Avoid linker bug on Microblaze (was Re: Default build-many-glibcs.py to GCC 7 branch [committed])

Message ID cf6f4870-9b83-dc0d-8c8c-38e7a7285bc4@panix.com
State Committed

Commit Message

Zack Weinberg May 31, 2017, 1:25 a.m. UTC
  On 05/10/2017 09:16 AM, Joseph Myers wrote:
> That said, 
> <https://lists.yoctoproject.org/pipermail/meta-xilinx/2016-November/002258.html> 
> seems to have a plausible explanation of the problem (alias to undefined 
> __libc_vfork, apparently triggering a linker bug).  I'd prefer making 
> MicroBlaze follow the same symbol handling as other architectures (so 
> defining __libc_vfork and then defining other symbols as aliases to it) 
> over the approach in that patch of a MicroBlaze-specific pt-vfork.S.

Indeed, this fixes the problem.  Is this roughly what you had in mind?
I'm probably gonna go ahead and check it in if I don't hear objections
in, like, 24 hours or so.



diff --git a/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
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
+   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)
+#if SHLIB_COMPAT (libpthread, GLIBC_2_0, GLIBC_2_20)
+compat_symbol (libpthread, vfork_compat, vfork, GLIBC_2_0)
+#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)
diff --git a/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)