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| author | H.J. Lu <hjl.tools@gmail.com> | 2015-05-23 06:05:19 -0700 |
|---|---|---|
| committer | H.J. Lu <hjl.tools@gmail.com> | 2015-05-23 06:12:17 -0700 |
| commit | df5dc4f32dc00eecd24534275ad82e1a3b49335a (patch) | |
| tree | 496602e5966934b8f9a98d53e64b139591856684 | |
| parent | 3e058c9d7eab6d6361e7cda5ba1394bc1757c9f6 (diff) | |
| download | glibc-hjl/pr18422.tar.gz | |
Don't build ld.so with -Wl,-z,nowhjl/pr18422
PLT entries 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 entries with -z now. elf/tst-audit2.c has
/* This calloc definition will be called by the dynamic linker itself.
We test that it has initialized our TLS block by the time it does so.
*/
void *
calloc (size_t n, size_t m)
{
if (magic[0] != MAGIC1 || magic[1] != MAGIC2)
{
printf ("{%x, %x} != {%x, %x}\n", magic[0], magic[1], MAGIC1, MAGIC2);
abort ();
}
magic[0] = MAGIC2;
magic[1] = MAGIC1;
Since ld.so is built with -z now, there are no PLT relocations and this
calloc won't be used:
Relocation section '.rela.dyn' at offset 0x66c contains 16 entries:
Offset Info Type Sym.Value Sym. Name + Addend
00222e88 00000008 R_X86_64_RELATIVE 10970
00222e8c 00000008 R_X86_64_RELATIVE f8f0
00222e90 00000008 R_X86_64_RELATIVE f6c0
00222e94 00000008 R_X86_64_RELATIVE 11bd0
00222e98 00000008 R_X86_64_RELATIVE a1b0
00222e9c 00000008 R_X86_64_RELATIVE 130c0
00222ea0 00000008 R_X86_64_RELATIVE 13c50
00222ea4 00000008 R_X86_64_RELATIVE 15fc0
00222ea8 00000008 R_X86_64_RELATIVE 12cd0
00222eac 00000008 R_X86_64_RELATIVE 17f90
00222fbc 00000a06 R_X86_64_GLOB_DAT 00018230 __libc_memalign@@GLIBC_2.16 + 0
00222fc4 00001506 R_X86_64_GLOB_DAT 00018300 malloc@@GLIBC_2.16 + 0
00222fcc 00000d06 R_X86_64_GLOB_DAT 00018310 calloc@@GLIBC_2.16 + 0
00222fd4 00000506 R_X86_64_GLOB_DAT 000184a0 realloc@@GLIBC_2.16 + 0
00222fdc 00000706 R_X86_64_GLOB_DAT 002239a0 _r_debug@@GLIBC_2.16 + 0
00222fe4 00000406 R_X86_64_GLOB_DAT 00018340 free@@GLIBC_2.16 + 0
Assuming we do want to keep PLT relocations in ld.so so that malloc
functions in ld.so can be overridden, ld.so should be built with -z now.
There is no reason to build ld.so with -z now since ld.so is the one
doing BIND_NOW. The only thing we get with -z now on ld.so is DT tag:
0x0000000000000018 (BIND_NOW)
0x000000006ffffffb (FLAGS_1) Flags: NOW
This patch removes -Wl,-z,now from ld.so build.
[BZ #18422]
* elf/Makefile (z-now-yes): Removed.
($(objpfx)ld.so): Remove $(z-now-$(bind-now)).
| -rw-r--r-- | elf/Makefile | 4 |
1 files changed, 1 insertions, 3 deletions
diff --git a/elf/Makefile b/elf/Makefile index 34450eaa5b..324b4a2556 100644 --- a/elf/Makefile +++ b/elf/Makefile @@ -349,13 +349,11 @@ $(objpfx)librtld.os: $(objpfx)dl-allobjs.os $(objpfx)rtld-libc.a generated += librtld.map librtld.mk rtld-libc.a librtld.os.map -z-now-yes = -Wl,-z,now - $(objpfx)ld.so: $(objpfx)librtld.os $(ld-map) # Link into a temporary file so that we don't touch $@ at all # if the sanity check below fails. $(LINK.o) -nostdlib -nostartfiles -shared -o $@.new \ - $(LDFLAGS-rtld) -Wl,-z,defs $(z-now-$(bind-now)) \ + $(LDFLAGS-rtld) -Wl,-z,defs \ $(filter-out $(map-file),$^) $(load-map-file) \ -Wl,-soname=$(rtld-installed-name) \ -Wl,-defsym=_begin=0 |