ring/cpu/arm.rs
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// Copyright 2016-2021 Brian Smith.
//
// Permission to use, copy, modify, and/or distribute this software for any
// purpose with or without fee is hereby granted, provided that the above
// copyright notice and this permission notice appear in all copies.
//
// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHORS DISCLAIM ALL WARRANTIES
// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY
// SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
// OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
// CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
#![cfg_attr(
not(any(target_arch = "aarch64", target_arch = "arm")),
allow(dead_code)
)]
#[cfg(all(
any(target_os = "android", target_os = "linux"),
any(target_arch = "aarch64", target_arch = "arm")
))]
fn detect_features() -> u32 {
use libc::c_ulong;
// XXX: The `libc` crate doesn't provide `libc::getauxval` consistently
// across all Android/Linux targets, e.g. musl.
extern "C" {
fn getauxval(type_: c_ulong) -> c_ulong;
}
const AT_HWCAP: c_ulong = 16;
#[cfg(target_arch = "aarch64")]
const HWCAP_NEON: c_ulong = 1 << 1;
#[cfg(target_arch = "arm")]
const HWCAP_NEON: c_ulong = 1 << 12;
let caps = unsafe { getauxval(AT_HWCAP) };
// We assume NEON is available on AARCH64 because it is a required
// feature.
#[cfg(target_arch = "aarch64")]
debug_assert!(caps & HWCAP_NEON == HWCAP_NEON);
let mut features = 0;
// OpenSSL and BoringSSL don't enable any other features if NEON isn't
// available.
if caps & HWCAP_NEON == HWCAP_NEON {
features = NEON.mask;
#[cfg(target_arch = "aarch64")]
const OFFSET: c_ulong = 3;
#[cfg(target_arch = "arm")]
const OFFSET: c_ulong = 0;
#[cfg(target_arch = "arm")]
let caps = {
const AT_HWCAP2: c_ulong = 26;
unsafe { getauxval(AT_HWCAP2) }
};
const HWCAP_AES: c_ulong = 1 << 0 + OFFSET;
const HWCAP_PMULL: c_ulong = 1 << 1 + OFFSET;
const HWCAP_SHA2: c_ulong = 1 << 3 + OFFSET;
if caps & HWCAP_AES == HWCAP_AES {
features |= AES.mask;
}
if caps & HWCAP_PMULL == HWCAP_PMULL {
features |= PMULL.mask;
}
if caps & HWCAP_SHA2 == HWCAP_SHA2 {
features |= SHA256.mask;
}
}
features
}
#[cfg(all(target_os = "fuchsia", target_arch = "aarch64"))]
fn detect_features() -> u32 {
type zx_status_t = i32;
#[link(name = "zircon")]
extern "C" {
fn zx_system_get_features(kind: u32, features: *mut u32) -> zx_status_t;
}
const ZX_OK: i32 = 0;
const ZX_FEATURE_KIND_CPU: u32 = 0;
const ZX_ARM64_FEATURE_ISA_ASIMD: u32 = 1 << 2;
const ZX_ARM64_FEATURE_ISA_AES: u32 = 1 << 3;
const ZX_ARM64_FEATURE_ISA_PMULL: u32 = 1 << 4;
const ZX_ARM64_FEATURE_ISA_SHA2: u32 = 1 << 6;
let mut caps = 0;
let rc = unsafe { zx_system_get_features(ZX_FEATURE_KIND_CPU, &mut caps) };
let mut features = 0;
// OpenSSL and BoringSSL don't enable any other features if NEON isn't
// available.
if rc == ZX_OK && (caps & ZX_ARM64_FEATURE_ISA_ASIMD == ZX_ARM64_FEATURE_ISA_ASIMD) {
features = NEON.mask;
if caps & ZX_ARM64_FEATURE_ISA_AES == ZX_ARM64_FEATURE_ISA_AES {
features |= AES.mask;
}
if caps & ZX_ARM64_FEATURE_ISA_PMULL == ZX_ARM64_FEATURE_ISA_PMULL {
features |= PMULL.mask;
}
if caps & ZX_ARM64_FEATURE_ISA_SHA2 == ZX_ARM64_FEATURE_ISA_SHA2 {
features |= 1 << 4;
}
}
features
}
#[cfg(all(target_os = "windows", target_arch = "aarch64"))]
fn detect_features() -> u32 {
// We do not need to check for the presence of NEON, as Armv8-A always has it
const _ASSERT_NEON_DETECTED: () = assert!((ARMCAP_STATIC & NEON.mask) == NEON.mask);
let mut features = ARMCAP_STATIC;
let result = unsafe {
windows_sys::Win32::System::Threading::IsProcessorFeaturePresent(
windows_sys::Win32::System::Threading::PF_ARM_V8_CRYPTO_INSTRUCTIONS_AVAILABLE,
)
};
if result != 0 {
// These are all covered by one call in Windows
features |= AES.mask;
features |= PMULL.mask;
features |= SHA256.mask;
}
features
}
macro_rules! features {
{
$(
$target_feature_name:expr => $name:ident {
mask: $mask:expr,
}
),+
, // trailing comma is required.
} => {
$(
#[allow(dead_code)]
pub(crate) const $name: Feature = Feature {
mask: $mask,
};
)+
const ARMCAP_STATIC: u32 = 0
$(
| (
if cfg!(all(any(target_arch = "aarch64", target_arch = "arm"),
target_feature = $target_feature_name)) {
$name.mask
} else {
0
}
)
)+;
#[cfg(all(test, any(target_arch = "arm", target_arch = "aarch64")))]
const ALL_FEATURES: [Feature; 4] = [
$(
$name
),+
];
}
}
pub(crate) struct Feature {
mask: u32,
}
impl Feature {
#[inline(always)]
pub fn available(&self, _: super::Features) -> bool {
if self.mask == self.mask & ARMCAP_STATIC {
return true;
}
#[cfg(all(
any(
target_os = "android",
target_os = "fuchsia",
target_os = "linux",
target_os = "windows"
),
any(target_arch = "arm", target_arch = "aarch64")
))]
{
// SAFETY: See `OPENSSL_armcap_P`'s safety documentation.
if self.mask == self.mask & unsafe { OPENSSL_armcap_P } {
return true;
}
}
false
}
}
// Assumes all target feature names are the same for ARM and AAarch64.
features! {
// Keep in sync with `ARMV7_NEON`.
"neon" => NEON {
mask: 1 << 0,
},
// Keep in sync with `ARMV8_AES`.
"aes" => AES {
mask: 1 << 2,
},
// Keep in sync with `ARMV8_SHA256`.
"sha2" => SHA256 {
mask: 1 << 4,
},
// Keep in sync with `ARMV8_PMULL`.
//
// TODO(MSRV): There is no "pmull" feature listed from
// `rustc --print cfg --target=aarch64-apple-darwin`. Originally ARMv8 tied
// PMULL detection into AES detection, but later versions split it; see
// https://developer.arm.com/downloads/-/exploration-tools/feature-names-for-a-profile
// "Features introduced prior to 2020." Change this to use "pmull" when
// that is supported.
"aes" => PMULL {
mask: 1 << 5,
},
}
// SAFETY:
// - This may only be called from within `cpu::features()` and only while it is initializing its
// `INIT`.
// - See the safety invariants of `OPENSSL_armcap_P` below.
#[cfg(all(
any(target_arch = "aarch64", target_arch = "arm"),
any(
target_os = "android",
target_os = "fuchsia",
target_os = "linux",
target_os = "windows"
)
))]
pub unsafe fn initialize_OPENSSL_armcap_P() {
let detected = detect_features();
let filtered = (if cfg!(feature = "unstable-testing-arm-no-hw") {
AES.mask | SHA256.mask | PMULL.mask
} else {
0
}) | (if cfg!(feature = "unstable-testing-arm-no-neon") {
NEON.mask
} else {
0
});
let detected = detected & !filtered;
OPENSSL_armcap_P = ARMCAP_STATIC | detected;
}
// Some non-Rust code still checks this even when it is statically known
// the given feature is available, so we have to ensure that this is
// initialized properly. Keep this in sync with the initialization in
// BoringSSL's crypto.c.
//
// TODO: This should have "hidden" visibility but we don't have a way of
// controlling that yet: https://github.com/rust-lang/rust/issues/73958.
//
// SAFETY:
// - Rust code only accesses this through `cpu::Features`, which acts as a witness that
// `cpu::features()` was called to initialize this.
// - Some assembly language functions access `OPENSSL_armcap_P` directly. Callers of those functions
// must obtain a `cpu::Features` before calling them.
// - An instance of `cpu::Features` is a witness that this was initialized.
// - The initialization of the `INIT` in `cpu::features()` initializes this, and that `OnceCell`
// implements acquire/release semantics that allow all the otherwise-apparently-unsynchronized
// access.
// - `OPENSSL_armcap_P` must always be a superset of `ARMCAP_STATIC`.
// TODO: Remove all the direct accesses of this from assembly language code, and then replace this
// with a `OnceCell<u32>` that will provide all the necessary safety guarantees.
#[cfg(any(target_arch = "arm", target_arch = "aarch64"))]
prefixed_export! {
#[allow(non_upper_case_globals)]
static mut OPENSSL_armcap_P: u32 = ARMCAP_STATIC;
}
// MSRV: Enforce 1.61.0 on some aarch64-* targets (aarch64-apple-*, in particular) prior to. Earlier
// versions of Rust before did not report the AAarch64 CPU features correctly for these targets.
// Cargo.toml specifies `rust-version` but versions before Rust 1.56 don't know about it.
//
// ```
// $ rustc +1.61.0 --print cfg --target=aarch64-apple-ios | grep -E "neon|aes|sha|pmull"
// target_feature="aes"
// target_feature="neon"
// target_feature="sha2"
// $ rustc +1.61.0 --print cfg --target=aarch64-apple-darwin | grep -E "neon|aes|sha|pmull"
// target_feature="aes"
// target_feature="neon"
// target_feature="sha2"
// target_feature="sha3"
// ```
#[allow(clippy::assertions_on_constants)]
const _AARCH64_HAS_NEON: () =
assert!(((ARMCAP_STATIC & NEON.mask) == NEON.mask) || !cfg!(target_arch = "aarch64"));
#[allow(clippy::assertions_on_constants)]
const _AARCH64_APPLE_FEATURES: u32 = NEON.mask | AES.mask | SHA256.mask | PMULL.mask;
#[allow(clippy::assertions_on_constants)]
const _AARCH64_APPLE_TARGETS_EXPECTED_FEATURES: () = assert!(
((ARMCAP_STATIC & _AARCH64_APPLE_FEATURES) == _AARCH64_APPLE_FEATURES)
|| !cfg!(all(target_arch = "aarch64", target_vendor = "apple"))
);
#[cfg(all(test, any(target_arch = "arm", target_arch = "aarch64")))]
mod tests {
use super::*;
#[test]
fn test_mask_abi() {
assert_eq!(NEON.mask, 1);
assert_eq!(AES.mask, 4);
assert_eq!(SHA256.mask, 16);
assert_eq!(PMULL.mask, 32);
}
#[test]
fn test_armcap_static_is_subset_of_armcap_dynamic() {
// Ensure `OPENSSL_armcap_P` is initialized.
let cpu = crate::cpu::features();
let armcap_dynamic = unsafe { OPENSSL_armcap_P };
assert_eq!(armcap_dynamic & ARMCAP_STATIC, ARMCAP_STATIC);
ALL_FEATURES.iter().for_each(|feature| {
if (ARMCAP_STATIC & feature.mask) != 0 {
assert!(feature.available(cpu));
}
})
}
}