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1void __init_cpu_features_resolver(unsigned long hwcap,2 const __ifunc_arg_t *arg) {3 if (__atomic_load_n(&__aarch64_cpu_features.features, __ATOMIC_RELAXED))4 return;5 6 // ifunc resolvers don't have hwcaps in arguments on Android API lower7 // than 30. If so, set feature detection done and keep all CPU features8 // unsupported (zeros). To detect this case in runtime we check existence9 // of memfd_create function from Standard C library which was introduced in10 // Android API 30.11 int memfd_create(const char *, unsigned int) __attribute__((weak));12 if (!memfd_create)13 return;14 15 __init_cpu_features_constructor(hwcap, arg);16}17 18void CONSTRUCTOR_ATTRIBUTE __init_cpu_features(void) {19 // CPU features already initialized.20 if (__atomic_load_n(&__aarch64_cpu_features.features, __ATOMIC_RELAXED))21 return;22 23 // Don't set any CPU features,24 // detection could be wrong on Exynos 9810.25 if (__isExynos9810())26 return;27 28 unsigned long hwcap = getauxval(AT_HWCAP);29 unsigned long hwcap2 = getauxval(AT_HWCAP2);30 unsigned long hwcap3 = getauxval(AT_HWCAP3);31 unsigned long hwcap4 = getauxval(AT_HWCAP4);32 33 __ifunc_arg_t arg;34 arg._size = sizeof(__ifunc_arg_t);35 arg._hwcap = hwcap;36 arg._hwcap2 = hwcap2;37 arg._hwcap3 = hwcap3;38 arg._hwcap4 = hwcap4;39 __init_cpu_features_constructor(hwcap | _IFUNC_ARG_HWCAP, &arg);40}41