Re: [committed, PATCH] Always create dynsym section with dynamic sections

["H.J. Lu" <hjl dot tools at gmail dot com>]

On Mon, Apr 25, 2016 at 6:41 AM, Alan Modra <amodra@gmail.com> wrote:
> On Mon, Apr 25, 2016 at 05:47:15AM -0700, H.J. Lu wrote:
>> On Sun, Apr 24, 2016 at 7:18 PM, Faraz Shahbazker
>> <faraz.shahbazker@imgtec.com> wrote:
>> > On 04/23/16 18:42, H.J. Lu wrote:
>> >> Here is a patch.  Does it work for you?
>> > Yes, this works.
>> >
>>
>> Any other comments, feedbacks for my patch?
>
> I think you'd better look at all places that test dynsymcount.  For
> instance, bfd_elf_size_dynsym_hash_dynstr.

I checked.  They look OK.

> This should really have been done when you committed
> https://sourceware.org/ml/binutils/2016-02/msg00326.html and that
> patch should have explained why the change was made.  "We should
> always create the dynsym section, even if it is empty, with dynamic
> sections" doesn't explain anything about why the change was made.  In
> fact, the explanation for the patch was no better than "We should do
> what this patch does".

The issue is some dynamic tags (sections) are mandatory in .dynamic
section even if they are empty.  MIPS backend use dynsymcount, which
is intended for the mandatory DT_SYMTAB (.dynsym section), to build
static executable, which doesn't have dynamic section.  Here is the
updated patch.  Is it OK for master?


-- 
H.J.

From 8d941b3f99a57f89f564ed16f94d5cdcad6fede3 Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <hjl.tools@gmail.com>
Date: Sat, 23 Apr 2016 18:37:59 -0700
Subject: [PATCH] Always count the NULL entry in dynamic symbol table

There is an unused NULL entry at the head of dynamic symbol table which
we must account for in our count even if the table is empty or unused
since it is intended for the mandatory DT_SYMTAB tag (.dynsym section)
in .dynamic section.

	* elf-bfd.h (elf_link_hash_table): Update comments for
	dynsymcount.
	* elflink.c (_bfd_elf_link_renumber_dynsyms): Always count for
	the unused NULL entry at the head of dynamic symbol table.
---
 bfd/elf-bfd.h |  4 ++--
 bfd/elflink.c | 10 +++++-----
 2 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/bfd/elf-bfd.h b/bfd/elf-bfd.h
index 5dce70e..7447629 100644
--- a/bfd/elf-bfd.h
+++ b/bfd/elf-bfd.h
@@ -520,8 +520,8 @@ struct elf_link_hash_table
   union gotplt_union init_got_offset;
   union gotplt_union init_plt_offset;
 
-  /* The number of symbols found in the link which must be put into
-     the .dynsym section.  */
+  /* The number of symbols found in the link which is intended for the
+     mandatory DT_SYMTAB tag (.dynsym section) in .dynamic section.  */
   bfd_size_type dynsymcount;
 
   /* The string table of dynamic symbols, which becomes the .dynstr
diff --git a/bfd/elflink.c b/bfd/elflink.c
index 6f67266..7babfb9 100644
--- a/bfd/elflink.c
+++ b/bfd/elflink.c
@@ -905,11 +905,11 @@ _bfd_elf_link_renumber_dynsyms (bfd *output_bfd,
 			  elf_link_renumber_hash_table_dynsyms,
 			  &dynsymcount);
 
-  /* There is an unused NULL entry at the head of the table which
-     we must account for in our count.  We always create the dynsym
-     section, even if it is empty, with dynamic sections.  */
-  if (elf_hash_table (info)->dynamic_sections_created)
-    ++dynsymcount;
+  /* There is an unused NULL entry at the head of the table which we
+     must account for in our count even if the table is empty since it
+     is intended for the mandatory DT_SYMTAB tag (.dynsym section) in
+     .dynamic section.  */
+  dynsymcount++;
 
   elf_hash_table (info)->dynsymcount = dynsymcount;
   return dynsymcount;
-- 
2.5.5