UBUNTU: SAUCE: x86/bugs: Concentrate bug reporting into a separate function

CVE-2018-3639 (x86)

Those SysFS functions have a similar preamble, as such make common
code to handle them.
Suggested-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Ingo Molnar <mingo@kernel.org>

[juergh:
 - Context adjustments.
 - X86_FEATURE_PTI -> X86_FEATURE_KAISER.
 - Drop eval of X86_FEATURE_USE_IBRS_FW for Spectre v2 (not implemented in
   Xenial).
 - Report state of OSB for Spectre v1.]
Signed-off-by: Juerg Haefliger <juergh@canonical.com>

arch/x86/kernel/cpu/bugs.c

@@ -340,15 +340,6 @@ static void __init spectre_v2_select_mitigation(void)
 #undef pr_fmt
 
 #ifdef CONFIG_SYSFS
-ssize_t cpu_show_meltdown(struct device *dev,
-			  struct device_attribute *attr, char *buf)
-{
-	if (!boot_cpu_has_bug(X86_BUG_CPU_MELTDOWN))
-		return sprintf(buf, "Not affected\n");
-	if (boot_cpu_has(X86_FEATURE_KAISER))
-		return sprintf(buf, "Mitigation: PTI\n");
-	return sprintf(buf, "Vulnerable\n");
-}
 
 #ifndef osb
 #define osb_is_enabled 	(0)
@@ -356,24 +347,50 @@ ssize_t cpu_show_meltdown(struct device *dev,
 #ifndef osb_is_enabled
 #define osb_is_enabled	(1)
 #endif
-ssize_t cpu_show_spectre_v1(struct device *dev,
-			    struct device_attribute *attr, char *buf)
+
+ssize_t cpu_show_common(struct device *dev, struct device_attribute *attr,
+			char *buf, unsigned int bug)
 {
-	if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V1))
+	if (!boot_cpu_has_bug(bug))
 		return sprintf(buf, "Not affected\n");
-	if (osb_is_enabled)
-		return sprintf(buf, "Mitigation: OSB (observable speculation barrier, Intel v6)\n");
+
+	switch (bug) {
+	case X86_BUG_CPU_MELTDOWN:
+		if (boot_cpu_has(X86_FEATURE_KAISER))
+			return sprintf(buf, "Mitigation: PTI\n");
+
+		break;
+
+	case X86_BUG_SPECTRE_V1:
+		if (osb_is_enabled)
+			return sprintf(buf, "Mitigation: OSB (observable speculation barrier, Intel v6)\n");
+
+		break;
+
+	case X86_BUG_SPECTRE_V2:
+		return sprintf(buf, "%s%s%s\n", spectre_v2_strings[spectre_v2_enabled],
+			       ibpb_inuse ? ", IBPB (Intel v4)" : "",
+			       spectre_v2_module_string());
+	default:
+		break;
+	}
+
 	return sprintf(buf, "Vulnerable\n");
 }
 
+ssize_t cpu_show_meltdown(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	return cpu_show_common(dev, attr, buf, X86_BUG_CPU_MELTDOWN);
+}
+
+ssize_t cpu_show_spectre_v1(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	return cpu_show_common(dev, attr, buf, X86_BUG_SPECTRE_V1);
+}
+
 ssize_t cpu_show_spectre_v2(struct device *dev,
 			    struct device_attribute *attr, char *buf)
 {
-	if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V2))
-		return sprintf(buf, "Not affected\n");
-
-	return sprintf(buf, "%s%s%s\n", spectre_v2_strings[spectre_v2_enabled],
-		       ibpb_inuse ? ", IBPB (Intel v4)" : "",
-		       spectre_v2_module_string());
+	return cpu_show_common(dev, attr, buf, X86_BUG_SPECTRE_V2);
 }
 #endif