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Commit c617e74f authored by Martin Schwidefsky's avatar Martin Schwidefsky Committed by Greg Kroah-Hartman
Browse files

s390: move spectre sysfs attribute code 



[ Upstream commit 4253b0e0627ee3461e64c2495c616f1c8f6b127b ]

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: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 90305465

arch/s390/kernel/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -49,6 +49,7 @@ 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)		+= s390_ksyms.o module.o

arch/s390/kernel/nospec-branch.c

+0 −18
Original line number Diff line number Diff line
@@ -44,24 +44,6 @@ 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);

arch/s390/kernel/nospec-sysfs.c

0 → 100644
+21 −0
Original line number Diff line number Diff line 
// 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");

}