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Init RNG with rdrand directly (without getrandom)

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Qingsong Chen
2024-07-02 02:12:06 +00:00
committed by Tate, Hongliang Tian
parent 9932ea0797
commit 98619f3482
4 changed files with 39 additions and 9 deletions
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24
ostd/src/arch/x86/mod.rs
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@ -19,7 +19,10 @@ pub(crate) mod tdx_guest;
pub mod timer;
pub mod trap;
use core::{arch::x86_64::_rdtsc, sync::atomic::Ordering};
use core::{
arch::x86_64::{_rdrand64_step, _rdtsc},
sync::atomic::Ordering,
};
#[cfg(feature = "intel_tdx")]
use ::tdx_guest::tdx_is_enabled;
@ -79,6 +82,25 @@ pub fn read_tsc() -> u64 {
unsafe { _rdtsc() }
}
/// Reads a hardware generated 64-bit random value.
///
/// Returns None if no random value was generated.
pub fn read_random() -> Option<u64> {
// Recommendation from "Intel® Digital Random Number Generator (DRNG) Software
// Implementation Guide" - Section 5.2.1 and "Intel® 64 and IA-32 Architectures
// Software Developer’s Manual" - Volume 1 - Section 7.3.17.1.
const RETRY_LIMIT: usize = 10;
for _ in 0..RETRY_LIMIT {
let mut val = 0;
let generated = unsafe { _rdrand64_step(&mut val) };
if generated == 1 {
return Some(val);
}
}
None
}
fn enable_common_cpu_features() {
use x86_64::registers::{control::Cr4Flags, model_specific::EferFlags, xcontrol::XCr0Flags};
let mut cr4 = x86_64::registers::control::Cr4::read();