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Re: PATCH: PRs binutils/3281/5037: Properly handle PT_GNU_RELRO segment


On Mon, Sep 17, 2007 at 07:18:48PM +0930, Alan Modra wrote:
> On Sun, Sep 16, 2007 at 12:55:41PM -0700, H.J. Lu wrote:
> > +		      else if (sect->next != NULL
> > +			  && (sect->next->flags & SEC_ALLOC) != 0)
> > +			p->p_filesz = sect->next->lma - lp->p_vaddr;
> 
> Subtracting a vma from an lma?  This can't be correct.
> 
> > +		      else
> > +			p->p_filesz += p->p_vaddr - lp->p_vaddr;
> 
> What is going on here?

I removed them in the patch enclosed. The PT_GNU_RELRO segment sizes
have to be valid when copying shared library/executables.


> 
> >  static bfd_boolean
> > -rewrite_elf_program_header (bfd *ibfd, bfd *obfd)
> > +rewrite_elf_program_header (bfd *ibfd, bfd *obfd,
> > +			    enum elf_section_status status)
> 
> I think the extra parameter should be "bfd_boolean remove_relro",
> and put all the code dealing with whether we can keep the gnu_relro
> header or not in copy_private_bfd_data.
> 
> > +  if (status == unknown)
> > +    {
> > +      /* We need to find out how we are changed.  */
> > +      num_segments = elf_elfheader (ibfd)->e_phnum;
> > +      for (i = 0, segment = elf_tdata (ibfd)->phdr;
> > +	   i < num_segments;
> > +	   i++, segment++)
> > +	{
> > +	  for (section = ibfd->sections;
> > +	       section != NULL; section = section->next)
> > +	    {
> > +	      osec = section->output_section;
> > +
> > +	      /* Check if this section is covered by the segment.  */
> > +	      this_hdr = &(elf_section_data(section)->this_hdr);
> > +	      if (ELF_IS_SECTION_IN_SEGMENT_FILE (this_hdr, segment))
> > +		{
> > +		  if (osec == NULL)
> > +		    status = removed;
> > +		  else if (section->flags != osec->flags
> > +			   || section->lma != osec->lma
> > +			   || section->vma != osec->vma
> > +			   || section->size != osec->size
> > +			   || section->rawsize != osec->rawsize
> > +			   || section->alignment_power != osec->alignment_power)
> > +		    {
> > +		      /* Stop if a section is modified.  */
> > +		      status = modified;
> > +		      break;
> > +		    }
> > +		}
> > +	    }
> > +	}
> > +    }
> 
> Why copy all the above?  Can't you set "status" in the existing loop?
> 

Here is the updated patch.


H.J.
-----
bfd/

2007-09-16  H.J. Lu  <hongjiu.lu@intel.com>

	PR binutils/3281
	PR binutils/5037
	* elf-bfd.h (elf_obj_tdata): Remove relro.

	* elf.c (get_program_header_size): Check info->relro instead
	of elf_tdata (abfd)->relro.
	(_bfd_elf_map_sections_to_segments): Likewise.
	(assign_file_positions_for_load_sections): Don't set
	PT_GNU_RELRO segment alignment here.
	(assign_file_positions_for_non_load_sections): Properly set up
	PT_GNU_RELRO segment for copying executable/shared library.
	(rewrite_elf_program_header): Remove PT_GNU_RELRO segment.
	(copy_elf_program_header): Set p_size and p_size_valid fields for
	PT_GNU_RELRO segment. 

include/elf/

2007-09-16  H.J. Lu  <hongjiu.lu@intel.com>

	PR binutils/3281
	PR binutils/5037
	* internal.h (elf_segment_map): Add p_size and p_size_valid.
	(ELF_IS_SECTION_IN_SEGMENT): Allow SHF_TLS sections in
	PT_GNU_RELRO segments.

ld/

2007-09-16  H.J. Lu  <hongjiu.lu@intel.com>

	PR binutils/3281
	PR binutils/5037
	* ldexp.h (ldexp_control): Add relro, relro_start_stat and
	relro_end_stat.

	* ldexp.c (fold_binary): Set expld.dataseg.relro to
	exp_dataseg_relro_start or exp_dataseg_relro_end when
	seeing DATA_SEGMENT_ALIGN or DATA_SEGMENT_RELRO_END,
	respectively.

	* ldlang.c (lang_size_sections_1): Properly set
	expld.dataseg.relro_start_stat and
	expld.dataseg.relro_end_stat.
	(find_relro_section_callback): New function.
	(lang_find_relro_sections_1): Likewise.
	(lang_find_relro_sections): Likewise.
	(lang_process): Call lang_find_relro_sections for
	non-relocatable link.

ld/testsuite/

2007-09-16  H.J. Lu  <hongjiu.lu@intel.com>

	PR binutils/3281
	PR binutils/5037
	* ld-elf/binutils.exp: Update "-z relro" tests to use relro1.s.
	Add "-z relro" tests with relro2.s.  Add "-z relro" tests with
	TLS for objcopy.

	* ld-elf/relro1.s: New file.
	* ld-elf/relro2.s: Likewise.

--- binutils/bfd/elf-bfd.h.relro	2007-09-17 06:49:32.000000000 -0700
+++ binutils/bfd/elf-bfd.h	2007-09-17 06:49:32.000000000 -0700
@@ -1427,9 +1427,6 @@ struct elf_obj_tdata
   /* Segment flags for the PT_GNU_STACK segment.  */
   unsigned int stack_flags;
 
-  /* Should the PT_GNU_RELRO segment be emitted?  */
-  bfd_boolean relro;
-
   /* Symbol version definitions in external objects.  */
   Elf_Internal_Verdef *verdef;
 
--- binutils/bfd/elf.c.relro	2007-09-17 06:49:32.000000000 -0700
+++ binutils/bfd/elf.c	2007-09-17 07:23:12.000000000 -0700
@@ -3361,7 +3361,7 @@ get_program_header_size (bfd *abfd, stru
       /* We need a PT_DYNAMIC segment.  */
       ++segs;
 
-      if (elf_tdata (abfd)->relro)
+      if (info->relro)
 	{
 	  /* We need a PT_GNU_RELRO segment only when there is a
 	     PT_DYNAMIC segment.  */
@@ -3989,7 +3989,7 @@ _bfd_elf_map_sections_to_segments (bfd *
 	  pm = &m->next;
 	}
 
-      if (dynsec != NULL && elf_tdata (abfd)->relro)
+      if (dynsec != NULL && info->relro)
 	{
 	  /* We make a PT_GNU_RELRO segment only when there is a
 	     PT_DYNAMIC segment.  */
@@ -4491,12 +4491,10 @@ assign_file_positions_for_load_sections 
 		    p->p_memsz += this_hdr->sh_size;
 		}
 
-	      if (p->p_type == PT_GNU_RELRO)
-		p->p_align = 1;
-	      else if (align > p->p_align
-		       && !m->p_align_valid
-		       && (p->p_type != PT_LOAD
-			   || (abfd->flags & D_PAGED) == 0))
+	      if (align > p->p_align
+		  && !m->p_align_valid
+		  && (p->p_type != PT_LOAD
+		      || (abfd->flags & D_PAGED) == 0))
 		p->p_align = align;
 	    }
 
@@ -4646,18 +4644,53 @@ assign_file_positions_for_non_load_secti
       if (m->count != 0)
 	{
 	  if (p->p_type != PT_LOAD
-	      && (p->p_type != PT_NOTE || bfd_get_format (abfd) != bfd_core))
+	      && (p->p_type != PT_NOTE
+		  || bfd_get_format (abfd) != bfd_core))
 	    {
 	      Elf_Internal_Shdr *hdr;
+	      asection *sect;
+
 	      BFD_ASSERT (!m->includes_filehdr && !m->includes_phdrs);
 
-	      hdr = &elf_section_data (m->sections[m->count - 1])->this_hdr;
-	      p->p_filesz = (m->sections[m->count - 1]->filepos
-			     - m->sections[0]->filepos);
+	      sect = m->sections[m->count - 1];
+	      hdr = &elf_section_data (sect)->this_hdr;
+	      p->p_filesz = sect->filepos - m->sections[0]->filepos;
 	      if (hdr->sh_type != SHT_NOBITS)
 		p->p_filesz += hdr->sh_size;
 
-	      p->p_offset = m->sections[0]->filepos;
+	      if (p->p_type == PT_GNU_RELRO)
+		{
+		  /* When we get here, we are copying executable
+		     or shared library. But we need to use the same
+		     linker logic.  */
+		  Elf_Internal_Phdr *lp;
+
+		  for (lp = phdrs; lp < phdrs + count; ++lp)
+		    {
+		      if (lp->p_type == PT_LOAD
+			  && lp->p_paddr == p->p_paddr)
+			break;
+		    }
+	  
+		  if (lp < phdrs + count)
+		    {
+		      /* We should use p_size if it is valid since it
+			 may contain the first few bytes of the next
+			 SEC_ALLOC section.  */
+		      if (m->p_size_valid)
+			p->p_filesz = m->p_size;
+		      else
+			abort ();
+		      p->p_vaddr = lp->p_vaddr;
+		      p->p_offset = lp->p_offset;
+		      p->p_memsz = p->p_filesz;
+		      p->p_align = 1;
+		    }
+		  else
+		    abort ();
+		}
+	      else
+		p->p_offset = m->sections[0]->filepos;
 	    }
 	}
       else
@@ -5246,7 +5279,12 @@ rewrite_elf_program_header (bfd *ibfd, b
 	    }
 
       if (segment->p_type != PT_LOAD)
-	continue;
+	{
+	  /* Remove PT_GNU_RELRO segment.  */
+	  if (segment->p_type == PT_GNU_RELRO)
+	    segment->p_type = PT_NULL;
+	  continue;
+	}
 
       /* Determine if this segment overlaps any previous segments.  */
       for (j = 0, segment2 = elf_tdata (ibfd)->phdr; j < i; j++, segment2 ++)
@@ -5770,6 +5808,17 @@ copy_elf_program_header (bfd *ibfd, bfd 
       map->p_align_valid = 1;
       map->p_vaddr_offset = 0;
 
+      if (map->p_type == PT_GNU_RELRO
+	  && segment->p_filesz == segment->p_memsz)
+	{
+	  /* The PT_GNU_RELRO segment may contain the first a few
+	     bytes in the .got.plt section even if the whole .got.plt
+	     section isn't in the PT_GNU_RELRO segment.  We won't
+	     change the size of the PT_GNU_RELRO segment.  */
+	  map->p_size = segment->p_filesz;
+	  map->p_size_valid = 1;
+	}
+
       /* Determine if this segment contains the ELF file header
 	 and if it contains the program headers themselves.  */
       map->includes_filehdr = (segment->p_offset == 0
--- binutils/bfd/elflink.c.relro	2007-09-17 06:49:32.000000000 -0700
+++ binutils/bfd/elflink.c	2007-09-17 06:49:32.000000000 -0700
@@ -5397,7 +5397,6 @@ bfd_elf_size_dynamic_sections (bfd *outp
     return TRUE;
 
   bed = get_elf_backend_data (output_bfd);
-  elf_tdata (output_bfd)->relro = info->relro;
   if (info->execstack)
     elf_tdata (output_bfd)->stack_flags = PF_R | PF_W | PF_X;
   else if (info->noexecstack)
--- binutils/include/elf/internal.h.relro	2007-05-03 14:07:31.000000000 -0700
+++ binutils/include/elf/internal.h	2007-09-17 06:49:32.000000000 -0700
@@ -239,6 +239,8 @@ struct elf_segment_map
   bfd_vma p_vaddr_offset;
   /* Program segment alignment.  */
   bfd_vma p_align;
+  /* Segment size in file and memory */
+  bfd_vma p_size;
   /* Whether the p_flags field is valid; if not, the flags are based
      on the section flags.  */
   unsigned int p_flags_valid : 1;
@@ -248,6 +250,9 @@ struct elf_segment_map
   /* Whether the p_align field is valid; if not, PT_LOAD segment
      alignment is based on the default maximum page size.  */
   unsigned int p_align_valid : 1;
+  /* Whether the p_size field is valid; if not, the size are based
+     on the section sizes.  */
+  unsigned int p_size_valid : 1;
   /* Whether this segment includes the file header.  */
   unsigned int includes_filehdr : 1;
   /* Whether this segment includes the program headers.  */
@@ -266,11 +271,12 @@ struct elf_segment_map
      || segment->p_type == PT_TLS) ? sec_hdr->sh_size : 0)
 
 /* Decide if the given sec_hdr is in the given segment.  PT_TLS segment
-   contains only SHF_TLS sections.  Only PT_LOAD and PT_TLS segments
-   can contain SHF_TLS sections.  */
+   contains only SHF_TLS sections.  Only PT_LOAD, PT_GNU_RELRO and
+   and PT_TLS segments can contain SHF_TLS sections.  */
 #define ELF_IS_SECTION_IN_SEGMENT(sec_hdr, segment)			\
   (((((sec_hdr->sh_flags & SHF_TLS) != 0)				\
      && (segment->p_type == PT_TLS					\
+	 || segment->p_type == PT_GNU_RELRO				\
 	 || segment->p_type == PT_LOAD))				\
     || ((sec_hdr->sh_flags & SHF_TLS) == 0				\
 	&& segment->p_type != PT_TLS))					\
--- binutils/ld/ldexp.c.relro	2007-08-18 06:22:30.000000000 -0700
+++ binutils/ld/ldexp.c	2007-09-17 06:49:32.000000000 -0700
@@ -390,6 +390,7 @@ fold_binary (etree_type *tree)
 	      break;
 
 	    case DATA_SEGMENT_ALIGN:
+	      expld.dataseg.relro = exp_dataseg_relro_start;
 	      if (expld.phase != lang_first_phase_enum
 		  && expld.section == bfd_abs_section_ptr
 		  && (expld.dataseg.phase == exp_dataseg_none
@@ -425,6 +426,7 @@ fold_binary (etree_type *tree)
 	      break;
 
 	    case DATA_SEGMENT_RELRO_END:
+	      expld.dataseg.relro = exp_dataseg_relro_end;
 	      if (expld.phase != lang_first_phase_enum
 		  && (expld.dataseg.phase == exp_dataseg_align_seen
 		      || expld.dataseg.phase == exp_dataseg_adjust
--- binutils/ld/ldexp.h.relro	2007-07-09 06:29:44.000000000 -0700
+++ binutils/ld/ldexp.h	2007-09-17 06:49:32.000000000 -0700
@@ -98,6 +98,8 @@ typedef enum {
   lang_final_phase_enum
 } lang_phase_type;
 
+union lang_statement_union;
+
 struct ldexp_control {
   /* Modify expression evaluation depending on this.  */
   lang_phase_type phase;
@@ -125,6 +127,15 @@ struct ldexp_control {
     } phase;
 
     bfd_vma base, min_base, relro_end, end, pagesize, maxpagesize;
+
+    enum {
+      exp_dataseg_relro_none,
+      exp_dataseg_relro_start,
+      exp_dataseg_relro_end,
+    } relro;
+
+    union lang_statement_union *relro_start_stat;
+    union lang_statement_union *relro_end_stat;
   } dataseg;
 };
 
--- binutils/ld/ldlang.c.relro	2007-08-31 16:00:04.000000000 -0700
+++ binutils/ld/ldlang.c	2007-09-17 06:49:32.000000000 -0700
@@ -4636,10 +4636,32 @@ lang_size_sections_1
 	    bfd_vma newdot = dot;
 	    etree_type *tree = s->assignment_statement.exp;
 
+	    expld.dataseg.relro = exp_dataseg_relro_none;
+
 	    exp_fold_tree (tree,
 			   output_section_statement->bfd_section,
 			   &newdot);
 
+	    if (expld.dataseg.relro == exp_dataseg_relro_start)
+	      {
+		if (!expld.dataseg.relro_start_stat)
+		  expld.dataseg.relro_start_stat = s;
+		else
+		  {
+		    ASSERT (expld.dataseg.relro_start_stat == s);
+		  }
+	      }
+	    else if (expld.dataseg.relro == exp_dataseg_relro_end)
+	      {
+		if (!expld.dataseg.relro_end_stat)
+		  expld.dataseg.relro_end_stat = s;
+		else
+		  {
+		    ASSERT (expld.dataseg.relro_end_stat == s);
+		  }
+	      }
+	    expld.dataseg.relro = exp_dataseg_relro_none;
+
 	    /* This symbol is relative to this section.  */
 	    if ((tree->type.node_class == etree_provided
 		 || tree->type.node_class == etree_assign)
@@ -5665,6 +5687,81 @@ lang_gc_sections (void)
     bfd_gc_sections (output_bfd, &link_info);
 }
 
+/* Worker for lang_find_relro_sections_1.  */
+
+static void
+find_relro_section_callback (lang_wild_statement_type *ptr ATTRIBUTE_UNUSED,
+			     struct wildcard_list *sec ATTRIBUTE_UNUSED,
+			     asection *section,
+			     lang_input_statement_type *file ATTRIBUTE_UNUSED,
+			     void *data)
+{
+  /* Discarded, excluded and ignored sections effectively have zero
+     size.  */
+  if (section->output_section != NULL
+      && section->output_section->owner == output_bfd
+      && (section->output_section->flags & SEC_EXCLUDE) == 0
+      && !IGNORE_SECTION (section)
+      && section->size != 0)
+    {
+      bfd_boolean *has_relro_section = (bfd_boolean *) data;
+      *has_relro_section = TRUE;
+    }
+}
+
+/* Iterate over sections for relro sections.  */
+
+static void
+lang_find_relro_sections_1 (lang_statement_union_type *s,
+			    bfd_boolean *has_relro_section)
+{
+  if (*has_relro_section)
+    return;
+
+  for (; s != NULL; s = s->header.next)
+    {
+      if (s == expld.dataseg.relro_end_stat)
+	break;
+
+      switch (s->header.type)
+	{
+	case lang_wild_statement_enum:
+	  walk_wild (&s->wild_statement,
+		     find_relro_section_callback,
+		     has_relro_section);
+	  break;
+	case lang_constructors_statement_enum:
+	  lang_find_relro_sections_1 (constructor_list.head,
+				      has_relro_section);
+	  break;
+	case lang_output_section_statement_enum:
+	  lang_find_relro_sections_1 (s->output_section_statement.children.head,
+				      has_relro_section);
+	  break;
+	case lang_group_statement_enum:
+	  lang_find_relro_sections_1 (s->group_statement.children.head,
+				      has_relro_section);
+	  break;
+	default:
+	  break;
+	}
+    }
+}
+
+static void
+lang_find_relro_sections (void)
+{
+  bfd_boolean has_relro_section = FALSE;
+
+  /* Check all sections in the link script.  */
+
+  lang_find_relro_sections_1 (expld.dataseg.relro_start_stat,
+			      &has_relro_section);
+
+  if (!has_relro_section)
+    link_info.relro = FALSE;
+}
+
 /* Relax all sections until bfd_relax_section gives up.  */
 
 static void
@@ -5792,6 +5889,10 @@ lang_process (void)
      section positions, since they will affect SIZEOF_HEADERS.  */
   lang_record_phdrs ();
 
+  /* Check relro sections.  */
+  if (link_info.relro && ! link_info.relocatable)
+    lang_find_relro_sections ();
+
   /* Size up the sections.  */
   lang_size_sections (NULL, !command_line.relax);
 
--- binutils/ld/testsuite/ld-elf/binutils.exp.relro	2007-08-28 06:49:05.000000000 -0700
+++ binutils/ld/testsuite/ld-elf/binutils.exp	2007-09-17 06:49:32.000000000 -0700
@@ -104,24 +104,42 @@ binutils_test strip "-shared" maxpage1
 binutils_test objcopy "" maxpage1
 binutils_test objcopy "-shared" maxpage1
 
-binutils_test strip "-z relro" maxpage1
-binutils_test strip "-z relro -shared" maxpage1
-binutils_test objcopy "-z relro" maxpage1
-binutils_test objcopy "-z relro -shared" maxpage1
+binutils_test strip "-z relro" relro1
+binutils_test strip "-z relro -shared" relro1
+binutils_test objcopy "-z relro" relro1
+binutils_test objcopy "-z relro -shared" relro1
+if { ([istarget "i?86-*-elf*"]		
+      || ([istarget "i?86-*-linux*"]
+	  && ![istarget "*-*-*aout*"]
+	  && ![istarget "*-*-*oldld*"])
+      || [istarget "x86_64-*-linux*"]
+      || [istarget "amd64-*-linux*"]) } {
+    binutils_test strip "-z relro -shared" relro2
+    binutils_test objcopy "-z relro -shared" relro2
+}
 
 binutils_test objcopy "" tbss1
+binutils_test objcopy "-z relro" tbss1
 binutils_test objcopy "-shared" tbss1
+binutils_test objcopy "-shared -z relro" tbss1
 binutils_test objcopy "-z max-page-size=0x100000" tbss1
 binutils_test objcopy "-z max-page-size=0x100000 -z common-page-size=0x1000" tbss1
 binutils_test objcopy "" tdata1
+binutils_test objcopy "-z relro" tdata1
 binutils_test objcopy "-shared" tdata1
+binutils_test objcopy "-shared -z relro" tdata1
 binutils_test objcopy "-z max-page-size=0x100000" tdata1
 binutils_test objcopy "-z max-page-size=0x100000 -z common-page-size=0x1000" tdata1
 binutils_test objcopy "" tbss2
+binutils_test objcopy "-z relro" tbss2
 binutils_test objcopy "-shared" tbss2
+binutils_test objcopy "-shared -z relro" tbss2
 binutils_test objcopy "-z max-page-size=0x100000" tbss2
 binutils_test objcopy "-z max-page-size=0x100000 -z common-page-size=0x1000" tbss2
-binutils_test objcopy "-z max-page-size=0x100000" tdata2
+
 binutils_test objcopy "" tdata2
+binutils_test objcopy "-z relro" tdata2
 binutils_test objcopy "-shared" tdata2
+binutils_test objcopy "-shared -z relro" tdata2
+binutils_test objcopy "-z max-page-size=0x100000" tdata2
 binutils_test objcopy "-z max-page-size=0x100000 -z common-page-size=0x1000" tdata2
--- binutils/ld/testsuite/ld-elf/relro1.s.relro	2007-09-17 06:49:32.000000000 -0700
+++ binutils/ld/testsuite/ld-elf/relro1.s	2007-09-17 06:49:32.000000000 -0700
@@ -0,0 +1,14 @@
+	.globl main
+	.globl start
+	.globl _start
+	.globl __start
+	.text
+main:
+start:
+_start:
+__start:
+	.long	0
+	.data
+	.long	0
+	.section .data.rel.ro,"aw",%progbits
+	.long	0
--- binutils/ld/testsuite/ld-elf/relro2.s.relro	2007-09-17 06:49:32.000000000 -0700
+++ binutils/ld/testsuite/ld-elf/relro2.s	2007-09-17 06:49:32.000000000 -0700
@@ -0,0 +1,5 @@
+	.text
+	.globl x
+	.type	x, @function
+x:
+	jmp foo@PLT


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