1  /* Global list of NSS service modules.
       2     Copyright (c) 2020-2023 Free Software Foundation, Inc.
       3     This file is part of the GNU C Library.
       4  
       5     The GNU C Library is free software; you can redistribute it and/or
       6     modify it under the terms of the GNU Lesser General Public
       7     License as published by the Free Software Foundation; either
       8     version 2.1 of the License, or (at your option) any later version.
       9  
      10     The GNU C Library is distributed in the hope that it will be useful,
      11     but WITHOUT ANY WARRANTY; without even the implied warranty of
      12     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
      13     Lesser General Public License for more details.
      14  
      15     You should have received a copy of the GNU Lesser General Public
      16     License along with the GNU C Library; if not, see
      17     <https://www.gnu.org/licenses/>.  */
      18  
      19  #ifndef _NSS_MODULE_H
      20  #define _NSS_MODULE_H
      21  
      22  #include <nss.h>
      23  #include <stdbool.h>
      24  
      25  /* See nss_database.h for a summary of how this relates.  */
      26  
      27  /* Typed function pointers for all functions that can be defined by a
      28     service module.  */
      29  struct nss_module_functions
      30  {
      31  #undef DEFINE_NSS_FUNCTION
      32  #define DEFINE_NSS_FUNCTION(f) nss_##f *f;
      33  #include "function.def"
      34  };
      35  
      36  /* Number of elements of the nss_module_functions_untyped array.  */
      37  enum
      38    {
      39      nss_module_functions_count = (sizeof (struct nss_module_functions)
      40                                    / sizeof (void *))
      41    };
      42  
      43  /* Untyped version of struct nss_module_functions, for consistent
      44     processing purposes.  */
      45  typedef void *nss_module_functions_untyped[nss_module_functions_count];
      46  
      47  /* Locate the nss_files functions, as if by dlopen/dlsym.  */
      48  void __nss_files_functions (nss_module_functions_untyped pointers)
      49    attribute_hidden;
      50  
      51  /* Initialization state of a NSS module.  */
      52  enum nss_module_state
      53  {
      54    nss_module_uninitialized,
      55    nss_module_loaded,
      56    nss_module_failed,
      57  };
      58  
      59  /* A NSS service module (potentially unloaded).  Client code should
      60     use the functions below.  */
      61  struct nss_module
      62  {
      63    /* Actual type is enum nss_module_state.  Use int due to atomic
      64       access.  Used in a double-checked locking idiom.  */
      65    int state;
      66  
      67    /* The function pointers in the module.  */
      68    union
      69    {
      70      struct nss_module_functions typed;
      71      nss_module_functions_untyped untyped;
      72    } functions;
      73  
      74    /* Only used for __libc_freeres unloading.  */
      75    void *handle;
      76  
      77    /* The next module in the list. */
      78    struct nss_module *next;
      79  
      80    /* The name of the module (as it appears in /etc/nsswitch.conf).  */
      81    char name[];
      82  };
      83  
      84  /* Allocates the NSS module NAME (of NAME_LENGTH bytes) and places it
      85     into the global list.  If it already exists in the list, return the
      86     pre-existing module.  This does not actually load the module.
      87     Returns NULL on memory allocation failure.  */
      88  struct nss_module *__nss_module_allocate (const char *name,
      89                                            size_t name_length) attribute_hidden;
      90  
      91  /* Ensures that MODULE is in a loaded or failed state.  */
      92  bool __nss_module_load (struct nss_module *module) attribute_hidden;
      93  
      94  /* Ensures that MODULE is loaded and returns a pointer to the function
      95     NAME defined in it.  Returns NULL if MODULE could not be loaded, or
      96     if the function NAME is not defined in the module.  */
      97  void *__nss_module_get_function (struct nss_module *module, const char *name)
      98    attribute_hidden;
      99  
     100  /* Block attempts to dlopen any module we haven't already opened.  */
     101  void __nss_module_disable_loading (void);
     102  
     103  #endif /* NSS_MODULE_H */