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#include <errno.h>
#include <stdint.h>
#include <sys/auxv.h>
#include <bits/ensure.h>
extern "C" uintptr_t *__dlapi_entrystack();
int peekauxval(unsigned long type, unsigned long *out) {
// Find the auxiliary vector by skipping args and environment.
auto aux = __dlapi_entrystack();
aux += *aux + 1; // Skip argc and all arguments
__ensure(!*aux);
aux++;
while(*aux) // Now, we skip the environment.
aux++;
aux++;
// Parse the auxiliary vector.
while(true) {
auto value = aux + 1;
if(*aux == AT_NULL) {
errno = ENOENT;
return -1;
}else if(*aux == type) {
*out = *value;
return 0;
}
aux += 2;
}
}
unsigned long getauxval(unsigned long type) {
unsigned long value = 0;
if(peekauxval(type, &value))
return 0;
return value;
}
// XXX(qookie):
// This is here because libgcc will call into __getauxval on glibc Linux
// (which is what it believes we are due to the aarch64-linux-gnu toolchain)
// in order to find AT_HWCAP to discover if LSE atomics are supported.
//
// This is not necessary on a custom Linux toolchain and is purely an artifact of
// using the host toolchain.
// __gnu_linux__ is the define checked by libgcc
#if defined(__aarch64__) && defined(__gnu_linux__)
extern "C" unsigned long __getauxval(unsigned long type) {
unsigned long value = 0;
if(peekauxval(type, &value))
return 0;
return value;
}
#endif
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