UBUNTU: SAUCE: cpu/speculation: Uninline and export CPU mitigations helpers

A kernel module may need to check the value of the "mitigations=" kernel
command line parameter as part of its setup when the module needs
to perform software mitigations for a CPU flaw. Uninline and export the
helper functions surrounding the cpu_mitigations enum to allow for their
usage from a module. Lastly, privatize the enum and cpu_mitigations
variable since the value of cpu_mitigations can be checked with the
exported helper functions.
Signed-off-by: Tyler Hicks <tyhicks@canonical.com>

CVE-2018-12207
Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

include/linux/cpu.h

@@ -321,28 +321,7 @@ static inline void cpu_smt_check_topology_early(void) { }
 static inline void cpu_smt_check_topology(void) { }
 #endif
 
-/*
- * These are used for a global "mitigations=" cmdline option for toggling
- * optional CPU mitigations.
- */
-enum cpu_mitigations {
-	CPU_MITIGATIONS_OFF,
-	CPU_MITIGATIONS_AUTO,
-	CPU_MITIGATIONS_AUTO_NOSMT,
-};
-
-extern enum cpu_mitigations cpu_mitigations;
-
-/* mitigations=off */
-static inline bool cpu_mitigations_off(void)
-{
-	return cpu_mitigations == CPU_MITIGATIONS_OFF;
-}
-
-/* mitigations=auto,nosmt */
-static inline bool cpu_mitigations_auto_nosmt(void)
-{
-	return cpu_mitigations == CPU_MITIGATIONS_AUTO_NOSMT;
-}
+extern bool cpu_mitigations_off(void);
+extern bool cpu_mitigations_auto_nosmt(void);
 
 #endif /* _LINUX_CPU_H_ */

kernel/cpu.c

@@ -1100,7 +1100,18 @@ void init_cpu_online(const struct cpumask *src)
 	cpumask_copy(to_cpumask(cpu_online_bits), src);
 }
 
-enum cpu_mitigations cpu_mitigations __ro_after_init = CPU_MITIGATIONS_AUTO;
+/*
+ * These are used for a global "mitigations=" cmdline option for toggling
+ * optional CPU mitigations.
+ */
+enum cpu_mitigations {
+	CPU_MITIGATIONS_OFF,
+	CPU_MITIGATIONS_AUTO,
+	CPU_MITIGATIONS_AUTO_NOSMT,
+};
+
+static enum cpu_mitigations cpu_mitigations __ro_after_init =
+	CPU_MITIGATIONS_AUTO;
 
 static int __init mitigations_parse_cmdline(char *arg)
 {
@@ -1117,3 +1128,17 @@ static int __init mitigations_parse_cmdline(char *arg)
 	return 0;
 }
 early_param("mitigations", mitigations_parse_cmdline);
+
+/* mitigations=off */
+bool cpu_mitigations_off(void)
+{
+	return cpu_mitigations == CPU_MITIGATIONS_OFF;
+}
+EXPORT_SYMBOL_GPL(cpu_mitigations_off);
+
+/* mitigations=auto,nosmt */
+bool cpu_mitigations_auto_nosmt(void)
+{
+	return cpu_mitigations == CPU_MITIGATIONS_AUTO_NOSMT;
+}
+EXPORT_SYMBOL_GPL(cpu_mitigations_auto_nosmt);