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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 available. 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. |
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bfd | ||
binutils | ||
config | ||
cpu | ||
elfcpp | ||
etc | ||
gas | ||
gdb | ||
gold | ||
gprof | ||
include | ||
intl | ||
ld | ||
libdecnumber | ||
libiberty | ||
opcodes | ||
readline | ||
sim | ||
texinfo | ||
.cvsignore | ||
.gitattributes | ||
.gitignore | ||
ChangeLog | ||
compile | ||
config-ml.in | ||
config.guess | ||
config.rpath | ||
config.sub | ||
configure | ||
configure.ac | ||
COPYING | ||
COPYING3 | ||
COPYING3.LIB | ||
COPYING.LIB | ||
COPYING.LIBGLOSS | ||
COPYING.NEWLIB | ||
depcomp | ||
djunpack.bat | ||
install-sh | ||
libtool.m4 | ||
lt~obsolete.m4 | ||
ltgcc.m4 | ||
ltmain.sh | ||
ltoptions.m4 | ||
ltsugar.m4 | ||
ltversion.m4 | ||
MAINTAINERS | ||
Makefile.def | ||
Makefile.in | ||
Makefile.tpl | ||
makefile.vms | ||
missing | ||
mkdep | ||
mkinstalldirs | ||
move-if-change | ||
README | ||
README-maintainer-mode | ||
setup.com | ||
src-release.sh | ||
symlink-tree | ||
ylwrap |
README for GNU development tools This directory contains various GNU compilers, assemblers, linkers, debuggers, etc., plus their support routines, definitions, and documentation. If you are receiving this as part of a GDB release, see the file gdb/README. If with a binutils release, see binutils/README; if with a libg++ release, see libg++/README, etc. That'll give you info about this package -- supported targets, how to use it, how to report bugs, etc. It is now possible to automatically configure and build a variety of tools with one command. To build all of the tools contained herein, run the ``configure'' script here, e.g.: ./configure make To install them (by default in /usr/local/bin, /usr/local/lib, etc), then do: make install (If the configure script can't determine your type of computer, give it the name as an argument, for instance ``./configure sun4''. You can use the script ``config.sub'' to test whether a name is recognized; if it is, config.sub translates it to a triplet specifying CPU, vendor, and OS.) If you have more than one compiler on your system, it is often best to explicitly set CC in the environment before running configure, and to also set CC when running make. For example (assuming sh/bash/ksh): CC=gcc ./configure make A similar example using csh: setenv CC gcc ./configure make Much of the code and documentation enclosed is copyright by the Free Software Foundation, Inc. See the file COPYING or COPYING.LIB in the various directories, for a description of the GNU General Public License terms under which you can copy the files. REPORTING BUGS: Again, see gdb/README, binutils/README, etc., for info on where and how to report problems.