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[v2] elf: Inline do_tunable_update_val/tunable_initialize [BZ #28712]

Message ID 20211218202743.3105160-1-hjl.tools@gmail.com
State Dropped
Headers show
Series [v2] elf: Inline do_tunable_update_val/tunable_initialize [BZ #28712] | expand

Checks

Context Check Description
dj/TryBot-apply_patch success Patch applied to master at the time it was sent
dj/TryBot-32bit success Build for i686

Commit Message

H.J. Lu Dec. 18, 2021, 8:27 p.m. UTC
Changes in v2:

1. Replace inline with __always_inline.

In static PIE, __tunables_init is called before _dl_relocate_static_pie
in LIBC_START_MAIN in csu/libc-start.c:

  __tunables_init (__environ);

  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 ();

Inline do_tunable_update_val and tunable_initialize to prevent compiler
from generating dynamic relocation against tunable_list which causes
__tunables_init to fail in static PIE on x86-64:

FAIL: elf/tst-env-setuid

since

.L35:
        movq    $-88, %rax
        subq    .LC3(%rip), %rax
	^^^^  This is executed before the .LC3 entry has been relocated.
        movq    %rax, 8(%rsp)
...
        .section        .data.rel.ro.local,"aw"
        .align 8
.LC3:
        .quad   tunable_list

Tested on x86-64, x32 and i686 with GCC 11 and GCC 12.

This fixes BZ #28712.
---
 elf/dl-tunables.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Comments

Florian Weimer Dec. 18, 2021, 10:46 p.m. UTC | #1
* H. J. Lu via Libc-alpha:

> Inline do_tunable_update_val and tunable_initialize to prevent compiler
> from generating dynamic relocation against tunable_list which causes
> __tunables_init to fail in static PIE on x86-64:
>
> FAIL: elf/tst-env-setuid
>
> since
>
> .L35:
>         movq    $-88, %rax
>         subq    .LC3(%rip), %rax
> 	^^^^  This is executed before the .LC3 entry has been relocated.
>         movq    %rax, 8(%rsp)
> ...
>         .section        .data.rel.ro.local,"aw"
>         .align 8
> .LC3:
>         .quad   tunable_list
>
> Tested on x86-64, x32 and i686 with GCC 11 and GCC 12.

This is a GCC bug that needs to be fixed, or we have to
PI_STATIC_AND_HIDDEN as 0 on x86-64, which has lots of unwanted
consequences.

Thanks,
Florian
diff mbox series

Patch

diff --git a/elf/dl-tunables.c b/elf/dl-tunables.c
index 497e948f1c..02402e2990 100644
--- a/elf/dl-tunables.c
+++ b/elf/dl-tunables.c
@@ -92,7 +92,7 @@  get_next_env (char **envp, char **name, size_t *namelen, char **val,
   return NULL;
 }
 
-static void
+static void __always_inline
 do_tunable_update_val (tunable_t *cur, const tunable_val_t *valp,
 		       const tunable_num_t *minp,
 		       const tunable_num_t *maxp)
@@ -139,7 +139,7 @@  do_tunable_update_val (tunable_t *cur, const tunable_val_t *valp,
 
 /* Validate range of the input value and initialize the tunable CUR if it looks
    good.  */
-static void
+static void __always_inline
 tunable_initialize (tunable_t *cur, const char *strval)
 {
   tunable_val_t val;