From 95ed43d7eeaa525d10ac97293ad6877c96c73788 Mon Sep 17 00:00:00 2001
From: Tony Arcieri <bascule@gmail.com>
Date: Wed, 26 May 2021 13:52:46 -0700
Subject: [PATCH] cpufeatures: add iOS support (static ARM64 capabilities only)

All Apple ARM64 hardware has the same baseline set of statically known
capabilities which can be assumed on all iOS (and macOS) platforms.

This commit adds support for those statically known capabilities on iOS.

Unfortunately it does not appear to be possible to access the
`sysctl(3)` namespace on iOS in order to determine the availability of
other CPU features which aren't part of this baseline set the same way
we can on macOS, so a static capability set is the best we can do.

See this issue for more information:

https://github.com/RustCrypto/utils/issues/378
---
 cpufeatures/src/aarch64.rs | 25 ++++++++++++++++++++++++-
 1 file changed, 24 insertions(+), 1 deletion(-)

diff --git a/cpufeatures/src/aarch64.rs b/cpufeatures/src/aarch64.rs
index 935d462b..e3489464 100644
--- a/cpufeatures/src/aarch64.rs
+++ b/cpufeatures/src/aarch64.rs
@@ -135,8 +135,31 @@ pub unsafe fn sysctlbyname(name: &[u8]) -> bool {
     value != 0
 }
 
+// iOS `check!` macro.
+//
+// Unfortunately iOS does not provide access to the `sysctl(3)` API which means
+// we can only return static values for CPU features which  can be assumed to
+// be present on all Apple ARM64 hardware.
+//
+// See discussion on this issue for more information:
+// <https://github.com/RustCrypto/utils/issues/378>
+#[cfg(target_os = "ios")]
+#[macro_export]
+#[doc(hidden)]
+macro_rules! check {
+    ("aes") => {
+        true
+    };
+    ("sha2") => {
+        true
+    };
+    ("sha3") => {
+        false
+    };
+}
+
 // On other targets, runtime CPU feature detection is unavailable
-#[cfg(not(any(target_os = "linux", target_os = "macos")))]
+#[cfg(not(any(target_os = "ios", target_os = "linux", target_os = "macos")))]
 #[macro_export]
 #[doc(hidden)]
 macro_rules! __detect_target_features {