open (nr 2)

Linux Signature

int open(const char *pathname, int flags, mode_t mode);

Description

Opens a file or directory at pathname and returns a file descriptor.

Current Implementation

1. Reads a null-terminated path string from user space (max 4096 bytes). Returns -EFAULT if the pointer is invalid.
2. Resolves the path relative to the process’s current working directory (cwd). Normalises . and .. components.
3. Unless O_DIRECTORY (0o200000) is set, first attempts to open as a file via devices::vfs::read_file() (through osl::blocking::blocking()). On success, the entire file content is loaded into a VfsHandle (buffered in kernel memory) and a new fd is allocated.
4. If the file open fails with VfsError::NotFound or VfsError::NotAFile, or O_DIRECTORY was requested, falls back to opening as a directory via devices::vfs::list_dir(). On success, creates a DirHandle with the directory listing and allocates a new fd.
5. Returns the new fd number on success, or a negative errno.

The VFS operations use osl::blocking::blocking() which spawns the async VFS call as a kernel task and blocks the calling user thread until it completes.

Flags supported: O_DIRECTORY (to explicitly request directory). O_RDONLY is implied for all opens. Other flags are accepted but ignored.

Source: osl/src/syscalls/fs.rs — sys_open

Errors

Future Work

• Support O_WRONLY, O_CREAT, O_TRUNC for writable files.
• Streaming reads instead of loading entire file into memory at open time.
• Proper mode handling.