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sh: Fix building with gcc5/6

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Build glibc for sh4-unknown-linux-gnu currently fails if one's
using GCC5/6: in dl-conflict.c, the elf_machine_rela() function
is called with NULL as its 3rd argument, sym. The implementation
of that function in sysdeps/sh/dl-machine.h dereferences that pointer:

const Elf32_Sym *const refsym = sym;
...
if (map == &GL(dl_rtld_map))
  value -= map->l_addr + refsym->st_value + reloc->r_addend;

GCC discovers a null pointer dereference, and in accordance with
-fdelete-null-pointer-checks (which is enabled in -O2) replaces this
code with a trap - which, as SH does not implement a trap pattern in
GCC, evaluates to an abort() call. This abort() call pulls many more
objects from libc_nonshared.a, eventually resulting in link failure
due to multiple definitions for a number of symbols.

As far as I see, the conditional before this code is always false in
rtld: _dl_resolve_conflicts() is called with main_map as the first
argument, not GL(_dl_rtld_map), but since that call is in yet another
compilation unit, GCC does not know about it. Patch that wraps this
conditional into !defined RESOLVE_CONFLICT_FIND_MAP attached.

	* sysdeps/sh/dl-machine.h (elf_machine_rela): The condition
	in R_SH_DIR32 case is always false when inlined from
	dl-conflict.c. Ifdef out to prevent GCC from insertin an
	abort() call.
This commit is contained in:
Alexey Neyman 2017-02-08 16:00:57 -02:00 committed by Adhemerval Zanella
parent cb09a3d497
commit d40dbe722f
2 changed files with 7 additions and 1 deletions
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6
ChangeLog
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@ -1,3 +1,9 @@
2017-03-12 Alexey Neyman <stilor@att.net>
* sysdeps/sh/dl-machine.h (elf_machine_rela): The condition
in R_SH_DIR32 case is always false when inlined from
dl-conflict.c. Ifdef out to prevent GCC from insertin an
2016-03-12 Marko Myllynen <myllynen@redhat.com>
* sysdeps/unix/sysv/linux/alpha/kernel-features.h

2
sysdeps/sh/dl-machine.h
View file

@ -389,7 +389,7 @@ elf_machine_rela (struct link_map *map, const Elf32_Rela *reloc,
break;
case R_SH_DIR32:
{
#ifndef RTLD_BOOTSTRAP
#if !defined RTLD_BOOTSTRAP && !defined RESOLVE_CONFLICT_FIND_MAP
/* This is defined in rtld.c, but nowhere in the static
libc.a; make the reference weak so static programs can
still link. This declaration cannot be done when