kern: syscall: Add initial write(2) stub

Here we add a write(2) stub and add it to the UNIX syscall interface. We
also move the UNIX syscall numbers into compat/unix/syscall.h

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

5 files changed, 182 insertions, 7 deletions

diff --git a/src/sys/compat/unix/os/os_filedesc.c b/src/sys/compat/unix/os/os_filedesc.c
new file mode 100644
index 0000000..f36bd02
--- /dev/null
+++ b/src/sys/compat/unix/os/os_filedesc.c
@@ -0,0 +1,52 @@
+/*
+ * 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/syscall.h>
+#include <sys/types.h>
+#include <os/filedesc.h>
+#include <compat/unix/syscall.h>
+
+#include <sys/syslog.h>
+
+/*
+ * Write syscall
+ *
+ * ARG0: (int)fd
+ * ARG1: (const void *)buf
+ * ARG2: (size_t)count
+ */
+scret_t
+sys_write(struct syscall_args *scargs)
+{
+    int fd = SCARG(scargs, int, 0);
+    const void *buf = SCARG(scargs, const void *, 1);
+    size_t count = SCARG(scargs, size_t, 2);
+
+    return write(fd, buf, count);
+}
diff --git a/src/sys/include/compat/unix/syscall.h b/src/sys/include/compat/unix/syscall.h
index 2bb699a..daca2dc 100644
--- a/src/sys/include/compat/unix/syscall.h
+++ b/src/sys/include/compat/unix/syscall.h
@@ -35,14 +35,27 @@
 #include <sys/syscall.h>
 
 /*
+ * Syscall numbers
+ */
+#define SYS_none    0x00
+#define SYS_exit    0x01
+#define SYS_write   0x02
+
+/*
  * Exit the current process - exit(2) syscall
  */
 scret_t sys_exit(struct syscall_args *scargs);
 
+/*
+ * Write to a file descriptor - write(2) syscall
+ */
+scret_t sys_write(struct syscall_args *scargs);
+
 #ifdef _NEED_UNIX_SCTAB
 scret_t(*g_unix_sctab[])(struct syscall_args *) = {
     [SYS_none]   = NULL,
-    [SYS_exit]   = sys_exit
+    [SYS_exit]   = sys_exit,
+    [SYS_write]  = sys_write
 };
 
 #endif  /* !_NEED_UNIX_SCTAB */
diff --git a/src/sys/include/os/filedesc.h b/src/sys/include/os/filedesc.h
new file mode 100644
index 0000000..9d6f229
--- /dev/null
+++ b/src/sys/include/os/filedesc.h
@@ -0,0 +1,47 @@
+/*
+ * 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.
+ */
+
+#ifndef _OS_FILEDESC_H_
+#define _OS_FILEDESC_H_ 1
+
+#include <sys/types.h>
+
+/*
+ * Write to a file descriptor
+ *
+ * @fd: File descriptor to write to
+ * @buf: Buffer to write
+ * @count: Buffer byte count
+ *
+ * Returns the number of bytes written on success, otherwise
+ * a less than zero value on error.
+ */
+ssize_t write(int fd, const void *buf, size_t count);
+
+#endif  /* !_OS_FILEDESC_H_ */
diff --git a/src/sys/include/sys/syscall.h b/src/sys/include/sys/syscall.h
index e0891e6..9d9c765 100644
--- a/src/sys/include/sys/syscall.h
+++ b/src/sys/include/sys/syscall.h
@@ -33,12 +33,6 @@
 #include <sys/types.h>
 #include <sys/limits.h>
 
-/*
- * Syscall numbers
- */
-#define SYS_none    0x00
-#define SYS_exit    0x01
-
 #if defined(_KERNEL)
 /*
  * Acquire a specific syscall argument
diff --git a/src/sys/os/os_filedes.c b/src/sys/os/os_filedes.c
new file mode 100644
index 0000000..ecb94ef
--- /dev/null
+++ b/src/sys/os/os_filedes.c
@@ -0,0 +1,69 @@
+/*
+ * 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/syscall.h>
+#include <sys/syslog.h>
+#include <sys/errno.h>
+#include <os/filedesc.h>
+#include <io/cons/cons.h>
+#include <sys/proc.h>
+#include <string.h>
+
+#define STDOUT_FILENO 1
+
+/*
+ * XXX: STUB
+ */
+ssize_t
+write(int fd, const void *buf, size_t count)
+{
+    int error;
+    char kbuf[1024];
+
+    /* Must be valid */
+    error = proc_check_addr(proc_self(), (uintptr_t)buf, count);
+    if (error < 0) {
+        return error;
+    }
+
+    memcpy(kbuf, buf, count);
+
+    switch (fd) {
+    case STDOUT_FILENO:
+        cons_putstr(
+            &g_root_scr, kbuf,
+            count
+        );
+        break;
+    default:
+        return -EBADF;
+    }
+
+    return count;
+}