elf: Add <dl-debug.h>

Add <dl-debug.h> to setup debugging entry in PT_DYNAMIC segment to support
DT_DEBUG, DT_MIPS_RLD_MAP_REL and DT_MIPS_RLD_MAP.

Tested on x86-64, x32 and i686 as well as with build-many-glibcs.py.

elf/dl-reloc-static-pie.c

@@ -24,6 +24,7 @@
 #include <ldsodefs.h>
 
 #include <dl-machine.h>
+#include <dl-debug.h>
 
 #define RESOLVE_MAP(map, scope, sym, version, flags) map
 #include "dynamic-link.h"
@@ -68,14 +69,6 @@ _dl_relocate_static_pie (void)
 
   /* Set up debugging before the debugger is notified for the first
      time.  */
-# ifdef ELF_MACHINE_DEBUG_SETUP
+  elf_setup_debug_entry (main_map, r);
-  /* Some machines (e.g. MIPS) don't use DT_DEBUG in this way.  */
-  ELF_MACHINE_DEBUG_SETUP (main_map, r);
-# else
-  if (main_map->l_info[DT_DEBUG] != NULL)
-    /* There is a DT_DEBUG entry in the dynamic section.  Fill it in
-       with the run-time address of the r_debug structure  */
-    main_map->l_info[DT_DEBUG]->d_un.d_ptr = (ElfW(Addr)) r;
-# endif
 }
 #endif

elf/rtld.c

@@ -63,6 +63,9 @@
 #define RESOLVE_MAP(map, scope, sym, version, flags) map
 #include "dynamic-link.h"
 
+/* Must include after <dl-machine.h> for DT_MIPS definition.  */
+#include <dl-debug.h>
+
 /* Only enables rtld profiling for architectures which provides non generic
    hp-timing support.  The generic support requires either syscall
    (clock_gettime), which will incur in extra overhead on loading time.
@@ -1776,15 +1779,7 @@ dl_main (const ElfW(Phdr) *phdr,
   size_t count_modids = _dl_count_modids ();
 
   /* Set up debugging before the debugger is notified for the first time.  */
-#ifdef ELF_MACHINE_DEBUG_SETUP
+  elf_setup_debug_entry (main_map, r);
-  /* Some machines (e.g. MIPS) don't use DT_DEBUG in this way.  */
-  ELF_MACHINE_DEBUG_SETUP (main_map, r);
-#else
-  if (main_map->l_info[DT_DEBUG] != NULL)
-    /* There is a DT_DEBUG entry in the dynamic section.  Fill it in
-       with the run-time address of the r_debug structure  */
-    main_map->l_info[DT_DEBUG]->d_un.d_ptr = (ElfW(Addr)) r;
-#endif
 
   /* We start adding objects.  */
   r->r_state = RT_ADD;

sysdeps/generic/dl-debug.h

@@ -0,0 +1,33 @@
+/* Debugging support.  Generic version.
+   Copyright (C) 2022 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
+   <https://www.gnu.org/licenses/>.  */
+
+#ifndef _DL_DEBUG_H
+#define _DL_DEBUG_H
+
+/* There is a DT_DEBUG entry in the dynamic section.  Fill it in with the
+   run-time address of the r_debug structure  */
+
+static inline void
+__attribute ((always_inline))
+elf_setup_debug_entry (struct link_map *l, struct r_debug *r)
+{
+  if (l->l_info[DT_DEBUG] != NULL)
+    l->l_info[DT_DEBUG]->d_un.d_ptr = (ElfW(Addr)) r;
+}
+
+#endif /* _DL_DEBUG_H */

sysdeps/mips/dl-debug.h

@@ -0,0 +1,41 @@
+/* Debugging support.  MIPS version.
+   Copyright (C) 2022 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
+   <https://www.gnu.org/licenses/>.  */
+
+#ifndef _DL_DEBUG_H
+#define _DL_DEBUG_H
+
+/* If there is a DT_MIPS_RLD_MAP_REL or DT_MIPS_RLD_MAP entry in the
+   dynamic section, fill in the debug map pointer with the run-time
+   address of the r_debug structure.  */
+
+static inline void
+__attribute ((always_inline))
+elf_setup_debug_entry (struct link_map *l, struct r_debug *r)
+{
+  if (l->l_info[DT_MIPS (RLD_MAP_REL)] != NULL)
+    {
+      char *ptr = (char *) l->l_info[DT_MIPS (RLD_MAP_REL)];
+      ptr += l->l_info[DT_MIPS (RLD_MAP_REL)]->d_un.d_val;
+      *(ElfW(Addr) *) ptr = (ElfW(Addr)) r;
+    }
+  else if (l->l_info[DT_MIPS (RLD_MAP)] != NULL)
+    *(ElfW(Addr) *) (l->l_info[DT_MIPS (RLD_MAP)]->d_un.d_ptr)
+      = (ElfW(Addr)) r;
+}
+
+#endif /* _DL_DEBUG_H */

sysdeps/mips/dl-machine.h

@@ -65,21 +65,6 @@
    in l_info array.  */
 #define DT_MIPS(x) (DT_MIPS_##x - DT_LOPROC + DT_NUM)
 
-/* If there is a DT_MIPS_RLD_MAP_REL or DT_MIPS_RLD_MAP entry in the dynamic
-   section, fill in the debug map pointer with the run-time address of the
-   r_debug structure.  */
-#define ELF_MACHINE_DEBUG_SETUP(l,r) \
-do { if ((l)->l_info[DT_MIPS (RLD_MAP_REL)]) \
-       { \
-	 char *ptr = (char *)(l)->l_info[DT_MIPS (RLD_MAP_REL)]; \
-	 ptr += (l)->l_info[DT_MIPS (RLD_MAP_REL)]->d_un.d_val; \
-	 *(ElfW(Addr) *)ptr = (ElfW(Addr)) (r); \
-       } \
-     else if ((l)->l_info[DT_MIPS (RLD_MAP)]) \
-       *(ElfW(Addr) *)((l)->l_info[DT_MIPS (RLD_MAP)]->d_un.d_ptr) = \
-       (ElfW(Addr)) (r); \
-   } while (0)
-
 #if ((defined __mips_nan2008 && !defined HAVE_MIPS_NAN2008) \
      || (!defined __mips_nan2008 && defined HAVE_MIPS_NAN2008))
 # error "Configuration inconsistency: __mips_nan2008 != HAVE_MIPS_NAN2008, overridden CFLAGS?"