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/* NSS actions, elements in a nsswitch.conf configuration line.
Copyright (c) 2020 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <nsswitch.h>
#include <string.h>
#include <libc-lock.h>
/* Maintain a global list of NSS action lists. Since most databases
use the same list of actions, this list is usually short.
Deduplication in __nss_action_allocate ensures that the list does
not grow without bounds. */
struct nss_action_list_wrapper
{
/* The next element of the list. */
struct nss_action_list_wrapper *next;
/* Number of elements in the list (excluding the terminator). */
size_t count;
/* NULL-terminated list of actions. */
struct nss_action actions[];
};
/* Toplevel list of allocated NSS action lists. */
static struct nss_action_list_wrapper *nss_actions;
/* Lock covers the nss_actions list. */
__libc_lock_define (static, nss_actions_lock);
/* Returns true if the actions are equal (same module, same actions
array). */
static bool
actions_equal (const struct nss_action *a, const struct nss_action *b)
{
return a->module == b->module && a->action_bits == b->action_bits;
}
/* Returns true if COUNT actions at A and B are equal (according to
actions_equal above). Caller must ensure that either A or B have at
least COUNT actions. */
static bool
action_lists_equal (const struct nss_action *a, const struct nss_action *b,
size_t count)
{
for (size_t i = 0; i < count; ++i)
if (!actions_equal (a + i, b + i))
return false;
return true;
}
/* Returns a pre-allocated action list for COUNT actions at ACTIONS,
or NULL if no such list exists. */
static nss_action_list
find_allocated (struct nss_action *actions, size_t count)
{
for (struct nss_action_list_wrapper *p = nss_actions; p != NULL; p = p->next)
if (p->count == count && action_lists_equal (p->actions, actions, count))
return p->actions;
return NULL;
}
nss_action_list
__nss_action_allocate (struct nss_action *actions, size_t count)
{
nss_action_list result = NULL;
__libc_lock_lock (nss_actions_lock);
result = find_allocated (actions, count);
if (result == NULL)
{
struct nss_action_list_wrapper *wrapper
= malloc (sizeof (*wrapper) + sizeof (*actions) * count);
if (wrapper != NULL)
{
wrapper->next = nss_actions;
wrapper->count = count;
memcpy (wrapper->actions, actions, sizeof (*actions) * count);
nss_actions = wrapper;
result = wrapper->actions;
}
}
__libc_lock_unlock (nss_actions_lock);
return result;
}
void __libc_freeres_fn_section
__nss_action_freeres (void)
{
struct nss_action_list_wrapper *current = nss_actions;
while (current != NULL)
{
struct nss_action_list_wrapper *next = current->next;
free (current);
current = next;
}
nss_actions = NULL;
}
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