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std_detect: Workaround Exynos 9810 bug on aarch64 Android

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Samsung Exynos 9810 has a bug that big and little cores have different
ISAs. And on older Android (pre-9), the kernel incorrectly reports
that features available only on some cores are available on all cores.

https://reviews.llvm.org/D114523
This commit is contained in:
Taiki Endo 2023-02-12 13:57:57 +09:00 • committed by Amanieu d'Antras
parent dc49234574
commit e9d18c6b18
1 changed files with 19 additions and 0 deletions
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19
library/stdarch/crates/std_detect/src/detect/os/linux/aarch64.rs
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@ -6,6 +6,25 @@ 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 {
#[cfg(all(target_arch = "aarch64", target_os = "android"))]
{
// Samsung Exynos 9810 has a bug that big and little cores have different
// ISAs. And on older Android (pre-9), the kernel incorrectly reports
// that features available only on some cores are available on all cores.
// https://reviews.llvm.org/D114523
let mut arch = [0_u8; libc::PROP_VALUE_MAX as usize];
let len = unsafe {
libc::__system_property_get(
b"ro.arch\0".as_ptr() as *const libc::c_char,
arch.as_mut_ptr() as *mut libc::c_char,
)
};
// On Exynos, ro.arch is not available on Android 12+, but it is fine
// because Android 9+ includes the fix.
if len > 0 && arch.starts_with(b"exynos9810") {
return cache::Initializer::default();
}
}
if let Ok(auxv) = auxvec::auxv() {
let hwcap: AtHwcap = auxv.into();
return hwcap.cache();