kern: Add /dev/null

Signed-off-by: Ian Moffett <ian@osmora.org>

1 files changed, 82 insertions, 0 deletions

diff --git a/src/sys/os/os_null.c b/src/sys/os/os_null.c
new file mode 100644
index 0000000..e142c6f
--- /dev/null
+++ b/src/sys/os/os_null.c
@@ -0,0 +1,82 @@
+/*
+ * Copyright (c) 2025 Ian Marco Moffett and L5 engineers
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the project nor the names of its
+ *    contributors may be used to endorse or promote products derived from
+ *    this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <sys/syslog.h>
+#include <os/module.h>
+#include <fs/devfs.h>
+
+static struct cdevsw null_cdev;
+
+/*
+ * Lie to the user and make them think they are
+ * reading data but give them nothing
+ */
+static ssize_t
+null_read(struct devfs_node *dnp, struct dev_iobuf *io, int flags)
+{
+    /* We give you a whole lot of nothing! */
+    return io->count;
+}
+
+/*
+ * Take the users carefully crafted bytes made with love
+ * and throw it in the trash
+ */
+static ssize_t
+null_write(struct devfs_node *dnp, struct dev_iobuf *io, int flags)
+{
+    return io->count;
+}
+
+static int
+init_devnull(struct module *modp)
+{
+    int error;
+
+    error = devfs_register(
+        "null",
+        DEVFS_CDEV,
+        &null_cdev,
+        0
+    );
+
+    if (error < 0) {
+        printf("null: could not create /dev/null\n");
+        return error;
+    }
+
+    return 0;
+}
+
+static struct cdevsw null_cdev = {
+    .read = null_read,
+    .write = null_write
+};
+
+MODULE_EXPORT("null", MODTYPE_GENERIC, init_devnull);