The patch below does not apply to the 4.16-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 c50c84c3ac4d5db683904bdb3257798b6ef980ae Mon Sep 17 00:00:00 2001

From: Martin Schwidefsky schwidefsky@de.ibm.com 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@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/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