This is a note to let you know that I've just added the patch titled

powerpc/64: Convert the syscall exit path to use RFI_TO_USER/KERNEL

to the 4.4-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: powerpc-64-convert-the-syscall-exit-path-to-use-rfi_to_user-kernel.patch and it can be found in the queue-4.4 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 b8e90cb7bc04a509e821e82ab6ed7a8ef11ba333 Mon Sep 17 00:00:00 2001

From: Nicholas Piggin npiggin@gmail.com Date: Wed, 10 Jan 2018 03:07:15 +1100 Subject: powerpc/64: Convert the syscall exit path to use RFI_TO_USER/KERNEL

From: Nicholas Piggin npiggin@gmail.com

commit b8e90cb7bc04a509e821e82ab6ed7a8ef11ba333 upstream.

In the syscall exit path we may be returning to user or kernel context. We already have a test for that, because we conditionally restore r13. So use that existing test and branch, and bifurcate the return based on that.

Signed-off-by: Nicholas Piggin npiggin@gmail.com Signed-off-by: Michael Ellerman mpe@ellerman.id.au Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

--- arch/powerpc/kernel/entry_64.S | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-)

--- a/arch/powerpc/kernel/entry_64.S +++ b/arch/powerpc/kernel/entry_64.S @@ -230,13 +230,23 @@ END_FTR_SECTION_IFCLR(CPU_FTR_STCX_CHECK ACCOUNT_CPU_USER_EXIT(r11, r12) HMT_MEDIUM_LOW_HAS_PPR ld r13,GPR13(r1) /* only restore r13 if returning to usermode */ + ld r2,GPR2(r1) + ld r1,GPR1(r1) + mtlr r4 + mtcr r5 + mtspr SPRN_SRR0,r7 + mtspr SPRN_SRR1,r8 + RFI_TO_USER + b . /* prevent speculative execution */ + + /* exit to kernel */ 1: ld r2,GPR2(r1) ld r1,GPR1(r1) mtlr r4 mtcr r5 mtspr SPRN_SRR0,r7 mtspr SPRN_SRR1,r8 - RFI + RFI_TO_KERNEL b . /* prevent speculative execution */

syscall_error:

Patches currently in stable-queue which might be from npiggin@gmail.com are

queue-4.4/powerpc-64s-simple-rfi-macro-conversions.patch queue-4.4/powerpc-64-add-macros-for-annotating-the-destination-of-rfid-hrfid.patch queue-4.4/powerpc-64s-allow-control-of-rfi-flush-via-debugfs.patch queue-4.4/powerpc-64s-convert-slb_miss_common-to-use-rfi_to_user-kernel.patch queue-4.4/powerpc-64-convert-the-syscall-exit-path-to-use-rfi_to_user-kernel.patch queue-4.4/powerpc-64s-add-support-for-rfi-flush-of-l1-d-cache.patch queue-4.4/powerpc-64-convert-fast_exception_return-to-use-rfi_to_user-kernel.patch