Add basic urandom device

etc/make/conf.mk

@@ -69,7 +69,8 @@ OBJS+=$(O)/sys/debug.o \
 	  $(O)/sys/net/netdev.o \
 	  $(O)/sys/vfs/pseudo.o \
 	  $(O)/sys/vfs/pty.o \
-	  $(O)/sys/reboot.o
+	  $(O)/sys/reboot.o \
+	  $(O)/sys/random.o
 
 ifeq ($(VESA_ENABLE),1)
 OBJS+=$(O)/sys/psf.o \

include/sys/random.h

@@ -0,0 +1,5 @@
+#pragma once
+#include "sys/types.h"
+
+void random_init(uint64_t seed);
+uint64_t random_single(void);

sys/amd64/kernel.c

@@ -14,6 +14,8 @@
 #include "sys/amd64/hw/ps2.h"
 #include "sys/amd64/hw/rtc.h"
 #include "sys/amd64/hw/con.h"
+#include "sys/random.h"
+#include "sys/time.h"
 #include "sys/panic.h"
 #include "sys/assert.h"
 #include "sys/fs/vfs.h"
@@ -24,6 +26,15 @@
 
 static multiboot_info_t *multiboot_info;
 
+static void amd64_make_random_seed(void) {
+    struct rtc_time t;
+    rtc_read(&t);
+
+    uint64_t s = 137831;
+    s += t.second + t.minute * 60 + t.hour * 3600 + t.day * 86400;
+    random_init(s + system_time);
+}
+
 void kernel_main(struct amd64_loader_data *data) {
     // Reinitialize RS232 properly
     ps2_init();
@@ -56,6 +67,9 @@ void kernel_main(struct amd64_loader_data *data) {
         tarfs_init();
     }
 
+    // Initial random seed
+    amd64_make_random_seed();
+
 #if defined(AMD64_SMP)
     amd64_smp_init();
 #endif

sys/random.c

@@ -0,0 +1,25 @@
+#include "sys/random.h"
+#include "sys/panic.h"
+#include "sys/debug.h"
+
+static int random_ready = 0;
+static uint64_t xs64_state;
+
+void random_init(uint64_t s) {
+    if (random_ready) {
+        kinfo("Random is ready already\n");
+    }
+    random_ready = 1;
+    xs64_state = s;
+}
+
+uint64_t random_single(void) {
+    if (!random_ready) {
+        panic("Random was not ready\n");
+    }
+    uint64_t x = xs64_state;
+    x ^= x << 13;
+    x ^= x >> 7;
+    x ^= x << 17;
+    return xs64_state = x;
+}

sys/vfs/pseudo.c

@@ -1,15 +1,31 @@
 #include "sys/string.h"
+#include "sys/random.h"
 #include "sys/panic.h"
+#include "sys/errno.h"
 #include "sys/attr.h"
 #include "sys/blk.h"
 #include "sys/dev.h"
 
 #define DEV_ZERO        0
 #define DEV_NULL        1
+#define DEV_URANDOM     2
 
 static ssize_t pseudo_write(struct blkdev *dev, const void *buf, size_t pos, size_t lim);
 static ssize_t pseudo_read(struct blkdev *dev, void *buf, size_t pos, size_t lim);
 
+static void urandom_fill(void *buf, size_t lim) {
+    uint64_t val;
+    size_t i = 0;
+
+    while (i < lim) {
+        val = random_single();
+
+        memcpy(buf + i, &val, MIN(lim - i, 8));
+
+        i += 8;
+    }
+}
+
 static struct blkdev _dev_null = {
     .dev_data = (void *) DEV_NULL,
     .write = pseudo_write,
@@ -32,12 +48,25 @@ static struct dev_entry _ent_zero = {
     .dev_subclass = DEV_BLOCK_PSEUDO,
     .dev_name = "zero"
 };
+static struct blkdev _dev_urandom = {
+    .dev_data = (void *) DEV_URANDOM,
+    .write = pseudo_write,
+    .read = pseudo_read
+};
+static struct dev_entry _ent_urandom = {
+    .dev = &_dev_urandom,
+    .dev_class = DEV_CLASS_BLOCK,
+    .dev_subclass = DEV_BLOCK_PSEUDO,
+    .dev_name = "urandom"
+};
 
 static ssize_t pseudo_write(struct blkdev *dev, const void *buf, size_t pos, size_t lim) {
     switch ((uint64_t) dev->dev_data) {
     case DEV_NULL:
     case DEV_ZERO:
         return lim;
+    case DEV_URANDOM:
+        return -EINVAL;
     default:
         panic("Unexpected dev id: %p\n", dev->dev_data);
     }
@@ -50,6 +79,9 @@ static ssize_t pseudo_read(struct blkdev *dev, void *buf, size_t pos, size_t lim
         return lim;
     case DEV_NULL:
         return 0;
+    case DEV_URANDOM:
+        urandom_fill(buf, lim);
+        return lim;
     default:
         panic("Unexpected dev id: %p\n", dev->dev_data);
     }
@@ -58,4 +90,5 @@ static ssize_t pseudo_read(struct blkdev *dev, void *buf, size_t pos, size_t lim
 static __init void pseudo_init(void) {
     dev_entry_add(&_ent_null);
     dev_entry_add(&_ent_zero);
+    dev_entry_add(&_ent_urandom);
 }