From 25461d1d5df8f6d1cf415eeb7d8d7c073171def5 Mon Sep 17 00:00:00 2001
From: Ian Moffett <ian@osmora.org>
Date: Mon, 6 Oct 2025 21:25:02 -0400
Subject: kern: filedesc: Add fd_open() function

Introduce the fd_open() function as apart of the kernel file
descriptor API to open a file and get a file descriptor.

Signed-off-by: Ian Moffett <ian@osmora.org>
---
 src/sys/include/os/filedesc.h | 11 +++++++++++
 src/sys/os/os_filedes.c       | 45 ++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 55 insertions(+), 1 deletion(-)

diff --git a/src/sys/include/os/filedesc.h b/src/sys/include/os/filedesc.h
index 87bf242..c339ed6 100644
--- a/src/sys/include/os/filedesc.h
+++ b/src/sys/include/os/filedesc.h
@@ -59,6 +59,17 @@ struct filedesc {
  */
 int fdtab_init(struct proc *procp);
 
+/*
+ * Open a file
+ *
+ * @path: Path to file in which we wish to open
+ * @mode: Mode of our desired file
+ *
+ * Returns the file descriptor on success,
+ * otherwise a less than zero value on failure.
+ */
+int fd_open(const char *path, mode_t mode);
+
 /*
  * Write to a file descriptor
  *
diff --git a/src/sys/os/os_filedes.c b/src/sys/os/os_filedes.c
index e7cc83a..dde7f22 100644
--- a/src/sys/os/os_filedes.c
+++ b/src/sys/os/os_filedes.c
@@ -31,10 +31,12 @@
 #include <sys/syslog.h>
 #include <sys/errno.h>
 #include <sys/limits.h>
+#include <sys/proc.h>
+#include <sys/namei.h>
 #include <os/filedesc.h>
 #include <os/kalloc.h>
 #include <io/cons/cons.h>
-#include <sys/proc.h>
+#include <compat/unix/syscall.h>
 #include <string.h>
 
 #define STDOUT_FILENO 1
@@ -86,6 +88,47 @@ fd_alloc(struct proc *procp, struct filedesc **fd_res)
     return -EMFILE;
 }
 
+int
+fd_open(const char *path, mode_t mode)
+{
+    struct filedesc *fd;
+    struct nameidata nd;
+    struct proc *self = proc_self();
+    struct vnode *vp;
+    int error;
+
+    /* We need the current proc */
+    if (self == NULL) {
+        return -ESRCH;
+    }
+
+    if (path == NULL) {
+        return -ESRCH;
+    }
+
+    /* Allocate a new file descriptor */
+    error = fd_alloc(self, &fd);
+    if (error < 0) {
+        return error;
+    }
+
+    /*
+     * Now we try to do the lookup, we'll need
+     * the vnode for file references to be
+     * useful
+     */
+    nd.path = path;
+    nd.flags = 0;
+    nd.vp_res = &vp;
+    error = namei(&nd);
+    if (error < 0) {
+        return error;
+    }
+
+    fd->vp = vp;
+    return fd->fdno;
+}
+
 /*
  * Initialize file descriptor table
  */
-- 
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