read (nr 0)

Linux Signature

ssize_t read(int fd, void *buf, size_t count);

Description

Reads up to count bytes from file descriptor fd into buf.

Current Implementation

Looks up fd in the current process’s per-process file descriptor table and calls FileHandle::read() on the handle.

• fd 0 (stdin) — ConsoleHandle: Reads raw bytes from the console input buffer (libkernel/src/console.rs). If the buffer is empty, blocks the current scheduler thread via block_current_thread() until the keyboard ISR delivers input via push_input(). Returns at least 1 byte per call.
• VFS file fds — VfsHandle: Reads from an in-memory buffer loaded at open() time. Maintains a per-handle read position. Returns 0 at EOF.
• Directory fds — DirHandle: Returns -EISDIR (-21).
• Invalid fds: Returns -EBADF (-9).

Validates that buf falls within user address space (< 0x0000_8000_0000_0000). Returns -EFAULT (-14) on invalid pointers. Returns 0 immediately if count is 0.

Source: osl/src/syscalls/io.rs — sys_read

Future Work

• Support partial reads and proper error handling for VFS files.
• SMAP enforcement for user buffer validation.