linux-kernel - [PATCH 4.9 12/96] s390/lib: use expoline for indirect branches

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Date:   Thu, 24 May 2018 11:37:55 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Hendrik Brueckner <brueckner@...ux.vnet.ibm.com>
Subject: [PATCH 4.9 12/96] s390/lib: use expoline for indirect branches

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Martin Schwidefsky <schwidefsky@...ibm.com>

[ Upstream commit 97489e0663fa700d6e7febddc43b58df98d7bcda ]

The return from the memmove, memset, memcpy, __memset16, __memset32 and
__memset64 functions are done with "br %r14". These are indirect branches
as well and need to use execute trampolines for CONFIG_EXPOLINE=y.

Cc: stable@...r.kernel.org # 4.16
Fixes: f19fbd5ed6 ("s390: introduce execute-trampolines for branches")
Reviewed-by: Hendrik Brueckner <brueckner@...ux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@...ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/s390/lib/mem.S |    9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

--- a/arch/s390/lib/mem.S
+++ b/arch/s390/lib/mem.S
@@ -6,6 +6,9 @@
 
 #include <linux/linkage.h>
 #include <asm/export.h>
+#include <asm/nospec-insn.h>
+
+	GEN_BR_THUNK %r14
 
 /*
  * memset implementation
@@ -39,7 +42,7 @@ ENTRY(memset)
 .Lmemset_clear_rest:
 	larl	%r3,.Lmemset_xc
 	ex	%r4,0(%r3)
-	br	%r14
+	BR_EX	%r14
 .Lmemset_fill:
 	stc	%r3,0(%r2)
 	cghi	%r4,1
@@ -56,7 +59,7 @@ ENTRY(memset)
 .Lmemset_fill_rest:
 	larl	%r3,.Lmemset_mvc
 	ex	%r4,0(%r3)
-	br	%r14
+	BR_EX	%r14
 .Lmemset_xc:
 	xc	0(1,%r1),0(%r1)
 .Lmemset_mvc:
@@ -79,7 +82,7 @@ ENTRY(memcpy)
 .Lmemcpy_rest:
 	larl	%r5,.Lmemcpy_mvc
 	ex	%r4,0(%r5)
-	br	%r14
+	BR_EX	%r14
 .Lmemcpy_loop:
 	mvc	0(256,%r1),0(%r3)
 	la	%r1,256(%r1)