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Re: [PATCH] login: Remove utmp backend jump tables [BZ #23518]
- From: Adhemerval Zanella <adhemerval dot zanella at linaro dot org>
- To: GNU C Library <libc-alpha at sourceware dot org>
- Date: Fri, 22 Mar 2019 16:43:20 -0300
- Subject: Re: [PATCH] login: Remove utmp backend jump tables [BZ #23518]
- References: <20180817144443.0993E4028A8FC@oldenburg.str.redhat.com>
On 17/08/2018 11:44, Florian Weimer wrote:
> There is just one file-based implementation, so this dispatch
> mechanism is unnecessary. Instead of the vtable pointer
> __libc_utmp_jump_table, use a non-negative file_fd as the indicator
> that the backend is initialized.
>
> 2018-08-15 Florian Weimer <fweimer@redhat.com>
>
> [BZ #23518]
> * login/uptmp-private.h (struct ufuncs): Remove definition.
> (__libc_utmp_file_functions, __libc_utmp_unknown_functions)
> (__libc_utmp_jump_table): Remove declarations.
> (__libc_setutent, __libc_getutent_r, __libc_getutid_r)
> (__libc_getutline_r, __libc_pututline, __libc_endutent)
> (__libc_updwtmp): Declare.
> * login/getutent_r.c (__libc_utmp_unknown_functions)
> (__libc_utmp_jump_table, setutent_unknown, getutent_r_unknown)
> (getutid_r_unknown, getutline_r_unknown, pututline_unknown)
> (endutent_unknown): Remove definitions.
> (__setutent): Call __libc_setutent.
> (__getutent_r): Call __libc_getutent_r.
> (__pututline): Call __libc_pututline.
> (__endutent): Call __libc_endutent.
> * login/getutid_r.c (__getutid_r): Call __libc_getutid_r.
> * login/getutline_r.c (__getutline_r): Call __libc_getutline_r.
> * login/updwtmp.c (__updwtmp): Call __libc_updwtmp.
> * login/utmp_file.c (__libc_utmp_file_functions): Remove definition
> (__libc_setutent): Rename from stetutent_file. Drop static.
> (maybe_setutent): New function.
> (__libc_getutent_r): Rename from getutent_r_file. Drop static.
> Check for initialization.
> (__libc_getutid_r): Rename from getutid_r_file. Drop static.
> Check for initialization.
> (__libc_getutline_r): Rename from getutline_r_file. Drop static.
> Check for initialization.
> (__libc_pututline): Rename from pututline_file. Drop static.
> Check for initialization.
> (__libc_endutent): Rename from endutent_file. Drop static. Check
> for initialization.
> (__libc_updwtmp): Rename from updwtmp_file. Drop static.
> * login/utmpname.c (__utmpname): Call __libc_endutent.
> * sysdeps/unix/getlogin_r (__getlogin_r): Call __libc_setutent,
> __libc_getutlien_r, __libc_endutent.
> * manual/users.texi (Who Logged In, Manipulating the Database):
> Adjust.
LGTM, thanks.
>
> diff --git a/login/getutent_r.c b/login/getutent_r.c
> index 6a244ba6e0..44239ecb81 100644
> --- a/login/getutent_r.c
> +++ b/login/getutent_r.c
> @@ -23,115 +23,16 @@
>
> #include "utmp-private.h"
>
> -
> -/* Functions defined here. */
> -static int setutent_unknown (void);
> -static int getutent_r_unknown (struct utmp *buffer, struct utmp **result);
> -static int getutid_r_unknown (const struct utmp *line, struct utmp *buffer,
> - struct utmp **result);
> -static int getutline_r_unknown (const struct utmp *id, struct utmp *buffer,
> - struct utmp **result);
> -static struct utmp *pututline_unknown (const struct utmp *data);
> -static void endutent_unknown (void);
> -
> -/* Initial Jump table. */
> -const struct utfuncs __libc_utmp_unknown_functions =
> -{
> - setutent_unknown,
> - getutent_r_unknown,
> - getutid_r_unknown,
> - getutline_r_unknown,
> - pututline_unknown,
> - endutent_unknown,
> - NULL
> -};
> -
> -/* Currently selected backend. */
> -const struct utfuncs *__libc_utmp_jump_table = &__libc_utmp_unknown_functions;
> -
> /* We need to protect the opening of the file. */
> __libc_lock_define_initialized (, __libc_utmp_lock attribute_hidden)
>
>
> -static int
> -setutent_unknown (void)
> -{
> - int result;
> -
> - result = (*__libc_utmp_file_functions.setutent) ();
> - if (result)
> - __libc_utmp_jump_table = &__libc_utmp_file_functions;
> -
> - return result;
> -}
> -
> -
> -static int
> -getutent_r_unknown (struct utmp *buffer, struct utmp **result)
> -{
> - /* The backend was not yet initialized. */
> - if (setutent_unknown ())
> - return (*__libc_utmp_jump_table->getutent_r) (buffer, result);
> -
> - /* Not available. */
> - *result = NULL;
> - return -1;
> -}
> -
> -
> -static int
> -getutid_r_unknown (const struct utmp *id, struct utmp *buffer,
> - struct utmp **result)
> -{
> - /* The backend was not yet initialized. */
> - if (setutent_unknown ())
> - return (*__libc_utmp_jump_table->getutid_r) (id, buffer, result);
> -
> - /* Not available. */
> - *result = NULL;
> - return -1;
> -}
> -
> -
> -static int
> -getutline_r_unknown (const struct utmp *line, struct utmp *buffer,
> - struct utmp **result)
> -{
> - /* The backend was not yet initialized. */
> - if (setutent_unknown ())
> - return (*__libc_utmp_jump_table->getutline_r) (line, buffer, result);
> -
> - /* Not available. */
> - *result = NULL;
> - return -1;
> -}
> -
> -
> -static struct utmp *
> -pututline_unknown (const struct utmp *data)
> -{
> - /* The backend was not yet initialized. */
> - if (setutent_unknown ())
> - return (*__libc_utmp_jump_table->pututline) (data);
> -
> - /* Not available. */
> - return NULL;
> -}
> -
> -
> -static void
> -endutent_unknown (void)
> -{
> - /* Nothing to do. */
> -}
> -
> -
Ok.
> void
> __setutent (void)
> {
> __libc_lock_lock (__libc_utmp_lock);
>
> - (*__libc_utmp_jump_table->setutent) ();
> + __libc_setutent ();
>
> __libc_lock_unlock (__libc_utmp_lock);
> }
> @@ -145,7 +46,7 @@ __getutent_r (struct utmp *buffer, struct utmp **result)
>
> __libc_lock_lock (__libc_utmp_lock);
>
> - retval = (*__libc_utmp_jump_table->getutent_r) (buffer, result);
> + retval = __libc_getutent_r (buffer, result);
>
> __libc_lock_unlock (__libc_utmp_lock);
>
> @@ -162,7 +63,7 @@ __pututline (const struct utmp *data)
>
> __libc_lock_lock (__libc_utmp_lock);
>
> - buffer = (*__libc_utmp_jump_table->pututline) (data);
> + buffer = __libc_pututline (data);
>
> __libc_lock_unlock (__libc_utmp_lock);
>
> @@ -177,8 +78,7 @@ __endutent (void)
> {
> __libc_lock_lock (__libc_utmp_lock);
>
> - (*__libc_utmp_jump_table->endutent) ();
> - __libc_utmp_jump_table = &__libc_utmp_unknown_functions;
> + __libc_endutent ();
>
> __libc_lock_unlock (__libc_utmp_lock);
> }
Ok.
> diff --git a/login/getutid_r.c b/login/getutid_r.c
> index b7d3dbac75..8cb6b16d73 100644
> --- a/login/getutid_r.c
> +++ b/login/getutid_r.c
> @@ -49,7 +49,7 @@ __getutid_r (const struct utmp *id, struct utmp *buffer, struct utmp **result)
>
> __libc_lock_lock (__libc_utmp_lock);
>
> - retval = (*__libc_utmp_jump_table->getutid_r) (id, buffer, result);
> + retval = __libc_getutid_r (id, buffer, result);
>
> __libc_lock_unlock (__libc_utmp_lock);
>
Ok.
> diff --git a/login/getutline_r.c b/login/getutline_r.c
> index 6996887f76..5607c19ed2 100644
> --- a/login/getutline_r.c
> +++ b/login/getutline_r.c
> @@ -36,7 +36,7 @@ __getutline_r (const struct utmp *line, struct utmp *buffer,
>
> __libc_lock_lock (__libc_utmp_lock);
>
> - retval = (*__libc_utmp_jump_table->getutline_r) (line, buffer, result);
> + retval = __libc_getutline_r (line, buffer, result);
>
> __libc_lock_unlock (__libc_utmp_lock);
>
Ok.
> diff --git a/login/updwtmp.c b/login/updwtmp.c
> index 56fb41916a..7ae96224ca 100644
> --- a/login/updwtmp.c
> +++ b/login/updwtmp.c
> @@ -29,7 +29,7 @@ __updwtmp (const char *wtmp_file, const struct utmp *utmp)
> {
> const char *file_name = TRANSFORM_UTMP_FILE_NAME (wtmp_file);
>
> - (*__libc_utmp_file_functions.updwtmp) (file_name, utmp);
> + __libc_updwtmp (file_name, utmp);
> }
> libc_hidden_def (__updwtmp)
> weak_alias (__updwtmp, updwtmp)
Ok.
> diff --git a/login/utmp-private.h b/login/utmp-private.h
> index bd8773984c..5c2048ee52 100644
> --- a/login/utmp-private.h
> +++ b/login/utmp-private.h
> @@ -24,24 +24,17 @@
> #include <utmp.h>
> #include <libc-lock.h>
>
> -/* The structure describing the functions in a backend. */
> -struct utfuncs
> -{
> - int (*setutent) (void);
> - int (*getutent_r) (struct utmp *, struct utmp **);
> - int (*getutid_r) (const struct utmp *, struct utmp *, struct utmp **);
> - int (*getutline_r) (const struct utmp *, struct utmp *, struct utmp **);
> - struct utmp *(*pututline) (const struct utmp *);
> - void (*endutent) (void);
> - int (*updwtmp) (const char *, const struct utmp *);
> -};
> -
> -/* The tables from the services. */
> -extern const struct utfuncs __libc_utmp_file_functions attribute_hidden;
> -extern const struct utfuncs __libc_utmp_unknown_functions attribute_hidden;
> -
> -/* Currently selected backend. */
> -extern const struct utfuncs *__libc_utmp_jump_table attribute_hidden;
> +/* These functions check for initialization, but not perform any
> + locking. */
> +int __libc_setutent (void) attribute_hidden;
> +int __libc_getutent_r (struct utmp *, struct utmp **) attribute_hidden;
> +int __libc_getutid_r (const struct utmp *, struct utmp *, struct utmp **)
> + attribute_hidden;
> +int __libc_getutline_r (const struct utmp *, struct utmp *, struct utmp **)
> + attribute_hidden;
> +struct utmp *__libc_pututline (const struct utmp *) attribute_hidden;
> +void __libc_endutent (void) attribute_hidden;
> +int __libc_updwtmp (const char *, const struct utmp *) attribute_hidden;
>
> /* Current file name. */
> extern const char *__libc_utmp_file_name attribute_hidden;
Ok.
> diff --git a/login/utmp_file.c b/login/utmp_file.c
> index 040a505711..069e6d0452 100644
> --- a/login/utmp_file.c
> +++ b/login/utmp_file.c
> @@ -105,37 +105,12 @@ static void timeout_handler (int signum) {};
> alarm (old_timeout); \
> } while (0)
>
> -
> -/* Functions defined here. */
> -static int setutent_file (void);
> -static int getutent_r_file (struct utmp *buffer, struct utmp **result);
> -static int getutid_r_file (const struct utmp *key, struct utmp *buffer,
> - struct utmp **result);
> -static int getutline_r_file (const struct utmp *key, struct utmp *buffer,
> - struct utmp **result);
> -static struct utmp *pututline_file (const struct utmp *data);
> -static void endutent_file (void);
> -static int updwtmp_file (const char *file, const struct utmp *utmp);
> -
> -/* Jump table for file functions. */
> -const struct utfuncs __libc_utmp_file_functions =
> -{
> - setutent_file,
> - getutent_r_file,
> - getutid_r_file,
> - getutline_r_file,
> - pututline_file,
> - endutent_file,
> - updwtmp_file
> -};
> -
> -
Ok.
> #ifndef TRANSFORM_UTMP_FILE_NAME
> # define TRANSFORM_UTMP_FILE_NAME(file_name) (file_name)
> #endif
>
> -static int
> -setutent_file (void)
> +int
> +__libc_setutent (void)
> {
> if (file_fd < 0)
> {
> @@ -166,15 +141,19 @@ setutent_file (void)
> return 1;
> }
>
> +/* Preform initialization if necessary. */
> +static bool
> +maybe_setutent (void)
> +{
> + return file_fd >= 0 || __libc_setutent ();
> +}
>
Ok, asserts out.
> -static int
> -getutent_r_file (struct utmp *buffer, struct utmp **result)
> +int
> +__libc_getutent_r (struct utmp *buffer, struct utmp **result)
> {
> ssize_t nbytes;
>
> - assert (file_fd >= 0);
> -
> - if (file_offset == -1l)
> + if (!maybe_setutent () || file_offset == -1l)
> {
> /* Not available. */
> *result = NULL;
> @@ -279,13 +258,11 @@ unlock_return:
>
> /* For implementing this function we don't use the getutent_r function
> because we can avoid the reposition on every new entry this way. */
> -static int
> -getutid_r_file (const struct utmp *id, struct utmp *buffer,
> - struct utmp **result)
> +int
> +__libc_getutid_r (const struct utmp *id, struct utmp *buffer,
> + struct utmp **result)
> {
> - assert (file_fd >= 0);
> -
> - if (file_offset == -1l)
> + if (!maybe_setutent () || file_offset == -1l)
> {
> *result = NULL;
> return -1;
> @@ -309,13 +286,11 @@ getutid_r_file (const struct utmp *id, struct utmp *buffer,
>
> /* For implementing this function we don't use the getutent_r function
> because we can avoid the reposition on every new entry this way. */
> -static int
> -getutline_r_file (const struct utmp *line, struct utmp *buffer,
> - struct utmp **result)
> +int
> +__libc_getutline_r (const struct utmp *line, struct utmp *buffer,
> + struct utmp **result)
> {
> - assert (file_fd >= 0);
> -
> - if (file_offset == -1l)
> + if (!maybe_setutent () || file_offset == -1l)
> {
> *result = NULL;
> return -1;
> @@ -361,15 +336,16 @@ unlock_return:
> }
>
>
> -static struct utmp *
> -pututline_file (const struct utmp *data)
> +struct utmp *
> +__libc_pututline (const struct utmp *data)
> {
> + if (!maybe_setutent ())
> + return NULL;
> +
> struct utmp buffer;
> struct utmp *pbuf;
> int found;
>
> - assert (file_fd >= 0);
> -
> if (! file_writable)
> {
> /* We must make the file descriptor writable before going on. */
> @@ -467,18 +443,19 @@ pututline_file (const struct utmp *data)
> }
>
>
> -static void
> -endutent_file (void)
> +void
> +__libc_endutent (void)
> {
> - assert (file_fd >= 0);
> -
> - __close_nocancel_nostatus (file_fd);
> - file_fd = -1;
> + if (file_fd >= 0)
> + {
> + __close_nocancel_nostatus (file_fd);
> + file_fd = -1;
> + }
> }
>
>
> -static int
> -updwtmp_file (const char *file, const struct utmp *utmp)
> +int
> +__libc_updwtmp (const char *file, const struct utmp *utmp)
> {
> int result = -1;
> off64_t offset;
Ok.
> diff --git a/login/utmpname.c b/login/utmpname.c
> index 21cb890a1a..73b19c33ce 100644
> --- a/login/utmpname.c
> +++ b/login/utmpname.c
> @@ -42,8 +42,7 @@ __utmpname (const char *file)
> __libc_lock_lock (__libc_utmp_lock);
>
> /* Close the old file. */
> - (*__libc_utmp_jump_table->endutent) ();
> - __libc_utmp_jump_table = &__libc_utmp_unknown_functions;
> + __libc_endutent ();
>
> if (strcmp (file, __libc_utmp_file_name) != 0)
> {
Ok.
> diff --git a/manual/users.texi b/manual/users.texi
> index 4ed79ba26f..a006bb58ac 100644
> --- a/manual/users.texi
> +++ b/manual/users.texi
> @@ -894,9 +894,9 @@ The @code{getlogin} function is declared in @file{unistd.h}, while
> @c ttyname_r dup @ascuheap @acsmem @acsfd
> @c strncpy dup ok
> @c libc_lock_lock dup @asulock @aculock
> -@c *libc_utmp_jump_table->setutent dup @mtasurace:utent @acsfd
> -@c *libc_utmp_jump_table->getutline_r dup @mtasurace:utent @mtascusig:ALRM @mtascutimer
> -@c *libc_utmp_jump_table->endutent dup @mtasurace:utent @asulock @aculock
> +@c __libc_setutent dup @mtasurace:utent @acsfd
> +@c __libc_getutline_r dup @mtasurace:utent @mtascusig:ALRM @mtascutimer
> +@c __libc_endutent dup @mtasurace:utent @asulock @aculock
> @c libc_lock_unlock dup ok
> @c strlen dup ok
> @c memcpy dup ok
> @@ -1111,7 +1111,7 @@ compatibility only, @file{utmp.h} defines @code{ut_time} as an alias for
>
> @c setutent @mtasurace:utent @asulock @aculock @acsfd
> @c libc_lock_lock dup @asulock @aculock
> -@c *libc_utmp_jump_table->setutent @mtasurace:utent @acsfd
> +@c __libc_setutent @mtasurace:utent @acsfd
> @c setutent_unknown @mtasurace:utent @acsfd
> @c *libc_utmp_file_functions.setutent = setutent_file @mtasurace:utent @acsfd
> @c open_not_cancel_2 dup @acsfd
> @@ -1152,7 +1152,7 @@ A null pointer is returned in case no further entry is available.
> @safety{@prelim{}@mtunsafe{@mtasurace{:utent}}@asunsafe{@asulock{}}@acunsafe{@aculock{} @acsfd{}}}
> @c endutent @mtasurace:utent @asulock @aculock @acsfd
> @c libc_lock_lock dup @asulock @aculock
> -@c *libc_utmp_jump_table->endutent @mtasurace:utent @acsfd
> +@c __libc_endutent @mtasurace:utent @acsfd
> @c endutent_unknown ok
> @c endutent_file @mtasurace:utent @acsfd
> @c close_not_cancel_no_status dup @acsfd
> @@ -1230,7 +1230,7 @@ over again.
> @safety{@prelim{}@mtunsafe{@mtasurace{:utent} @mtascusig{:ALRM} @mtascutimer{}}@asunsafe{@asulock{}}@acunsafe{@aculock{} @acsfd{}}}
> @c pututline @mtasurace:utent @mtascusig:ALRM @mtascutimer @asulock @aculock @acsfd
> @c libc_lock_lock dup @asulock @aculock
> -@c *libc_utmp_jump_table->pututline @mtasurace:utent @mtascusig:ALRM @mtascutimer @acsfd
> +@c __libc_pututline @mtasurace:utent @mtascusig:ALRM @mtascutimer @acsfd
> @c pututline_unknown @mtasurace:utent @acsfd
> @c setutent_unknown dup @mtasurace:utent @acsfd
> @c pututline_file @mtascusig:ALRM @mtascutimer @acsfd
> @@ -1282,7 +1282,7 @@ user-provided buffer.
> @safety{@prelim{}@mtunsafe{@mtasurace{:utent} @mtascusig{:ALRM} @mtascutimer{}}@asunsafe{@asulock{}}@acunsafe{@aculock{} @acsfd{}}}
> @c getutent_r @mtasurace:utent @mtascusig:ALRM @mtascutimer @asulock @aculock @acsfd
> @c libc_lock_lock dup @asulock @aculock
> -@c *libc_utmp_jump_table->getutent_r @mtasurace:utent @mtascusig:ALRM @mtascutimer @acsfd
> +@c __libc_getutent_r @mtasurace:utent @mtascusig:ALRM @mtascutimer @acsfd
> @c getutent_r_unknown @mtasurace:utent @acsfd
> @c setutent_unknown dup @mtasurace:utent @acsfd
> @c getutent_r_file @mtasurace:utent @mtascusig:ALRM @mtascutimer
> @@ -1319,7 +1319,7 @@ This function is a GNU extension.
> @safety{@prelim{}@mtunsafe{@mtasurace{:utent} @mtascusig{:ALRM} @mtascutimer{}}@asunsafe{@asulock{}}@acunsafe{@aculock{} @acsfd{}}}
> @c getutid_r @mtasurace:utent @mtascusig:ALRM @mtascutimer @asulock @aculock @acsfd
> @c libc_lock_lock dup @asulock @aculock
> -@c *libc_utmp_jump_table->getutid_r @mtasurace:utent @mtascusig:ALRM @mtascutimer @acsfd
> +@c __libc_getutid_r @mtasurace:utent @mtascusig:ALRM @mtascutimer @acsfd
> @c getutid_r_unknown @mtasurace:utent @acsfd
> @c setutent_unknown dup @mtasurace:utent @acsfd
> @c getutid_r_file @mtascusig:ALRM @mtascutimer
> @@ -1349,7 +1349,7 @@ This function is a GNU extension.
> @safety{@prelim{}@mtunsafe{@mtasurace{:utent} @mtascusig{:ALRM} @mtascutimer{}}@asunsafe{@asulock{}}@acunsafe{@aculock{} @acsfd{}}}
> @c getutline_r @mtasurace:utent @mtascusig:ALRM @mtascutimer @asulock @aculock @acsfd
> @c libc_lock_lock dup @asulock @aculock
> -@c *libc_utmp_jump_table->getutline_r @mtasurace:utent @mtascusig:ALRM @mtascutimer @acsfd
> +@c __libc_getutline_r @mtasurace:utent @mtascusig:ALRM @mtascutimer @acsfd
> @c getutline_r_unknown @mtasurace:utent @acsfd
> @c setutent_unknown dup @mtasurace:utent @acsfd
> @c getutline_r_file @mtasurace:utent @mtascusig:ALRM @mtascutimer
> @@ -1393,7 +1393,7 @@ be used.
> @safety{@prelim{}@mtunsafe{@mtasurace{:utent}}@asunsafe{@asulock{} @ascuheap{}}@acunsafe{@aculock{} @acsmem{}}}
> @c utmpname @mtasurace:utent @asulock @ascuheap @aculock @acsmem
> @c libc_lock_lock dup @asulock @aculock
> -@c *libc_utmp_jump_table->endutent dup @mtasurace:utent
> +@c __libc_endutent dup @mtasurace:utent
> @c strcmp dup ok
> @c free dup @ascuheap @acsmem
> @c strdup dup @ascuheap @acsmem
Ok.
> diff --git a/sysdeps/unix/getlogin_r.c b/sysdeps/unix/getlogin_r.c
> index 444df7e4d3..180c0bbca1 100644
> --- a/sysdeps/unix/getlogin_r.c
> +++ b/sysdeps/unix/getlogin_r.c
> @@ -64,8 +64,8 @@ __getlogin_r (char *name, size_t name_len)
> held so that our search is thread-safe. */
>
> __libc_lock_lock (__libc_utmp_lock);
> - (*__libc_utmp_jump_table->setutent) ();
> - result = (*__libc_utmp_jump_table->getutline_r) (&line, &buffer, &ut);
> + __libc_setutent ();
> + result = __libc_getutline_r (&line, &buffer, &ut);
> if (result < 0)
> {
> if (errno == ESRCH)
> @@ -74,8 +74,7 @@ __getlogin_r (char *name, size_t name_len)
> else
> result = errno;
> }
> - (*__libc_utmp_jump_table->endutent) ();
> - __libc_utmp_jump_table = &__libc_utmp_unknown_functions;
> + __libc_endutent ();
> __libc_lock_unlock (__libc_utmp_lock);
>
> if (result == 0)
>
Ok.