From 1f7e7501660123ff8f26e8c65e75c2b282b933ef Mon Sep 17 00:00:00 2001
From: dzwdz
Date: Fri, 8 Jul 2022 14:40:44 +0200
Subject: syscall/fs_respond: get the file id from the buf argument

Previously, file ids could only be positive integers, so their range
was 31 bits - not enough to represent the entire memory. Now, pointers
can be safely used as file ids.
---
 src/kernel/arch/i386/driver/fsroot.c | 7 ++++---
 src/kernel/handle.h                  | 2 +-
 src/kernel/syscalls.c                | 4 ++--
 src/kernel/vfs/request.c             | 7 ++++---
 src/kernel/vfs/request.h             | 6 +++---
 5 files changed, 14 insertions(+), 12 deletions(-)

(limited to 'src/kernel')

diff --git a/src/kernel/arch/i386/driver/fsroot.c b/src/kernel/arch/i386/driver/fsroot.c
index ccba0b6..e16dd80 100644
--- a/src/kernel/arch/i386/driver/fsroot.c
+++ b/src/kernel/arch/i386/driver/fsroot.c
@@ -45,6 +45,7 @@ static void req_preprocess(struct vfs_request *req, size_t max_len) {
 
 static int handle(struct vfs_request *req) {
 	assert(req->caller);
+	int id = (int)req->id;
 	switch (req->type) {
 		case VFSOP_OPEN:
 			if (req->flags & OPEN_CREATE) return -1;
@@ -65,7 +66,7 @@ static int handle(struct vfs_request *req) {
 			return -1;
 
 		case VFSOP_READ:
-			switch (req->id) {
+			switch (id) {
 				case HANDLE_ROOT: {
 					// TODO document directory read format
 					const char src[] =
@@ -106,7 +107,7 @@ static int handle(struct vfs_request *req) {
 					char buf[512];
 					uint32_t sector = req->offset / 512;
 					size_t len = min(req->output.len, 512 - ((size_t)req->offset & 511));
-					ata_read(req->id - HANDLE_ATA, sector, buf);
+					ata_read(id - HANDLE_ATA, sector, buf);
 					virt_cpy_to(req->caller->pages, req->output.buf, buf, len);
 					return len;
 				}
@@ -114,7 +115,7 @@ static int handle(struct vfs_request *req) {
 			}
 
 		case VFSOP_WRITE:
-			switch (req->id) {
+			switch (id) {
 				case HANDLE_VGA: {
 					void *vga = (void*)0xB8000;
 					req_preprocess(req, 80*25*2);
diff --git a/src/kernel/handle.h b/src/kernel/handle.h
index 423ea88..4a5cab2 100644
--- a/src/kernel/handle.h
+++ b/src/kernel/handle.h
@@ -16,7 +16,7 @@ enum handle_type {
 struct handle {
 	enum handle_type type;
 	struct vfs_backend *backend; // HANDLE_FILE | HANDLE_FS_FRONT
-	int file_id; // only applicable to HANDLE_FILE
+	void __user *file_id; // only applicable to HANDLE_FILE
 	struct {
 		struct process *reader, *writer;
 	} pipe;
diff --git a/src/kernel/syscalls.c b/src/kernel/syscalls.c
index cb26b70..e639d1f 100644
--- a/src/kernel/syscalls.c
+++ b/src/kernel/syscalls.c
@@ -246,7 +246,7 @@ int _syscall_fs_wait(char __user *buf, int max_len, struct fs_wait_response __us
 	return -1; // dummy
 }
 
-int _syscall_fs_respond(char __user *buf, int ret, int flags) {
+int _syscall_fs_respond(void __user *buf, int ret, int flags) {
 	struct vfs_request *req = process_current->handled_req;
 	if (!req) SYSCALL_RETURN(-1);
 
@@ -261,7 +261,7 @@ int _syscall_fs_respond(char __user *buf, int ret, int flags) {
 	}
 
 	process_current->handled_req = NULL;
-	vfsreq_finish(req, ret, flags, process_current);
+	vfsreq_finish(req, buf, ret, flags, process_current);
 	SYSCALL_RETURN(0);
 }
 
diff --git a/src/kernel/vfs/request.c b/src/kernel/vfs/request.c
index dfbd5cd..7c677cc 100644
--- a/src/kernel/vfs/request.c
+++ b/src/kernel/vfs/request.c
@@ -29,7 +29,9 @@ void vfsreq_create(struct vfs_request req_) {
 	vfs_backend_tryaccept(req->backend);
 }
 
-void vfsreq_finish(struct vfs_request *req, int ret, int flags, struct process *handler) {
+void vfsreq_finish(struct vfs_request *req, char __user *stored, int ret,
+		int flags, struct process *handler)
+{
 	if (req->type == VFSOP_OPEN && ret >= 0) {
 		// TODO write tests for caller getting killed while opening a file
 		if (!req->caller) panic_unimplemented();
@@ -43,8 +45,7 @@ void vfsreq_finish(struct vfs_request *req, int ret, int flags, struct process *
 			struct handle *backing = handle_init(HANDLE_FILE);
 			backing->backend = req->backend;
 			req->backend->refcount++;
-			// TODO file ids can only be 31bit long, so they can't be pointers
-			backing->file_id = ret;
+			backing->file_id = stored;
 			req->caller->handles[handle] = backing;
 		} else {
 			/* delegating - moving a handle to the caller */
diff --git a/src/kernel/vfs/request.h b/src/kernel/vfs/request.h
index 7d36a5d..29f1ee9 100644
--- a/src/kernel/vfs/request.h
+++ b/src/kernel/vfs/request.h
@@ -47,7 +47,7 @@ struct vfs_request {
 		size_t len;
 	} output;
 
-	int id; // handle.file.id
+	void __user *id; // handle.file.id
 	int offset;
 	int flags;
 
@@ -59,10 +59,10 @@ struct vfs_request {
 
 /** Assigns the vfs_request to the caller, and dispatches the call */
 void vfsreq_create(struct vfs_request);
-void vfsreq_finish(struct vfs_request*, int ret, int flags, struct process *handler);
+void vfsreq_finish(struct vfs_request*, char __user *stored, int ret, int flags, struct process *handler);
 
 static inline void vfsreq_finish_short(struct vfs_request *req, int ret) {
-	vfsreq_finish(req, ret, 0, NULL);
+	vfsreq_finish(req, (void __user *)ret, ret, 0, NULL);
 }
 
 /** Try to accept an enqueued request */
-- 
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