[PATCH COMMITTED] Avoid tickling a linker bug from microblaze pt-vfork.S.

[Zack Weinberg <zackw at panix dot com>]

libpthread used to have its own vfork implementation that differed
from libc's only in having a pointless micro-optimization.  There is
no longer any use to having a separate copy in libpthread, but the
historical ABI requires a compatibility shim.  microblaze was trying
to be slightly too clever about how it did this, and tickled a linker
bug.  The linker bug should get fixed eventually, but there's no
reason for us to keep tickling it in the meantime.

This doesn't reuse the generic pt-vfork.c because microblaze doesn't
have IFUNC support yet, and it doesn't reuse aarch64/pt-vfork.c
because that fails to generate a tailcall (with GCC 7.1.1).

	* sysdeps/unix/sysv/linux/microblaze/pt-vfork.S: Don't include
	alpha/pt-vfork.S.  Provide own compat shim for vfork and __vfork.
	* sysdeps/unix/sysv/linux/microblaze/vfork.S: Add __libc_vfork alias.
	* sysdeps/unix/sysv/linux/microblaze/localplt.data:
	libpthread.so no longer references __errno_location.
---
 sysdeps/unix/sysv/linux/microblaze/localplt.data |  1 -
 sysdeps/unix/sysv/linux/microblaze/pt-vfork.S    | 50 +++++++++++++++++++++++-
 sysdeps/unix/sysv/linux/microblaze/vfork.S       |  1 +
 3 files changed, 50 insertions(+), 2 deletions(-)

diff --git a/sysdeps/unix/sysv/linux/microblaze/localplt.data b/sysdeps/unix/sysv/linux/microblaze/localplt.data
index a61b94dfb8..ca476bedd8 100644
--- a/sysdeps/unix/sysv/linux/microblaze/localplt.data
+++ b/sysdeps/unix/sysv/linux/microblaze/localplt.data
@@ -5,7 +5,6 @@ libc.so: malloc
 libc.so: memalign
 libc.so: realloc
 libm.so: matherr
-libpthread.so: __errno_location
 # The dynamic loader needs __tls_get_addr for TLS.
 ld.so: __tls_get_addr ?
 # The main malloc is interposed into the dynamic linker, for
diff --git a/sysdeps/unix/sysv/linux/microblaze/pt-vfork.S b/sysdeps/unix/sysv/linux/microblaze/pt-vfork.S
index 65cc3823ac..f201f0429f 100644
--- a/sysdeps/unix/sysv/linux/microblaze/pt-vfork.S
+++ b/sysdeps/unix/sysv/linux/microblaze/pt-vfork.S
@@ -1 +1,49 @@
-#include <sysdeps/unix/sysv/linux/alpha/pt-vfork.S>
+/* vfork ABI-compatibility entry points for libpthread.
+   Copyright (C) 2014-2017 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 <sysdep.h>
+#include <shlib-compat.h>
+
+/* libpthread used to have its own vfork implementation that differed
+   from libc's only in having a pointless micro-optimization.  There
+   is no longer any use to having a separate copy in libpthread, but
+   the historical ABI requires it.  For static linking, there is no
+   need to provide anything here--the libc version will be linked in.
+   For shared library ABI compatibility, there must be __vfork and
+   vfork symbols in libpthread.so.
+
+   As of GCC 7, microblaze can *not* rely on the compiler to generate
+   a tail call from this vfork to __libc_vfork.  */
+
+#if (SHLIB_COMPAT (libpthread, GLIBC_2_0, GLIBC_2_20) \
+       || SHLIB_COMPAT (libpthread, GLIBC_2_1_2, GLIBC_2_20))
+
+ENTRY (vfork_compat)
+	bri	__libc_vfork
+END (vfork_compat)
+
+#endif
+
+#if SHLIB_COMPAT (libpthread, GLIBC_2_0, GLIBC_2_20)
+compat_symbol (libpthread, vfork_compat, vfork, GLIBC_2_0)
+#endif
+
+#if SHLIB_COMPAT (libpthread, GLIBC_2_1_2, GLIBC_2_20)
+strong_alias (vfork_compat, vfork_compat2)
+compat_symbol (libpthread, vfork_compat2, __vfork, GLIBC_2_1_2)
+#endif
diff --git a/sysdeps/unix/sysv/linux/microblaze/vfork.S b/sysdeps/unix/sysv/linux/microblaze/vfork.S
index 1ad86229a9..f1e4508d20 100644
--- a/sysdeps/unix/sysv/linux/microblaze/vfork.S
+++ b/sysdeps/unix/sysv/linux/microblaze/vfork.S
@@ -43,3 +43,4 @@ PSEUDO_END (__vfork)
 libc_hidden_def (__vfork)
 
 weak_alias (__vfork, vfork)
+strong_alias (__vfork, __libc_vfork)
-- 
2.11.0