diff --git a/src/linux_android.rs b/src/linux_android.rs index 2d260755a..1b7280df9 100644 --- a/src/linux_android.rs +++ b/src/linux_android.rs @@ -16,6 +16,8 @@ use core::cell::RefCell; use core::num::NonZeroU32; use core::sync::atomic::{AtomicBool, Ordering}; +// This flag tells getrandom() to return EAGAIN instead of blocking. +const GRND_NONBLOCK: libc::c_uint = 0x0001; static RNG_INIT: AtomicBool = AtomicBool::new(false); enum RngSource { @@ -27,9 +29,10 @@ thread_local!( static RNG_SOURCE: RefCell> = RefCell::new(None); ); -fn syscall_getrandom(dest: &mut [u8]) -> Result<(), io::Error> { +fn syscall_getrandom(dest: &mut [u8], block: bool) -> Result<(), io::Error> { + let flags = if block { 0 } else { GRND_NONBLOCK }; let ret = unsafe { - libc::syscall(libc::SYS_getrandom, dest.as_mut_ptr(), dest.len(), 0) + libc::syscall(libc::SYS_getrandom, dest.as_mut_ptr(), dest.len(), flags) }; if ret < 0 || (ret as usize) != dest.len() { error!("Linux getrandom syscall failed with return value {}", ret); @@ -56,7 +59,7 @@ pub fn getrandom_inner(dest: &mut [u8]) -> Result<(), Error> { Ok(s) }, |f| { match f { - RngSource::GetRandom => syscall_getrandom(dest), + RngSource::GetRandom => syscall_getrandom(dest, true), RngSource::Device(f) => f.read_exact(dest), }.map_err(From::from) }) @@ -71,7 +74,7 @@ fn is_getrandom_available() -> bool { CHECKER.call_once(|| { let mut buf: [u8; 0] = []; - let available = match syscall_getrandom(&mut buf) { + let available = match syscall_getrandom(&mut buf, false) { Ok(()) => true, Err(err) => err.raw_os_error() != Some(libc::ENOSYS), };