1// Copyright 2018 Developers of the Rand project.
2//
3// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
4// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
5// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
6// option. This file may not be copied, modified, or distributed
7// except according to those terms.
8
9//! Implementation for Linux / Android
10use crate::{
11 util::LazyBool,
12 util_libc::{last_os_error, sys_fill_exact},
13 {use_file, Error},
14};
15use core::mem::MaybeUninit;
16
17pub fn getrandom_inner(dest: &mut [MaybeUninit<u8>]) -> Result<(), Error> {
18 // getrandom(2) was introduced in Linux 3.17
19 static HAS_GETRANDOM: LazyBool = LazyBool::new();
20 if HAS_GETRANDOM.unsync_init(is_getrandom_available) {
21 sys_fill_exact(dest, |buf| unsafe {
22 getrandom(buf.as_mut_ptr() as *mut libc::c_void, buf.len(), 0)
23 })
24 } else {
25 use_file::getrandom_inner(dest)
26 }
27}
28
29fn is_getrandom_available() -> bool {
30 let res = unsafe { getrandom(core::ptr::null_mut(), 0, libc::GRND_NONBLOCK) };
31 if res < 0 {
32 match last_os_error().raw_os_error() {
33 Some(libc::ENOSYS) => false, // No kernel support
34 Some(libc::EPERM) => false, // Blocked by seccomp
35 _ => true,
36 }
37 } else {
38 true
39 }
40}
41
42unsafe fn getrandom(
43 buf: *mut libc::c_void,
44 buflen: libc::size_t,
45 flags: libc::c_uint,
46) -> libc::ssize_t {
47 libc::syscall(libc::SYS_getrandom, buf, buflen, flags) as libc::ssize_t
48}
49