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