[PATCH 4.9 11/96] s390/crc32-vx: use expoline for indirect branches

From: Greg Kroah-Hartman
Date: Thu May 24 2018 - 06:56:37 EST


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

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

From: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>

[ Upstream commit 467a3bf219cee12259182c5cb4821f88fd518a51 ]

The return from the crc32_le_vgfm_16/crc32c_le_vgfm_16 and the
crc32_be_vgfm_16 functions are done with "br %r14". These are indirect
branches as well and need to use execute trampolines for CONFIG_EXPOLINE=y.

Cc: stable@xxxxxxxxxxxxxxx # 4.16
Fixes: f19fbd5ed6 ("s390: introduce execute-trampolines for branches")
Reviewed-by: Hendrik Brueckner <brueckner@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/s390/crypto/crc32be-vx.S | 5 ++++-
arch/s390/crypto/crc32le-vx.S | 4 +++-
2 files changed, 7 insertions(+), 2 deletions(-)

--- a/arch/s390/crypto/crc32be-vx.S
+++ b/arch/s390/crypto/crc32be-vx.S
@@ -12,6 +12,7 @@
*/

#include <linux/linkage.h>
+#include <asm/nospec-insn.h>
#include <asm/vx-insn.h>

/* Vector register range containing CRC-32 constants */
@@ -66,6 +67,8 @@

.previous

+ GEN_BR_THUNK %r14
+
.text
/*
* The CRC-32 function(s) use these calling conventions:
@@ -202,6 +205,6 @@ ENTRY(crc32_be_vgfm_16)

.Ldone:
VLGVF %r2,%v2,3
- br %r14
+ BR_EX %r14

.previous
--- a/arch/s390/crypto/crc32le-vx.S
+++ b/arch/s390/crypto/crc32le-vx.S
@@ -13,6 +13,7 @@
*/

#include <linux/linkage.h>
+#include <asm/nospec-insn.h>
#include <asm/vx-insn.h>

/* Vector register range containing CRC-32 constants */
@@ -75,6 +76,7 @@

.previous

+ GEN_BR_THUNK %r14

.text

@@ -263,6 +265,6 @@ crc32_le_vgfm_generic:

.Ldone:
VLGVF %r2,%v2,2
- br %r14
+ BR_EX %r14

.previous