init/fs: tmpfs driver with support for creating new files

1 files changed, 92 insertions, 0 deletions

diff --git a/src/init/driver/tmpfs.c b/src/init/driver/tmpfs.c
new file mode 100644
index 0000000..17b5b9b
--- /dev/null
+++ b/src/init/driver/tmpfs.c
@@ -0,0 +1,92 @@
+#include <init/malloc.h>
+#include <shared/mem.h>
+#include <shared/syscalls.h>
+#include <stddef.h>
+
+struct node {
+	const char *name;
+	size_t len;
+	struct node *next;
+};
+
+struct node *root = NULL;
+
+static struct node *lookup(const char *path, size_t len) {
+	for (struct node *iter = root; iter; iter = iter->next) {
+		if (iter->len == len && !memcmp(path, iter->name, len))
+			return iter;
+	}
+	return NULL;
+}
+
+static int tmpfs_open(const char *path, struct fs_wait_response *res) {
+	if (res->len == 0) return -1;
+	path++;
+	res->len--;
+
+	if (res->len == 0) return 0; /* root */
+
+	// no directory support (yet)
+	if (memchr(path, '/', res->len)) return -1;
+
+	if (res->flags & OPEN_CREATE) {
+		if (lookup(path, res->len)) return -1; /* already exists */
+		struct node *new = malloc(sizeof *new);
+		char *namebuf = malloc(res->len);
+		memcpy(namebuf, path, res->len);
+		new->name = namebuf;
+		new->len = res->len;
+		new->next = root;
+		root = new;
+		return 1;
+	}
+
+	return lookup(path, res->len) != 0 ? 1 : -1;
+}
+
+void tmpfs_drv(void) {
+	// TODO replace all the static allocations in drivers with mallocs
+	static char buf[512];
+	struct fs_wait_response res;
+	while (!_syscall_fs_wait(buf, sizeof buf, &res)) {
+		switch (res.op) {
+			case VFSOP_OPEN:
+				_syscall_fs_respond(NULL, tmpfs_open(buf, &res));
+				break;
+
+			case VFSOP_READ:
+				if (res.id != 0) {
+					// rw unimplemented
+					_syscall_fs_respond(NULL, -1);
+					break;
+				}
+				size_t buf_pos = 0;
+				size_t to_skip = res.offset;
+
+				for (struct node *iter = root; iter; iter = iter->next) {
+					if (iter->len <= to_skip) {
+						to_skip -= iter->len;
+						continue;
+					}
+
+					if (iter->len + buf_pos - to_skip >= sizeof(buf)) {
+						memcpy(buf + buf_pos, iter->name + to_skip, sizeof(buf) - buf_pos - to_skip);
+						buf_pos = sizeof(buf);
+						break;
+					}
+					memcpy(buf + buf_pos, iter->name + to_skip, iter->len - to_skip);
+					buf_pos += iter->len - to_skip;
+					buf[buf_pos++] = '\0';
+					to_skip = 0;
+				}
+				_syscall_fs_respond(buf, buf_pos);
+				break;
+
+			default:
+				_syscall_fs_respond(NULL, -1);
+				break;
+		}
+	}
+
+	_syscall_exit(1);
+}