This is the mail archive of the
src-cvs@sourceware.org
mailing list .
gdb and binutils branch hjl/plt.got created. d195d38882082a19481c72082d76dbaaff97ef68
- From: hjl at sourceware dot org
- To: src-cvs at sourceware dot org
- Date: 23 Nov 2014 15:08:11 -0000
- Subject: gdb and binutils branch hjl/plt.got created. d195d38882082a19481c72082d76dbaaff97ef68
This is an automated email from the git hooks/post-receive script. It was
generated because a ref change was pushed to the repository containing
the project "gdb and binutils".
The branch, hjl/plt.got has been created
at d195d38882082a19481c72082d76dbaaff97ef68 (commit)
- Log -----------------------------------------------------------------
https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=d195d38882082a19481c72082d76dbaaff97ef68
commit d195d38882082a19481c72082d76dbaaff97ef68
Author: H.J. Lu <hjl.tools@gmail.com>
Date: Wed Nov 19 11:51:07 2014 -0800
Optimize out i386/x86-64 JUMP_SLOT relocation
When there are both PLT and GOT references to the same function symbol,
linker will create a GOTPLT slot for PLT entry and a GOT slot for GOT
reference. A run-time JUMP_SLOT relocation is created to update the
GOTPLT slot and a run-time GLOB_DAT relocation is created to update the
GOT slot. Both JUMP_SLOT and GLOB_DAT relocations will apply the same
symbol value to GOTPLT and GOT slots, respectively, at run-time.
This optimization combines GOTPLT and GOT slots into a single GOT slot
and removes the run-time JUMP_SLOT relocation. It replaces the regular
PLT entry:
indirect jump [GOTPLT slot]
push relocation index
jump PLT0
with an GOT PLT entry with an indirect jump via the GOT slot:
indirect jump [GOT slot]
nop
and resolves PLT reference to the GOT PLT entry.
We must avoid this optimization if pointer equality is needed since
we don't clear symbol value in this case and the dynamic linker won't
update the GOT slot. Otherwise, the resulting binary will get into an
infinite loop at run-time.
bfd/
* elf32-i386.c (elf_i386_got_plt_entry): New.
(elf_i386_pic_got_plt_entry): Likewise.
(elf_i386_link_hash_entry): Add plt_got.
(elf_i386_link_hash_table): Likewise.
(elf_i386_link_hash_newfunc): Initialize plt_got.offset to -1.
(elf_i386_get_local_sym_hash): Likewise.
(elf_i386_check_relocs): Create the GOT PLT if there are both
PLT and GOT references when the regular PLT is used.
(elf_i386_allocate_dynrelocs): Use the GOT PLT if there are
both PLT and GOT references unless pointer equality is needed.
(elf_i386_relocate_section): Also check the GOT PLT when
resolving R_386_PLT32.
(elf_i386_finish_dynamic_symbol): Use the GOT PLT if it is
available.
* elf64-x86-64.c (elf_x86_64_link_hash_entry): Add plt_got.
(elf_x86_64_link_hash_table): Likewise.
(elf_x86_64_link_hash_newfunc): Initialize plt_got.offset to -1.
(elf_x86_64_get_local_sym_hash): Likewise.
(elf_x86_64_check_relocs): Create the GOT PLT if there are both
PLT and GOT references when the regular PLT is used.
(elf_x86_64_allocate_dynrelocs): Use the GOT PLT if there are
both PLT and GOT references unless pointer equality is needed.
(elf_x86_64_relocate_section): Also check the GOT PLT when
resolving R_X86_64_PLT32.
(elf_x86_64_finish_dynamic_symbol): Use the GOT PLT if it is
ld/
* emulparams/elf_i386.sh (TINY_READONLY_SECTION): New.
* emulparams/elf_x86_64.sh (TINY_READONLY_SECTION): Add .plt.got.
ld/testsuite/
* ld-i386/i386.exp: Add run-time relocation tests for plt-main.
* ld-i386/plt-main.rd: New file.
* ld-x86-64/plt-main-bnd.dd: Likewise.
* ld-x86-64/plt-main.rd: Likewise.
* ld-x86-64/x86-64.exp: Add run-time relocation tests for
plt-main.
-----------------------------------------------------------------------
hooks/post-receive
--
gdb and binutils