nptl: Remove vfork IFUNC-based forwarder from libpthread [BZ #20188]

With commit f0b2132 ("ld.so:
Support moving versioned symbols between sonames [BZ #24741]"), the
dynamic linker will find the definition of vfork in libc and binds
a vfork reference to that symbol, even if the soname in the version
reference says that the symbol should be located in libpthread.

As a result, the forwarder (whether it's IFUNC-based or a duplicate
of the libc implementation) is no longer necessary.

On older architectures, a placeholder symbol is required, to make sure
that the GLIBC_2.1.2 symbol version does not go away, or is turned in
to a weak symbol definition by the link editor.  (The symbol version
needs to preserved so that the symbol coverage check in
elf/dl-version.c does not fail for old binaries.)

mips32 is an outlier: It defined __vfork@@GLIBC_2.2, but the
baseline is GLIBC_2.0.  Since there are other @@GLIBC_2.2 symbols,
the placeholder symbol is not needed there.

ChangeLog

@@ -1,3 +1,84 @@
+2019-07-01  Florian Weimer  <[email protected]>
+
+	[BZ #20188]
+	* nptl/Versions (libpthread): Remove __fork from GLIBC_2.0.
+	Replace __vfork with __libpthread_version_placeholder for
+	GLIBC_2.1.2.
+	(libc): Remove __libc_vfork from GLIBC_PRIVATE.
+	* nptl/Makefile (libpthread-routines): Remove pt-vfork.  Add
+	libpthread-compat.
+	* nptl/pt-vfork.c: Remove file.
+	* sysdeps/unix/sysv/linux/aarch64/pt-vfork.c: Likewise.
+	* sysdeps/unix/sysv/linux/alpha/pt-vfork.S: Likewise.
+	* sysdeps/unix/sysv/linux/csky/pt-vfork.S: Likewise.
+	* sysdeps/unix/sysv/linux/hppa/pt-vfork.S: Likewise.
+	* sysdeps/unix/sysv/linux/ia64/pt-vfork.S: Likewise.
+	* sysdeps/unix/sysv/linux/m68k/pt-vfork.c: Likewise.
+	* sysdeps/unix/sysv/linux/microblaze/pt-vfork.S: Likewise.
+	* sysdeps/unix/sysv/linux/mips/pt-vfork.S: Likewise.
+	* sysdeps/unix/sysv/linux/nios2/pt-vfork.S: Likewise.
+	* sysdeps/unix/sysv/linux/riscv/pt-vfork.S: Likewise.
+	* sysdeps/unix/sysv/linux/s390/pt-vfork.S: Likewise.
+	* sysdeps/unix/sysv/linux/sh/pt-vfork.S: Likewise.
+	* sysdeps/unix/sysv/linux/sparc/pt-vfork.S: Likewise.
+	* sysdeps/unix/sysv/linux/aarch64/libpthread.abilist (GLIBC_2.17):
+	Remove vfork, __vfork.
+	* sysdeps/unix/sysv/linux/alpha/libpthread.abilist (GLIBC_2.0):
+	Remove vfork.
+	(GLIBC_2.1.2): Replace __vfork with
+	__libpthread_version_placeholder.
+	* sysdeps/unix/sysv/linux/arm/libpthread.abilist (GLIBC_2.4):
+	Remove vfork, __vfork.
+	* sysdeps/unix/sysv/linux/hppa/libpthread.abilist (GLIBC_2.2):
+	Likewise.
+	* sysdeps/unix/sysv/linux/i386/libpthread.abilist (GLIBC_2.0):
+	Remove vfork.
+	(GLIBC_2.1.2): Replace __vfork with
+	__libpthread_version_placeholder.
+	* sysdeps/unix/sysv/linux/ia64/libpthread.abilist (GLIBC_2.2):
+	Remove vfork.
+	* sysdeps/unix/sysv/linux/m68k/coldfire/libpthread.abilist
+	(GLIBC_2.4): Remove vfork, __vfork.
+	* sysdeps/unix/sysv/linux/m68k/m680x0/libpthread.abilist
+	(GLIBC_2.0): Remove vfork.
+	(GLIBC_2.1.2): Replace __vfork with
+	__libpthread_version_placeholder.
+	* sysdeps/unix/sysv/linux/microblaze/libpthread.abilist
+	(GLIBC_2.18): Remove vfork, __vfork.
+	* sysdeps/unix/sysv/linux/mips/mips32/libpthread.abilist
+	(GLIBC_2.0): Remove vfork.
+	(GLIBC_2.2): Remove __vfork.
+	* sysdeps/unix/sysv/linux/mips/mips64/libpthread.abilist:
+	(GLIBC_2.2): Remove vfork, __vfork.
+	* sysdeps/unix/sysv/linux/powerpc/powerpc32/libpthread.abilist:
+	(GLIBC_2.0): Remove vfork.
+	(GLIBC_2.1.2): Replace __vfork with
+	__libpthread_version_placeholder.
+	* sysdeps/unix/sysv/linux/powerpc/powerpc64/be/libpthread.abilist
+	(GLIBC_2.3): Remove vfork, __vfork.
+	* sysdeps/unix/sysv/linux/powerpc/powerpc64/le/libpthread.abilist
+	(GLIBC_2.17): Likewise.
+	* sysdeps/unix/sysv/linux/s390/s390-32/libpthread.abilist
+	(GLIBC_2.0): Remove vfork.
+	(GLIBC_2.1.2): Replace __vfork with
+	__libpthread_version_placeholder.
+	* sysdeps/unix/sysv/linux/s390/s390-64/libpthread.abilist
+	(GLIBC_2.2): Remove vfork, __vfork.
+	* sysdeps/unix/sysv/linux/sh/libpthread.abilist (GLIBC_2.2):
+	Likewise.
+	* sysdeps/unix/sysv/linux/sparc/sparc32/libpthread.abilist
+	(GLIBC_2.0): Remove vfork.
+	(GLIBC_2.1.2): Replace __vfork with
+	__libpthread_version_placeholder.
+	* sysdeps/unix/sysv/linux/sparc/sparc64/libpthread.abilist
+	(GLIBC_2.2): Remove vfork, __vfork.
+	* sysdeps/unix/sysv/linux/x86_64/64/libpthread.abilist
+	(GLIBC_2.2.5): Likewise.
+	* sysdeps/unix/sysv/linux/x86_64/x32/libpthread.abilist
+	(GLIBC_2.16): Likewise.
+	* sysdeps/unix/sysv/linux/hppa/localplt.data (libpthread.so):
+	Remove __errno_location.
+
 2019-07-02  Florian Weimer  <[email protected]>
 
 	[BZ #24757]

nptl/Makefile

@@ -120,7 +120,7 @@ libpthread-routines = nptl-init nptlfreeres vars events version pt-interp \
 		      cancellation \
 		      lowlevellock \
 		      lll_timedlock_wait \
-		      pt-fork pt-vfork pt-fcntl \
+		      pt-fork pt-fcntl \
 		      $(pthread-compat-wrappers) \
 		      pt-raise pt-system \
 		      flockfile ftrylockfile funlockfile \
@@ -144,7 +144,8 @@ libpthread-routines = nptl-init nptlfreeres vars events version pt-interp \
 		      mtx_destroy mtx_init mtx_lock mtx_timedlock \
 		      mtx_trylock mtx_unlock call_once cnd_broadcast \
 		      cnd_destroy cnd_init cnd_signal cnd_timedwait cnd_wait \
-		      tss_create tss_delete tss_get tss_set pthread_mutex_conf
+		      tss_create tss_delete tss_get tss_set pthread_mutex_conf \
+		      libpthread-compat
 #		      pthread_setuid pthread_seteuid pthread_setreuid \
 #		      pthread_setresuid \
 #		      pthread_setgid pthread_setegid pthread_setregid \

nptl/Versions

@@ -36,7 +36,6 @@ libc {
     __libc_alloca_cutoff;
     # Internal libc interface to libpthread
     __libc_dl_error_tsd;
-    __libc_vfork;
     __libc_pthread_init;
     __libc_current_sigrtmin_private; __libc_current_sigrtmax_private;
     __libc_allocate_rtsig_private;
@@ -98,7 +97,7 @@ libpthread {
     sem_destroy; sem_getvalue; sem_init; sem_post; sem_trywait; sem_wait;
 
     # Special fork handling.
-    fork; __fork; vfork;
+    fork; __fork;
 
     # Cancellation points.
     close; __close; fcntl; __fcntl; read; __read; write; __write; accept;
@@ -152,7 +151,7 @@ libpthread {
   }
 
   GLIBC_2.1.2 {
-    __vfork;
+    __libpthread_version_placeholder;
   }
 
   GLIBC_2.2 {

nptl/libpthread-compat.c

@@ -0,0 +1,37 @@
+/* Placeholder definitions to pull in removed symbol versions.
+   Copyright (C) 2019 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <shlib-compat.h>
+
+/* This is an unused compatibility symbol definition, to prevent ld
+   from creating a weak version definition for GLIBC_2.1.2.  (__vfork
+   used to be defined at that version, but it is now provided by libc,
+   and there are no versions left in libpthread for that symbol
+   version.)  If the ABI baseline for glibc is the GLIBC_2.2 symbol
+   version or later, the placeholder symbol is not needed because
+   there are plenty of other symbols which populate those later
+   versions.  */
+#if (SHLIB_COMPAT (libpthread, GLIBC_2_1_2, GLIBC_2_2))
+void
+attribute_compat_text_section
+__libpthread_version_placeholder (void)
+{
+}
+compat_symbol (libpthread, __libpthread_version_placeholder,
+               __libpthread_version_placeholder, GLIBC_2_1_2);
+#endif

sysdeps/unix/sysv/linux/aarch64/libpthread.abilist

@@ -45,7 +45,6 @@ GLIBC_2.17 __read F
 GLIBC_2.17 __res_state F
 GLIBC_2.17 __send F
 GLIBC_2.17 __sigaction F
-GLIBC_2.17 __vfork F
 GLIBC_2.17 __wait F
 GLIBC_2.17 __write F
 GLIBC_2.17 _pthread_cleanup_pop F
@@ -216,7 +215,6 @@ GLIBC_2.17 siglongjmp F
 GLIBC_2.17 sigwait F
 GLIBC_2.17 system F
 GLIBC_2.17 tcdrain F
-GLIBC_2.17 vfork F
 GLIBC_2.17 wait F
 GLIBC_2.17 waitpid F
 GLIBC_2.17 write F

sysdeps/unix/sysv/linux/alpha/libpthread.abilist

@@ -114,7 +114,6 @@ GLIBC_2.0 siglongjmp F
 GLIBC_2.0 sigwait F
 GLIBC_2.0 system F
 GLIBC_2.0 tcdrain F
-GLIBC_2.0 vfork F
 GLIBC_2.0 wait F
 GLIBC_2.0 waitpid F
 GLIBC_2.0 write F
@@ -155,7 +154,7 @@ GLIBC_2.1 sem_wait F
 GLIBC_2.1.1 sem_close F
 GLIBC_2.1.1 sem_open F
 GLIBC_2.1.1 sem_unlink F
-GLIBC_2.1.2 __vfork F
+GLIBC_2.1.2 __libpthread_version_placeholder F
 GLIBC_2.11 pthread_sigqueue F
 GLIBC_2.12 pthread_getname_np F
 GLIBC_2.12 pthread_mutex_consistent F

sysdeps/unix/sysv/linux/arm/libpthread.abilist

@@ -74,7 +74,6 @@ GLIBC_2.4 __read F
 GLIBC_2.4 __res_state F
 GLIBC_2.4 __send F
 GLIBC_2.4 __sigaction F
-GLIBC_2.4 __vfork F
 GLIBC_2.4 __wait F
 GLIBC_2.4 __write F
 GLIBC_2.4 _pthread_cleanup_pop F
@@ -239,7 +238,6 @@ GLIBC_2.4 siglongjmp F
 GLIBC_2.4 sigwait F
 GLIBC_2.4 system F
 GLIBC_2.4 tcdrain F
-GLIBC_2.4 vfork F
 GLIBC_2.4 wait F
 GLIBC_2.4 waitpid F
 GLIBC_2.4 write F

sysdeps/unix/sysv/linux/hppa/libpthread.abilist

@@ -46,7 +46,6 @@ GLIBC_2.2 __read F
 GLIBC_2.2 __res_state F
 GLIBC_2.2 __send F
 GLIBC_2.2 __sigaction F
-GLIBC_2.2 __vfork F
 GLIBC_2.2 __wait F
 GLIBC_2.2 __write F
 GLIBC_2.2 _pthread_cleanup_pop F
@@ -192,7 +191,6 @@ GLIBC_2.2 siglongjmp F
 GLIBC_2.2 sigwait F
 GLIBC_2.2 system F
 GLIBC_2.2 tcdrain F
-GLIBC_2.2 vfork F
 GLIBC_2.2 wait F
 GLIBC_2.2 waitpid F
 GLIBC_2.2 write F