[PATCHv2] powerpc: Fix syscalls during early process initialization [BZ #22685]

["Tulio Magno Quites Machado Filho" <tuliom at linux dot vnet dot ibm dot com>]

Changes since v1:
 - Re-implemented the patch to re-define a powerpc-specific
   __access_noerrno.

--- 8< ---

The tunables framework needs to execute syscall early in process
initialization, before the TCB is available for consumption.  This
behavior conflicts with powerpc{|64|64le}'s lock elision code, that
checks the TCB before trying to abort transactions immediately before
executing a syscall.

This patch adds a powerpc-specific implementation of __access_noerrno
that does not abort transactions before the executing syscall.

Tested on powerpc{|64|64le}.

2018-01-12  Tulio Magno Quites Machado Filho  <tuliom@linux.vnet.ibm.com>

	[BZ #22685]
	* sysdeps/unix/sysv/linux/powerpc/not-errno.h: New file.  Reuse
	Linux code, but remove the code that aborts transactions.

Signed-off-by: Tulio Magno Quites Machado Filho <tuliom@linux.vnet.ibm.com>
Tested-by: Aurelien Jarno <aurelien@aurel32.net>
---
 sysdeps/unix/sysv/linux/powerpc/not-errno.h | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)
 create mode 100644 sysdeps/unix/sysv/linux/powerpc/not-errno.h

diff --git a/sysdeps/unix/sysv/linux/powerpc/not-errno.h b/sysdeps/unix/sysv/linux/powerpc/not-errno.h
new file mode 100644
index 0000000..642cb8a
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/powerpc/not-errno.h
@@ -0,0 +1,25 @@
+/* Syscall wrapper that do not set errno.  Linux powerpc version.
+   Copyright (C) 2018 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/>.  */
+
+/* __access_noerrno is used during process initialization in elf/dl-tunables.c
+   before the TCB is initialized, prohibiting the usage of
+   ABORT_TRANSACTION.  */
+#undef ABORT_TRANSACTION
+#define ABORT_TRANSACTION
+
+#include "sysdeps/unix/sysv/linux/not-errno.h"
-- 
2.9.5