From e1789ffa14826e0c7378f974ac68c2c04ba8640c Mon Sep 17 00:00:00 2001
From: dzwdz
Date: Sat, 11 Sep 2021 18:22:21 +0200
Subject: add some helper functions for copying between virtual and physical
 memory

this was already possible, but now it's slightly safer
---
 src/kernel/mem/virt.c |  3 ++-
 src/kernel/mem/virt.h | 11 +++++++++++
 src/kernel/syscalls.c |  9 +++------
 3 files changed, 16 insertions(+), 7 deletions(-)

(limited to 'src/kernel')

diff --git a/src/kernel/mem/virt.c b/src/kernel/mem/virt.c
index e0d8e44..7a38a88 100644
--- a/src/kernel/mem/virt.c
+++ b/src/kernel/mem/virt.c
@@ -41,7 +41,8 @@ bool virt_iter_next(struct virt_iter *iter) {
 		}
 	} else {
 		// "iterate" over physical memory
-		iter->frag = (void*) iter->_virt;
+		// the double cast supresses the warning about changing address spaces
+		iter->frag = (void*)(uintptr_t)iter->_virt;
 	}
 
 	iter->frag_len    = partial;
diff --git a/src/kernel/mem/virt.h b/src/kernel/mem/virt.h
index 7dac887..78d0cb3 100644
--- a/src/kernel/mem/virt.h
+++ b/src/kernel/mem/virt.h
@@ -27,3 +27,14 @@ bool virt_iter_next(struct virt_iter *);
 bool virt_cpy(
 		struct pagedir *dest_pages,       void __user *dest,
 		struct pagedir  *src_pages, const void __user *src, size_t length);
+
+
+inline bool virt_cpy_to(struct pagedir *dest_pages, // physical -> virtual
+		void __user *dest, const void *src, size_t length) {
+	return virt_cpy(dest_pages, dest, NULL, (userptr_t)src, length);
+}
+
+inline bool virt_cpy_from(struct pagedir *src_pages, // virtual -> physical
+		void *dest, const void __user *src, size_t length) {
+	return virt_cpy(NULL, (userptr_t)dest, src_pages, src, length);
+}
diff --git a/src/kernel/syscalls.c b/src/kernel/syscalls.c
index ab4fdbb..743d5c5 100644
--- a/src/kernel/syscalls.c
+++ b/src/kernel/syscalls.c
@@ -83,8 +83,7 @@ handle_t _syscall_open(const char __user *path, int len) {
 	//       it can handle copies to physical memory too, though
 	// note 2: path_buf gets freed in vfs_backend_finish
 	path_buf = kmalloc(len);
-	if (!virt_cpy(NULL, path_buf,
-				process_current->pages, path, len))
+	if (!virt_cpy_from(process_current->pages, path_buf, path, len))
 		goto fail;
 
 	len = path_simplify(path_buf, path_buf, len);
@@ -118,8 +117,7 @@ int _syscall_mount(handle_t handle, const char __user *path, int len) {
 
 	// copy the path to the kernel
 	path_buf = kmalloc(len);
-	if (!virt_cpy(NULL, path_buf,
-				process_current->pages, path, len))
+	if (!virt_cpy_from(process_current->pages, path_buf, path, len))
 		goto fail;
 
 	// simplify it
@@ -179,8 +177,7 @@ handle_t _syscall_fs_create(handle_t __user *back_user) {
 	process_current->handles[back].type = HANDLE_FS_BACK;
 
 	// copy the back handle to back_user
-	if (!virt_cpy(process_current->pages, back_user,
-			NULL, &back, sizeof(handle_t)))
+	if (!virt_cpy_to(process_current->pages, back_user, &back, sizeof(back)))
 		goto fail;
 
 	backend = kmalloc(sizeof *backend); // TODO never freed
-- 
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