Delay initialization of CPU features struct in static binaries

Allow the CPU features structure set up to be overridden by tunables
by delaying it to until after tunables are initialized.  The
initialization is already delayed in dynamically linked glibc, it is
only in static binaries that the initialization is set early to allow
it to influence IFUNC relocations that happen in libc-start.  It is a
bit too early however and there is a good place between tunables
initialization and IFUNC relocations where this can be done.

Verified that this does not regress the testsuite.

	* csu/libc-start.c [!ARCH_INIT_CPU_FEATURES]: Define
	ARCH_INIT_CPU_FEATURES.
	(LIBC_START_MAIN): Call it.
	* sysdeps/unix/sysv/linux/aarch64/libc-start.c
	(__libc_start_main): Remove.
	(ARCH_INIT_CPU_FEATURES): New macro.
	* sysdeps/x86/libc-start.c (__libc_start_main): Remove.
	(ARCH_INIT_CPU_FEATURES): New macro.

4 files changed, 27 insertions, 36 deletions

diff --git a/ChangeLog b/ChangeLog
index 876244a00a..859f582c3a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,14 @@
+2017-05-31  Siddhesh Poyarekar  <siddhesh@sourceware.org>
+
+	* csu/libc-start.c [!ARCH_INIT_CPU_FEATURES]: Define
+	ARCH_INIT_CPU_FEATURES.
+	(LIBC_START_MAIN): Call it.
+	* sysdeps/unix/sysv/linux/aarch64/libc-start.c
+	(__libc_start_main): Remove.
+	(ARCH_INIT_CPU_FEATURES): New macro.
+	* sysdeps/x86/libc-start.c (__libc_start_main): Remove.
+	(ARCH_INIT_CPU_FEATURES): New macro.
+
 2017-05-30  Dennis Wölfing  <denniswoelfing@gmx.de>
 	    Rüdiger Sonderfeld  <ruediger@c-plusplus.de>
 
diff --git a/csu/libc-start.c b/csu/libc-start.c
index 9a56dcbbae..c2dd1593eb 100644
--- a/csu/libc-start.c
+++ b/csu/libc-start.c
@@ -104,6 +104,10 @@ apply_irel (void)
 # define MAIN_AUXVEC_PARAM
 #endif
 
+#ifndef ARCH_INIT_CPU_FEATURES
+# define ARCH_INIT_CPU_FEATURES()
+#endif
+
 STATIC int LIBC_START_MAIN (int (*main) (int, char **, char **
 					 MAIN_AUXVEC_DECL),
 			    int argc,
@@ -182,6 +186,8 @@ LIBC_START_MAIN (int (*main) (int, char **, char ** MAIN_AUXVEC_DECL),
 
   __tunables_init (__environ);
 
+  ARCH_INIT_CPU_FEATURES ();
+
   /* Perform IREL{,A} relocations.  */
   apply_irel ();
 
diff --git a/sysdeps/unix/sysv/linux/aarch64/libc-start.c b/sysdeps/unix/sysv/linux/aarch64/libc-start.c
index a5babd49ea..089a728a87 100644
--- a/sysdeps/unix/sysv/linux/aarch64/libc-start.c
+++ b/sysdeps/unix/sysv/linux/aarch64/libc-start.c
@@ -16,26 +16,13 @@
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
-#ifdef SHARED
-# include <csu/libc-start.c>
-# else
-/* The main work is done in the generic function.  */
-# define LIBC_START_DISABLE_INLINE
-# define LIBC_START_MAIN generic_start_main
-# include <csu/libc-start.c>
+#ifndef SHARED
+# include <ldsodefs.h>
 # include <cpu-features.c>
 
 extern struct cpu_features _dl_aarch64_cpu_features;
 
-int
-__libc_start_main (int (*main) (int, char **, char ** MAIN_AUXVEC_DECL),
-		   int argc, char **argv,
-		   __typeof (main) init,
-		   void (*fini) (void),
-		   void (*rtld_fini) (void), void *stack_end)
-{
-  init_cpu_features (&_dl_aarch64_cpu_features);
-  return generic_start_main (main, argc, argv, init, fini, rtld_fini,
-			     stack_end);
-}
+# define ARCH_INIT_CPU_FEATURES() init_cpu_features (&_dl_aarch64_cpu_features)
+
 #endif
+#include <csu/libc-start.c>
diff --git a/sysdeps/x86/libc-start.c b/sysdeps/x86/libc-start.c
index 9a56adc3ec..e11b490f5c 100644
--- a/sysdeps/x86/libc-start.c
+++ b/sysdeps/x86/libc-start.c
@@ -15,27 +15,14 @@
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
-#ifdef SHARED
-# include <csu/libc-start.c>
-# else
-/* The main work is done in the generic function.  */
-# define LIBC_START_DISABLE_INLINE
-# define LIBC_START_MAIN generic_start_main
-# include <csu/libc-start.c>
+#ifndef SHARED
+#include <ldsodefs.h>
 # include <cpu-features.h>
 # include <cpu-features.c>
 
 extern struct cpu_features _dl_x86_cpu_features;
 
-int
-__libc_start_main (int (*main) (int, char **, char ** MAIN_AUXVEC_DECL),
-		   int argc, char **argv,
-		   __typeof (main) init,
-		   void (*fini) (void),
-		   void (*rtld_fini) (void), void *stack_end)
-{
-  init_cpu_features (&_dl_x86_cpu_features);
-  return generic_start_main (main, argc, argv, init, fini, rtld_fini,
-			     stack_end);
-}
+#define ARCH_INIT_CPU_FEATURES() init_cpu_features (&_dl_x86_cpu_features)
+
 #endif
+# include <csu/libc-start.c>