kernel: Add basic file descriptor support

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

4 files changed, 191 insertions, 0 deletions

diff --git a/sys/include/sys/filedesc.h b/sys/include/sys/filedesc.h
new file mode 100644
index 0000000..ef74fb1
--- /dev/null
+++ b/sys/include/sys/filedesc.h
@@ -0,0 +1,53 @@
+/*
+ * Copyright (c) 2023-2024 Ian Marco Moffett and the Osmora Team.
+ * 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 Hyra 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 _SYS_FILEDESC_H_
+#define _SYS_FILEDESC_H_
+
+#include <sys/vnode.h>
+#include <sys/spinlock.h>
+#include <sys/types.h>
+
+struct proc;
+
+struct filedesc {
+    int fdno;
+    off_t offset;
+    bool is_dir;
+    struct vnode *vnode;
+    struct spinlock lock;
+};
+
+#if defined(_KERNEL)
+struct filedesc *fd_alloc(struct proc *td);
+struct filedesc *fd_from_fdnum(const struct proc *td, int fdno);
+void fd_close_fdnum(struct proc *td, int fdno);
+#endif
+
+#endif
diff --git a/sys/include/sys/proc.h b/sys/include/sys/proc.h
index 7181ecb..c6046d7 100644
--- a/sys/include/sys/proc.h
+++ b/sys/include/sys/proc.h
@@ -32,11 +32,14 @@
 
 #include <sys/types.h>
 #include <sys/queue.h>
+#include <sys/filedesc.h>
 #include <machine/cpu.h>
 #include <machine/frame.h>
 #include <machine/pcb.h>
 #include <vm/vm.h>
 
+#define PROC_MAX_FDS 256
+
 /*
  * A task running on the CPU e.g., a process or
  * a thread.
@@ -49,6 +52,7 @@ struct proc {
     struct vas addrsp;
     uintptr_t stack_base;
     uint8_t is_user;
+    struct filedesc *fds[PROC_MAX_FDS];
     TAILQ_ENTRY(proc) link;
 };
 
diff --git a/sys/kern/kern_filedesc.c b/sys/kern/kern_filedesc.c
new file mode 100644
index 0000000..a943714
--- /dev/null
+++ b/sys/kern/kern_filedesc.c
@@ -0,0 +1,123 @@
+/*
+ * Copyright (c) 2023-2024 Ian Marco Moffett and the Osmora Team.
+ * 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 Hyra 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/filedesc.h>
+#include <sys/proc.h>
+#include <sys/sched.h>
+#include <vm/dynalloc.h>
+#include <assert.h>
+#include <string.h>
+
+/*
+ * Allocate a file descriptor.
+ *
+ * @td: Thread to allocate from, NULL for current thread.
+ */
+struct filedesc *
+fd_alloc(struct proc *td)
+{
+    struct filedesc *fd;
+
+    if (td == NULL) {
+        td = this_td();
+        __assert(td != NULL);
+    }
+
+    for (size_t i = 0; i < PROC_MAX_FDS; ++i) {
+        if (td->fds[i] != NULL) {
+            continue;
+        }
+
+        fd = dynalloc(sizeof(struct filedesc));
+        memset(fd, 0, sizeof(struct filedesc));
+
+        if (fd == NULL) {
+            return NULL;
+        }
+
+        fd->fdno = i;
+        td->fds[i] = fd;
+        return fd;
+    }
+
+    return NULL;
+}
+
+/*
+ * Fetch a file descriptor from a file descriptor
+ * number.
+ *
+ * @td: Thread to fetch from, NULL for current thread.
+ * @fdno: File descriptor to fetch
+ */
+struct filedesc *
+fd_from_fdnum(const struct proc *td, int fdno)
+{
+    if (td == NULL) {
+        td = this_td();
+        __assert(td != NULL);
+    }
+
+    if (fdno < 0 || fdno > PROC_MAX_FDS) {
+        return NULL;
+    }
+
+    for (size_t i = 0; i < PROC_MAX_FDS; ++i) {
+        if (i == fdno && td->fds[i] != NULL) {
+            return td->fds[i];
+        }
+    }
+
+    return NULL;
+}
+
+/*
+ * Close a file descriptor from its fd number.
+ *
+ * @td: Thread to fetch from, NULL for current thread.
+ * @fdno: File descriptor number to close.
+ */
+void
+fd_close_fdnum(struct proc *td, int fdno)
+{
+    struct filedesc *fd;
+
+    if (td == NULL) {
+        td = this_td();
+        __assert(td != NULL);
+    }
+
+    fd = fd_from_fdnum(td, fdno);
+    if (fd == NULL) {
+        return;
+    }
+
+    dynfree(fd);
+    td->fds[fdno] = NULL;
+}
diff --git a/sys/kern/kern_sched.c b/sys/kern/kern_sched.c
index bd59e41..77aab54 100644
--- a/sys/kern/kern_sched.c
+++ b/sys/kern/kern_sched.c
@@ -37,6 +37,7 @@
 #include <sys/loader.h>
 #include <sys/panic.h>
 #include <sys/machdep.h>
+#include <sys/filedesc.h>
 #include <fs/initramfs.h>
 #include <vm/dynalloc.h>
 #include <vm/physseg.h>
@@ -268,6 +269,11 @@ sched_create_td(uintptr_t rip, char *argvp[], char *envp[], struct auxval auxv,
     td->is_user = is_user;
     processor_init_pcb(td);
 
+    /* Allocate standard file descriptors */
+    __assert(fd_alloc(td) != NULL);       /* STDIN */
+    __assert(fd_alloc(td) != NULL);       /* STDOUT */
+    __assert(fd_alloc(td) != NULL);       /* STDERR */
+
     /* Setup trapframe */
     if (!is_user) {
         init_frame(tf, rip, (uintptr_t)stack);
@@ -294,6 +300,11 @@ sched_destroy_td(struct proc *td)
         dynfree((void *)td->stack_base);
     }
 
+    /* Close all of the file descriptors */
+    for (size_t i = 0; i < PROC_MAX_FDS; ++i) {
+        fd_close_fdnum(td, i);
+    }
+
     pmap_free_vas(vm_get_ctx(), td->addrsp);
     dynfree(td);
 }