fusl/src/thread/pthread_getattr_np.c

#define _GNU_SOURCE
#include "pthread_impl.h"
#include "libc.h"
#include <sys/mman.h>

int pthread_getattr_np(pthread_t t, pthread_attr_t* a) {
  *a = (pthread_attr_t){0};
  a->_a_detach = !!t->detached;
  if (t->stack) {
    a->_a_stackaddr = (uintptr_t)t->stack;
    a->_a_stacksize = t->stack_size - DEFAULT_STACK_SIZE;
  } else {
    char* p = (void*)libc.auxv;
    size_t l = PAGE_SIZE;
    p += -(uintptr_t)p & PAGE_SIZE - 1;
    a->_a_stackaddr = (uintptr_t)p;
    while (mremap(p - l - PAGE_SIZE, PAGE_SIZE, 2 * PAGE_SIZE, 0) ==
               MAP_FAILED &&
           errno == ENOMEM)
      l += PAGE_SIZE;
    a->_a_stacksize = l - DEFAULT_STACK_SIZE;
  }
  return 0;
}