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nss_files: Add generic code for set*ent, end*ent and file open

Browse Source 
This reduces RSS usage if nss_files is not actually used, and can
be used later to make NSS data thread-specific.  It also results in
a small code size reduction.

Before:

   text	   data	    bss	    dec	    hex	filename
   2288	      0	     72	   2360	    938	nss/files-alias.os
   1807	      0	     72	   1879	    757	nss/files-ethers.os
   1371	      0	     72	   1443	    5a3	nss/files-grp.os
   6246	      0	     72	   6318	   18ae	nss/files-hosts.os
    869	      0	      0	    869	    365	nss/files-initgroups.os
    666	      0	      0	    666	    29a	nss/files-init.os
   1934	      0	      0	   1934	    78e	nss/files-netgrp.os
   2353	      0	     72	   2425	    979	nss/files-network.os
   2130	      0	     72	   2202	    89a	nss/files-proto.os
   1372	      0	     72	   1444	    5a4	nss/files-pwd.os
   2124	      0	     72	   2196	    894	nss/files-rpc.os
   2265	      0	     72	   2337	    921	nss/files-service.os
   1125	      0	     72	   1197	    4ad	nss/files-sgrp.os
   1124	      0	     72	   1196	    4ac	nss/files-spwd.os

After:

   text	   data	    bss	    dec	    hex	filename
   2040	      0	      0	   2040	    7f8	nss/files-alias.os
   1599	      0	      0	   1599	    63f	nss/files-ethers.os
   1155	      0	      0	   1155	    483	nss/files-grp.os
   6010	      0	      0	   6010	   177a	nss/files-hosts.os
    869	      0	      0	    869	    365	nss/files-initgroups.os
    666	      0	      0	    666	    29a	nss/files-init.os
   1934	      0	      0	   1934	    78e	nss/files-netgrp.os
   2129	      0	      0	   2129	    851	nss/files-network.os
   1914	      0	      0	   1914	    77a	nss/files-proto.os
   1156	      0	      0	   1156	    484	nss/files-pwd.os
   1908	      0	      0	   1908	    774	nss/files-rpc.os
   2057	      0	      0	   2057	    809	nss/files-service.os
    909	      0	      0	    909	    38d	nss/files-sgrp.os
    908	      0	      0	    908	    38c	nss/files-spwd.os
   1090	      0	      8	   1098	    44a	nss/nss_files_data.os

27674 code bytes before, 26344 code bytes after, so it is an overall
win despite the extra initialization code.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
This commit is contained in:
Florian Weimer 2021-07-07 18:33:52 +02:00
parent f0c28504a9
commit 36861a968a
7 changed files with 259 additions and 108 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

60
include/nss_files.h
View File

@ -20,6 +20,9 @@
#define _NSS_FILES_H
#include <stdio.h>
#if IS_IN (libc)
#include <libc-lock.h>
#endif
/* Open PATH for reading, as a data source for nss_files. */
FILE *__nss_files_fopen (const char *path);
@ -47,6 +50,63 @@ int __nss_readline_seek (FILE *fp, off64_t offset) attribute_hidden;
int __nss_parse_line_result (FILE *fp, off64_t offset, int parse_line_result);
libc_hidden_proto (__nss_parse_line_result)
/* Per-file data. Used by the *ent functions that need to preserve
state across calls. */
struct nss_files_per_file_data
{
FILE *stream;
#if IS_IN (libc)
/* The size of locks changes between libc and nss_files, so this
member must be last and is only available in libc. */
__libc_lock_define (, lock);
#endif
};
/* File index for __nss_files_data_get. */
enum nss_files_file
{
nss_file_aliasent,
nss_file_etherent,
nss_file_grent,
nss_file_hostent,
nss_file_netent,
nss_file_protoent,
nss_file_pwent,
nss_file_rpcent,
nss_file_servent,
nss_file_sgent,
nss_file_spent,
nss_file_count
};
/* Obtains a pointer to the per-file data for FILE, which is written
to *PDATA, and tries to open the file at PATH for it. On success,
returns NSS_STATUS_SUCCESS, and the caller must later call
__nss_files_data_put. On failure, NSS_STATUS_TRYAGAIN is returned,
and *ERRNOP and *HERRNOP are updated if these pointers are not
null. */
enum nss_status __nss_files_data_open (struct nss_files_per_file_data **pdata,
enum nss_files_file file,
const char *path,
int *errnop, int *herrnop);
libc_hidden_proto (__nss_files_data_open)
/* Unlock the per-file data, previously obtained by
__nss_files_data_open. */
void __nss_files_data_put (struct nss_files_per_file_data *data);
libc_hidden_proto (__nss_files_data_put)
/* Performs the set*ent operation for FILE. PATH is the file to
open. */
enum nss_status __nss_files_data_setent (enum nss_files_file file,
const char *path);
libc_hidden_proto (__nss_files_data_setent)
/* Performs the end*ent operation for FILE. */
enum nss_status __nss_files_data_endent (enum nss_files_file file);
libc_hidden_proto (__nss_files_data_endent)
struct parser_data;
/* Instances of the parse_line function from

2
nss/Makefile
View File

@ -31,7 +31,7 @@ routines = nsswitch getnssent getnssent_r digits_dots \
compat-lookup nss_hash nss_files_fopen \
nss_readline nss_parse_line_result \
nss_fgetent_r nss_module nss_action \
nss_action_parse nss_database
nss_action_parse nss_database nss_files_data
# These are the databases that go through nss dispatch.
# Caution: if you add a database here, you must add its real name

4
nss/Versions
View File

@ -19,6 +19,10 @@ libc {
__nss_services_lookup2; __nss_next2; __nss_lookup;
__nss_hash; __nss_database_get;
__nss_files_fopen; __nss_readline; __nss_parse_line_result;
__nss_files_data_endent;
__nss_files_data_open;
__nss_files_data_put;
__nss_files_data_setent;
}
}

67
nss/nss_files/files-XXX.c
View File

@ -45,10 +45,12 @@
# include <netdb.h>
# define H_ERRNO_PROTO , int *herrnop
# define H_ERRNO_ARG , herrnop
# define H_ERRNO_ARG_OR_NULL herrnop
# define H_ERRNO_SET(val) (*herrnop = (val))
#else
# define H_ERRNO_PROTO
# define H_ERRNO_ARG
# define H_ERRNO_ARG_OR_NULL NULL
# define H_ERRNO_SET(val) ((void) 0)
#endif
@ -58,15 +60,11 @@
# define EXTRA_ARGS_VALUE
#endif
/* Locks the static variables in this file. */
__libc_lock_define_initialized (static, lock)
/* Maintenance of the stream open on the database file. For getXXent
operations the stream needs to be held open across calls, the other
getXXbyYY operations all use their own stream. */
static FILE *stream;
/* Open database file if not already opened. */
static enum nss_status
internal_setent (FILE **stream)
@ -91,41 +89,13 @@ internal_setent (FILE **stream)
enum nss_status
CONCAT(_nss_files_set,ENTNAME) (int stayopen)
{
enum nss_status status;
__libc_lock_lock (lock);
status = internal_setent (&stream);
__libc_lock_unlock (lock);
return status;
return __nss_files_data_setent (CONCAT (nss_file_, ENTNAME), DATAFILE);
}
/* Close the database file. */
static void
internal_endent (FILE **stream)
{
if (*stream != NULL)
{
fclose (*stream);
*stream = NULL;
}
}
/* Thread-safe, exported version of that. */
enum nss_status
CONCAT(_nss_files_end,ENTNAME) (void)
{
__libc_lock_lock (lock);
internal_endent (&stream);
__libc_lock_unlock (lock);
return NSS_STATUS_SUCCESS;
return __nss_files_data_endent (CONCAT (nss_file_, ENTNAME));
}
@ -194,26 +164,19 @@ CONCAT(_nss_files_get,ENTNAME_r) (struct STRUCTURE *result, char *buffer,
size_t buflen, int *errnop H_ERRNO_PROTO)
{
/* Return next entry in host file. */
enum nss_status status = NSS_STATUS_SUCCESS;
__libc_lock_lock (lock);
struct nss_files_per_file_data *data;
enum nss_status status = __nss_files_data_open (&data,
CONCAT (nss_file_, ENTNAME),
DATAFILE,
errnop, H_ERRNO_ARG_OR_NULL);
if (status != NSS_STATUS_SUCCESS)
return status;
/* Be prepared that the set*ent function was not called before. */
if (stream == NULL)
{
int save_errno = errno;
status = internal_setent (&stream);
__set_errno (save_errno);
}
if (status == NSS_STATUS_SUCCESS)
status = internal_getent (stream, result, buffer, buflen, errnop
H_ERRNO_ARG EXTRA_ARGS_VALUE);
__libc_lock_unlock (lock);
status = internal_getent (data->stream, result, buffer, buflen, errnop
H_ERRNO_ARG EXTRA_ARGS_VALUE);
__nss_files_data_put (data);
return status;
}
@ -248,7 +211,7 @@ _nss_files_get##name##_r (proto, \
== NSS_STATUS_SUCCESS) \
{ break_if_match } \
\
internal_endent (&stream); \
fclose (stream); \
} \
\
return status; \

69
nss/nss_files/files-alias.c
View File

@ -33,16 +33,11 @@
NSS_DECLARE_MODULE_FUNCTIONS (files)
/* Locks the static variables in this file. */
__libc_lock_define_initialized (static, lock)
/* Maintenance of the stream open on the database file. For getXXent
operations the stream needs to be held open across calls, the other
getXXbyYY operations all use their own stream. */
static FILE *stream;
static enum nss_status
internal_setent (FILE **stream)
{
@ -66,41 +61,13 @@ internal_setent (FILE **stream)
enum nss_status
_nss_files_setaliasent (void)
{
enum nss_status status;
__libc_lock_lock (lock);
status = internal_setent (&stream);
__libc_lock_unlock (lock);
return status;
return __nss_files_data_setent (nss_file_aliasent, "/etc/aliases");
}
/* Close the database file. */
static void
internal_endent (FILE **stream)
{
if (*stream != NULL)
{
fclose (*stream);
*stream = NULL;
}
}
/* Thread-safe, exported version of that. */
enum nss_status
_nss_files_endaliasent (void)
{
__libc_lock_lock (lock);
internal_endent (&stream);
__libc_lock_unlock (lock);
return NSS_STATUS_SUCCESS;
return __nss_files_data_endent (nss_file_aliasent);
}
/* Parsing the database file into `struct aliasent' data structures. */
@ -369,26 +336,22 @@ _nss_files_getaliasent_r (struct aliasent *result, char *buffer, size_t buflen,
int *errnop)
{
/* Return next entry in host file. */
enum nss_status status = NSS_STATUS_SUCCESS;
__libc_lock_lock (lock);
struct nss_files_per_file_data *data;
enum nss_status status = __nss_files_data_open (&data, nss_file_aliasent,
"/etc/aliases", errnop, NULL);
if (status != NSS_STATUS_SUCCESS)
return status;
/* Be prepared that the set*ent function was not called before. */
if (stream == NULL)
status = internal_setent (&stream);
result->alias_local = 1;
if (status == NSS_STATUS_SUCCESS)
{
result->alias_local = 1;
/* Read lines until we get a definite result. */
do
status = get_next_alias (stream, NULL, result, buffer, buflen, errnop);
while (status == NSS_STATUS_RETURN);
}
__libc_lock_unlock (lock);
/* Read lines until we get a definite result. */
do
status = get_next_alias (data->stream, NULL, result, buffer, buflen,
errnop);
while (status == NSS_STATUS_RETURN);
__nss_files_data_put (data);
return status;
}
@ -418,9 +381,9 @@ _nss_files_getaliasbyname_r (const char *name, struct aliasent *result,
do
status = get_next_alias (stream, name, result, buffer, buflen, errnop);
while (status == NSS_STATUS_RETURN);
}
internal_endent (&stream);
fclose (stream);
}
return status;
}

4
nss/nss_files/files-hosts.c
View File

@ -349,7 +349,7 @@ _nss_files_gethostbyname3_r (const char *name, int af, struct hostent *result,
status = gethostbyname3_multi
(stream, name, af, result, buffer, buflen, errnop, herrnop);
internal_endent (&stream);
fclose (stream);
}
if (canonp && status == NSS_STATUS_SUCCESS)
@ -475,7 +475,7 @@ _nss_files_gethostbyname4_r (const char *name, struct gaih_addrtuple **pat,
status = NSS_STATUS_SUCCESS;
}
internal_endent (&stream);
fclose (stream);
}
else if (status == NSS_STATUS_TRYAGAIN)
{

161
nss/nss_files_data.c Normal file
View File

@ -0,0 +1,161 @@
/* Returns a pointer to the global nss_files data structure.
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_files.h>
#include <allocate_once.h>
#include <errno.h>
#include <netdb.h>
#include <nss.h>
#include <stdlib.h>
/* This collects all per file-data. */
struct nss_files_data
{
struct nss_files_per_file_data files[nss_file_count];
};
/* For use with allocate_once. */
static void *nss_files_global;
static void *
nss_files_global_allocate (void *closure)
{
struct nss_files_data *result = malloc (sizeof (*result));
if (result != NULL)
{
for (int i = 0; i < nss_file_count; ++i)
{
result->files[i].stream = NULL;
__libc_lock_init (result->files[i].lock);
}
}
return result;
}
/* Like __nss_files_data_open, but does not perform the open call. */
static enum nss_status
__nss_files_data_get (struct nss_files_per_file_data **pdata,
enum nss_files_file file, int *errnop, int *herrnop)
{
struct nss_files_data *data = allocate_once (&nss_files_global,
nss_files_global_allocate,
NULL, NULL);
if (data == NULL)
{
if (errnop != NULL)
*errnop = errno;
if (herrnop != NULL)
{
__set_h_errno (NETDB_INTERNAL);
*herrnop = NETDB_INTERNAL;
}
return NSS_STATUS_TRYAGAIN;
}
*pdata = &data->files[file];
__libc_lock_lock ((*pdata)->lock);
return NSS_STATUS_SUCCESS;
}
/* Helper function for opening the backing file at PATH. */
static enum nss_status
__nss_files_data_internal_open (struct nss_files_per_file_data *data,
const char *path)
{
enum nss_status status = NSS_STATUS_SUCCESS;
if (data->stream == NULL)
{
data->stream = __nss_files_fopen (path);
if (data->stream == NULL)
status = errno == EAGAIN ? NSS_STATUS_TRYAGAIN : NSS_STATUS_UNAVAIL;
}
return status;
}
enum nss_status
__nss_files_data_open (struct nss_files_per_file_data **pdata,
enum nss_files_file file, const char *path,
int *errnop, int *herrnop)
{
enum nss_status status = __nss_files_data_get (pdata, file, errnop, herrnop);
if (status != NSS_STATUS_SUCCESS)
return status;
/* Be prepared that the set*ent function was not called before. */
if ((*pdata)->stream == NULL)
{
int saved_errno = errno;
status = __nss_files_data_internal_open (*pdata, path);
__set_errno (saved_errno);
if (status != NSS_STATUS_SUCCESS)
__nss_files_data_put (*pdata);
}
return status;
}
libc_hidden_def (__nss_files_data_open)
void
__nss_files_data_put (struct nss_files_per_file_data *data)
{
__libc_lock_unlock (data->lock);
}
libc_hidden_def (__nss_files_data_put)
enum nss_status
__nss_files_data_setent (enum nss_files_file file, const char *path)
{
struct nss_files_per_file_data *data;
enum nss_status status = __nss_files_data_get (&data, file, NULL, NULL);
if (status != NSS_STATUS_SUCCESS)
return status;
if (data->stream == NULL)
status = __nss_files_data_internal_open (data, path);
else
rewind (data->stream);
__nss_files_data_put (data);
return status;
}
libc_hidden_def (__nss_files_data_setent)
enum nss_status
__nss_files_data_endent (enum nss_files_file file)
{
/* No cleanup is necessary if not initialized. */
struct nss_files_data *data = atomic_load_acquire (&nss_files_global);
if (data == NULL)
return NSS_STATUS_SUCCESS;
struct nss_files_per_file_data *fdata = &data->files[file];
__libc_lock_lock (fdata->lock);
if (fdata->stream != NULL)
{
fclose (fdata->stream);
fdata->stream = NULL;
}
__libc_lock_unlock (fdata->lock);
return NSS_STATUS_SUCCESS;
}
libc_hidden_def (__nss_files_data_endent)