com Signed-off-by: Ard Biesheuvel ard.biesheuvel@linaro.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/arm64/include/asm/barrier.h | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+)
--- a/arch/arm64/include/asm/barrier.h +++ b/arch/arm64/include/asm/barrier.h @@ -40,6 +40,27 @@ #define dma_rmb() dmb(oshld) #define dma_wmb() dmb(oshst)
+/* + * Generate a mask for array_index__nospec() that is ~0UL when 0 <= idx < sz + * and 0 otherwise. + */ +#define array_index_mask_nospec array_index_mask_nospec +static inline unsigned long array_index_mask_nospec(unsigned long idx, + unsigned long sz) +{ + unsigned long mask; + + asm volatile( + " cmp %1, %2\n" + " sbc %0, xzr, xzr\n" + : "=r" (mask) + : "r" (idx), "Ir" (sz) + : "cc"); + + csdb(); + return mask; +} + #define __smp_mb() dmb(ish) #define __smp_rmb() dmb(ishld) #define __smp_wmb() dmb(ishst)
Patches currently in stable-queue which might be from robin.murphy@arm.com are
queue-4.14/arm64-make-user_ds-an-inclusive-limit.patch queue-4.14/arm64-uaccess-don-t-bother-eliding-access_ok-checks-in-__-get-put-_user.patch queue-4.14/arm-arm64-smccc-make-function-identifiers-an-unsigned-quantity.patch queue-4.14/firmware-psci-expose-psci-conduit.patch queue-4.14/firmware-psci-expose-smccc-version-through-psci_ops.patch queue-4.14/arm64-use-pointer-masking-to-limit-uaccess-speculation.patch queue-4.14/arm-arm64-smccc-implement-smccc-v1.1-inline-primitive.patch queue-4.14/arm64-implement-array_index_mask_nospec.patch