vendor/getrandom/src/linux_android.rs

   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
  10 use crate::util::LazyBool;
  11 use crate::util_libc::{last_os_error, sys_fill_exact};
  12 use crate::{use_file, Error};
  13
  14 pub fn getrandom_inner(dest: &mut [u8]) -> Result<(), Error> {
  15     static HAS_GETRANDOM: LazyBool = LazyBool::new();
  16     if HAS_GETRANDOM.unsync_init(is_getrandom_available) {
  17         sys_fill_exact(dest, |buf| unsafe {
  18             getrandom(buf.as_mut_ptr() as *mut libc::c_void, buf.len(), 0)
  19         })
  20     } else {
  21         use_file::getrandom_inner(dest)
  22     }
  23 }
  24
  25 fn is_getrandom_available() -> bool {
  26     let res = unsafe { getrandom(core::ptr::null_mut(), 0, libc::GRND_NONBLOCK) };
  27     if res < 0 {
  28         match last_os_error().raw_os_error() {
  29             Some(libc::ENOSYS) => false, // No kernel support
  30             Some(libc::EPERM) => false,  // Blocked by seccomp
  31             _ => true,
  32         }
  33     } else {
  34         true
  35     }
  36 }
  37
  38 unsafe fn getrandom(
  39     buf: *mut libc::c_void,
  40     buflen: libc::size_t,
  41     flags: libc::c_uint,
  42 ) -> libc::ssize_t {
  43     libc::syscall(libc::SYS_getrandom, buf, buflen, flags) as libc::ssize_t
  44 }