From: Jakub Jelinek <jakub@redhat.com>
To: binutils@sources.redhat.com
Subject: [RFC PATCH] Don't put local or undefined symbols into .hash
Date: Mon, 26 Jun 2006 13:02:00 -0000 [thread overview]
Message-ID: <20060626123238.GU3823@sunsite.mff.cuni.cz> (raw)
Hi!
It seems an average shared library has roughly 25% of undefined symbols
in its .dynsym section.
Currently, the linker puts all dynamic symbols (except the special ones like
section symbols or symbol 0) into the .hash section, but the dynamic linker
will always skip STB_LOCAL symbols or undefined symbols (except those with
st_value != 0) - it is always looking for symbol definitions.
Is there any reason why we put even the undefined or local symbols into
.hash? It just makes the .hash buckets array larger and/or the hash chains
longer than necessary.
Or is there something that relies on all symbols being there?
So far I have noticed just readelf -Ds (but in that case it is questionable
if readelf -Ds would need to change or stay as is).
2006-06-26 Jakub Jelinek <jakub@redhat.com>
* elflink.c (elf_collect_hash_codes): Set u.elf_hash_value to ~0
for local or undefined symbols, don't include it into hashcodes
array.
(elf_link_output_extsym): Don't put symbols with u.elf_hash_value
~0 into the .hash section.
--- bfd/elflink.c.jj 2006-06-20 18:34:53.000000000 +0200
+++ bfd/elflink.c 2006-06-26 14:04:49.000000000 +0200
@@ -4785,6 +4785,17 @@ elf_collect_hash_codes (struct elf_link_
if (h->dynindx == -1)
return TRUE;
+ /* Ignore also local symbols and undefined symbols. */
+ if (h->forced_local
+ || h->root.type == bfd_link_hash_undefined
+ || h->root.type == bfd_link_hash_undefweak)
+ {
+ /* bfd_elf_hash values never have topmost 4 bits set,
+ so ~0 don't collide with any valid hash value. */
+ h->u.elf_hash_value = ~(unsigned long) 0;
+ return TRUE;
+ }
+
name = h->root.root.string;
p = strchr (name, ELF_VER_CHR);
if (p != NULL)
@@ -6678,16 +6689,24 @@ elf_link_output_extsym (struct elf_link_
bed->s->swap_symbol_out (finfo->output_bfd, &sym, esym, 0);
bucketcount = elf_hash_table (finfo->info)->bucketcount;
- bucket = h->u.elf_hash_value % bucketcount;
- hash_entry_size
- = elf_section_data (finfo->hash_sec)->this_hdr.sh_entsize;
- bucketpos = ((bfd_byte *) finfo->hash_sec->contents
- + (bucket + 2) * hash_entry_size);
- chain = bfd_get (8 * hash_entry_size, finfo->output_bfd, bucketpos);
- bfd_put (8 * hash_entry_size, finfo->output_bfd, h->dynindx, bucketpos);
- bfd_put (8 * hash_entry_size, finfo->output_bfd, chain,
- ((bfd_byte *) finfo->hash_sec->contents
- + (bucketcount + 2 + h->dynindx) * hash_entry_size));
+ if (h->u.elf_hash_value == ~(unsigned long) 0)
+ BFD_ASSERT (h->forced_local
+ || h->root.type == bfd_link_hash_undefined
+ || h->root.type == bfd_link_hash_undefweak);
+ else
+ {
+ bucket = h->u.elf_hash_value % bucketcount;
+ hash_entry_size
+ = elf_section_data (finfo->hash_sec)->this_hdr.sh_entsize;
+ bucketpos = ((bfd_byte *) finfo->hash_sec->contents
+ + (bucket + 2) * hash_entry_size);
+ chain = bfd_get (8 * hash_entry_size, finfo->output_bfd, bucketpos);
+ bfd_put (8 * hash_entry_size, finfo->output_bfd, h->dynindx,
+ bucketpos);
+ bfd_put (8 * hash_entry_size, finfo->output_bfd, chain,
+ ((bfd_byte *) finfo->hash_sec->contents
+ + (bucketcount + 2 + h->dynindx) * hash_entry_size));
+ }
if (finfo->symver_sec != NULL && finfo->symver_sec->contents != NULL)
{
Jakub
next reply other threads:[~2006-06-26 12:32 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-06-26 13:02 Jakub Jelinek [this message]
2006-06-26 13:10 ` Daniel Jacobowitz
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20060626123238.GU3823@sunsite.mff.cuni.cz \
--to=jakub@redhat.com \
--cc=binutils@sources.redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).