Possible fix for bug #77357

Don't invoke CPUID with feature levels above the supported maximum.
In this case CPUID will return the highest supported basic information
leaf, which will have unrelated bits in the relevant positions.

Author: nikic

Diff for: Zend/zend_cpuinfo.c

@@ -77,16 +77,24 @@ void zend_cpu_startup(void)
 {
 	if (!cpuinfo.initialized) {
 		zend_cpu_info ebx;
+		int max_feature;
 
 		cpuinfo.initialized = 1;
 		__zend_cpuid(0, 0, &cpuinfo);
-		if (cpuinfo.eax == 0) {
+		max_feature = cpuinfo.eax;
+		if (max_feature == 0) {
 			return;
 		}
+
 		__zend_cpuid(1, 0, &cpuinfo);
+
 		/* for avx2 */
-		__zend_cpuid(7, 0, &ebx);
-		cpuinfo.ebx = ebx.ebx;
+		if (max_feature >= 7) {
+			__zend_cpuid(7, 0, &ebx);
+			cpuinfo.ebx = ebx.ebx;
+		} else {
+			cpuinfo.ebx = 0;
+		}
 	}
 }