1 files changed, 79 insertions, 0 deletions
diff --git a/library/stdarch/crates/std_detect/src/detect/os/linux/arm.rs b/library/stdarch/crates/std_detect/src/detect/os/linux/arm.rs
new file mode 100644
index 000000000..7383e487f
--- /dev/null
+++ b/library/stdarch/crates/std_detect/src/detect/os/linux/arm.rs
@@ -0,0 +1,79 @@
+//! Run-time feature detection for ARM on Linux.
+
+use super::auxvec;
+use crate::detect::{bit, cache, Feature};
+
+/// Try to read the features from the auxiliary vector, and if that fails, try
+/// to read them from /proc/cpuinfo.
+pub(crate) fn detect_features() -> cache::Initializer {
+    let mut value = cache::Initializer::default();
+    let enable_feature = |value: &mut cache::Initializer, f, enable| {
+        if enable {
+            value.set(f as u32);
+        }
+    };
+
+    // The values are part of the platform-specific [asm/hwcap.h][hwcap]
+    //
+    // [hwcap]: https://github.com/torvalds/linux/blob/master/arch/arm/include/uapi/asm/hwcap.h
+    if let Ok(auxv) = auxvec::auxv() {
+        enable_feature(&mut value, Feature::neon, bit::test(auxv.hwcap, 12));
+        enable_feature(&mut value, Feature::pmull, bit::test(auxv.hwcap2, 1));
+        enable_feature(&mut value, Feature::crc, bit::test(auxv.hwcap2, 4));
+        enable_feature(
+            &mut value,
+            Feature::crypto,
+            bit::test(auxv.hwcap2, 0)
+                && bit::test(auxv.hwcap2, 1)
+                && bit::test(auxv.hwcap2, 2)
+                && bit::test(auxv.hwcap2, 3),
+        );
+        enable_feature(&mut value, Feature::aes, bit::test(auxv.hwcap2, 0));
+        // SHA2 requires SHA1 & SHA2 features
+        enable_feature(
+            &mut value,
+            Feature::sha2,
+            bit::test(auxv.hwcap2, 2) && bit::test(auxv.hwcap2, 3),
+        );
+        return value;
+    }
+
+    #[cfg(feature = "std_detect_file_io")]
+    if let Ok(c) = super::cpuinfo::CpuInfo::new() {
+        enable_feature(
+            &mut value,
+            Feature::neon,
+            c.field("Features").has("neon") && !has_broken_neon(&c),
+        );
+        enable_feature(&mut value, Feature::pmull, c.field("Features").has("pmull"));
+        enable_feature(&mut value, Feature::crc, c.field("Features").has("crc32"));
+        enable_feature(
+            &mut value,
+            Feature::crypto,
+            c.field("Features").has("aes")
+                && c.field("Features").has("pmull")
+                && c.field("Features").has("sha1")
+                && c.field("Features").has("sha2"),
+        );
+        enable_feature(&mut value, Feature::aes, c.field("Features").has("aes"));
+        enable_feature(
+            &mut value,
+            Feature::sha2,
+            c.field("Features").has("sha1") && c.field("Features").has("sha2"),
+        );
+        return value;
+    }
+    value
+}
+
+/// Is the CPU known to have a broken NEON unit?
+///
+/// See https://crbug.com/341598.
+#[cfg(feature = "std_detect_file_io")]
+fn has_broken_neon(cpuinfo: &super::cpuinfo::CpuInfo) -> bool {
+    cpuinfo.field("CPU implementer") == "0x51"
+        && cpuinfo.field("CPU architecture") == "7"
+        && cpuinfo.field("CPU variant") == "0x1"
+        && cpuinfo.field("CPU part") == "0x04d"
+        && cpuinfo.field("CPU revision") == "0"
+}