new vfs impl pt. 1: implement open()

8 files changed, 113 insertions, 15 deletions

diff --git a/src/kernel/handle.h b/src/kernel/handle.h
index aae8937..0bf0f33 100644
--- a/src/kernel/handle.h
+++ b/src/kernel/handle.h
@@ -1,5 +1,6 @@
 #pragma once
 #include <kernel/types.h>
+#include <kernel/vfs/mount.h>
 #include <stddef.h>
 
 #define HANDLE_MAX 16
@@ -8,8 +9,15 @@ typedef int handle_t; // TODO duplicated in syscalls.h
 
 enum handle_type {
 	HANDLE_EMPTY,
+	HANDLE_FILE,
 };
 
 struct handle {
 	enum handle_type type;
+	union {
+		struct {
+			struct vfs_backend *backend;
+			int id;
+		} file;
+	};
 };
diff --git a/src/kernel/syscalls.c b/src/kernel/syscalls.c
index 002f3fd..8f520ab 100644
--- a/src/kernel/syscalls.c
+++ b/src/kernel/syscalls.c
@@ -89,16 +89,19 @@ handle_t _syscall_fs_open(const user_ptr path, int len) {
 	mount = vfs_mount_resolve(process_current->mount, buffer, len);
 	if (!mount) return -1;
 
-	res = -1; // TODO pass to filesystem
-	if (res < 0)
-		return res;
-	else
-		return handle;
+	vfs_backend_dispatch(mount->backend, (struct vfs_op) {
+			.type = VFSOP_OPEN,
+			.open = {
+				.path     = &buffer[mount->prefix_len],
+				.path_len = len - mount->prefix_len,
+			}
+		});
+	// doesn't return. TODO mark as noreturn
 }
 
 int _syscall_fd_mount(handle_t handle, const user_ptr path, int len) {
 	struct virt_iter iter;
-	struct vfs_mount *mount;
+	struct vfs_mount *mount = NULL;
 	char *path_buf;
 	int res;
 
diff --git a/src/kernel/vfs/backend.c b/src/kernel/vfs/backend.c
new file mode 100644
index 0000000..cf73ef0
--- /dev/null
+++ b/src/kernel/vfs/backend.c
@@ -0,0 +1,42 @@
+#include <kernel/panic.h>
+#include <kernel/proc.h>
+#include <kernel/vfs/backend.h>
+#include <kernel/vfs/root.h>
+
+// dispatches a VFS operation to the correct process
+_Noreturn void vfs_backend_dispatch(struct vfs_backend *backend, struct vfs_op op) {
+	struct vfs_op_request req = {
+		.op = op,
+		.caller = process_current,
+	};
+	switch (backend->type) {
+		case VFS_BACK_ROOT:
+			int ret = vfs_root_handler(&req);
+			vfs_backend_finish(&req, ret);
+		default:
+			panic();
+	}
+}
+
+// returns from a VFS operation to the calling process
+_Noreturn void vfs_backend_finish(struct vfs_op_request *req, int ret) {
+	if (req->op.type == VFSOP_OPEN && ret >= 0) {
+		// open() calls need special handling
+		// we need to wrap the id returned by the VFS in a handle passed to
+		// the client
+		handle_t handle = process_find_handle(req->caller);
+		if (handle < 0) panic();
+		req->caller->handles[handle] = (struct handle){
+			.type = HANDLE_FILE,
+			.file = {
+				.backend = req->backend,
+				.id = ret,
+			},
+		};
+		ret = handle;
+	} 
+
+	req->caller->state = PS_RUNNING;
+	regs_savereturn(&req->caller->regs, ret);
+	process_switch(req->caller);
+}
diff --git a/src/kernel/vfs/backend.h b/src/kernel/vfs/backend.h
new file mode 100644
index 0000000..6a8bee6
--- /dev/null
+++ b/src/kernel/vfs/backend.h
@@ -0,0 +1,23 @@
+#pragma once
+#include <shared/vfs.h>
+
+enum vfs_backend_type {
+	VFS_BACK_ROOT,
+};
+
+// describes something which can acts as an access function
+struct vfs_backend {
+	enum vfs_backend_type type;
+};
+
+// describes an in-progress vfs call
+struct vfs_op_request {
+	struct vfs_op op;
+	struct process *caller;
+	struct vfs_backend *backend;
+};
+
+
+// these can switch processes
+_Noreturn void vfs_backend_dispatch(struct vfs_backend *backend, struct vfs_op op);
+_Noreturn void vfs_backend_finish(struct vfs_op_request *, int ret);
diff --git a/src/kernel/vfs/mount.c b/src/kernel/vfs/mount.c
index 9d66f0b..07eed0d 100644
--- a/src/kernel/vfs/mount.c
+++ b/src/kernel/vfs/mount.c
@@ -3,15 +3,15 @@
 #include <kernel/vfs/mount.h>
 
 struct vfs_mount *vfs_mount_seed(void) {
-	struct vfs_mount *mount = NULL; /*kmalloc(sizeof(struct vfs_mount));
+	struct vfs_mount   *mount   = kmalloc(sizeof(struct vfs_mount));
+	struct vfs_backend *backend = kmalloc(sizeof(struct vfs_backend));
+	backend->type = VFS_BACK_ROOT;
 	*mount = (struct vfs_mount){
 		.prev = NULL,
-		.prefix = "/tty",
-		.prefix_len = 4,
-		.handle = {
-			.type = HANDLE_SPECIAL_TTY,
-		},
-	};*/
+		.prefix = "",
+		.prefix_len = 0,
+		.backend = backend,
+	};
 	return mount;
 }
 
diff --git a/src/kernel/vfs/mount.h b/src/kernel/vfs/mount.h
index b7029cd..ac55184 100644
--- a/src/kernel/vfs/mount.h
+++ b/src/kernel/vfs/mount.h
@@ -1,14 +1,15 @@
 #pragma once
-#include <kernel/handle.h>
+#include <kernel/vfs/backend.h>
+#include <stddef.h>
 
 struct vfs_mount {
 	struct vfs_mount *prev;
 	char *prefix;
 	size_t prefix_len;
+	struct vfs_backend *backend;
 };
 
 // prepares init's filesystem view
 struct vfs_mount *vfs_mount_seed(void);
 struct vfs_mount *vfs_mount_resolve(
 		struct vfs_mount *top, const char *path, size_t path_len);
-
diff --git a/src/kernel/vfs/root.c b/src/kernel/vfs/root.c
new file mode 100644
index 0000000..c90557b
--- /dev/null
+++ b/src/kernel/vfs/root.c
@@ -0,0 +1,16 @@
+#include <kernel/vfs/root.h>
+#include <kernel/util.h>
+#include <kernel/panic.h>
+
+int vfs_root_handler(struct vfs_op_request *req) {
+	switch (req->op.type) {
+		case VFSOP_OPEN:
+			if (req->op.open.path_len == 4
+					&& !memcmp(req->op.open.path, "/tty", 4)) {
+				return 0;
+			}
+			return -1;
+		default:
+			panic();
+	}
+}
diff --git a/src/kernel/vfs/root.h b/src/kernel/vfs/root.h
new file mode 100644
index 0000000..617ba1c
--- /dev/null
+++ b/src/kernel/vfs/root.h
@@ -0,0 +1,5 @@
+#pragma once
+#include <kernel/vfs/mount.h>
+
+// the VFS provided to init
+int vfs_root_handler(struct vfs_op_request *);