From e785da6cb3643fef61b1609a8a6dcc6e0f7652d3 Mon Sep 17 00:00:00 2001
From: Matheus <matheusuky@gmail.com>
Date: Tue, 9 May 2023 00:13:51 -0300
Subject: [PATCH] kernel: file_t, fd_t and a few helper functions

---
 kernel-src/fs/file.c                  | 125 ++++++++++++++++++++++++++
 kernel-src/include/kernel/file.h      |  27 ++++++
 kernel-src/include/kernel/scheduler.h |   4 +
 kernel-src/sys/scheduler.c            |  11 +++
 4 files changed, 167 insertions(+)
 create mode 100644 kernel-src/fs/file.c
 create mode 100644 kernel-src/include/kernel/file.h

diff --git a/kernel-src/fs/file.c b/kernel-src/fs/file.c
new file mode 100644
index 00000000..d318f258
--- /dev/null
+++ b/kernel-src/fs/file.c
@@ -0,0 +1,125 @@
+#include <kernel/file.h>
+#include <kernel/slab.h>
+#include <kernel/interrupt.h>
+#include <logging.h>
+#include <errno.h>
+#include <kernel/alloc.h>
+
+// TODO have a limit for the fd table
+
+static scache_t *filecache;
+#define FILE_HOLD(f) __atomic_add_fetch(&(f)->refcount, 1, __ATOMIC_SEQ_CST)
+
+#define FILE_RELEASE(f) \
+		if (__atomic_sub_fetch(&(f)->refcount, 1, __ATOMIC_SEQ_CST) == 0) {\
+			cleanfile(f); \
+		}
+
+static void ctor(scache_t *cache, void *obj) {
+	file_t *file = obj;
+	file->vnode = NULL;
+	MUTEX_INIT(&file->mutex);
+	file->refcount = 1;
+	file->offset = 0;
+}
+
+static file_t* newfile() {
+	if (filecache == NULL) {
+		filecache = slab_newcache(sizeof(file_t), 0, ctor, ctor);
+		__assert(filecache);
+	}
+
+	return slab_allocate(filecache);
+}
+
+static void cleanfile(file_t *file) {
+	__assert(!"UNIMPLEMENTED");
+}
+
+file_t *fd_get(int fd) {
+	proc_t *proc = _cpu()->thread->proc;
+	bool intstatus = interrupt_set(false);
+	spinlock_acquire(&proc->fdlock);
+
+	file_t *file = fd < proc->fdcount ? proc->fd[fd].file : NULL;
+	if (file)
+		FILE_HOLD(file);
+
+	spinlock_release(&proc->fdlock);
+	interrupt_set(intstatus);
+
+	if (file)
+		MUTEX_ACQUIRE(&file->mutex, false);
+
+	return file;
+}
+
+void fd_release(file_t *file) {
+	MUTEX_RELEASE(&file->mutex);
+	FILE_RELEASE(file);
+}
+
+int fd_new(vnode_t *vnode, int flags, file_t **rfile, int *rfd) {
+	file_t *file = newfile();
+	if (file == NULL)
+		return ENOMEM;
+
+	proc_t *proc = _cpu()->thread->proc;
+	spinlock_acquire(&proc->fdlock);
+
+	// find first free fd
+	int fd = -1;
+	for (fd = proc->fdfirst; fd < proc->fdcount && proc->fd[fd].file; ++fd);
+
+	// resize table if not found
+	if (fd == -1) {
+		void *newtable = realloc(proc->fd, sizeof(fd_t) * (proc->fdcount + 1));
+		if (newtable == NULL) {
+			spinlock_release(&proc->fdlock);
+			cleanfile(file);
+			return ENOMEM;
+		}
+
+		proc->fd = newtable;
+		fd = proc->fdcount;
+		++proc->fdcount;
+	}
+
+	proc->fdfirst = fd + 1;
+	proc->fd[fd].file = file;
+	proc->fd[fd].flags = flags;
+	MUTEX_ACQUIRE(&file->mutex, false);
+	FILE_HOLD(file);
+
+	spinlock_release(&proc->fdlock);
+
+	VOP_HOLD(vnode);
+	file->vnode = vnode;
+	*rfile = file;
+	*rfd = fd;
+	return 0;
+}
+
+int fd_close(int fd) {
+	proc_t *proc = _cpu()->thread->proc;
+	bool intstatus = interrupt_set(false);
+	spinlock_acquire(&proc->fdlock);
+
+	file_t *file = fd < proc->fdcount ? proc->fd[fd].file : NULL;
+	if (file) {
+		proc->fd[fd].file = NULL;
+		proc->fdfirst = fd;
+	}
+
+	spinlock_release(&proc->fdlock);
+	interrupt_set(intstatus);
+
+	if (file) {
+		FILE_RELEASE(file);
+	}
+	else {
+		return EBADF;
+	}
+
+	return 0;
+}
diff --git a/kernel-src/include/kernel/file.h b/kernel-src/include/kernel/file.h
new file mode 100644
index 00000000..5005d15c
--- /dev/null
+++ b/kernel-src/include/kernel/file.h
@@ -0,0 +1,27 @@
+#ifndef FILE_H
+#define FILE_H
+
+#include <kernel/vfs.h>
+#include <mutex.h>
+
+typedef struct file_t {
+	vnode_t *vnode;
+	mutex_t mutex;
+	int refcount;
+	mode_t mode;
+	uintmax_t offset;
+	int flags;
+} file_t;
+
+typedef struct fd_t {
+	file_t *file;
+	int flags;
+} fd_t;
+
+file_t *fd_get(int fd);
+void fd_release(file_t *file);
+int fd_new(vnode_t *node, int flags, file_t **file, int *fd);
+int fd_close(int fd);
+int fd_dup(int oldfd, int newfd, bool exact, int flags, int *ret);
+
+#endif
diff --git a/kernel-src/include/kernel/scheduler.h b/kernel-src/include/kernel/scheduler.h
index 234482d5..e361aa5c 100644
--- a/kernel-src/include/kernel/scheduler.h
+++ b/kernel-src/include/kernel/scheduler.h
@@ -42,6 +42,10 @@ typedef struct proc_t {
 	thread_t **threads;
 	size_t threadtablesize;
 	size_t runningthreadcount;
+	size_t fdcount;
+	uintmax_t fdfirst;
+	spinlock_t fdlock;
+	struct fd_t *fd;
 	mode_t umask;
 	int flags;
 	vnode_t *cwd;
diff --git a/kernel-src/sys/scheduler.c b/kernel-src/sys/scheduler.c
index 69c95d0b..605b2a21 100644
--- a/kernel-src/sys/scheduler.c
+++ b/kernel-src/sys/scheduler.c
@@ -7,6 +7,7 @@
 #include <kernel/alloc.h>
 #include <errno.h>
 #include <kernel/elf.h>
+#include <kernel/file.h>
 
 #define QUANTUM_US 100000
 #define SCHEDULER_STACK_SIZE 4096
@@ -39,6 +40,16 @@ proc_t *sched_newproc() {
 	proc->threadtablesize = 1;
 	proc->runningthreadcount = 1;
 	SPINLOCK_INIT(proc->lock);
+	proc->fdcount = 3;
+	proc->fdfirst = 3;
+	SPINLOCK_INIT(proc->fdlock);
+
+	proc->fd = alloc(sizeof(fd_t) * 3);
+	if (proc->fd == NULL) {
+		free(proc->threads);
+		slab_free(processcache, proc);
+		return NULL;
+	}
 
 	return proc;
 }