Re: DT_TEXTREL/.dynamic issue with the binutils 2.15 linker on ARM and Linux

[David Poole <daveml@mbuf.com>]

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On May 29, 2004, at 12:06 AM, Alan Modra wrote:

> On Fri, May 28, 2004 at 10:56:09AM -0400, Daniel Jacobowitz wrote:
>> I don't know why DT_TEXTREL isn't there for this case.  It should be.
>
> Perhaps because elf32-arm.h doesn't have something like
> readonly_dynrelocs as implemented in other backends.

Looking at elf32-i386.c and elf32-s390.c, I copied the 
readonly_dynrelocs() and the call in 
elf_(i386|s390)_size_dynamic_sections.


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diff -uNr binutils-2.15.orig/ binutils-2.15
diff -uNr binutils-2.15.orig/bfd/elf32-arm.h binutils-2.15/bfd/elf32-arm.h
--- binutils-2.15.orig/bfd/elf32-arm.h  2004-05-17 13:35:58.000000000 -0600
+++ binutils-2.15/bfd/elf32-arm.h       2004-06-01 10:44:52.000000000 -0600
@@ -87,6 +87,8 @@
 #endif
 static bfd_boolean allocate_dynrelocs 
   PARAMS ((struct elf_link_hash_entry *h, PTR inf));
+static bfd_boolean elf32_arm_readonly_dynrelocs
+  PARAMS ((struct elf_link_hash_entry *, PTR));
 static bfd_boolean create_got_section 
   PARAMS ((bfd * dynobj, struct bfd_link_info * info));
 static bfd_boolean elf32_arm_create_dynamic_sections 
@@ -3457,6 +3459,37 @@
   return TRUE;
 }
 
+/* Find any dynamic relocs that apply to read-only sections.  */
+
+static bfd_boolean
+elf32_arm_readonly_dynrelocs (h, inf)
+     struct elf_link_hash_entry *h;
+     PTR inf;
+{
+  struct elf32_arm_link_hash_entry *eh;
+  struct elf32_arm_relocs_copied *p;
+
+  if (h->root.type == bfd_link_hash_warning)
+    h = (struct elf_link_hash_entry *) h->root.u.i.link;
+
+  eh = (struct elf32_arm_link_hash_entry *) h;
+  for (p = eh->relocs_copied; p != NULL; p = p->next)
+    {
+      asection *s = p->section;
+
+      if (s != NULL && (s->flags & SEC_READONLY) != 0)
+       {
+         struct bfd_link_info *info = (struct bfd_link_info *) inf;
+
+         info->flags |= DF_TEXTREL;
+
+         /* Not an error, just cut short the traversal.  */
+         return FALSE;
+       }
+    }
+  return TRUE;
+}
+
 /* Set the sizes of the dynamic sections.  */
 
 static bfd_boolean
@@ -3666,6 +3699,12 @@
            return FALSE;
        }
 
+      /* If any dynamic relocs apply to a read-only section,
+         then we need a DT_TEXTREL entry.  */
+      if ((info->flags & DF_TEXTREL) == 0)
+        elf_link_hash_traverse (&htab->root, elf32_arm_readonly_dynrelocs,
+                                (PTR) info);
+
       if ((info->flags & DF_TEXTREL) != 0)
        {
          if (!add_dynamic_entry (DT_TEXTREL, 0))

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Solves my DT_TEXTREL problem but needs more testing.

As a related question, in the original elf32-arm.h, the check for 
DF_TEXTREL was done outside the if(relocs):

      if (relocs)
         {
           if (   !add_dynamic_entry (DT_REL, 0)
               || !add_dynamic_entry (DT_RELSZ, 0)
               || !add_dynamic_entry (DT_RELENT, sizeof 
(Elf32_External_Rel)))
             return FALSE;
         }

       if ((info->flags & DF_TEXTREL) != 0)
         {
           if (!add_dynamic_entry (DT_TEXTREL, 0))
             return FALSE;
           info->flags |= DF_TEXTREL;
         }

but in elf32-i386.c and elf32-s390.c, the DF_TEXTREL handling is done 
inside the if(relocs):

       if (relocs)
         {
           if (!add_dynamic_entry (DT_REL, 0)
               || !add_dynamic_entry (DT_RELSZ, 0)
               || !add_dynamic_entry (DT_RELENT, sizeof 
(Elf32_External_Rel)))
             return FALSE;

           /* If any dynamic relocs apply to a read-only section,
              then we need a DT_TEXTREL entry.  */
           if ((info->flags & DF_TEXTREL) == 0)
             elf_link_hash_traverse (&htab->elf, readonly_dynrelocs,
                                     (PTR) info);

           if ((info->flags & DF_TEXTREL) != 0)
             {
               if (!add_dynamic_entry (DT_TEXTREL, 0))
                 return FALSE;
             }
         }

Is this an issue in elf32-arm.h or a simply small optimization that 
causes no trouble otherwise?

-- 
David Poole <dpoole _at_ mobl.com>
Mobility Electronics, Idaho   http://www.mobl.com
960 Broadway Avenue, Suite 300
Boise, ID  83706