Function sys_getenv 

#[unsafe(no_mangle)]
pub unsafe extern "C" fn sys_getenv(
    out_words: *mut u32,
    out_nwords: usize,
    varname: *const u8,
    varname_len: usize,
) -> usize

Retrieves the value of an environment variable, and stores as much of it as it can it in the memory at [out_words, out_words + out_nwords).

Returns the length of the value, in bytes, or usize::MAX if the variable is not set.

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

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

Safety

out_words and varname must be aligned and dereferenceable.