/* Copyright (c) 2015, Google Inc.
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
 * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
 * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
 * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */

#include "internal.h"

#if defined(OPENSSL_WINDOWS)

#pragma warning(push, 3)
#include <windows.h>
#pragma warning(pop)

#include <assert.h>
#include <string.h>

#include <openssl/mem.h>


void CRYPTO_once(CRYPTO_once_t *in_once, void (*init)(void)) {
  volatile LONG *once = (LONG*) in_once;

  assert(sizeof(LONG) == sizeof(CRYPTO_once_t));
  /* Values must be aligned. */
  assert((((uintptr_t) once) & 3) == 0);

  /* This assumes that reading *once has acquire semantics. This should be true
   * on x86 and x86-64, where we expect Windows to run. */
#if !defined(OPENSSL_X86) && !defined(OPENSSL_X86_64)
#error "Windows once code may not work on other platforms." \
       "You can use InitOnceBeginInitialize on >=Vista"
#endif
  if (*once == 1) {
    return;
  }

  for (;;) {
    switch (InterlockedCompareExchange(once, 2, 0)) {
      case 0:
        /* The value was zero so we are the first thread to call |CRYPTO_once|
         * on it. */
        init();
        /* Write one to indicate that initialisation is complete. */
        InterlockedExchange(once, 1);
        return;

      case 1:
        /* Another thread completed initialisation between our fast-path check
         * and |InterlockedCompareExchange|. */
        return;

      case 2:
        /* Another thread is running the initialisation. Switch to it then try
         * again. */
        SwitchToThread();
        break;

      default:
        abort();
    }
  }
}

static CRITICAL_SECTION g_destructors_lock;
static thread_local_destructor_t g_destructors[NUM_OPENSSL_THREAD_LOCALS];

static CRYPTO_once_t g_thread_local_init_once = CRYPTO_ONCE_INIT;
static DWORD g_thread_local_key;
static int g_thread_local_failed;

static void thread_local_init(void) {
  if (!InitializeCriticalSectionAndSpinCount(&g_destructors_lock, 0x400)) {
    g_thread_local_failed = 1;
    return;
  }
  g_thread_local_key = TlsAlloc();
  g_thread_local_failed = (g_thread_local_key == TLS_OUT_OF_INDEXES);
}

static void NTAPI thread_local_destructor(PVOID module,
                                          DWORD reason, PVOID reserved) {
  if (DLL_THREAD_DETACH != reason && DLL_PROCESS_DETACH != reason) {
    return;
  }

  CRYPTO_once(&g_thread_local_init_once, thread_local_init);
  if (g_thread_local_failed) {
    return;
  }

  void **pointers = (void**) TlsGetValue(g_thread_local_key);
  if (pointers == NULL) {
    return;
  }

  thread_local_destructor_t destructors[NUM_OPENSSL_THREAD_LOCALS];

  EnterCriticalSection(&g_destructors_lock);
  memcpy(destructors, g_destructors, sizeof(destructors));
  LeaveCriticalSection(&g_destructors_lock);

  unsigned i;
  for (i = 0; i < NUM_OPENSSL_THREAD_LOCALS; i++) {
    if (destructors[i] != NULL) {
      destructors[i](pointers[i]);
    }
  }

  OPENSSL_free(pointers);
}

/* Thread Termination Callbacks.
 *
 * Windows doesn't support a per-thread destructor with its TLS primitives.
 * So, we build it manually by inserting a function to be called on each
 * thread's exit. This magic is from http://www.codeproject.com/threads/tls.asp
 * and it works for VC++ 7.0 and later.
 *
 * Force a reference to _tls_used to make the linker create the TLS directory
 * if it's not already there. (E.g. if __declspec(thread) is not used). Force
 * a reference to p_thread_callback_boringssl to prevent whole program
 * optimization from discarding the variable. */
#ifdef _WIN64
#pragma comment(linker, "/INCLUDE:_tls_used")
#pragma comment(linker, "/INCLUDE:p_thread_callback_boringssl")
#else
#pragma comment(linker, "/INCLUDE:__tls_used")
#pragma comment(linker, "/INCLUDE:_p_thread_callback_boringssl")
#endif

/* .CRT$XLA to .CRT$XLZ is an array of PIMAGE_TLS_CALLBACK pointers that are
 * called automatically by the OS loader code (not the CRT) when the module is
 * loaded and on thread creation. They are NOT called if the module has been
 * loaded by a LoadLibrary() call. It must have implicitly been loaded at
 * process startup.
 *
 * By implicitly loaded, I mean that it is directly referenced by the main EXE
 * or by one of its dependent DLLs. Delay-loaded DLL doesn't count as being
 * implicitly loaded.
 *
 * See VC\crt\src\tlssup.c for reference. */

/* The linker must not discard p_thread_callback_boringssl. (We force a reference
 * to this variable with a linker /INCLUDE:symbol pragma to ensure that.) If
 * this variable is discarded, the OnThreadExit function will never be
 * called. */
#ifdef _WIN64

/* .CRT section is merged with .rdata on x64 so it must be constant data. */
#pragma const_seg(".CRT$XLC")
/* When defining a const variable, it must have external linkage to be sure the
 * linker doesn't discard it. */
extern const PIMAGE_TLS_CALLBACK p_thread_callback_boringssl;
const PIMAGE_TLS_CALLBACK p_thread_callback_boringssl = thread_local_destructor;
/* Reset the default section. */
#pragma const_seg()

#else

#pragma data_seg(".CRT$XLC")
PIMAGE_TLS_CALLBACK p_thread_callback_boringssl = thread_local_destructor;
/* Reset the default section. */
#pragma data_seg()

#endif  /* _WIN64 */

void *CRYPTO_get_thread_local(thread_local_data_t index) {
  CRYPTO_once(&g_thread_local_init_once, thread_local_init);
  if (g_thread_local_failed) {
    return NULL;
  }

  void **pointers = TlsGetValue(g_thread_local_key);
  if (pointers == NULL) {
    return NULL;
  }
  return pointers[index];
}

int CRYPTO_set_thread_local(thread_local_data_t index, void *value,
                            thread_local_destructor_t destructor) {
  CRYPTO_once(&g_thread_local_init_once, thread_local_init);
  if (g_thread_local_failed) {
    destructor(value);
    return 0;
  }

  void **pointers = TlsGetValue(g_thread_local_key);
  if (pointers == NULL) {
    pointers = OPENSSL_malloc(sizeof(void *) * NUM_OPENSSL_THREAD_LOCALS);
    if (pointers == NULL) {
      destructor(value);
      return 0;
    }
    memset(pointers, 0, sizeof(void *) * NUM_OPENSSL_THREAD_LOCALS);
    if (TlsSetValue(g_thread_local_key, pointers) == 0) {
      OPENSSL_free(pointers);
      destructor(value);
      return 0;
    }
  }

  EnterCriticalSection(&g_destructors_lock);
  g_destructors[index] = destructor;
  LeaveCriticalSection(&g_destructors_lock);

  pointers[index] = value;
  return 1;
}

#endif  /* OPENSSL_WINDOWS */