Function sys_argv 

pub unsafe extern "C" fn sys_argv(
    out_words: *mut u32,
    out_nwords: usize,
    arg_index: usize,
) -> usize

Retrieves the argument with arg_index, and stores as much of it as it can it in the memory at [out_words, out_words + out_nwords).

Returns the length, in bytes, of the argument string. If the requested argument index does not exist (i.e. arg_index >= argc) then this syscall will not return.

This is normally called twice to read an argument: Once to get the length of the value, and once to fill in allocated memory.

NOTE: Repeated calls to sys_argv are not guaranteed to result in the same data being returned. Returned data is entirely in the control of the host.

Safety

out_words must be aligned and dereferenceable.