The patch below does not apply to the 4.19-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@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 97489e0663fa700d6e7febddc43b58df98d7bcda Mon Sep 17 00:00:00 2001

From: Martin Schwidefsky schwidefsky@de.ibm.com Date: Mon, 23 Apr 2018 14:31:36 +0200 Subject: [PATCH] s390/lib: use expoline for indirect branches

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@vger.kernel.org # 4.16 Fixes: f19fbd5ed6 ("s390: introduce execute-trampolines for branches") Reviewed-by: Hendrik Brueckner brueckner@linux.vnet.ibm.com Signed-off-by: Martin Schwidefsky schwidefsky@de.ibm.com

diff --git a/arch/s390/lib/mem.S b/arch/s390/lib/mem.S index 495c9c4bacc7..2311f15be9cf 100644 --- a/arch/s390/lib/mem.S +++ b/arch/s390/lib/mem.S @@ -7,6 +7,9 @@

#include <linux/linkage.h> #include <asm/export.h> +#include <asm/nospec-insn.h> + + GEN_BR_THUNK %r14

/* * void *memmove(void *dest, const void *src, size_t n) @@ -33,14 +36,14 @@ ENTRY(memmove) .Lmemmove_forward_remainder: larl %r5,.Lmemmove_mvc ex %r4,0(%r5) - br %r14 + BR_EX %r14 .Lmemmove_reverse: ic %r0,0(%r4,%r3) stc %r0,0(%r4,%r1) brctg %r4,.Lmemmove_reverse ic %r0,0(%r4,%r3) stc %r0,0(%r4,%r1) - br %r14 + BR_EX %r14 .Lmemmove_mvc: mvc 0(1,%r1),0(%r3) EXPORT_SYMBOL(memmove) @@ -77,7 +80,7 @@ ENTRY(memset) .Lmemset_clear_remainder: larl %r3,.Lmemset_xc ex %r4,0(%r3) - br %r14 + BR_EX %r14 .Lmemset_fill: cghi %r4,1 lgr %r1,%r2 @@ -95,10 +98,10 @@ ENTRY(memset) stc %r3,0(%r1) larl %r5,.Lmemset_mvc ex %r4,0(%r5) - br %r14 + BR_EX %r14 .Lmemset_fill_exit: stc %r3,0(%r1) - br %r14 + BR_EX %r14 .Lmemset_xc: xc 0(1,%r1),0(%r1) .Lmemset_mvc: @@ -121,7 +124,7 @@ ENTRY(memcpy) .Lmemcpy_remainder: 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) @@ -159,10 +162,10 @@ ENTRY(__memset\bits) \insn %r3,0(%r1) larl %r5,.L__memset_mvc\bits ex %r4,0(%r5) - br %r14 + BR_EX %r14 .L__memset_exit\bits: \insn %r3,0(%r2) - br %r14 + BR_EX %r14 .L__memset_mvc\bits: mvc \bytes(1,%r1),0(%r1) .endm