random numer generation

kernel/include/random.h

@@ -0,0 +1,8 @@
+#ifndef _RANDOM_H
+#define _RANDOM_H
+
+#include <types.h>
+void rand_init();
+
+extern uint64_t (*get_random_number)();
+#endif

kernel/src/random.c

@@ -0,0 +1,52 @@
+#include "kernel.h"
+#include <system.h>
+#include <types.h>
+
+uint64_t (*get_random_number)();
+
+// this starting value it truly random i have thrown a dice few times
+uint64_t LFSR = 61113534451;
+
+// RDSEED may be backdoored by NSA
+extern uint64_t rand_rdrand();
+asm(".intel_syntax noprefix\n"
+    ".global rand_rdrand\n"
+    "rand_rdrand:"
+    "   rdrand rax\n"
+    "   ret\n"
+    ".att_syntax prefix\n");
+
+uint64_t rand_software() {
+	uint64_t lsb = LFSR & 1;
+	LFSR >>= 1;
+	if (lsb) {
+		LFSR ^= 0x800000000000000DULL;
+	}
+	return LFSR;
+}
+
+void rand_init() {
+	uint32_t eax = 1, ebx = 0, ecx = 0, edx = 0;
+	cpuid(&eax, &ebx, &ecx, &edx);
+
+	// check for RDRAND
+	if ((ecx >> 30) & 1) {
+		get_random_number = rand_rdrand;
+	} else {
+		printk("[\e[33mWARNING\e[0m] RDRAND not available falling back "
+		       "to software\n");
+		// check for RDSEED
+		if ((ebx >> 18) & 1) {
+			asm(".intel_syntax noprefix\n"
+			    "rdseed %0\n"
+			    ".att_syntax prefix\n"
+			    : "=r"(LFSR));
+		} else {
+			printk("[\e[\e[33mWARNING\e[0m] RDSEED not available "
+			       "falling back "
+			       "to developers dice trows\n");
+		}
+		get_random_number = rand_software;
+	}
+    printk("[\e[32mINFO\e[0m] RNG initialized!\n");
+}