[binutils-gdb] ELF checks for orphan placement

[Alan Modra <amodra at sourceware dot org>]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=2e9246e077cdbbff0a56a810c5750cc895382ba3

commit 2e9246e077cdbbff0a56a810c5750cc895382ba3
Author: Alan Modra <amodra@gmail.com>
Date:   Thu Aug 3 14:01:34 2017 +0930

    ELF checks for orphan placement
    
    The loop checking for previous orphan placement should run even when
    the output is non-ELF.
    
    	PR ld/21884
    	* emultempl/elf32.em (gld${EMULATION_NAME}_place_orphan): Revert
    	last change.  Rename iself to elfinput.  Expand comments.  Condition
    	ELF checks on having both input and output ELF files.  Extract..
    	(elf_orphan_compatible): ..this new function.

Diff:
---
 ld/ChangeLog          |  8 ++++++
 ld/emultempl/elf32.em | 76 +++++++++++++++++++++++++++++++--------------------
 2 files changed, 55 insertions(+), 29 deletions(-)

diff --git a/ld/ChangeLog b/ld/ChangeLog
index 3b9162d..efae36c 100644
--- a/ld/ChangeLog
+++ b/ld/ChangeLog
@@ -1,3 +1,11 @@
+2017-08-03  Alan Modra  <amodra@gmail.com>
+
+	PR ld/21884
+	* emultempl/elf32.em (gld${EMULATION_NAME}_place_orphan): Revert
+	last change.  Rename iself to elfinput.  Expand comments.  Condition
+	ELF checks on having both input and output ELF files.  Extract..
+	(elf_orphan_compatible): ..this new function.
+
 2017-08-02  H.J. Lu  <hongjiu.lu@intel.com>
 
 	PR ld/21884
diff --git a/ld/emultempl/elf32.em b/ld/emultempl/elf32.em
index 75ded12..9ac1840 100644
--- a/ld/emultempl/elf32.em
+++ b/ld/emultempl/elf32.em
@@ -2008,6 +2008,29 @@ output_rel_find (asection *sec, int isdyn)
   return last;
 }
 
+/* Return whether IN is suitable to be part of OUT.  */
+
+static bfd_boolean
+elf_orphan_compatible (asection *in, asection *out)
+{
+  /* Non-zero sh_info implies a section with SHF_INFO_LINK with
+     unknown semantics for the generic linker, or a SHT_REL/SHT_RELA
+     section where sh_info specifies a symbol table.  (We won't see
+     SHT_GROUP, SHT_SYMTAB or SHT_DYNSYM sections here.)  We clearly
+     can't merge SHT_REL/SHT_RELA using differing symbol tables, and
+     shouldn't merge sections with differing unknown semantics.  */
+  if (elf_section_data (out)->this_hdr.sh_info
+      != elf_section_data (in)->this_hdr.sh_info)
+    return FALSE;
+  /* We can't merge two sections with differing SHF_EXCLUDE when doing
+     a relocatable link.  */
+  if (bfd_link_relocatable (&link_info)
+      && ((elf_section_flags (out) ^ elf_section_flags (in)) & SHF_EXCLUDE) != 0)
+    return FALSE;
+  return _bfd_elf_match_sections_by_type (link_info.output_bfd, out,
+					  in->owner, in);
+}
+
 /* Place an orphan section.  We use this to put random SHF_ALLOC
    sections in the right segment.  */
 
@@ -2064,8 +2087,9 @@ gld${EMULATION_NAME}_place_orphan (asection *s,
   lang_output_section_statement_type *os;
   lang_output_section_statement_type *match_by_name = NULL;
   int isdyn = 0;
-  int iself = s->owner->xvec->flavour == bfd_target_elf_flavour;
-  unsigned int sh_type = iself ? elf_section_type (s) : SHT_NULL;
+  int elfinput = s->owner->xvec->flavour == bfd_target_elf_flavour;
+  int elfoutput = link_info.output_bfd->xvec->flavour == bfd_target_elf_flavour;
+  unsigned int sh_type = elfinput ? elf_section_type (s) : SHT_NULL;
   flagword flags;
   asection *nexts;
 
@@ -2073,7 +2097,7 @@ gld${EMULATION_NAME}_place_orphan (asection *s,
       && link_info.combreloc
       && (s->flags & SEC_ALLOC))
     {
-      if (iself)
+      if (elfinput)
 	switch (sh_type)
 	  {
 	  case SHT_RELA:
@@ -2095,6 +2119,8 @@ gld${EMULATION_NAME}_place_orphan (asection *s,
     }
 
   if (!bfd_link_relocatable (&link_info)
+      && elfinput
+      && elfoutput
       && (s->flags & SEC_ALLOC) != 0
       && (elf_section_flags (s) & SHF_GNU_MBIND) != 0)
     {
@@ -2135,9 +2161,11 @@ gld${EMULATION_NAME}_place_orphan (asection *s,
 	secname = ".mbind.text";
     }
 
-  /* Look through the script to see where to place this section.  */
-  if (constraint == 0
-      && link_info.output_bfd->xvec->flavour == bfd_target_elf_flavour)
+  /* Look through the script to see where to place this section.  The
+     script includes entries added by previous lang_insert_orphan
+     calls, so this loop puts multiple compatible orphans of the same
+     name into a single output section.  */
+  if (constraint == 0)
     for (os = lang_output_section_find (secname);
 	 os != NULL;
 	 os = next_matching_output_section_statement (os, 0))
@@ -2146,29 +2174,19 @@ gld${EMULATION_NAME}_place_orphan (asection *s,
 	   lang_insert_orphan to create a new output section.  */
 	constraint = SPECIAL;
 
-	/* SEC_EXCLUDE is cleared when doing a relocatable link.  But
-	   we can't merge 2 input sections with the same name when only
-	   one of them has SHF_EXCLUDE.  Don't merge 2 sections with
-	   different sh_info.  */
+	/* Check to see if we already have an output section statement
+	   with this name, and its bfd section has compatible flags.
+	   If the section already exists but does not have any flags
+	   set, then it has been created by the linker, possibly as a
+	   result of a --section-start command line switch.  */
 	if (os->bfd_section != NULL
-	    && (elf_section_data (os->bfd_section)->this_hdr.sh_info
-		== elf_section_data (s)->this_hdr.sh_info)
 	    && (os->bfd_section->flags == 0
-		|| ((!bfd_link_relocatable (&link_info)
-		     || (iself && (((elf_section_flags (s)
-				     ^ elf_section_flags (os->bfd_section))
-				    & SHF_EXCLUDE) == 0)))
-		    && ((s->flags ^ os->bfd_section->flags)
+		|| (((s->flags ^ os->bfd_section->flags)
 		     & (SEC_LOAD | SEC_ALLOC)) == 0
-		    && _bfd_elf_match_sections_by_type (link_info.output_bfd,
-							os->bfd_section,
-							s->owner, s))))
+		    && (!elfinput
+			|| !elfoutput
+			|| elf_orphan_compatible (s, os->bfd_section)))))
 	  {
-	    /* We already have an output section statement with this
-	       name, and its bfd section has compatible flags.
-	       If the section already exists but does not have any flags
-	       set, then it has been created by the linker, probably as a
-	       result of a --section-start command line switch.  */
 	    lang_add_section (&os->children, s, NULL, os);
 	    return os;
 	  }
@@ -2244,8 +2262,8 @@ gld${EMULATION_NAME}_place_orphan (asection *s,
   else if ((flags & SEC_ALLOC) == 0)
     ;
   else if ((flags & SEC_LOAD) != 0
-	   && ((iself && sh_type == SHT_NOTE)
-	       || (!iself && CONST_STRNEQ (secname, ".note"))))
+	   && ((elfinput && sh_type == SHT_NOTE)
+	       || (!elfinput && CONST_STRNEQ (secname, ".note"))))
     place = &hold[orphan_interp];
   else if ((flags & (SEC_LOAD | SEC_HAS_CONTENTS | SEC_THREAD_LOCAL)) == 0)
     place = &hold[orphan_bss];
@@ -2255,8 +2273,8 @@ gld${EMULATION_NAME}_place_orphan (asection *s,
     place = &hold[orphan_tdata];
   else if ((flags & SEC_READONLY) == 0)
     place = &hold[orphan_data];
-  else if (((iself && (sh_type == SHT_RELA || sh_type == SHT_REL))
-	    || (!iself && CONST_STRNEQ (secname, ".rel")))
+  else if (((elfinput && (sh_type == SHT_RELA || sh_type == SHT_REL))
+	    || (!elfinput && CONST_STRNEQ (secname, ".rel")))
 	   && (flags & SEC_LOAD) != 0)
     place = &hold[orphan_rel];
   else if ((flags & SEC_CODE) == 0)