1 files changed, 80 insertions, 0 deletions
diff --git a/libs/libc/rand.c b/libs/libc/rand.c
new file mode 100644
index 0000000..268a21f
--- /dev/null
+++ b/libs/libc/rand.c
@@ -0,0 +1,80 @@
+// MIT License, Copyright (c) 2020 Marvin Borner
+
+#include <def.h>
+#include <mem.h>
+#include <rand.h>
+
+#ifdef KERNEL
+#include <cpu.h>
+#endif
+
+static u32 g_seed = 1;
+
+void srand(u32 seed)
+{
+	g_seed = seed;
+}
+
+static u32 rand_default(void)
+{
+	g_seed = g_seed * 1103515245 + 12345;
+	return (g_seed >> 16) & 0x7FFF;
+}
+
+static u32 rand_once(void)
+{
+#ifdef KERNEL
+	u32 val = 0;
+	if (cpu_extended_features.ebx & CPUID_EXT_FEAT_EBX_RDSEED) {
+		__asm__ volatile("1:\n"
+				 "rdseed %0\n"
+				 "jnc 1b\n"
+				 : "=r"(val));
+	} else if (cpu_features.ecx & CPUID_FEAT_ECX_RDRND) {
+		__asm__ volatile("1:\n"
+				 "rdrand %0\n"
+				 "jnc 1b\n"
+				 : "=r"(val));
+	} else {
+		val = rand_default();
+	}
+
+	return val;
+#else
+	return rand_default();
+#endif
+}
+
+u32 rand(void)
+{
+	u32 ret = 0;
+	ret |= (rand_once() & (0xffu << 0));
+	ret |= (rand_once() & (0xffu << 8));
+	ret |= (rand_once() & (0xffu << 16));
+	ret |= (rand_once() & (0xffu << 24));
+	return ret;
+}
+
+void rand_fill(void *buf, u32 size)
+{
+	for (u32 i = 0; i < size; i++)
+		((u8 *)buf)[i] = rand_once() & 0xff;
+}
+
+char *randstr(u32 size)
+{
+	if (!size)
+		return NULL;
+
+	char *buf = malloc(size + 1);
+	const char charset[] = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
+
+	size--;
+	for (u32 i = 0; i < size; i++) {
+		int key = rand() % (sizeof(charset) - 1);
+		buf[i] = charset[key];
+	}
+	buf[size] = '\0';
+
+	return buf;
+}