1void __init_cpu_features_resolver(unsigned long hwcap,
2                                  const __ifunc_arg_t *arg) {
3  if (__aarch64_cpu_features.features)
4    return;
5
6  // ifunc resolvers don't have hwcaps in arguments on Android API lower
7  // than 30. If so, set feature detection done and keep all CPU features
8  // unsupported (zeros). To detect this case in runtime we check existence
9  // of memfd_create function from Standard C library which was introduced in
10  // 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 (__aarch64_cpu_features.features)
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
31  __ifunc_arg_t arg;
32  arg._size = sizeof(__ifunc_arg_t);
33  arg._hwcap = hwcap;
34  arg._hwcap2 = hwcap2;
35  __init_cpu_features_constructor(hwcap | _IFUNC_ARG_HWCAP, &arg);
36}
37