1//! Implementation for Linux / Android
2use crate::{
3 lazy::LazyBool,
4 util_libc::{last_os_error, sys_fill_exact},
5 {use_file, Error},
6};
7use core::mem::MaybeUninit;
8
9pub fn getrandom_inner(dest: &mut [MaybeUninit<u8>]) -> Result<(), Error> {
10 // getrandom(2) was introduced in Linux 3.17
11 static HAS_GETRANDOM: LazyBool = LazyBool::new();
12 if HAS_GETRANDOM.unsync_init(is_getrandom_available) {
13 sys_fill_exact(buf:dest, |buf: &mut [MaybeUninit]| unsafe {
14 getrandom(buf:buf.as_mut_ptr() as *mut libc::c_void, buflen:buf.len(), flags:0)
15 })
16 } else {
17 use_file::getrandom_inner(dest)
18 }
19}
20
21fn is_getrandom_available() -> bool {
22 let res: isize = unsafe { getrandom(buf:core::ptr::null_mut(), buflen:0, flags:libc::GRND_NONBLOCK) };
23 if res < 0 {
24 match last_os_error().raw_os_error() {
25 Some(libc::ENOSYS) => false, // No kernel support
26 Some(libc::EPERM) => false, // Blocked by seccomp
27 _ => true,
28 }
29 } else {
30 true
31 }
32}
33
34unsafe fn getrandom(
35 buf: *mut libc::c_void,
36 buflen: libc::size_t,
37 flags: libc::c_uint,
38) -> libc::ssize_t {
39 libc::syscall(num:libc::SYS_getrandom, buf, buflen, flags) as libc::ssize_t
40}
41