The patch below does not apply to the 4.9-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 4253b0e0627ee3461e64c2495c616f1c8f6b127b Mon Sep 17 00:00:00 2001

From: Martin Schwidefsky schwidefsky@de.ibm.com Date: Tue, 24 Apr 2018 08:23:54 +0200 Subject: [PATCH] s390: move spectre sysfs attribute code

The nospec-branch.c file is compiled without the gcc options to generate expoline thunks. The return branch of the sysfs show functions cpu_show_spectre_v1 and cpu_show_spectre_v2 is an indirect branch as well. These need to be compiled with expolines.

Move the sysfs functions for spectre reporting to a separate file and loose an '.' for one of the messages.

Cc: stable@vger.kernel.org # 4.16 Fixes: d424986f1d ("s390: add sysfs attributes for spectre") Signed-off-by: Martin Schwidefsky schwidefsky@de.ibm.com

diff --git a/arch/s390/kernel/Makefile b/arch/s390/kernel/Makefile index 84ea6225efb4..f92dd8ed3884 100644 --- a/arch/s390/kernel/Makefile +++ b/arch/s390/kernel/Makefile @@ -65,6 +65,7 @@ obj-y += nospec-branch.o

extra-y += head.o head64.o vmlinux.lds

+obj-$(CONFIG_SYSFS) += nospec-sysfs.o CFLAGS_REMOVE_nospec-branch.o += $(CC_FLAGS_EXPOLINE)

obj-$(CONFIG_MODULES) += module.o diff --git a/arch/s390/kernel/nospec-branch.c b/arch/s390/kernel/nospec-branch.c index 46d49a11663f..834cf29f2599 100644 --- a/arch/s390/kernel/nospec-branch.c +++ b/arch/s390/kernel/nospec-branch.c @@ -1,7 +1,6 @@ // SPDX-License-Identifier: GPL-2.0 #include <linux/module.h> #include <linux/device.h> -#include <linux/cpu.h> #include <asm/nospec-branch.h>

static int __init nobp_setup_early(char *str) @@ -44,24 +43,6 @@ static int __init nospec_report(void) } arch_initcall(nospec_report);

-#ifdef CONFIG_SYSFS -ssize_t cpu_show_spectre_v1(struct device *dev, - struct device_attribute *attr, char *buf) -{ - return sprintf(buf, "Mitigation: __user pointer sanitization\n"); -} - -ssize_t cpu_show_spectre_v2(struct device *dev, - struct device_attribute *attr, char *buf) -{ - if (IS_ENABLED(CC_USING_EXPOLINE) && !nospec_disable) - return sprintf(buf, "Mitigation: execute trampolines\n"); - if (__test_facility(82, S390_lowcore.alt_stfle_fac_list)) - return sprintf(buf, "Mitigation: limited branch prediction.\n"); - return sprintf(buf, "Vulnerable\n"); -} -#endif - #ifdef CONFIG_EXPOLINE

int nospec_disable = IS_ENABLED(CONFIG_EXPOLINE_OFF); diff --git a/arch/s390/kernel/nospec-sysfs.c b/arch/s390/kernel/nospec-sysfs.c new file mode 100644 index 000000000000..8affad5f18cb --- /dev/null +++ b/arch/s390/kernel/nospec-sysfs.c @@ -0,0 +1,21 @@ +// SPDX-License-Identifier: GPL-2.0 +#include <linux/device.h> +#include <linux/cpu.h> +#include <asm/facility.h> +#include <asm/nospec-branch.h> + +ssize_t cpu_show_spectre_v1(struct device *dev, + struct device_attribute *attr, char *buf) +{ + return sprintf(buf, "Mitigation: __user pointer sanitization\n"); +} + +ssize_t cpu_show_spectre_v2(struct device *dev, + struct device_attribute *attr, char *buf) +{ + if (IS_ENABLED(CC_USING_EXPOLINE) && !nospec_disable) + return sprintf(buf, "Mitigation: execute trampolines\n"); + if (__test_facility(82, S390_lowcore.alt_stfle_fac_list)) + return sprintf(buf, "Mitigation: limited branch prediction\n"); + return sprintf(buf, "Vulnerable\n"); +}