kernel: urandom device

kernel-src/include/kernel/devfs.h

@@ -13,6 +13,7 @@
 #define DEV_MAJOR_KEYBOARD 6
 #define DEV_MAJOR_BLOCK 7
 #define DEV_MAJOR_E9 8
+#define DEV_MAJOR_URANDOM 9
 
 typedef struct {
 	int (*open)(int minor, int flags);

kernel-src/io/pseudodevices.c

@@ -2,6 +2,7 @@
 #include <errno.h>
 #include <string.h>
 #include <logging.h>
+#include <kernel/timekeeper.h>
 
 static int null_write(int minor, void *buffer, size_t count, uintmax_t offset, int flags, size_t *wcount) {
 	*wcount = count;
@@ -23,6 +24,22 @@ static int null_read(int minor, void *buffer, size_t count, uintmax_t offset, in
 	return 0;
 }
 
+static long current = 0xdeadbeefbadc0ffe;
+
+static uint8_t getrand8() {
+	current += timekeeper_timefromboot().ns * timekeeper_timefromboot().s - timekeeper_time().ns * timekeeper_time().s + timekeeper_time().s;
+	return current & 0xff;
+}
+
+static int urandom_read(int minor, void *_buffer, size_t count, uintmax_t offset, int flags, size_t *rcount) {
+	uint8_t *buffer = _buffer;
+	for (int i = 0; i < count; ++i)
+		buffer[i] = getrand8();
+
+	*rcount = count;
+	return 0;
+}
+
 static devops_t nullops = {
 	.read = null_read,
 	.write = null_write
@@ -38,8 +55,14 @@ static devops_t zeroops = {
 	.write = null_write
 };
 
+static devops_t urandomops = {
+	.read = urandom_read,
+	.write = null_write
+};
+
 void pseudodevices_init() {
 	__assert(devfs_register(&nullops, "null", V_TYPE_CHDEV, DEV_MAJOR_NULL, 0, 0644) == 0);
 	__assert(devfs_register(&fullops, "full", V_TYPE_CHDEV, DEV_MAJOR_FULL, 0, 0644) == 0);
 	__assert(devfs_register(&zeroops, "zero", V_TYPE_CHDEV, DEV_MAJOR_ZERO, 0, 0644) == 0);
+	__assert(devfs_register(&urandomops, "urandom", V_TYPE_CHDEV, DEV_MAJOR_URANDOM, 0, 0644) == 0);
 }