From bb3dea72205df8496e3b811940265edfff876318 Mon Sep 17 00:00:00 2001
From: Ian Moffett <ian@osmora.org>
Date: Fri, 26 Sep 2025 12:24:11 -0400
Subject: kernel: filedesc: Allocate standard streams

Signed-off-by: Ian Moffett <ian@osmora.org>
---
 src/sys/include/os/filedesc.h | 27 ++++++++++++++++
 src/sys/include/sys/limits.h  |  1 +
 src/sys/include/sys/proc.h    |  2 ++
 src/sys/os/os_filedes.c       | 71 +++++++++++++++++++++++++++++++++++++++++++
 src/sys/os/os_proc.c          |  6 ++++
 5 files changed, 107 insertions(+)

diff --git a/src/sys/include/os/filedesc.h b/src/sys/include/os/filedesc.h
index 9d6f229..87bf242 100644
--- a/src/sys/include/os/filedesc.h
+++ b/src/sys/include/os/filedesc.h
@@ -31,6 +31,33 @@
 #define _OS_FILEDESC_H_ 1
 
 #include <sys/types.h>
+#include <os/vnode.h>
+
+struct proc;
+
+/*
+ * Represents a file descriptor
+ *
+ * @fdno: File descriptor index
+ * @vp: Vnode this fd is linked with
+ * @mode: File attributes
+ */
+struct filedesc {
+    int fdno;
+    struct vnode *vp;
+    mode_t mode;
+};
+
+/*
+ * Initialize a process file descriptor table
+ * and set up standard streams
+ *
+ * @procp: Process of fd table to init
+ *
+ * Returns zero on success, less than zero values
+ * indicate failure.
+ */
+int fdtab_init(struct proc *procp);
 
 /*
  * Write to a file descriptor
diff --git a/src/sys/include/sys/limits.h b/src/sys/include/sys/limits.h
index d2cefb6..5e32233 100644
--- a/src/sys/include/sys/limits.h
+++ b/src/sys/include/sys/limits.h
@@ -36,5 +36,6 @@
 #define CPU_MAX 256
 #define SC_MAX 64       /* Max syscalls */
 #define SCWIN_MAX 2    /* Max syscall windows */
+#define FD_MAX 256      /* Max file descriptors */
 
 #endif  /* !_SYS_LIMITS_H_ */
diff --git a/src/sys/include/sys/proc.h b/src/sys/include/sys/proc.h
index 43772be..c31cc4c 100644
--- a/src/sys/include/sys/proc.h
+++ b/src/sys/include/sys/proc.h
@@ -36,6 +36,7 @@
 #include <sys/param.h>
 #include <sys/queue.h>
 #include <os/mac.h>
+#include <os/filedesc.h>
 #include <vm/vm.h>
 #include <machine/pcb.h>    /* standard */
 
@@ -63,6 +64,7 @@ struct proc {
     uint32_t flags;
     struct md_pcb pcb;
     struct syscall_domain scdom;
+    struct filedesc *fdtab[FD_MAX];
     mac_level_t level;
     TAILQ_HEAD(, vm_range) maplist;
     TAILQ_ENTRY(proc) link;
diff --git a/src/sys/os/os_filedes.c b/src/sys/os/os_filedes.c
index ecb94ef..e7cc83a 100644
--- a/src/sys/os/os_filedes.c
+++ b/src/sys/os/os_filedes.c
@@ -30,13 +30,84 @@
 #include <sys/syscall.h>
 #include <sys/syslog.h>
 #include <sys/errno.h>
+#include <sys/limits.h>
 #include <os/filedesc.h>
+#include <os/kalloc.h>
 #include <io/cons/cons.h>
 #include <sys/proc.h>
 #include <string.h>
 
 #define STDOUT_FILENO 1
 
+/*
+ * Allocate a file descriptor from a specific process's
+ * file descriptor table
+ *
+ * @procp: Process to allocate fd from
+ * @fd_res: Result pointer is written here
+ *
+ * Returns zero on success, otherwise a less than
+ * zero value upon failure
+ */
+static int
+fd_alloc(struct proc *procp, struct filedesc **fd_res)
+{
+    struct filedesc *fd;
+
+    if (procp == NULL) {
+        return -EINVAL;
+    }
+
+    /*
+     * Find an entry that is free and allocate a new
+     * file descriptor for it.
+     */
+    for (int i = 0; i < FD_MAX; ++i) {
+        if (procp->fdtab[i] != NULL) {
+            continue;
+        }
+
+        fd = kalloc(sizeof(*fd));
+        if (fd == NULL) {
+            return -EINVAL;
+        }
+
+        /* Zero and assign */
+        memset(fd, 0, sizeof(*fd));
+        procp->fdtab[i] = fd;
+        fd->fdno = i;
+        if (fd_res != NULL) {
+            *fd_res = fd;
+        }
+
+        return 0;
+    }
+
+    return -EMFILE;
+}
+
+/*
+ * Initialize file descriptor table
+ */
+int
+fdtab_init(struct proc *procp)
+{
+    if (procp == NULL) {
+        return -EINVAL;
+    }
+
+    /* Don't do it twice */
+    if (procp->fdtab[0] != NULL) {
+        printf("fdtab: fd table already initialized\n");
+        return -1;
+    }
+
+    fd_alloc(procp, NULL);  /* stdin */
+    fd_alloc(procp, NULL);  /* stdout */
+    fd_alloc(procp, NULL);  /* stderr */
+    return 0;
+}
+
 /*
  * XXX: STUB
  */
diff --git a/src/sys/os/os_proc.c b/src/sys/os/os_proc.c
index f21fc69..448402f 100644
--- a/src/sys/os/os_proc.c
+++ b/src/sys/os/os_proc.c
@@ -36,6 +36,7 @@
 #include <vm/vm.h>
 #include <vm/physseg.h>
 #include <os/kalloc.h>
+#include <os/filedesc.h>
 #include <string.h>
 
 static pid_t next_pid = 0;
@@ -97,6 +98,11 @@ proc_init(struct proc *procp, int flags)
 
     procp->pid = atomic_inc_int(&next_pid);
     error = md_proc_init(procp, flags);
+    if (error < 0) {
+        return error;
+    }
+
+    error = fdtab_init(procp);
     return error;
 }
 
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