Patch "powerpc/64: Convert the syscall exit path to use RFI_TO_USER/KERNEL" has been added to the 4.9-stable tree

[<gregkh@linuxfoundation.org>]

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 4.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

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-4.9 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
@@ -251,13 +251,23 @@ BEGIN_FTR_SECTION
 END_FTR_SECTION_IFSET(CPU_FTR_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-4.9/powerpc-64-add-macros-for-annotating-the-destination-of-rfid-hrfid.patch
queue-4.9/powerpc-64s-allow-control-of-rfi-flush-via-debugfs.patch
queue-4.9/powerpc-64s-convert-slb_miss_common-to-use-rfi_to_user-kernel.patch
queue-4.9/powerpc-64-convert-the-syscall-exit-path-to-use-rfi_to_user-kernel.patch
queue-4.9/powerpc-64s-add-support-for-rfi-flush-of-l1-d-cache.patch
queue-4.9/powerpc-64-convert-fast_exception_return-to-use-rfi_to_user-kernel.patch