fix[addr_space]: ensure data is copied to kernel address space before convert VA to PA (#52)

Underlying driver assumes a linear mapping between virtual address and physical address when converting them, which is only present in kernel address space. So under circumstance related to physical address, we should copy the buffer to kernel space.

- `sys_write` will finally call `axfs::dev::Disk::write_one` in dev.rs, which will use the buffer directly.
- read from stdin will finally call `console_read_bytes`， which will also use the buffer directly.

Author: eternalcomet

modules/axfs/src/dev.rs

@@ -70,7 +70,11 @@ impl Disk {
     pub fn write_one(&mut self, buf: &[u8]) -> DevResult<usize> {
         let write_size = if self.offset == 0 && buf.len() >= BLOCK_SIZE {
             // whole block
-            self.dev.write_block(self.block_id, &buf[0..BLOCK_SIZE])?;
+            // copy data to kernel address space
+            // Because underlying driver assumes a linear mapping between virtual address and
+            // physical address when converting them, which is only present in kernel address space.
+            let data = buf[0..BLOCK_SIZE].to_vec();
+            self.dev.write_block(self.block_id, &data)?;
             self.block_id += 1;
             BLOCK_SIZE
         } else {