getrandom/
linux_android.rs

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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}
getrandom/linux_android.rs

getrandom/
linux_android.rs
