Add sysfs VFS driver, SYS_OPEN/CLOSE syscalls, cat app
Sysfs:
- New VFS driver mounted at /sys that lets kernel drivers expose
virtual text files via namespace registration
- Drivers call sysfs_register(name, ops, ctx) with list/read/write
callbacks for their namespace
- IDE driver registers 'ide' namespace exposing per-device attributes:
model, type, channel, drive, sectors, sector_size
- Tested: ls /sys -> ide, ls /sys/ide -> hdd1 cd1,
cat /sys/ide/hdd1/model -> QEMU HARDDISK
Syscalls:
- Added SYS_OPEN (11) and SYS_CLOSE (12) for file I/O from userspace
- Extended SYS_READ/SYS_WRITE to handle VFS file descriptors (fd >= 3)
- Updated userspace syscalls.h with open()/close() wrappers
Apps:
- New 'cat' app: reads and displays file contents via open/read/close
- Updated 'ls' to accept path argument via ARG1 env var
- Updated shell to pass ARG1 env var to external commands
d1bf69ce0d