PLT relocations aren't required when -z now used. Linker on master with:
commit 25070364b0ce33eed46aa5d78ebebbec6accec7e
Author: H.J. Lu <hjl.tools@gmail.com>
Date: Sat May 16 07:00:21 2015 -0700
Don't generate PLT relocations for now binding
There is no need for PLT relocations with -z now. We can use GOT
relocations, which take less space, instead and replace 16-byte .plt
entres with 8-byte .plt.got entries.
bfd/
* elf32-i386.c (elf_i386_check_relocs): Create .plt.got section
for now binding.
(elf_i386_allocate_dynrelocs): Use .plt.got section for now
binding.
* elf64-x86-64.c (elf_x86_64_check_relocs): Create .plt.got
section for now binding.
(elf_x86_64_allocate_dynrelocs): Use .plt.got section for now
binding.
won't generate PLT relocations with -z now. elf/tst-audit2.c expect
certain order of execution in ld.so. With PLT relocations, the GOTPLT
entry of calloc is update to calloc defined in tst-audit2:
(gdb) bt
skip_ifunc=<optimized out>, reloc_addr_arg=<optimized out>,
version=<optimized out>, sym=<optimized out>, map=<optimized out>)
at ../sysdeps/i386/dl-machine.h:329
out>,
nrelative=<optimized out>, relsize=<optimized out>,
reladdr=<optimized out>, map=<optimized out>) at do-rel.h:137
reloc_mode=reloc_mode@entry=0,
consider_profiling=1, consider_profiling@entry=0) at dl-reloc.c:258
user_entry=0xffffcf1c, auxv=0xffffd0a8) at rtld.c:2133
start_argptr=start_argptr@entry=0xffffcfb0,
dl_main=dl_main@entry=0xf7fda6f0 <dl_main>) at
../elf/dl-sysdep.c:249
from /export/build/gnu/glibc-32bit/build-i686-linux/elf/ld.so
(gdb)
and then calloc is called:
(gdb) c
Continuing.
Breakpoint 4, calloc (n=n@entry=20, m=4) at tst-audit2.c:18
18 {
(gdb) bt
reloc_mode=reloc_mode@entry=0, consider_profiling=1,
consider_profiling@entry=0) at dl-reloc.c:272
user_entry=0xffffcf1c, auxv=0xffffd0a8) at rtld.c:2133
start_argptr=start_argptr@entry=0xffffcfb0,
dl_main=dl_main@entry=0xf7fda6f0 <dl_main>) at
../elf/dl-sysdep.c:249
from /export/build/gnu/glibc-32bit/build-i686-linux/elf/ld.so
(gdb)
With GOT relocation, calloc in ld.so is called first:
(gdb) bt
consider_profiling=1) at dl-reloc.c:272
user_entry=0xffffcf0c, auxv=0xffffd098) at rtld.c:2074
start_argptr=start_argptr@entry=0xffffcfa0,
dl_main=dl_main@entry=0xf7fda6c0 <dl_main>) at
../elf/dl-sysdep.c:249
from /export/build/gnu/glibc-32bit-test/build-i686-linux/elf/ld.so
(gdb)
and then the GOT entry of calloc is updated:
(gdb) bt
skip_ifunc=<optimized out>, reloc_addr_arg=<optimized out>,
version=<optimized out>, sym=<optimized out>, map=<optimized out>)
at ../sysdeps/i386/dl-machine.h:329
out>,
nrelative=<optimized out>, relsize=<optimized out>,
reladdr=<optimized out>, map=<optimized out>) at do-rel.h:137
reloc_mode=reloc_mode@entry=0,
consider_profiling=1, consider_profiling@entry=0) at dl-reloc.c:258
user_entry=0xffffcf0c, auxv=0xffffd098) at rtld.c:2133
start_argptr=start_argptr@entry=0xffffcfa0,
dl_main=dl_main@entry=0xf7fda6c0 <dl_main>) at
../elf/dl-sysdep.c:249
from /export/build/gnu/glibc-32bit-test/build-i686-linux/elf/ld.so
(gdb)
After that, since calloc isn't called from ld.so nor any other modules,
magic in tst-audit2 isn't updated. Both orders are correct. This patch
makes sure that calloc in tst-audit2.c is called at least once from ld.so.
[BZ #18422]
* Makefile ($(objpfx)tst-audit2): Depend on $(libdl).
($(objpfx)tst-audit2.out): Also depend on
$(objpfx)tst-auditmod9b.so.
* elf/tst-audit2.c: Include <dlfcn.h>.
(calloc_called): New.
(calloc): Allow to be called more than once.
(do_test): dllopen/dlclose $ORIGIN/tst-auditmod9b.so.
From Alexandre Oliva <aoliva@redhat.com>.
* elf/tst-audit2.c: New file.
* elf/Makefile (tests): Add it.
($(objpfx)tst-audit2.out): New target.
(tst-audit2-ENV): New variable.
* elf/tst-leaks1.c: Include <stdio.h>.
