elf: Make the tunable struct definition internal only

The representation of the tunables including type information and
the tunable list structure are only used in the implementation not
in the tunables api that is exposed to usage within glibc.

This patch moves the representation related definitions into the
existing dl-tunable-types.h and uses that only for implementation.

The tunable callback and related types are moved to dl-tunables.h
because they are part of the tunables api.

This reduces the details exposed in the tunables api so the internals
are easier to change.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

elf/dl-tunable-types.h

@@ -1,4 +1,4 @@
-/* Tunable type information.
+/* Internal representation of tunables.
 
    Copyright (C) 2016-2021 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
@@ -18,8 +18,14 @@
    <https://www.gnu.org/licenses/>.  */
 
 #ifndef _TUNABLE_TYPES_H_
-# define _TUNABLE_TYPES_H_
+#define _TUNABLE_TYPES_H_
+
+/* Note: This header is included in the generated dl-tunables-list.h and
+   only used internally in the tunables implementation in dl-tunables.c.  */
+
+#include <stdbool.h>
 #include <stddef.h>
+#include <stdint.h>
 
 typedef enum
 {
@@ -36,14 +42,6 @@ typedef struct
   int64_t max;
 } tunable_type_t;
 
-typedef union
-{
-  int64_t numval;
-  const char *strval;
-} tunable_val_t;
-
-typedef void (*tunable_callback_t) (tunable_val_t *);
-
 /* Security level for tunables.  This decides what to do with individual
    tunables for AT_SECURE binaries.  */
 typedef enum
@@ -58,5 +56,29 @@ typedef enum
   TUNABLE_SECLEVEL_NONE = 2,
 } tunable_seclevel_t;
 
+/* A tunable.  */
+struct _tunable
+{
+  const char *name;			/* Internal name of the tunable.  */
+  tunable_type_t type;			/* Data type of the tunable.  */
+  tunable_val_t val;			/* The value.  */
+  bool initialized;			/* Flag to indicate that the tunable is
+					   initialized.  */
+  tunable_seclevel_t security_level;	/* Specify the security level for the
+					   tunable with respect to AT_SECURE
+					   programs.  See description of
+					   tunable_seclevel_t to see a
+					   description of the values.
+
+					   Note that even if the tunable is
+					   read, it may not get used by the
+					   target module if the value is
+					   considered unsafe.  */
+  /* Compatibility elements.  */
+  const char *env_alias;		/* The compatibility environment
+					   variable name.  */
+};
+
+typedef struct _tunable tunable_t;
 
 #endif

elf/dl-tunables.h

@@ -21,8 +21,6 @@
 #ifndef _TUNABLES_H_
 #define _TUNABLES_H_
 
-#include <stdbool.h>
-
 #if !HAVE_TUNABLES
 static inline void
 __always_inline
@@ -31,34 +29,17 @@ __tunables_init (char **unused __attribute__ ((unused)))
   /* This is optimized out if tunables are not enabled.  */
 }
 #else
-
+# include <stdbool.h>
 # include <stddef.h>
-# include "dl-tunable-types.h"
+# include <stdint.h>
 
-/* A tunable.  */
-struct _tunable
+typedef union
 {
-  const char *name;			/* Internal name of the tunable.  */
-  tunable_type_t type;			/* Data type of the tunable.  */
-  tunable_val_t val;			/* The value.  */
-  bool initialized;			/* Flag to indicate that the tunable is
-					   initialized.  */
-  tunable_seclevel_t security_level;	/* Specify the security level for the
-					   tunable with respect to AT_SECURE
-					   programs.  See description of
-					   tunable_seclevel_t to see a
-					   description of the values.
+  int64_t numval;
+  const char *strval;
+} tunable_val_t;
 
-					   Note that even if the tunable is
-					   read, it may not get used by the
-					   target module if the value is
-					   considered unsafe.  */
-  /* Compatibility elements.  */
-  const char *env_alias;		/* The compatibility environment
-					   variable name.  */
-};
-
-typedef struct _tunable tunable_t;
+typedef void (*tunable_callback_t) (tunable_val_t *);
 
 /* Full name for a tunable is top_ns.tunable_ns.id.  */
 # define TUNABLE_NAME_S(top,ns,id) #top "." #ns "." #id

scripts/gen-tunables.awk

@@ -156,8 +156,10 @@ END {
   }
   print "} tunable_id_t;\n"
 
-  # Finally, the tunable list.
   print "\n#ifdef TUNABLES_INTERNAL"
+  # Internal definitions.
+  print "# include \"dl-tunable-types.h\""
+  # Finally, the tunable list.
   print "static tunable_t tunable_list[] attribute_relro = {"
   for (tnm in types) {
     split (tnm, indices, SUBSEP);