Clean up NPTL system to be compat-only.

ChangeLog

@@ -1,5 +1,9 @@
 2015-02-06  Roland McGrath  <roland@hack.frob.com>
 
+	* nptl/pt-system.c: Rewritten.  Put everything under
+	[SHLIB_COMPAT (libpthread, GLIBC_2_0, GLIBC_2_22)].
+	Use IFUNC to redirect when possible.
+
 	* nptl/pt-longjmp.c: Rewritten.  Put everything under
 	[SHLIB_COMPAT (libpthread, GLIBC_2_0, GLIBC_2_22)].
 	Use IFUNC to redirect when possible.

nptl/pt-system.c

@@ -1,4 +1,5 @@
-/* Copyright (C) 2002-2015 Free Software Foundation, Inc.
+/* ABI compatibility for 'system' symbol in libpthread ABI.
+   Copyright (C) 2002-2015 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
    Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
 
@@ -16,17 +17,48 @@
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
-#include <errno.h>
 #include <stdlib.h>
-#include <sysdep.h>
-#include "pthreadP.h"
+#include <shlib-compat.h>
 
+/* libpthread once had its own 'system', though there was no apparent
+   reason for it.  There is no use in having a separate symbol 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 a
+   'system' symbol in libpthread.so; so we define it using IFUNC to
+   redirect to the libc function.  */
 
-int
-system (const char *line)
+#if SHLIB_COMPAT (libpthread, GLIBC_2_0, GLIBC_2_22)
+
+# if HAVE_IFUNC
+
+static __typeof (system) *
+__attribute__ ((used))
+system_resolve (void)
+{
+  return &__libc_system;
+}
+
+asm (".globl system_ifunc\n"
+     ".type system_ifunc, %gnu_indirect_function");
+
+#  ifdef HAVE_ASM_SET_DIRECTIVE
+asm (".set system_ifunc, system_resolve");
+#  else
+asm ("system_ifunc = system_resolve");
+#  endif
+
+# else  /* !HAVE_IFUNC */
+
+static int __attribute__ ((used))
+system_compat (const char *line)
 {
   return __libc_system (line);
 }
+strong_alias (system_compat, system_ifunc)
+
+# endif  /* HAVE_IFUNC */
+
+compat_symbol (libpthread, system_ifunc, system, GLIBC_2_0);
 
-/* __libc_system in libc.so handles cancellation.  */
-LIBC_CANCEL_HANDLED ();
+#endif