x86/cpufeature: Cleanup get_cpu_cap()

CVE-2018-3639 (x86)

Add an enum for the ->x86_capability array indices and cleanup
get_cpu_cap() by killing some redundant local vars.
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: http://lkml.kernel.org/r/1449481182-27541-3-git-send-email-bp@alien8.deSigned-off-by: Thomas Gleixner <tglx@linutronix.de>
(backported from commit 39c06df4)
[juergh:
 - Context adjustments.
 - Use CPUID_8000_0008_EBX enum in __do_cpuid_ent().]
Signed-off-by: Juerg Haefliger <juergh@canonical.com>

arch/x86/include/asm/cpufeature.h

@@ -8,6 +8,26 @@
 #include <asm/asm.h>
 #include <linux/bitops.h>
 
+enum cpuid_leafs
+{
+	CPUID_1_EDX		= 0,
+	CPUID_8000_0001_EDX,
+	CPUID_8086_0001_EDX,
+	CPUID_LNX_1,
+	CPUID_1_ECX,
+	CPUID_C000_0001_EDX,
+	CPUID_8000_0001_ECX,
+	CPUID_LNX_2,
+	CPUID_LNX_3,
+	CPUID_7_0_EBX,
+	CPUID_D_1_EAX,
+	CPUID_F_0_EDX,
+	CPUID_F_1_EDX,
+	CPUID_8000_0008_EBX,
+	CPUID_6_EAX,
+	CPUID_8000_000A_EDX,
+};
+
 #ifdef CONFIG_X86_FEATURE_NAMES
 extern const char * const x86_cap_flags[NCAPINTS*32];
 extern const char * const x86_power_flags[32];

arch/x86/kernel/cpu/centaur.c

@@ -43,7 +43,7 @@ static void init_c3(struct cpuinfo_x86 *c)
 		/* store Centaur Extended Feature Flags as
 		 * word 5 of the CPU capability bit array
 		 */
-		c->x86_capability[5] = cpuid_edx(0xC0000001);
+		c->x86_capability[CPUID_C000_0001_EDX] = cpuid_edx(0xC0000001);
 	}
 #ifdef CONFIG_X86_32
 	/* Cyrix III family needs CX8 & PGE explicitly enabled. */

arch/x86/kernel/cpu/common.c

@@ -676,52 +676,46 @@ static void apply_forced_caps(struct cpuinfo_x86 *c)
 
 void get_cpu_cap(struct cpuinfo_x86 *c)
 {
-	u32 tfms, xlvl;
-	u32 ebx;
+	u32 eax, ebx, ecx, edx;
 
 	/* Intel-defined flags: level 0x00000001 */
 	if (c->cpuid_level >= 0x00000001) {
-		u32 capability, excap;
+		cpuid(0x00000001, &eax, &ebx, &ecx, &edx);
 
-		cpuid(0x00000001, &tfms, &ebx, &excap, &capability);
-		c->x86_capability[0] = capability;
-		c->x86_capability[4] = excap;
+		c->x86_capability[CPUID_1_ECX] = ecx;
+		c->x86_capability[CPUID_1_EDX] = edx;
 	}
 
 	/* Additional Intel-defined flags: level 0x00000007 */
 	if (c->cpuid_level >= 0x00000007) {
-		u32 eax, ebx, ecx, edx;
-
 		cpuid_count(0x00000007, 0, &eax, &ebx, &ecx, &edx);
 
-		c->x86_capability[9] = ebx;
+		c->x86_capability[CPUID_7_0_EBX] = ebx;
 
-		c->x86_capability[14] = cpuid_eax(0x00000006);
+		c->x86_capability[CPUID_6_EAX] = cpuid_eax(0x00000006);
 	}
 
 	/* Extended state features: level 0x0000000d */
 	if (c->cpuid_level >= 0x0000000d) {
-		u32 eax, ebx, ecx, edx;
-
 		cpuid_count(0x0000000d, 1, &eax, &ebx, &ecx, &edx);
 
-		c->x86_capability[10] = eax;
+		c->x86_capability[CPUID_D_1_EAX] = eax;
 	}
 
 	/* Additional Intel-defined flags: level 0x0000000F */
 	if (c->cpuid_level >= 0x0000000F) {
-		u32 eax, ebx, ecx, edx;
 
 		/* QoS sub-leaf, EAX=0Fh, ECX=0 */
 		cpuid_count(0x0000000F, 0, &eax, &ebx, &ecx, &edx);
-		c->x86_capability[11] = edx;
+		c->x86_capability[CPUID_F_0_EDX] = edx;
+
 		if (cpu_has(c, X86_FEATURE_CQM_LLC)) {
 			/* will be overridden if occupancy monitoring exists */
 			c->x86_cache_max_rmid = ebx;
 
 			/* QoS sub-leaf, EAX=0Fh, ECX=1 */
 			cpuid_count(0x0000000F, 1, &eax, &ebx, &ecx, &edx);
-			c->x86_capability[12] = edx;
+			c->x86_capability[CPUID_F_1_EDX] = edx;
 
 			if ((cpu_has(c, X86_FEATURE_CQM_OCCUP_LLC)) ||
 			      ((cpu_has(c, X86_FEATURE_CQM_MBM_TOTAL)) ||
@@ -736,22 +730,24 @@ void get_cpu_cap(struct cpuinfo_x86 *c)
 	}
 
 	/* AMD-defined flags: level 0x80000001 */
-	xlvl = cpuid_eax(0x80000000);
-	c->extended_cpuid_level = xlvl;
+	eax = cpuid_eax(0x80000000);
+	c->extended_cpuid_level = eax;
+
+	if ((eax & 0xffff0000) == 0x80000000) {
+		if (eax >= 0x80000001) {
+			cpuid(0x80000001, &eax, &ebx, &ecx, &edx);
 
-	if ((xlvl & 0xffff0000) == 0x80000000) {
-		if (xlvl >= 0x80000001) {
-			c->x86_capability[1] = cpuid_edx(0x80000001);
-			c->x86_capability[6] = cpuid_ecx(0x80000001);
+			c->x86_capability[CPUID_8000_0001_ECX] = ecx;
+			c->x86_capability[CPUID_8000_0001_EDX] = edx;
 		}
 	}
 
 	if (c->extended_cpuid_level >= 0x80000008) {
-		u32 eax = cpuid_eax(0x80000008);
+		cpuid(0x80000008, &eax, &ebx, &ecx, &edx);
 
 		c->x86_virt_bits = (eax >> 8) & 0xff;
 		c->x86_phys_bits = eax & 0xff;
-		c->x86_capability[13] = cpuid_ebx(0x80000008);
+		c->x86_capability[CPUID_8000_0008_EBX] = ebx;
 	}
 #ifdef CONFIG_X86_32
 	else if (cpu_has(c, X86_FEATURE_PAE) || cpu_has(c, X86_FEATURE_PSE36))
@@ -762,7 +758,7 @@ void get_cpu_cap(struct cpuinfo_x86 *c)
 		c->x86_power = cpuid_edx(0x80000007);
 
 	if (c->extended_cpuid_level >= 0x8000000a)
-		c->x86_capability[15] = cpuid_edx(0x8000000a);
+		c->x86_capability[CPUID_8000_000A_EDX] = cpuid_edx(0x8000000a);
 
 	init_scattered_cpuid_features(c);
 }

arch/x86/kernel/cpu/transmeta.c

@@ -12,7 +12,7 @@ static void early_init_transmeta(struct cpuinfo_x86 *c)
 	xlvl = cpuid_eax(0x80860000);
 	if ((xlvl & 0xffff0000) == 0x80860000) {
 		if (xlvl >= 0x80860001)
-			c->x86_capability[2] = cpuid_edx(0x80860001);
+			c->x86_capability[CPUID_8086_0001_EDX] = cpuid_edx(0x80860001);
 	}
 }
 
@@ -82,7 +82,7 @@ static void init_transmeta(struct cpuinfo_x86 *c)
 	/* Unhide possibly hidden capability flags */
 	rdmsr(0x80860004, cap_mask, uk);
 	wrmsr(0x80860004, ~0, uk);
-	c->x86_capability[0] = cpuid_edx(0x00000001);
+	c->x86_capability[CPUID_1_EDX] = cpuid_edx(0x00000001);
 	wrmsr(0x80860004, cap_mask, uk);
 
 	/* All Transmeta CPUs have a constant TSC */

arch/x86/kvm/cpuid.c

@@ -602,7 +602,7 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
 			g_phys_as = phys_as;
 		entry->eax = g_phys_as | (virt_as << 8);
 		entry->ebx &= kvm_cpuid_80000008_0_ebx_x86_features;
-		cpuid_mask(&entry->ebx, 13 /* CPUID_8000_0008_EBX */);
+		cpuid_mask(&entry->ebx, CPUID_8000_0008_EBX);
 		entry->edx = 0;
 		break;
 	}