Update.

2004-01-13  Ulrich Drepper  <drepper@redhat.com>

	* Makeconfig: Define relro-LDFLAGS if have-z-relro==yes.  Add it to
	LDFLAGS.so and LDFLAGS-rtld.
	(+link): Add relro-LDFLAGS.
	* Makeconfig (shlib.lds): Place __libc_subfreeres, __libc_atexit, and
	__libc_thread_subfreeres sections after .jcr section.
	* config.make.in: Add have-z-relro.
	* configure.in: Add check for -z relro option.
	* include/link.h (struct link_map): Add relro_addr and relro_size
	members.
	* elf/dl-load.c (_dl_map_object_from_fd): Recognize PT_GNU_RELRO.
	* elf/dl-reloc.c (_dl_relocate_object): At the end, make relro
	part of loaded segments read-only.
	* elf/elf.h: Define PT_GNU_RELRO.
	* elf/rtld.c (_dl_start): Recognize PT_GNU_RELRO of ld.so.
	(dl_main): Recognize PT_GNU_RELRO of the application.  Call
	_dl_debug_initialize and initialize l_info[DT_DEBUG] before
	relocations.

ChangeLog

@@ -1,3 +1,23 @@
+2004-01-13  Ulrich Drepper  <drepper@redhat.com>
+
+	* Makeconfig: Define relro-LDFLAGS if have-z-relro==yes.  Add it to
+	LDFLAGS.so and LDFLAGS-rtld.
+	(+link): Add relro-LDFLAGS.
+	* Makeconfig (shlib.lds): Place __libc_subfreeres, __libc_atexit, and
+	__libc_thread_subfreeres sections after .jcr section.
+	* config.make.in: Add have-z-relro.
+	* configure.in: Add check for -z relro option.
+	* include/link.h (struct link_map): Add relro_addr and relro_size
+	members.
+	* elf/dl-load.c (_dl_map_object_from_fd): Recognize PT_GNU_RELRO.
+	* elf/dl-reloc.c (_dl_relocate_object): At the end, make relro
+	part of loaded segments read-only.
+	* elf/elf.h: Define PT_GNU_RELRO.
+	* elf/rtld.c (_dl_start): Recognize PT_GNU_RELRO of ld.so.
+	(dl_main): Recognize PT_GNU_RELRO of the application.  Call
+	_dl_debug_initialize and initialize l_info[DT_DEBUG] before
+	relocations.
+
 2004-01-12  Jakub Jelinek  <jakub@redhat.com>
 
 	* sysdeps/x86_64/strcspn.S: Fix typo in last patch.

Makerules

@@ -1,4 +1,4 @@
-# Copyright (C) 1991-2002, 2003 Free Software Foundation, Inc.
+# Copyright (C) 1991-2002, 2003, 2004 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
@@ -488,7 +488,17 @@ $(common-objpfx)shlib.lds: $(common-objpfx)config.make $(..)Makerules
 	      -e 's/^.*\*(\.dynbss).*$$/& \
 		 PROVIDE(__start___libc_freeres_ptrs = .); \
 		 *(__libc_freeres_ptrs) \
-		 PROVIDE(__stop___libc_freeres_ptrs = .);/'
+		 PROVIDE(__stop___libc_freeres_ptrs = .);/'\
+	      -e 's/^.*\*(\.jcr).*$$/&\n\
+		 PROVIDE(__start___libc_subfreeres = .);\n\
+		 __libc_subfreeres : { *(__libc_subfreeres) }\n\
+		 PROVIDE(__stop___libc_subfreeres = .);\n\
+		 PROVIDE(__start___libc_atexit = .);\n\
+		 __libc_atexit : { *(__libc_atexit) }\n\
+		 PROVIDE(__stop___libc_atexit = .);\n\
+		 PROVIDE(__start___libc_thread_subfreeres = .);\n\
+		 __libc_thread_subfreeres : { *(__libc_thread_subfreeres) }\n\
+		 PROVIDE(__stop___libc_thread_subfreeres = .);/'
 	mv -f $@T $@
 common-generated += shlib.lds
 

config.make.in

@@ -44,6 +44,7 @@ have-z-initfirst = @libc_cv_z_initfirst@
 have-z-combreloc = @libc_cv_z_combreloc@
 have-z-execstack = @libc_cv_z_execstack@
 have-initfini = @libc_cv_have_initfini@
+have-z-relro = @libc_cv_z_relro@
 have-Bgroup = @libc_cv_Bgroup@
 need-nopic-initfini = @nopic_initfini@
 with-fp = @with_fp@

configure

@@ -313,7 +313,7 @@ ac_includes_default="\
 # include <unistd.h>
 #endif"
 
-ac_subst_vars='SHELL PATH_SEPARATOR PACKAGE_NAME PACKAGE_TARNAME PACKAGE_VERSION PACKAGE_STRING PACKAGE_BUGREPORT exec_prefix prefix program_transform_name bindir sbindir libexecdir datadir sysconfdir sharedstatedir localstatedir libdir includedir oldincludedir infodir mandir build_alias host_alias target_alias DEFS ECHO_C ECHO_N ECHO_T LIBS with_fp with_cvs enable_check_abi oldest_abi subdirs force_install all_warnings build build_cpu build_vendor build_os host host_cpu host_vendor host_os base_machine sysnames INSTALL_PROGRAM INSTALL_SCRIPT INSTALL_DATA LN_S CC CFLAGS LDFLAGS CPPFLAGS ac_ct_CC OBJEXT BUILD_CC cross_compiling CPP CXX CXXFLAGS ac_ct_CXX AR OBJDUMP RANLIB ac_ct_RANLIB MIG AS LD PWD_P MAKE MSGFMT MAKEINFO SED AUTOCONF CCVERSION SYSINCLUDES libc_cv_gcc_static_libgcc BASH libc_cv_have_bash2 KSH libc_cv_have_ksh AWK PERL INSTALL_INFO BISON VERSIONING libc_cv_asm_protected_directive libc_cv_initfinit_array libc_cv_cc_with_libunwind libc_cv_z_nodelete libc_cv_z_nodlopen libc_cv_z_initfirst libc_cv_Bgroup ASFLAGS_config libc_cv_z_combreloc libc_cv_z_execstack libc_cv_fpie fno_unit_at_a_time libc_cv_have_initfini libc_cv_cpp_asm_debuginfo no_whole_archive exceptions LIBGD EGREP sizeof_long_double libc_cv_gcc_unwind_find_fde uname_sysname uname_release uname_version old_glibc_headers libc_cv_slibdir libc_cv_localedir libc_cv_sysconfdir libc_cv_rootsbindir libc_cv_forced_unwind use_ldconfig ldd_rewrite_script gnu_ld gnu_as elf xcoff static shared pic_default profile omitfp bounded static_nss nopic_initfini DEFINES linux_doors mach_interface_list VERSION RELEASE LIBOBJS LTLIBOBJS'
+ac_subst_vars='SHELL PATH_SEPARATOR PACKAGE_NAME PACKAGE_TARNAME PACKAGE_VERSION PACKAGE_STRING PACKAGE_BUGREPORT exec_prefix prefix program_transform_name bindir sbindir libexecdir datadir sysconfdir sharedstatedir localstatedir libdir includedir oldincludedir infodir mandir build_alias host_alias target_alias DEFS ECHO_C ECHO_N ECHO_T LIBS with_fp with_cvs enable_check_abi oldest_abi subdirs force_install all_warnings build build_cpu build_vendor build_os host host_cpu host_vendor host_os base_machine sysnames INSTALL_PROGRAM INSTALL_SCRIPT INSTALL_DATA LN_S CC CFLAGS LDFLAGS CPPFLAGS ac_ct_CC OBJEXT BUILD_CC cross_compiling CPP CXX CXXFLAGS ac_ct_CXX AR OBJDUMP RANLIB ac_ct_RANLIB MIG AS LD PWD_P MAKE MSGFMT MAKEINFO SED AUTOCONF CCVERSION SYSINCLUDES libc_cv_gcc_static_libgcc BASH libc_cv_have_bash2 KSH libc_cv_have_ksh AWK PERL INSTALL_INFO BISON VERSIONING libc_cv_asm_protected_directive libc_cv_initfinit_array libc_cv_cc_with_libunwind libc_cv_z_nodelete libc_cv_z_nodlopen libc_cv_z_initfirst libc_cv_z_relro libc_cv_Bgroup ASFLAGS_config libc_cv_z_combreloc libc_cv_z_execstack libc_cv_fpie fno_unit_at_a_time libc_cv_have_initfini libc_cv_cpp_asm_debuginfo no_whole_archive exceptions LIBGD EGREP sizeof_long_double libc_cv_gcc_unwind_find_fde uname_sysname uname_release uname_version old_glibc_headers libc_cv_slibdir libc_cv_localedir libc_cv_sysconfdir libc_cv_rootsbindir libc_cv_forced_unwind use_ldconfig ldd_rewrite_script gnu_ld gnu_as elf xcoff static shared pic_default profile omitfp bounded static_nss nopic_initfini DEFINES linux_doors mach_interface_list VERSION RELEASE LIBOBJS LTLIBOBJS'
 ac_subst_files=''
 
 # Initialize some variables set by options.
@@ -5496,6 +5496,27 @@ echo "$as_me:$LINENO: result: $libc_cv_z_initfirst" >&5
 echo "${ECHO_T}$libc_cv_z_initfirst" >&6
 
 
+  echo "$as_me:$LINENO: checking for -z relro option" >&5
+echo $ECHO_N "checking for -z relro option... $ECHO_C" >&6
+if test "${libc_cv_z_relro+set}" = set; then
+  echo $ECHO_N "(cached) $ECHO_C" >&6
+else
+    if { ac_try='${CC-cc} -v --help 2>&1|grep "z relro" 1>&5'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; }
+  then
+    libc_cv_z_relro=yes
+  else
+    libc_cv_z_relro=no
+  fi
+fi
+echo "$as_me:$LINENO: result: $libc_cv_z_relro" >&5
+echo "${ECHO_T}$libc_cv_z_relro" >&6
+
+
   echo "$as_me:$LINENO: checking for -Bgroup option" >&5
 echo $ECHO_N "checking for -Bgroup option... $ECHO_C" >&6
 if test "${libc_cv_Bgroup+set}" = set; then
@@ -8175,6 +8196,7 @@ s,@libc_cv_cc_with_libunwind@,$libc_cv_cc_with_libunwind,;t t
 s,@libc_cv_z_nodelete@,$libc_cv_z_nodelete,;t t
 s,@libc_cv_z_nodlopen@,$libc_cv_z_nodlopen,;t t
 s,@libc_cv_z_initfirst@,$libc_cv_z_initfirst,;t t
+s,@libc_cv_z_relro@,$libc_cv_z_relro,;t t
 s,@libc_cv_Bgroup@,$libc_cv_Bgroup,;t t
 s,@ASFLAGS_config@,$ASFLAGS_config,;t t
 s,@libc_cv_z_combreloc@,$libc_cv_z_combreloc,;t t

configure.in

@@ -1283,6 +1283,16 @@ EOF
   rm -f conftest*])
   AC_SUBST(libc_cv_z_initfirst)
 
+  AC_CACHE_CHECK(for -z relro option,
+		 libc_cv_z_relro, [dnl
+  if AC_TRY_COMMAND([${CC-cc} -v --help 2>&1|grep "z relro" 1>&AS_MESSAGE_LOG_FD])
+  then
+    libc_cv_z_relro=yes
+  else
+    libc_cv_z_relro=no
+  fi])
+  AC_SUBST(libc_cv_z_relro)
+
   AC_CACHE_CHECK(for -Bgroup option,
 		 libc_cv_Bgroup, [dnl
   cat > conftest.c <<EOF

elf/dl-load.c

@@ -1,5 +1,5 @@
 /* Map in a shared object's segments from the file.
-   Copyright (C) 1995-2002, 2003 Free Software Foundation, Inc.
+   Copyright (C) 1995-2002, 2003, 2004 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
@@ -1065,6 +1065,11 @@ cannot allocate TLS data structures for initial thread");
 	case PT_GNU_STACK:
 	  stack_flags = ph->p_flags;
 	  break;
+
+	case PT_GNU_RELRO:
+	  l->l_relro_addr = ph->p_vaddr;
+	  l->l_relro_size = ph->p_memsz;
+	  break;
 	}
 
     if (__builtin_expect (nloadcmds == 0, 0))

elf/dl-reloc.c

@@ -1,5 +1,5 @@
 /* Relocate a shared object and resolve its references to other loaded objects.
-   Copyright (C) 1995-2002, 2003 Free Software Foundation, Inc.
+   Copyright (C) 1995-2002, 2003, 2004 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
@@ -307,6 +307,24 @@ _dl_relocate_object (struct link_map *l, struct r_scope_elem *scope[],
 
       textrels = textrels->next;
     }
+
+  /* In case we can protect the data now that the relocations are
+     done, do it.  */
+  if (l->l_relro_size != 0)
+    {
+      ElfW(Addr) start = ((l->l_addr + l->l_relro_addr)
+			  & ~(GL(dl_pagesize) - 1));
+      ElfW(Addr) end = ((l->l_addr + l->l_relro_addr + l->l_relro_size)
+			& ~(GL(dl_pagesize) - 1));
+
+      if (start != end
+	  && __mprotect ((void *) start, end - start, PROT_READ) < 0)
+	{
+	  errstring = N_("\
+cannot apply additional memory protection after relocation");
+	  goto call_error;
+	}
+    }
 }
 INTDEF (_dl_relocate_object)
 

elf/elf.h

@@ -1,5 +1,5 @@
 /* This file defines standard ELF types, structures, and macros.
-   Copyright (C) 1995-1999,2000,2001,2002,2003 Free Software Foundation, Inc.
+   Copyright (C) 1995-2003, 2004 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
@@ -567,6 +567,7 @@ typedef struct
 #define PT_LOOS		0x60000000	/* Start of OS-specific */
 #define PT_GNU_EH_FRAME	0x6474e550	/* GCC .eh_frame_hdr segment */
 #define PT_GNU_STACK	0x6474e551	/* Indicates stack executability */
+#define PT_GNU_RELRO	0x6474e552	/* Read-only after relocation */
 #define PT_LOSUNW	0x6ffffffa
 #define PT_SUNWBSS	0x6ffffffa	/* Sun Specific segment */
 #define PT_SUNWSTACK	0x6ffffffb	/* Stack segment */

elf/rtld.c

@@ -1,5 +1,5 @@
 /* Run time dynamic linker.
-   Copyright (C) 1995-2002, 2003 Free Software Foundation, Inc.
+   Copyright (C) 1995-2002, 2003, 2004 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
@@ -332,13 +332,14 @@ _dl_start (void *arg)
   bootstrap_map.l_tls_offset = NO_TLS_OFFSET;
 #endif
 
-#if USE___THREAD
   /* Get the dynamic linker's own program header.  First we need the ELF
      file header.  The `_begin' symbol created by the linker script points
      to it.  When we have something like GOTOFF relocs, we can use a plain
      reference to find the runtime address.  Without that, we have to rely
      on the `l_addr' value, which is not the value we want when prelinked.  */
+#if USE___THREAD
   dtv_t initdtv[3];
+#endif	/* USE___THREAD */
   ElfW(Ehdr) *ehdr
 # ifdef DONT_USE_BOOTSTRAP_MAP
     = (ElfW(Ehdr) *) &_begin;
@@ -348,6 +349,7 @@ _dl_start (void *arg)
   ElfW(Phdr) *phdr = (ElfW(Phdr) *) ((void *) ehdr + ehdr->e_phoff);
   size_t cnt = ehdr->e_phnum;	/* PT_TLS is usually the last phdr.  */
   while (cnt-- > 0)
+#if USE___THREAD
     if (phdr[cnt].p_type == PT_TLS)
       {
 	void *tlsblock;
@@ -442,11 +444,14 @@ _dl_start (void *arg)
 
 	/* So far this is module number one.  */
 	bootstrap_map.l_tls_modid = 1;
-
-	/* There can only be one PT_TLS entry.  */
-	break;
       }
+    else
 #endif	/* USE___THREAD */
+      if (phdr[cnt].p_type == PT_GNU_RELRO)
+	{
+	  bootstrap_map.l_relro_addr = phdr[cnt].p_vaddr;
+	  bootstrap_map.l_relro_size = phdr[cnt].p_memsz;
+	}
 
 #ifdef ELF_MACHINE_BEFORE_RTLD_RELOC
   ELF_MACHINE_BEFORE_RTLD_RELOC (bootstrap_map.l_info);
@@ -777,6 +782,11 @@ of this helper program; chances are you did not intend to run this program.\n\
 	    GL(dl_stack_flags) = ph->p_flags;
 	    break;
 	  }
+	else if (ph->p_type == PT_GNU_RELRO)
+	  {
+	    GL(dl_loaded)->l_relro_addr = ph->p_vaddr;
+	    GL(dl_loaded)->l_relro_size = ph->p_memsz;
+	  }
 
       if (__builtin_expect (mode, normal) == verify)
 	{
@@ -1598,6 +1608,35 @@ cannot allocate TLS data structures for initial thread");
 	_dl_printf ("\nprelink checking: %s\n", prelinked ? "ok" : "failed");
     }
 
+
+  /* Initialize _r_debug.  */
+  struct r_debug *r = _dl_debug_initialize (GL(dl_rtld_map).l_addr);
+  {
+    struct link_map *l;
+
+    l = GL(dl_loaded);
+
+#ifdef ELF_MACHINE_DEBUG_SETUP
+
+    /* Some machines (e.g. MIPS) don't use DT_DEBUG in this way.  */
+
+    ELF_MACHINE_DEBUG_SETUP (l, r);
+    ELF_MACHINE_DEBUG_SETUP (&GL(dl_rtld_map), r);
+
+#else
+
+    if (l->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  */
+      l->l_info[DT_DEBUG]->d_un.d_ptr = (ElfW(Addr)) r;
+
+    /* Fill in the pointer in the dynamic linker's own dynamic section, in
+       case you run gdb on the dynamic linker directly.  */
+    if (GL(dl_rtld_map).l_info[DT_DEBUG] != NULL)
+      GL(dl_rtld_map).l_info[DT_DEBUG]->d_un.d_ptr = (ElfW(Addr)) r;
+#endif
+  }
+
   if (prelinked)
     {
       struct link_map *l;
@@ -1738,38 +1777,9 @@ cannot allocate TLS data structures for initial thread");
 #endif
     NONTLS_INIT_TP;
 
-  {
-    /* Initialize _r_debug.  */
-    struct r_debug *r = _dl_debug_initialize (GL(dl_rtld_map).l_addr);
-    struct link_map *l;
-
-    l = GL(dl_loaded);
-
-#ifdef ELF_MACHINE_DEBUG_SETUP
-
-    /* Some machines (e.g. MIPS) don't use DT_DEBUG in this way.  */
-
-    ELF_MACHINE_DEBUG_SETUP (l, r);
-    ELF_MACHINE_DEBUG_SETUP (&GL(dl_rtld_map), r);
-
-#else
-
-    if (l->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  */
-      l->l_info[DT_DEBUG]->d_un.d_ptr = (ElfW(Addr)) r;
-
-    /* Fill in the pointer in the dynamic linker's own dynamic section, in
-       case you run gdb on the dynamic linker directly.  */
-    if (GL(dl_rtld_map).l_info[DT_DEBUG] != NULL)
-      GL(dl_rtld_map).l_info[DT_DEBUG]->d_un.d_ptr = (ElfW(Addr)) r;
-
-#endif
-
   /* Notify the debugger that all objects are now mapped in.  */
   r->r_state = RT_ADD;
   INTUSE(_dl_debug_state) ();
-  }
 
 #ifndef MAP_COPY
   /* We must munmap() the cache file.  */

include/link.h

@@ -1,6 +1,6 @@
 /* Data structure for communication from the run-time dynamic linker for
    loaded ELF shared objects.
-   Copyright (C) 1995-2002, 2003 Free Software Foundation, Inc.
+   Copyright (C) 1995-2002, 2003, 2004 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
@@ -280,6 +280,11 @@ struct link_map
     /* Index of the module in the dtv array.  */
     size_t l_tls_modid;
 #endif
+
+    /* Information used to change permission after the relocations are
+       done.  */
+    ElfW(Addr) l_relro_addr;
+    size_t l_relro_size;
   };
 
 struct dl_phdr_info