Library call for cpu features; make kernel and vm use this to query cpu

features (specifically: 4MB pages and TLB global bit).  Only enable
these features in CR4 if available. 4MB pages to be used in the near
future.

lib/i386/misc/Makefile.in

@@ -6,6 +6,7 @@ LIBRARIES=libc
 
 libc_FILES=" \
 	_cpuid.s \
+	_cpufeature.c \
 	alloca.s \
 	get_bp.s \
 	getprocessor.s \

lib/i386/misc/_cpufeature.c

@@ -0,0 +1,34 @@
+
+#include <stdint.h>
+#include <minix/minlib.h>
+#include <minix/cpufeature.h>
+#include <sys/vm_i386.h>
+
+int _cpufeature(int cpufeature)
+{
+	u32_t cpuid_feature_edx = 0;
+	int proc;
+
+	proc = getprocessor();
+
+	/* If processor supports CPUID and its CPUID supports enough
+	 * parameters, retrieve EDX feature flags to test against.
+	 */
+	if(proc >= 586) {
+		u32_t params, a, b, c, d;
+		_cpuid(0, &params, &b, &c, &d);
+		if(params > 0) {
+			_cpuid(1, &a, &b, &c, &cpuid_feature_edx);
+		}
+	}
+
+	switch(cpufeature) {
+		case _CPUF_I386_PSE:
+			return cpuid_feature_edx & CPUID1_EDX_PSE;
+		case _CPUF_I386_PGE:
+			return cpuid_feature_edx & CPUID1_EDX_PGE;
+	}
+
+	return 0;
+}
+