elf: Add <dl-r_debug.h>

Add <dl-r_debug.h> to get the adddress of the r_debug structure after
relocation and its offset before relocation from the PT_DYNAMIC segment
to support DT_DEBUG, DT_MIPS_RLD_MAP_REL and DT_MIPS_RLD_MAP.

Co-developed-by: Xi Ruoyao <xry111@mengyan1223.wang>

elf/pldd-xx.c

@@ -22,6 +22,8 @@
 #define EW_(e, w, t) EW__(e, w, _##t)
 #define EW__(e, w, t) e##w##t
 
+#include <dl-r_debug.h>
+
 struct E(link_map)
 {
   EW(Addr) l_addr;
@@ -126,21 +128,25 @@ E(find_maps) (const char *exe, int memfd, pid_t pid, void *auxv,
 	    != p[i].p_filesz)
 	  error (EXIT_FAILURE, 0, gettext ("cannot read dynamic section"));
 
-	/* Search for the DT_DEBUG entry.  */
+	/* Search for the struct r_debug.  */
 	for (unsigned int j = 0; j < p[i].p_filesz / sizeof (EW(Dyn)); ++j)
-	  if (dyn[j].d_tag == DT_DEBUG && dyn[j].d_un.d_ptr != 0)
+	  {
-	    {
+	    EW(Addr) off = offset + p[i].p_vaddr + sizeof (EW(Dyn)) * j;
-	      struct E(r_debug) r;
+	    off = E(r_debug_offset) (&dyn[j], memfd, off);
-	      if (pread (memfd, &r, sizeof (r), dyn[j].d_un.d_ptr)
+	    if (off != 0)
-		  != sizeof (r))
+	      {
-		error (EXIT_FAILURE, 0, gettext ("cannot read r_debug"));
+		struct E(r_debug) r;
+		if (pread (memfd, &r, sizeof (r), off)
+		    != sizeof (r))
+		  error (EXIT_FAILURE, 0, gettext ("cannot read r_debug"));
 
-	      if (r.r_map != 0)
+		if (r.r_map != 0)
-		{
+		  {
-		  list = r.r_map;
+		    list = r.r_map;
-		  break;
+		    break;
-		}
+		  }
-	    }
+	      }
+	  }
 
 	free (dyn);
 	break;

elf/tst-dlmopen4.c

@@ -25,16 +25,9 @@
 #include <support/check.h>
 #include <support/test-driver.h>
 
-#ifndef ELF_MACHINE_GET_R_DEBUG
+#define E(x) x
-# define ELF_MACHINE_GET_R_DEBUG(d) \
+#define EW(x) ElfW(x)
-    (__extension__ ({ 						\
+#include <dl-r_debug.h>
-      struct r_debug_extended *debug;				\
-      if ((d)->d_tag == DT_DEBUG)				\
-	debug = (struct r_debug_extended *) (d)->d_un.d_ptr;	\
-      else							\
-	debug = NULL;						\
-      debug; }))
-#endif
 
 static int
 do_test (void)
@@ -44,7 +37,7 @@ do_test (void)
 
   for (d = _DYNAMIC; d->d_tag != DT_NULL; ++d)
     {
-      debug = ELF_MACHINE_GET_R_DEBUG (d);
+      debug = (struct r_debug_extended *) r_debug_address (d);
       if (debug != NULL)
 	break;
     }

sysdeps/generic/dl-r_debug.h

@@ -0,0 +1,36 @@
+/* Function to access r_debug structure.  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/>.  */
+
+/* Return the address of the struct r_debug after relocation.  */
+
+static inline EW(Addr)
+E(r_debug_address) (EW(Dyn) *d)
+{
+  if (d->d_tag == DT_DEBUG)
+    return (EW(Addr)) d->d_un.d_ptr;
+
+  return 0;
+}
+
+/* Return the offset of the struct r_debug before relocation.  */
+
+static inline EW(Addr)
+E(r_debug_offset) (EW(Dyn) *d, int fd, EW(Addr) offset)
+{
+  return E(r_debug_address) (d);
+}

sysdeps/mips/dl-r_debug.h

@@ -0,0 +1,64 @@
+/* Function to access r_debug structure.  MIPS specific 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/>.  */
+
+#ifdef EW_
+/* Return the offset of the struct r_debug before relocation.  */
+
+static inline EW(Addr)
+E(r_debug_offset) (EW(Dyn) *d, int fd, EW(Addr) offset)
+{
+  switch (d->d_tag)
+    {
+    case DT_MIPS_RLD_MAP_REL:
+      offset += d->d_un.d_val;
+      break;
+    case DT_MIPS_RLD_MAP:
+      offset = d->d_un.d_ptr;
+      break;
+    default:
+      return 0;
+    }
+
+  if (pread (fd, &offset, sizeof (offset), offset) != sizeof (offset))
+    return 0;
+
+  return offset;
+}
+#else
+/* Return the address of the struct r_debug after relocation.  */
+
+static inline EW(Addr)
+E(r_debug_address) (EW(Dyn) *d)
+{
+  EW(Addr) ptr;
+
+  switch (d->d_tag)
+    {
+    case DT_MIPS_RLD_MAP_REL:
+      ptr = ((EW(Addr)) d) + d->d_un.d_val;
+      break;
+    case DT_MIPS_RLD_MAP:
+      ptr = d->d_un.d_ptr;
+      break;
+    default:
+      return 0;
+    }
+
+  return *(EW(Addr) *) ptr;
+}
+#endif