rdrand: Reuse CPU feature detection to check for RDRAND instructions

src/libstrongswan/plugins/rdrand/rdrand_plugin.c

@@ -20,6 +20,7 @@
 
 #include <library.h>
 #include <utils/debug.h>
+#include <utils/cpu_feature.h>
 
 typedef struct private_rdrand_plugin_t private_rdrand_plugin_t;
 typedef enum cpuid_feature_t cpuid_feature_t;
@@ -35,56 +36,6 @@ struct private_rdrand_plugin_t {
 	rdrand_plugin_t public;
 };
 
-/**
- * CPU feature flags, returned via cpuid(1)
- */
-enum cpuid_feature_t {
-	CPUID_RDRAND =		(1<<30),
-};
-
-/**
- * Get cpuid for info, return eax, ebx, ecx and edx.
- * -fPIC requires to save ebx on IA-32.
- */
-static void cpuid(u_int op, u_int *a, u_int *b, u_int *c, u_int *d)
-{
-#ifdef __x86_64__
-	asm("cpuid" : "=a" (*a), "=b" (*b), "=c" (*c), "=d" (*d) : "a" (op));
-#else /* __i386__ */
-	asm("pushl %%ebx;"
-		"cpuid;"
-		"movl %%ebx, %1;"
-		"popl %%ebx;"
-		: "=a" (*a), "=r" (*b), "=c" (*c), "=d" (*d) : "a" (op));
-#endif /* __x86_64__ / __i386__*/
-}
-
-/**
- * Check if we have RDRAND instruction
- */
-static bool have_rdrand()
-{
-	char vendor[3 * sizeof(u_int32_t) + 1];
-	u_int a, b, c, d;
-
-	cpuid(0, &a, &b, &c, &d);
-	/* VendorID string is in b-d-c (yes, in this order) */
-	snprintf(vendor, sizeof(vendor), "%.4s%.4s%.4s", &b, &d, &c);
-
-	/* check if we have an Intel CPU */
-	if (streq(vendor, "GenuineIntel"))
-	{
-		cpuid(1, &a, &b, &c, &d);
-		if (c & CPUID_RDRAND)
-		{
-			DBG2(DBG_LIB, "detected RDRAND support on %s CPU", vendor);
-			return TRUE;
-		}
-	}
-	DBG2(DBG_LIB, "no RDRAND support on %s CPU, disabled", vendor);
-	return FALSE;
-}
-
 METHOD(plugin_t, get_name, char*,
 	private_rdrand_plugin_t *this)
 {
@@ -102,10 +53,12 @@ METHOD(plugin_t, get_features, int,
 				PLUGIN_DEPENDS(CRYPTER, ENCR_AES_CBC, 16),
 	};
 	*features = f;
-	if (have_rdrand())
+	if (cpu_feature_available(CPU_FEATURE_RDRAND))
 	{
+		DBG2(DBG_LIB, "detected RDRAND support, enabled");
 		return countof(f);
 	}
+	DBG2(DBG_LIB, "no RDRAND support detected, disabled");
 	return 0;
 }