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//! Implementation for Linux / Android with `/dev/urandom` fallback
use crate::{
lazy::LazyBool,
util_libc::{getrandom_syscall, last_os_error, sys_fill_exact},
{use_file, Error},
};
use core::mem::MaybeUninit;
pub fn getrandom_inner(dest: &mut [MaybeUninit<u8>]) -> Result<(), Error> {
// getrandom(2) was introduced in Linux 3.17
static HAS_GETRANDOM: LazyBool = LazyBool::new();
if HAS_GETRANDOM.unsync_init(is_getrandom_available) {
sys_fill_exact(dest, getrandom_syscall)
} else {
use_file::getrandom_inner(dest)
}
}
fn is_getrandom_available() -> bool {
if getrandom_syscall(&mut []) < 0 {
match last_os_error().raw_os_error() {
Some(libc::ENOSYS) => false, // No kernel support
// The fallback on EPERM is intentionally not done on Android since this workaround
// seems to be needed only for specific Linux-based products that aren't based
// on Android. See https://github.com/rust-random/getrandom/issues/229.
#[cfg(target_os = "linux")]
Some(libc::EPERM) => false, // Blocked by seccomp
_ => true,
}
} else {
true
}
}
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