The patch below does not apply to the 4.4-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@xxxxxxxxxxxxxxx>.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
>From c50c84c3ac4d5db683904bdb3257798b6ef980ae Mon Sep 17 00:00:00 2001
From: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
Date: Wed, 25 Apr 2018 18:41:30 +0200
Subject: [PATCH] s390/kernel: use expoline for indirect branches
The assember code in arch/s390/kernel uses a few more indirect branches
which need to be done with 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>
diff --git a/arch/s390/kernel/base.S b/arch/s390/kernel/base.S
index f6c56009e822..b65874b0b412 100644
--- a/arch/s390/kernel/base.S
+++ b/arch/s390/kernel/base.S
@@ -9,18 +9,22 @@
#include <linux/linkage.h>
#include <asm/asm-offsets.h>
+#include <asm/nospec-insn.h>
#include <asm/ptrace.h>
#include <asm/sigp.h>
+ GEN_BR_THUNK %r9
+ GEN_BR_THUNK %r14
+
ENTRY(s390_base_mcck_handler)
basr %r13,0
0: lg %r15,__LC_PANIC_STACK # load panic stack
aghi %r15,-STACK_FRAME_OVERHEAD
larl %r1,s390_base_mcck_handler_fn
- lg %r1,0(%r1)
- ltgr %r1,%r1
+ lg %r9,0(%r1)
+ ltgr %r9,%r9
jz 1f
- basr %r14,%r1
+ BASR_EX %r14,%r9
1: la %r1,4095
lmg %r0,%r15,__LC_GPREGS_SAVE_AREA-4095(%r1)
lpswe __LC_MCK_OLD_PSW
@@ -37,10 +41,10 @@ ENTRY(s390_base_ext_handler)
basr %r13,0
0: aghi %r15,-STACK_FRAME_OVERHEAD
larl %r1,s390_base_ext_handler_fn
- lg %r1,0(%r1)
- ltgr %r1,%r1
+ lg %r9,0(%r1)
+ ltgr %r9,%r9
jz 1f
- basr %r14,%r1
+ BASR_EX %r14,%r9
1: lmg %r0,%r15,__LC_SAVE_AREA_ASYNC
ni __LC_EXT_OLD_PSW+1,0xfd # clear wait state bit
lpswe __LC_EXT_OLD_PSW
@@ -57,10 +61,10 @@ ENTRY(s390_base_pgm_handler)
basr %r13,0
0: aghi %r15,-STACK_FRAME_OVERHEAD
larl %r1,s390_base_pgm_handler_fn
- lg %r1,0(%r1)
- ltgr %r1,%r1
+ lg %r9,0(%r1)
+ ltgr %r9,%r9
jz 1f
- basr %r14,%r1
+ BASR_EX %r14,%r9
lmg %r0,%r15,__LC_SAVE_AREA_SYNC
lpswe __LC_PGM_OLD_PSW
1: lpswe disabled_wait_psw-0b(%r13)
@@ -117,7 +121,7 @@ ENTRY(diag308_reset)
larl %r4,.Lcontinue_psw # Restore PSW flags
lpswe 0(%r4)
.Lcontinue:
- br %r14
+ BR_EX %r14
.align 16
.Lrestart_psw:
.long 0x00080000,0x80000000 + .Lrestart_part2
diff --git a/arch/s390/kernel/reipl.S b/arch/s390/kernel/reipl.S
index 73cc3750f0d3..7f14adf512c6 100644
--- a/arch/s390/kernel/reipl.S
+++ b/arch/s390/kernel/reipl.S
@@ -7,8 +7,11 @@
#include <linux/linkage.h>
#include <asm/asm-offsets.h>
+#include <asm/nospec-insn.h>
#include <asm/sigp.h>
+ GEN_BR_THUNK %r9
+
#
# Issue "store status" for the current CPU to its prefix page
# and call passed function afterwards
@@ -67,9 +70,9 @@ ENTRY(store_status)
st %r4,0(%r1)
st %r5,4(%r1)
stg %r2,8(%r1)
- lgr %r1,%r2
+ lgr %r9,%r2
lgr %r2,%r3
- br %r1
+ BR_EX %r9
.section .bss
.align 8
diff --git a/arch/s390/kernel/swsusp.S b/arch/s390/kernel/swsusp.S
index e99187149f17..a049a7b9d6e8 100644
--- a/arch/s390/kernel/swsusp.S
+++ b/arch/s390/kernel/swsusp.S
@@ -13,6 +13,7 @@
#include <asm/ptrace.h>
#include <asm/thread_info.h>
#include <asm/asm-offsets.h>
+#include <asm/nospec-insn.h>
#include <asm/sigp.h>
/*
@@ -24,6 +25,8 @@
* (see below) in the resume process.
* This function runs with disabled interrupts.
*/
+ GEN_BR_THUNK %r14
+
.section .text
ENTRY(swsusp_arch_suspend)
stmg %r6,%r15,__SF_GPRS(%r15)
@@ -103,7 +106,7 @@ ENTRY(swsusp_arch_suspend)
spx 0x318(%r1)
lmg %r6,%r15,STACK_FRAME_OVERHEAD + __SF_GPRS(%r15)
lghi %r2,0
- br %r14
+ BR_EX %r14
/*
* Restore saved memory image to correct place and restore register context.
@@ -197,11 +200,10 @@ pgm_check_entry:
larl %r15,init_thread_union
ahi %r15,1<<(PAGE_SHIFT+THREAD_SIZE_ORDER)
larl %r2,.Lpanic_string
- larl %r3,sclp_early_printk
lghi %r1,0
sam31
sigp %r1,%r0,SIGP_SET_ARCHITECTURE
- basr %r14,%r3
+ brasl %r14,sclp_early_printk
larl %r3,.Ldisabled_wait_31
lpsw 0(%r3)
4:
@@ -267,7 +269,7 @@ restore_registers:
/* Return 0 */
lmg %r6,%r15,STACK_FRAME_OVERHEAD + __SF_GPRS(%r15)
lghi %r2,0
- br %r14
+ BR_EX %r14
.section .data..nosave,"aw",@progbits
.align 8
