Add framework for tunables

The tunables framework allows us to uniformly manage and expose global
variables inside glibc as switches to users.  tunables/README has
instructions for glibc developers to add new tunables.

Tunables support can be enabled by passing the --enable-tunables
configure flag to the configure script.  This patch only adds a
framework and does not pose any limitations on how tunable values are
read from the user.  It also adds environment variables used in malloc
behaviour tweaking to the tunables framework as a PoC of the
compatibility interface.

	* manual/install.texi: Add --enable-tunables option.
	* INSTALL: Regenerate.
	* README.tunables: New file.
	* Makeconfig (CPPFLAGS): Define TOP_NAMESPACE.
	(before-compile): Generate dl-tunable-list.h early.
	* config.h.in: Add HAVE_TUNABLES.
	* config.make.in: Add have-tunables.
	* configure.ac: Add --enable-tunables option.
	* configure: Regenerate.
	* csu/init-first.c (__libc_init_first): Move
	__libc_init_secure earlier...
	* csu/init-first.c (LIBC_START_MAIN):... to here.
	Include dl-tunables.h, libc-internal.h.
	(LIBC_START_MAIN) [!SHARED]: Initialize tunables for static
	binaries.
	* elf/Makefile (dl-routines): Add dl-tunables.
	* elf/Versions (ld): Add __tunable_set_val to GLIBC_PRIVATE
	namespace.
	* elf/dl-support (_dl_nondynamic_init): Unset MALLOC_CHECK_
	only when !HAVE_TUNABLES.
	* elf/rtld.c (process_envvars): Likewise.
	* elf/dl-sysdep.c [HAVE_TUNABLES]: Include dl-tunables.h
	(_dl_sysdep_start): Call __tunables_init.
	* elf/dl-tunable-types.h: New file.
	* elf/dl-tunables.c: New file.
	* elf/dl-tunables.h: New file.
	* elf/dl-tunables.list: New file.
	* malloc/tst-malloc-usable-static.c: New test case.
	* malloc/Makefile (tests-static): Add it.
	* malloc/arena.c [HAVE_TUNABLES]: Include dl-tunables.h.
	Define TUNABLE_NAMESPACE.
	(DL_TUNABLE_CALLBACK (set_mallopt_check)): New function.
	(DL_TUNABLE_CALLBACK_FNDECL): New macro.  Use it to define
	callback functions.
	(ptmalloc_init): Set tunable values.
	* scripts/gen-tunables.awk: New file.
	* sysdeps/mach/hurd/dl-sysdep.c: Include dl-tunables.h.
	(_dl_sysdep_start): Call __tunables_init.

1 files changed, 54 insertions, 0 deletions

diff --git a/malloc/arena.c b/malloc/arena.c
index eed4247..234035f 100644
--- a/malloc/arena.c
+++ b/malloc/arena.c
@@ -19,6 +19,11 @@
 
 #include <stdbool.h>
 
+#if HAVE_TUNABLES
+# define TUNABLE_NAMESPACE malloc
+#endif
+#include <elf/dl-tunables.h>
+
 /* Compile-time constants.  */
 
 #define HEAP_MIN_SIZE (32 * 1024)
@@ -204,6 +209,34 @@ __malloc_fork_unlock_child (void)
   __libc_lock_init (list_lock);
 }
 
+#if HAVE_TUNABLES
+static inline int do_set_mallopt_check (int32_t value);
+void
+DL_TUNABLE_CALLBACK (set_mallopt_check) (void *valp)
+{
+  int32_t value = *(int32_t *) valp;
+  do_set_mallopt_check (value);
+  if (check_action != 0)
+    __malloc_check_init ();
+}
+
+# define DL_TUNABLE_CALLBACK_FNDECL(__name, __type) \
+static inline int do_ ## __name (__type value);				      \
+void									      \
+DL_TUNABLE_CALLBACK (__name) (void *valp)				      \
+{									      \
+  __type value = *(__type *) valp;					      \
+  do_ ## __name (value);						      \
+}
+
+DL_TUNABLE_CALLBACK_FNDECL (set_mmap_threshold, size_t)
+DL_TUNABLE_CALLBACK_FNDECL (set_mmaps_max, int32_t)
+DL_TUNABLE_CALLBACK_FNDECL (set_top_pad, size_t)
+DL_TUNABLE_CALLBACK_FNDECL (set_perturb_byte, int32_t)
+DL_TUNABLE_CALLBACK_FNDECL (set_trim_threshold, size_t)
+DL_TUNABLE_CALLBACK_FNDECL (set_arena_max, size_t)
+DL_TUNABLE_CALLBACK_FNDECL (set_arena_test, size_t)
+#else
 /* Initialization routine. */
 #include <string.h>
 extern char **_environ;
@@ -238,6 +271,7 @@ next_env_entry (char ***position)
 
   return result;
 }
+#endif
 
 
 #ifdef SHARED
@@ -272,6 +306,24 @@ ptmalloc_init (void)
 #endif
 
   thread_arena = &main_arena;
+
+#if HAVE_TUNABLES
+  /* Ensure initialization/consolidation and do it under a lock so that a
+     thread attempting to use the arena in parallel waits on us till we
+     finish.  */
+  __libc_lock_lock (main_arena.mutex);
+  malloc_consolidate (&main_arena);
+
+  TUNABLE_SET_VAL_WITH_CALLBACK (check, NULL, set_mallopt_check);
+  TUNABLE_SET_VAL_WITH_CALLBACK (top_pad, NULL, set_top_pad);
+  TUNABLE_SET_VAL_WITH_CALLBACK (perturb, NULL, set_perturb_byte);
+  TUNABLE_SET_VAL_WITH_CALLBACK (mmap_threshold, NULL, set_mmap_threshold);
+  TUNABLE_SET_VAL_WITH_CALLBACK (trim_threshold, NULL, set_trim_threshold);
+  TUNABLE_SET_VAL_WITH_CALLBACK (mmap_max, NULL, set_mmaps_max);
+  TUNABLE_SET_VAL_WITH_CALLBACK (arena_max, NULL, set_arena_max);
+  TUNABLE_SET_VAL_WITH_CALLBACK (arena_test, NULL, set_arena_test);
+  __libc_lock_unlock (main_arena.mutex);
+#else
   const char *s = NULL;
   if (__glibc_likely (_environ != NULL))
     {
@@ -340,6 +392,8 @@ ptmalloc_init (void)
       if (check_action != 0)
         __malloc_check_init ();
     }
+#endif
+
 #if HAVE_MALLOC_INIT_HOOK
   void (*hook) (void) = atomic_forced_read (__malloc_initialize_hook);
   if (hook != NULL)