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csu: Move static pie self relocation later [BZ #27072]

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IFUNC resolvers may depend on tunables and cpu feature setup so
move static pie self relocation after those.

It is hard to guarantee that the ealy startup code does not rely
on relocations so this is a bit fragile. It would be more robust
to handle RELATIVE relocs early and only IRELATIVE relocs later,
but the current relocation processing code cannot do that.

The early startup code up to relocation processing includes

  _dl_aux_init (auxvec);
  __libc_init_secure ();
  __tunables_init (__environ);
  ARCH_INIT_CPU_FEATURES ();
  _dl_relocate_static_pie ();

These are simple enough that RELATIVE relocs can be avoided.

The following steps include

  ARCH_SETUP_IREL ();
  ARCH_SETUP_TLS ();
  ARCH_APPLY_IREL ();

On some targets IRELATIVE processing relies on TLS setup on
others TLS setup relies on IRELATIVE relocs, so the right
position for _dl_relocate_static_pie is target dependent.
For now move self relocation as early as possible on targets
that support static PIE.

Fixes bug 27072.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
This commit is contained in:
Szabolcs Nagy 2021-01-19 17:17:01 +00:00
parent 47618209d0
commit 86d439b06f
1 changed files with 5 additions and 2 deletions
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7
csu/libc-start.c
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@ -146,8 +146,6 @@ LIBC_START_MAIN (int (*main) (int, char **, char ** MAIN_AUXVEC_DECL),
int result;
#ifndef SHARED
_dl_relocate_static_pie ();
char **ev = &argv[argc + 1];
__environ = ev;
@ -199,6 +197,11 @@ LIBC_START_MAIN (int (*main) (int, char **, char ** MAIN_AUXVEC_DECL),
ARCH_INIT_CPU_FEATURES ();
/* Do static pie self relocation after tunables and cpu features
are setup for ifunc resolvers. Before this point relocations
must be avoided. */
_dl_relocate_static_pie ();
/* Perform IREL{,A} relocations. */
ARCH_SETUP_IREL ();