fs: implement read syscall

kernel/fs/read.c

@@ -0,0 +1,57 @@
+/* SPDX-License-Identifier: BSD-3-Clause */
+/* See the end of this file for copyright, licensing, and warranty information. */
+
+#include <ardix/malloc.h>
+#include <ardix/serial.h>
+#include <ardix/syscall.h>
+#include <ardix/userspace.h>
+
+#include <errno.h>
+#include <stddef.h>
+#include <toolchain.h>
+
+ssize_t sys_read(int fd, __user void *buf, size_t len)
+{
+	ssize_t ret;
+	void *copy;
+
+	if (fd != 0) /* we only support stdin (serial console) right now */
+		return -EBADF;
+
+	copy = malloc(len);
+	if (copy == NULL)
+		return -ENOMEM;
+
+	ret = serial_read(copy, serial_default_interface, len);
+	if (ret > 0)
+		copy_to_user(buf, copy, (size_t)ret);
+
+	free(copy);
+
+	return ret;
+}
+
+/*
+ * Copyright (c) 2020 Felix Kopp <sandtler@sandtler.club>
+ *
+ * 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 copyright holder 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 HOLDER 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.
+ */

kernel/syscall.c

@@ -11,7 +11,7 @@
 __rodata
 const int (*sys_table[NSYSCALLS])(sysarg_t arg1, sysarg_t arg2, sysarg_t arg3,
 				  sysarg_t arg4, sysarg_t arg5, sysarg_t arg6) = {
-	sys_table_entry(SYSCALL_READ, &sys_stub),
+	sys_table_entry(SYSCALL_READ, &sys_read),
 	sys_table_entry(SYSCALL_WRITE, &sys_write),
 };