sysfs/cpu: Add vulnerability folder

commit 87590ce6e373d1a5401f6539f0c59ef92dd924a9 upstream.

As the meltdown/spectre problem affects several CPU architectures, it makes
sense to have common way to express whether a system is affected by a
particular vulnerability or not. If affected the way to express the
mitigation should be common as well.

Create /sys/devices/system/cpu/vulnerabilities folder and files for
meltdown, spectre_v1 and spectre_v2.

Allow architectures to override the show function.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Linus Torvalds <torvalds@linuxfoundation.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: David Woodhouse <dwmw@amazon.co.uk>
Link: https://lkml.kernel.org/r/20180107214913.096657732@linutronix.de
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu
index acb9bfc89b4879c7f1f7c6815959baa4c819154b..5850723194a444662ca3e1b4193c360d86aeb717 100644 (file)
--- a/Documentation/ABI/testing/sysfs-devices-system-cpu
+++ b/Documentation/ABI/testing/sysfs-devices-system-cpu
@@ -224,3 +224,19 @@ Description:       Parameters for the Intel P-state driver
                frequency range.
 
                More details can be found in Documentation/cpu-freq/intel-pstate.txt
+
+What:          /sys/devices/system/cpu/vulnerabilities
+               /sys/devices/system/cpu/vulnerabilities/meltdown
+               /sys/devices/system/cpu/vulnerabilities/spectre_v1
+               /sys/devices/system/cpu/vulnerabilities/spectre_v2
+Date:          Januar 2018
+Contact:       Linux kernel mailing list <linux-kernel@vger.kernel.org>
+Description:   Information about CPU vulnerabilities
+
+               The files are named after the code names of CPU
+               vulnerabilities. The output of those files reflects the
+               state of the CPUs in the system. Possible output values:
+
+               "Not affected"    CPU is not affected by the vulnerability
+               "Vulnerable"      CPU is affected and no mitigation in effect
+               "Mitigation: $M"  CPU is affetcted and mitigation $M is in effect

diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig
index 23b8726962aff4d65227463fe9b5242f11abc931..209eea947568fc400c7c01d7cdcb4d1592a8cf14 100644 (file)
--- a/drivers/base/Kconfig
+++ b/drivers/base/Kconfig
@@ -193,6 +193,9 @@ config GENERIC_CPU_DEVICES
 config GENERIC_CPU_AUTOPROBE
        bool
 
+config GENERIC_CPU_VULNERABILITIES
+       bool
+
 config SOC_BUS
        bool
 

diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
index 006b1bc5297d292ba4d6e649b87c24f9bf1a9a82..9175c84161ec6bfceb0333aaef554a05ddb2450e 100644 (file)
--- a/drivers/base/cpu.c
+++ b/drivers/base/cpu.c
@@ -418,10 +418,58 @@ static void __init cpu_dev_register_generic(void)
 #endif
 }
 
+#ifdef CONFIG_GENERIC_CPU_VULNERABILITIES
+
+ssize_t __weak cpu_show_meltdown(struct device *dev,
+                                struct device_attribute *attr, char *buf)
+{
+       return sprintf(buf, "Not affected\n");
+}
+
+ssize_t __weak cpu_show_spectre_v1(struct device *dev,
+                                  struct device_attribute *attr, char *buf)
+{
+       return sprintf(buf, "Not affected\n");
+}
+
+ssize_t __weak cpu_show_spectre_v2(struct device *dev,
+                                  struct device_attribute *attr, char *buf)
+{
+       return sprintf(buf, "Not affected\n");
+}
+
+static DEVICE_ATTR(meltdown, 0444, cpu_show_meltdown, NULL);
+static DEVICE_ATTR(spectre_v1, 0444, cpu_show_spectre_v1, NULL);
+static DEVICE_ATTR(spectre_v2, 0444, cpu_show_spectre_v2, NULL);
+
+static struct attribute *cpu_root_vulnerabilities_attrs[] = {
+       &dev_attr_meltdown.attr,
+       &dev_attr_spectre_v1.attr,
+       &dev_attr_spectre_v2.attr,
+       NULL
+};
+
+static const struct attribute_group cpu_root_vulnerabilities_group = {
+       .name  = "vulnerabilities",
+       .attrs = cpu_root_vulnerabilities_attrs,
+};
+
+static void __init cpu_register_vulnerabilities(void)
+{
+       if (sysfs_create_group(&cpu_subsys.dev_root->kobj,
+                              &cpu_root_vulnerabilities_group))
+               pr_err("Unable to register CPU vulnerabilities\n");
+}
+
+#else
+static inline void cpu_register_vulnerabilities(void) { }
+#endif
+
 void __init cpu_dev_init(void)
 {
        if (subsys_system_register(&cpu_subsys, cpu_root_attr_groups))
                panic("Failed to register CPU subsystem");
 
        cpu_dev_register_generic();
+       cpu_register_vulnerabilities();
 }

diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index 3b73e762b2f5b7d002930e10a7902fa368107f4a..0441fa7c20b1ca2d121ffb61377bc0328ec769cd 100644 (file)
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -39,6 +39,13 @@ extern void cpu_remove_dev_attr(struct device_attribute *attr);
 extern int cpu_add_dev_attr_group(struct attribute_group *attrs);
 extern void cpu_remove_dev_attr_group(struct attribute_group *attrs);
 
+extern ssize_t cpu_show_meltdown(struct device *dev,
+                                struct device_attribute *attr, char *buf);
+extern ssize_t cpu_show_spectre_v1(struct device *dev,
+                                  struct device_attribute *attr, char *buf);
+extern ssize_t cpu_show_spectre_v2(struct device *dev,
+                                  struct device_attribute *attr, char *buf);
+
 #ifdef CONFIG_HOTPLUG_CPU
 extern void unregister_cpu(struct cpu *cpu);
 extern ssize_t arch_cpu_probe(const char *, size_t);