This partially fixes static-only NSS support (bug 27959): The dns
module no longer needs dlopen. Support for the files module remains
to be added, and also support for disabling dlopen altogher.
---
include/nss_dns.h | 13 ++++++-----
nss/nss_module.c | 31 ++++++++++++++++++++++++-
nss/nss_module.h | 10 +++++++--
resolv/Makefile | 1 +
resolv/nss_dns_functions.c | 46 ++++++++++++++++++++++++++++++++++++++
5 files changed, 93 insertions(+), 8 deletions(-)
create mode 100644 resolv/nss_dns_functions.c
@@ -24,13 +24,16 @@
NSS_DECLARE_MODULE_FUNCTIONS (dns)
libc_hidden_proto (_nss_dns_getcanonname_r)
-libc_hidden_proto (_nss_dns_gethostbyname3_r)
-libc_hidden_proto (_nss_dns_gethostbyname2_r)
-libc_hidden_proto (_nss_dns_gethostbyname_r)
-libc_hidden_proto (_nss_dns_gethostbyname4_r)
libc_hidden_proto (_nss_dns_gethostbyaddr2_r)
libc_hidden_proto (_nss_dns_gethostbyaddr_r)
-libc_hidden_proto (_nss_dns_getnetbyname_r)
+libc_hidden_proto (_nss_dns_gethostbyname2_r)
+libc_hidden_proto (_nss_dns_gethostbyname3_r)
+libc_hidden_proto (_nss_dns_gethostbyname4_r)
+libc_hidden_proto (_nss_dns_gethostbyname_r)
libc_hidden_proto (_nss_dns_getnetbyaddr_r)
+libc_hidden_proto (_nss_dns_getnetbyname_r)
+
+void __nss_dns_functions (nss_module_functions_untyped pointers)
+ attribute_hidden;
#endif
@@ -26,6 +26,7 @@
#include <dlfcn.h>
#include <gnu/lib-names.h>
#include <libc-lock.h>
+#include <nss_dns.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
@@ -110,10 +111,36 @@ static const function_name nss_function_name_array[] =
#include "function.def"
};
+static bool
+module_load_nss_dns (struct nss_module *module)
+{
+ /* Initialize the function pointers, following the double-checked
+ locking idiom. */
+ __libc_lock_lock (nss_module_list_lock);
+ switch ((enum nss_module_state) atomic_load_acquire (&module->state))
+ {
+ case nss_module_uninitialized:
+ case nss_module_failed:
+ __nss_dns_functions (module->functions.untyped);
+ module->handle = NULL;
+ /* Synchronizes with unlocked __nss_module_load atomic_load_acquire. */
+ atomic_store_release (&module->state, nss_module_loaded);
+ break;
+ case nss_module_loaded:
+ /* Nothing to clean up. */
+ break;
+ }
+ __libc_lock_unlock (nss_module_list_lock);
+ return true;
+}
+
/* Internal implementation of __nss_module_load. */
static bool
module_load (struct nss_module *module)
{
+ if (strcmp (module->name, "dns") == 0)
+ return module_load_nss_dns (module);
+
void *handle;
{
char *shlib_name;
@@ -360,7 +387,9 @@ __nss_module_freeres (void)
struct nss_module *current = nss_module_list;
while (current != NULL)
{
- if (current->state == nss_module_loaded)
+ /* Ignore built-in modules (which have a NULL handle). */
+ if (current->state == nss_module_loaded
+ && current->handle != NULL)
__libc_dlclose (current->handle);
struct nss_module *next = current->next;
@@ -33,10 +33,16 @@ struct nss_module_functions
#include "function.def"
};
+/* Number of elements of the nss_module_functions_untyped array. */
+enum
+ {
+ nss_module_functions_count = (sizeof (struct nss_module_functions)
+ / sizeof (void *))
+ };
+
/* Untyped version of struct nss_module_functions, for consistent
processing purposes. */
-typedef void *nss_module_functions_untyped[sizeof (struct nss_module_functions)
- / sizeof (void *)];
+typedef void *nss_module_functions_untyped[nss_module_functions_count];
/* Initialization state of a NSS module. */
enum nss_module_state
@@ -48,6 +48,7 @@ routines := \
ns_name_unpack \
ns_samename \
nsap_addr \
+ nss_dns_functions \
res-close \
res-name-checking \
res-state \
new file mode 100644
@@ -0,0 +1,46 @@
+/* Direct access for nss_dns functions for NSS module loading.
+ Copyright (C) 2021 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 <nss/nss_module.h>
+#include <nss_dns.h>
+#include <string.h>
+#include <sysdep.h>
+
+void
+__nss_dns_functions (nss_module_functions_untyped pointers)
+{
+ struct nss_module_functions typed =
+ {
+ .getcanonname_r = &_nss_dns_getcanonname_r,
+ .gethostbyname3_r = &_nss_dns_gethostbyname3_r,
+ .gethostbyname2_r = &_nss_dns_gethostbyname2_r,
+ .gethostbyname_r = &_nss_dns_gethostbyname_r,
+ .gethostbyname4_r = &_nss_dns_gethostbyname4_r,
+ .gethostbyaddr2_r = &_nss_dns_gethostbyaddr2_r,
+ .gethostbyaddr_r = &_nss_dns_gethostbyaddr_r,
+ .getnetbyname_r = &_nss_dns_getnetbyname_r,
+ .getnetbyaddr_r = &_nss_dns_getnetbyaddr_r,
+ };
+
+ memcpy (pointers, &typed, sizeof (nss_module_functions_untyped));
+
+#ifdef PTR_MANGLE
+ for (int i = 0; i < nss_module_functions_count; ++i)
+ PTR_MANGLE (pointers[i]);
+#endif
+}