4.9-stable review patch. If anyone has any objections, please let me know.
------------------
From: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
[ Upstream commit d424986f1d6b16079b3231db0314923f4f8deed1 ]
Set CONFIG_GENERIC_CPU_VULNERABILITIES and provide the two functions
cpu_show_spectre_v1 and cpu_show_spectre_v2 to report the spectre
mitigations.
Signed-off-by: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/s390/Kconfig | 1 +
arch/s390/kernel/nospec-branch.c | 19 +++++++++++++++++++
2 files changed, 20 insertions(+)
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -118,6 +118,7 @@ config S390
select GENERIC_CLOCKEVENTS
select GENERIC_CPU_AUTOPROBE
select GENERIC_CPU_DEVICES if !SMP
+ select GENERIC_CPU_VULNERABILITIES
select GENERIC_FIND_FIRST_BIT
select GENERIC_SMP_IDLE_THREAD
select GENERIC_TIME_VSYSCALL
--- a/arch/s390/kernel/nospec-branch.c
+++ b/arch/s390/kernel/nospec-branch.c
@@ -1,5 +1,6 @@
// SPDX-License-Identifier: GPL-2.0
#include <linux/module.h>
+#include <linux/device.h>
#include <asm/facility.h>
#include <asm/nospec-branch.h>
@@ -43,6 +44,24 @@ 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);