fusl/src/thread/arm/__set_thread_area.c

#include <stdint.h>
#include <elf.h>
#include "pthread_impl.h"
#include "libc.h"

#define HWCAP_TLS (1 << 15)

extern const unsigned char __attribute__((__visibility__("hidden")))
__a_barrier_dummy[],
    __a_barrier_oldkuser[], __a_barrier_v6[], __a_barrier_v7[], __a_cas_dummy[],
    __a_cas_v6[], __a_cas_v7[], __a_gettp_dummy[];

#define __a_barrier_kuser 0xffff0fa0
#define __a_cas_kuser 0xffff0fc0
#define __a_gettp_kuser 0xffff0fe0

extern uintptr_t __attribute__((__visibility__("hidden"))) __a_barrier_ptr,
    __a_cas_ptr, __a_gettp_ptr;

#define SET(op, ver) \
  (__a_##op##_ptr = (uintptr_t)__a_##op##_##ver - (uintptr_t)__a_##op##_dummy)

int __set_thread_area(void* p) {
#if !__ARM_ARCH_7A__ && !__ARM_ARCH_7R__ && __ARM_ARCH < 7
  if (__hwcap & HWCAP_TLS) {
    size_t* aux;
    SET(cas, v7);
    SET(barrier, v7);
    for (aux = libc.auxv; *aux; aux += 2) {
      if (*aux != AT_PLATFORM)
        continue;
      const char* s = (void*)aux[1];
      if (s[0] != 'v' || s[1] != '6' || s[2] - '0' < 10u)
        break;
      SET(cas, v6);
      SET(barrier, v6);
      break;
    }
  } else {
    int ver = *(int*)0xffff0ffc;
    SET(gettp, kuser);
    SET(cas, kuser);
    SET(barrier, kuser);
    if (ver < 2)
      a_crash();
    if (ver < 3)
      SET(barrier, oldkuser);
  }
#endif
  return __syscall(0xf0005, p);
}