Descriptive error codes in syscall API

[atwardzik]

Task Description

Some functions from the syscall API return not meaningful error codes.

Goal

Ensure that every sys_ function on failure returns descriptive error code from the errno.h. Adding new error codes may be required.

Please note that in kernel code the returned values are negative, e.g. -ESOCKTNOSUPPORT.

Affected Syscalls

• sys_kill
• sys_open
• sys_read
• sys_write
• sys_readdir
• sys_chdir
• sys_fstat
• sys_spawnp_process

Notes

• Error codes must follow POSIX conventions where applicable
• Similar failure cases across syscalls should return consistent error codes