commit 1a7fe2ebe52b3c8bf465d1756e69452d05c1c103

Author: Florian Weimer <fweimer@redhat.com>

Date:   Mon Aug 5 15:54:10 2019 +0200

    login: Remove utmp backend jump tables [BZ #23518]

    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.

diff --git a/login/getutent_r.c b/login/getutent_r.c

index 6a244ba6e0b86da7..44239ecb81bacea4 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.  */

-}

-

-

 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);

 }

diff --git a/login/getutid_r.c b/login/getutid_r.c

index b7d3dbac75774b0a..8cb6b16d735e8265 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);

diff --git a/login/getutline_r.c b/login/getutline_r.c

index 6996887f76b28816..5607c19ed2e1ca66 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);

diff --git a/login/updwtmp.c b/login/updwtmp.c

index 56fb41916a776c0a..7ae96224ca789b6d 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)

diff --git a/login/utmp-private.h b/login/utmp-private.h

index bd8773984cfc56de..5c2048ee52dc3cee 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;

diff --git a/login/utmp_file.c b/login/utmp_file.c

index 040a5057116bb69d..069e6d0452e333ad 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

-};

-

-

 #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 ();

+}

-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;

diff --git a/login/utmpname.c b/login/utmpname.c

index 21cb890a1a2fdc92..73b19c33ceab4dd7 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)

     {

diff --git a/manual/users.texi b/manual/users.texi

index 4ed79ba26fc8e9d0..a006bb58acfd0568 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

diff --git a/sysdeps/unix/getlogin_r.c b/sysdeps/unix/getlogin_r.c

index 444df7e4d3210cf6..180c0bbca13d0f87 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)