FILE_DESCRIPTORS.md

File Descriptors and User Paths

Scopes 44–46 expose bounded user/kernel data transfer for paths and file I/O through the hardware syscall table.

Scope 44 — User Paths

user_path::copy_path_from_user validates a NUL-terminated path in user memory (length cap, no kernel pointers). Syscall ReadPathProbe (id 65) round-trips a probe string for smoke tests.

Boot smoke:

See [VALIDATION_GATES.md](VALIDATION_GATES.md) for gate serial lines.

Scope 45 — FD Table

Per-process tables hold up to 64 open descriptors (kernel/src/fd_table.rs::MAX_FDS). Syscalls:

• OpenFile (66) — open by path with permission checks
• CloseFile (67)

Boot smoke:

See [VALIDATION_GATES.md](VALIDATION_GATES.md) for gate serial lines.

Scope 46 — FD I/O

• ReadFd (68) — read into user buffer with copy_to_user
• WriteFd (69) — write from user buffer with copy_from_user

Boot smoke:

See [VALIDATION_GATES.md](VALIDATION_GATES.md) for gate serial lines.

Hardware syscall dispatch passes arg1/arg2 from rsi/rdx for these calls.

Validation

python scripts/gate/run.py --gate dynamic_runtime --timeout 180
python scripts/gate/run.py --gate dynamic_runtime --timeout 180
python scripts/gate/run.py --gate dynamic_runtime --timeout 180

Deferred

• Pipes, sockets, and non-storage backends beyond current pipe/serial paths
• select / poll integration