Patch "powerpc/tm: do not use r13 for tabort_syscall" has been added to the 4.4-stable tree

Patch "powerpc/tm: do not use r13 for tabort_syscall" has been added to the 4.4-stable tree

[gregkh]

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

    powerpc/tm: do not use r13 for tabort_syscall

to the 4.4-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-tm-do-not-use-r13-for-tabort_syscall.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 cc7786d3ee7e3c979799db834b528db2c0834c2e Mon Sep 17 00:00:00 2001
From: Nicholas Piggin <npiggin@gmail.com>
Date: Mon, 25 Jul 2016 14:26:51 +1000
Subject: powerpc/tm: do not use r13 for tabort_syscall

From: Nicholas Piggin <npiggin@gmail.com>

commit cc7786d3ee7e3c979799db834b528db2c0834c2e upstream.

tabort_syscall runs with RI=1, so a nested recoverable machine
check will load the paca into r13 and overwrite what we loaded
it with, because exceptions returning to privileged mode do not
restore r13.

Fixes: b4b56f9ecab4 (powerpc/tm: Abort syscalls in active transactions)
Signed-off-by: Nick Piggin <npiggin@gmail.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/powerpc/kernel/entry_64.S |   12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -334,13 +334,13 @@ syscall_exit_work:
 tabort_syscall:
 	/* Firstly we need to enable TM in the kernel */
 	mfmsr	r10
-	li	r13, 1
-	rldimi	r10, r13, MSR_TM_LG, 63-MSR_TM_LG
+	li	r9, 1
+	rldimi	r10, r9, MSR_TM_LG, 63-MSR_TM_LG
 	mtmsrd	r10, 0
 
 	/* tabort, this dooms the transaction, nothing else */
-	li	r13, (TM_CAUSE_SYSCALL|TM_CAUSE_PERSISTENT)
-	TABORT(R13)
+	li	r9, (TM_CAUSE_SYSCALL|TM_CAUSE_PERSISTENT)
+	TABORT(R9)
 
 	/*
 	 * Return directly to userspace. We have corrupted user register state,
@@ -348,8 +348,8 @@ tabort_syscall:
 	 * resume after the tbegin of the aborted transaction with the
 	 * checkpointed register state.
 	 */
-	li	r13, MSR_RI
-	andc	r10, r10, r13
+	li	r9, MSR_RI
+	andc	r10, r10, r9
 	mtmsrd	r10, 1
 	mtspr	SPRN_SRR0, r11
 	mtspr	SPRN_SRR1, r12


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

queue-4.4/powerpc-tm-do-not-use-r13-for-tabort_syscall.patch
queue-4.4/sched-core-fix-a-race-between-try_to_wake_up-and-a-woken-up-task.patch