/* fat-setup.h

   Copyright (C) 2015 Niels Möller

   This file is part of GNU Nettle.

   GNU Nettle is free software: you can redistribute it and/or
   modify it under the terms of either:

     * the GNU Lesser General Public License as published by the Free
       Software Foundation; either version 3 of the License, or (at your
       option) any later version.

   or

     * the GNU General Public License as published by the Free
       Software Foundation; either version 2 of the License, or (at your
       option) any later version.

   or both in parallel, as here.

   GNU Nettle is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   General Public License for more details.

   You should have received copies of the GNU General Public License and
   the GNU Lesser General Public License along with this program.  If
   not, see http://www.gnu.org/licenses/.
*/

/* Fat library initialization works as follows. The main function is
   fat_init. We try to do initialization only once, but since it is
   idempotent, there's no harm if it is in some cases called multiple
   times from several threads. For correctness, we rely on atomic
   writes, but not on memory barriers or any other synchronization
   mechanism.

   The fat_init function checks the cpuid flags, and sets function
   pointers, e.g, _nettle_aes_encrypt_vec, to point to the appropriate
   implementation.

   To get everything hooked in, we use a belt-and-suspenders approach.

   We try to register fat_init as a constructor function to be called
   at load time. If this is unavailable or non-working, we instead
   arrange fat_init to be called lazily.

   For the actual indirection, there are two cases. 

   * If ifunc support is available, function pointers are statically
     initialized to NULL, and we register resolver functions, e.g.,
     _nettle_aes_encrypt_resolve, which call fat_init, and then return
     the function pointer, e.g., the value of _nettle_aes_encrypt_vec.

   * If ifunc is not available, we have to define a wrapper function
     to jump via the function pointer. (FIXME: For internal calls, we
     could do this as a macro).

     We statically initialize each function pointer to point to a
     special initialization function, e.g., _nettle_aes_encrypt_init,
     which calls fat_init, and then invokes the right function. This
     way, all pointers are setup correctly at the first call to any
     fat function.

     And atomic writes are required for correctness in the case that
     several threads do "first call to any fat function" at the same
     time.
*/

#if HAVE_GCC_ATTRIBUTE
# define CONSTRUCTOR __attribute__ ((constructor))
#else
# define CONSTRUCTOR
# if defined (__sun)
#  pragma init(fat_init)
# endif
#endif

/* Disable use of ifunc for now. Problem is, there's no guarantee that
   one can call any libc functions from the ifunc resolver. On x86 and
   x86_64, the corresponding IRELATIVE relocs are supposed to be
   processed last, but that doesn't seem to happen, and its a
   platform-specific feature. To trigger problems, simply try dlopen
   ("libnettle.so", RTLD_NOW), which crashes in an uninitialized plt
   entry. */
#undef HAVE_LINK_IFUNC

#if !HAVE_SECURE_GETENV
#define secure_getenv(s) NULL
#endif

#define ENV_VERBOSE "NETTLE_FAT_VERBOSE"
#define ENV_OVERRIDE "NETTLE_FAT_OVERRIDE"

struct chacha_ctx;
struct salsa20_ctx;

/* DECLARE_FAT_FUNC(name, ftype)
 *
 *   name is the public function, e.g., _nettle_aes_encrypt.
 *   ftype is its type, e.g., aes_crypt_internal_func.
 *
 * DECLARE_FAT_VAR(name, type, var)
 *
 *   name is name without _nettle prefix.
 *   type is its type.
 *   var is the variant, used as a suffix on the symbol name.
 *
 * DEFINE_FAT_FUNC(name, rtype, prototype, args)
 *
 *   name is the public function.
 *   rtype its return type.
 *   prototype is the list of formal arguments, with types.
 *   args contain the argument list without any types.
 */

#if HAVE_LINK_IFUNC
#define IFUNC(resolve) __attribute__ ((ifunc (resolve)))
#define DECLARE_FAT_FUNC(name, ftype)	\
  ftype name IFUNC(#name"_resolve");	\
  static ftype *name##_vec = NULL;

#define DEFINE_FAT_FUNC(name, rtype, prototype, args)		  \
  static void_func * name##_resolve(void)			  \
  {								  \
    if (getenv (ENV_VERBOSE))					  \
      fprintf (stderr, "libnettle: "#name"_resolve\n");		  \
    if (!name##_vec)						  \
      fat_init();						  \
    return (void_func *) name##_vec;				  \
  }

#else /* !HAVE_LINK_IFUNC */
#define DECLARE_FAT_FUNC(name, ftype)		\
  ftype name;					\
  static ftype name##_init;			\
  static ftype *name##_vec = name##_init;				

#define DEFINE_FAT_FUNC(name, rtype, prototype, args)		\
  rtype name prototype						\
  {								\
    return name##_vec args;					\
  }								\
  static rtype name##_init prototype {				\
    if (getenv (ENV_VERBOSE))					\
      fprintf (stderr, "libnettle: "#name"_init\n");		\
    if (name##_vec == name##_init)				\
      fat_init();						\
    assert (name##_vec != name##_init);				\
    return name##_vec args;					\
  }
#endif /* !HAVE_LINK_IFUNC */

#define DECLARE_FAT_FUNC_VAR(name, type, var)	\
       type _nettle_##name##_##var;

typedef void void_func (void);

typedef void aes_crypt_internal_func (unsigned rounds, const uint32_t *keys,
				      const struct aes_table *T,
				      size_t length, uint8_t *dst,
				      const uint8_t *src);

struct gcm_key;
typedef void gcm_init_key_func (union nettle_block16 *table);

typedef void gcm_hash_func (const struct gcm_key *key, union nettle_block16 *x,
			    size_t length, const uint8_t *data);

typedef void *(memxor_func)(void *dst, const void *src, size_t n);

typedef void salsa20_core_func (uint32_t *dst, const uint32_t *src, unsigned rounds);
typedef void salsa20_crypt_func (struct salsa20_ctx *ctx, unsigned rounds,
				 size_t length, uint8_t *dst,
				 const uint8_t *src);

typedef void sha1_compress_func(uint32_t *state, const uint8_t *input);
typedef void sha256_compress_func(uint32_t *state, const uint8_t *input, const uint32_t *k);

struct sha3_state;
typedef void sha3_permute_func (struct sha3_state *state);

typedef void sha512_compress_func (uint64_t *state, const uint8_t *input, const uint64_t *k);

typedef uint64_t umac_nh_func (const uint32_t *key, unsigned length, const uint8_t *msg);
typedef void umac_nh_n_func (uint64_t *out, unsigned n, const uint32_t *key,
			     unsigned length, const uint8_t *msg);

typedef void chacha_core_func(uint32_t *dst, const uint32_t *src, unsigned rounds);

typedef void chacha_crypt_func(struct chacha_ctx *ctx,
			       size_t length,
			       uint8_t *dst,
			       const uint8_t *src);
