fusl/src/env/__init_tls.c

#include <elf.h>
#include <limits.h>
#include <sys/mman.h>
#include <string.h>
#include <stddef.h>
#include "pthread_impl.h"
#include "libc.h"
#include "atomic.h"
#include "syscall.h"

int __init_tp(void* p) {
  pthread_t td = p;
  td->self = td;
  int r = __set_thread_area(TP_ADJ(p));
  if (r < 0)
    return -1;
  if (!r)
    libc.can_do_threads = 1;
  td->tid = __syscall(SYS_set_tid_address, &td->tid);
  td->locale = &libc.global_locale;
  td->robust_list.head = &td->robust_list.head;
  return 0;
}

static struct builtin_tls {
  char c;
  struct pthread pt;
  void* space[16];
} builtin_tls[1];
#define MIN_TLS_ALIGN offsetof(struct builtin_tls, pt)

static struct tls_module main_tls;

void* __copy_tls(unsigned char* mem) {
  pthread_t td;
  struct tls_module* p;
  size_t i;
  void** dtv;

#ifdef TLS_ABOVE_TP
  dtv = (void**)(mem + libc.tls_size) - (libc.tls_cnt + 1);

  mem += -((uintptr_t)mem + sizeof(struct pthread)) & (libc.tls_align - 1);
  td = (pthread_t)mem;
  mem += sizeof(struct pthread);

  for (i = 1, p = libc.tls_head; p; i++, p = p->next) {
    dtv[i] = mem + p->offset;
    memcpy(dtv[i], p->image, p->len);
  }
#else
  dtv = (void**)mem;

  mem += libc.tls_size - sizeof(struct pthread);
  mem -= (uintptr_t)mem & (libc.tls_align - 1);
  td = (pthread_t)mem;

  for (i = 1, p = libc.tls_head; p; i++, p = p->next) {
    dtv[i] = mem - p->offset;
    memcpy(dtv[i], p->image, p->len);
  }
#endif
  dtv[0] = (void*)libc.tls_cnt;
  td->dtv = td->dtv_copy = dtv;
  return td;
}

#if ULONG_MAX == 0xffffffff
typedef Elf32_Phdr Phdr;
#else
typedef Elf64_Phdr Phdr;
#endif

static void static_init_tls(size_t* aux) {
  unsigned char* p;
  size_t n;
  Phdr *phdr, *tls_phdr = 0;
  size_t base = 0;
  void* mem;

  for (p = (void*)aux[AT_PHDR], n = aux[AT_PHNUM]; n; n--, p += aux[AT_PHENT]) {
    phdr = (void*)p;
    if (phdr->p_type == PT_PHDR)
      base = aux[AT_PHDR] - phdr->p_vaddr;
    if (phdr->p_type == PT_TLS)
      tls_phdr = phdr;
  }

  if (tls_phdr) {
    main_tls.image = (void*)(base + tls_phdr->p_vaddr);
    main_tls.len = tls_phdr->p_filesz;
    main_tls.size = tls_phdr->p_memsz;
    main_tls.align = tls_phdr->p_align;
    libc.tls_cnt = 1;
    libc.tls_head = &main_tls;
  }

  main_tls.size +=
      (-main_tls.size - (uintptr_t)main_tls.image) & (main_tls.align - 1);
  if (main_tls.align < MIN_TLS_ALIGN)
    main_tls.align = MIN_TLS_ALIGN;
#ifndef TLS_ABOVE_TP
  main_tls.offset = main_tls.size;
#endif

  libc.tls_align = main_tls.align;
  libc.tls_size = 2 * sizeof(void*) + sizeof(struct pthread) + main_tls.size +
                      main_tls.align + MIN_TLS_ALIGN - 1 &
                  -MIN_TLS_ALIGN;

  if (libc.tls_size > sizeof builtin_tls) {
#ifndef SYS_mmap2
#define SYS_mmap2 SYS_mmap
#endif
    mem = (void*)__syscall(SYS_mmap2, 0, libc.tls_size, PROT_READ | PROT_WRITE,
                           MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
    /* -4095...-1 cast to void * will crash on dereference anyway,
     * so don't bloat the init code checking for error codes and
     * explicitly calling a_crash(). */
  } else {
    mem = builtin_tls;
  }

  /* Failure to initialize thread pointer is always fatal. */
  if (__init_tp(__copy_tls(mem)) < 0)
    a_crash();
}

weak_alias(static_init_tls, __init_tls);