cpufeatures: map aarch64 HWCAPs to target features; add crypto

Closes #395

The HWCAPs provided by Linux are finer-grained than LLVM target
features. This crate is trying to detect the latter, so we need to group
together these finer grained features detected via HWCAPs.

This commit attempts to group together finer grained HWCAPs into coarser
grained target features, ensuring all of the relevant HWCAPs for a given
target feature are available.

Additionally, this adds support for the `crypto` target feature, which
implies `aes` (and with it PMULL), along with `sha2` and `neon`
(although the latter is always present on `aarch64`)

cpufeatures/Cargo.toml

@@ -15,7 +15,7 @@ edition = "2018"
 readme = "README.md"
 
 [target.aarch64-apple-darwin.dependencies]
-libc = "0.2"
+libc = "0.2.95"
 
 [target.'cfg(all(target_arch = "aarch64", target_os = "linux"))'.dependencies]
-libc = "0.2"
+libc = "0.2.95"

cpufeatures/src/aarch64.rs

@@ -66,21 +66,27 @@ macro_rules! __expand_check_macro {
 // Linux `expand_check_macro`
 #[cfg(target_os = "linux")]
 __expand_check_macro! {
-    ("aes",  HWCAP_AES),  // Enable AES support.
-    ("sha2", HWCAP_SHA2), // Enable SHA1 and SHA256 support.
-    ("sha3", HWCAP_SHA3), // Enable SHA512 and SHA3 support.
+    ("aes",    AES),    // Enable AES support.
+    ("crypto", CRYPTO), // Enable cryptographic instructions.
+    ("sha2",   SHA2),   // Enable SHA1 and SHA256 support.
+    ("sha3",   SHA3),   // Enable SHA512 and SHA3 support.
 }
 
-/// Linux hardware capabilities
+/// Linux hardware capabilities mapped to target features.
 ///
-/// Workaround for these being missing from certain environments (i.e. Musl)
-/// See: <https://github.com/rust-lang/libc/issues/2171>
+/// Note that LLVM target features are coarser grained than what Linux supports
+/// and imply more capabilities under each feature. This module attempts to
+/// provide that mapping accordingly.
+///
+/// See this issue for more info: <https://github.com/RustCrypto/utils/issues/395>
 #[cfg(target_os = "linux")]
 pub mod hwcaps {
-    pub const HWCAP_AES: libc::c_ulong = 1 << 3;
-    pub const HWCAP_NEON: libc::c_ulong = 1 << 12;
-    pub const HWCAP_SHA2: libc::c_ulong = 1 << 6;
-    pub const HWCAP_SHA3: libc::c_ulong = 1 << 17;
+    use libc::c_ulong;
+
+    pub const AES: c_ulong = libc::HWCAP_AES | libc::HWCAP_PMULL;
+    pub const CRYPTO: c_ulong = AES | SHA2;
+    pub const SHA2: c_ulong = libc::HWCAP_SHA2;
+    pub const SHA3: c_ulong = libc::HWCAP_SHA3 | libc::HWCAP_SHA512;
 }
 
 // macOS `check!` macro.
@@ -101,11 +107,18 @@ macro_rules! check {
     ("aes") => {
         true
     };
+    ("crypto") => {
+        true
+    };
     ("sha2") => {
         true
     };
     ("sha3") => {
-        unsafe { $crate::aarch64::sysctlbyname(b"hw.optional.armv8_2_sha3\0") }
+        unsafe {
+            // `sha3` target feature implies SHA-512 as well
+            $crate::aarch64::sysctlbyname(b"hw.optional.armv8_2_sha512\0")
+                && $crate::aarch64::sysctlbyname(b"hw.optional.armv8_2_sha3\0")
+        }
     };
 }