[PATCH 3.16 10/76] sysfs/cpu: Add vulnerability folder

[Ben Hutchings]

3.16.56-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>

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@xxxxxxxxxxxxx>
Reviewed-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: David Woodhouse <dwmw@xxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/20180107214913.096657732@xxxxxxxxxxxxx
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 Documentation/ABI/testing/sysfs-devices-system-cpu | 16 ++++++++
 drivers/base/Kconfig                               |  3 ++
 drivers/base/cpu.c                                 | 48 ++++++++++++++++++++++
 include/linux/cpu.h                                |  7 ++++
 4 files changed, 74 insertions(+)

--- 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-
 		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@xxxxxxxxxxxxxxx>
+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
--- 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
 
--- a/drivers/base/cpu.c
+++ b/drivers/base/cpu.c
@@ -418,10 +418,58 @@ static void __init cpu_dev_register_gene
 #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();
 }
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -39,6 +39,13 @@ extern void cpu_remove_dev_attr(struct d
 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);