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

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Message-Id: <20180524093606.229986742@linuxfoundation.org>
Date:   Thu, 24 May 2018 11:37:54 +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 11/96] s390/crc32-vx: 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 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@...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/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