[Bug libc/18572] New: [arm] Lazy TLSDESC relocation has data race

[Bug libc/18572] New: [arm] Lazy TLSDESC relocation has data race

[nszabolcs at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=18572

            Bug ID: 18572
           Summary: [arm] Lazy TLSDESC relocation has data race
           Product: glibc
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: libc
          Assignee: unassigned at sourceware dot org
          Reporter: nszabolcs at gmail dot com
                CC: drepper.fsp at gmail dot com
  Target Milestone: ---

same as bug 18034 but for 32bit arm.

With -mtls-dialect=gnu2, gcc generates TLSDESC code for TLS access on arm.

In glibc the arm TLSDESC entry functions in sysdeps/arm/dl-tlsdesc.S don't
synchronize with the initializer in tlsdesc.c, so an entry function may read
stale argument if the initialization happened concurrently on another cpu.

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[Bug dynamic-link/18572] [arm] Lazy TLSDESC relocation has data race

[jsm28 at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=18572

Joseph Myers <jsm28 at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|libc                        |dynamic-link

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[Bug dynamic-link/18572] [arm] Lazy TLSDESC relocation has data race

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=18572

--- Comment #1 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> ---
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       via  1fae5a6800b07d0a8225664ac65a628bbe98cae7 (commit)
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- Log -----------------------------------------------------------------
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=1fae5a6800b07d0a8225664ac65a628bbe98cae7

commit 1fae5a6800b07d0a8225664ac65a628bbe98cae7
Author: Szabolcs Nagy <szabolcs.nagy@arm.com>
Date:   Wed Oct 14 16:58:41 2015 +0100

    [BZ #19129][ARM] Fix _dl_tlsdesc_resolve_hold to save r0

    _dl_tlsdesc_resolve_hold calls into a C function that clobbers r0,
    but it assumes the original argument is still in r0 after the call.
    This can cause crash in case of concurrent TLS access when TLSDESC
    is in use (-mtls-dialect=gnu2).

    Run into this while fixing BZ 18572.

    Both r0 and r1 are saved/restored so the stack remains 8 byte aligned.

        [BZ #19129]
        * sysdeps/arm/dl-tlsdesc.S (_dl_tlsdesc_resolve_hold): Save and restore
        r0 and r1.

-----------------------------------------------------------------------

Summary of changes:
 ChangeLog                |    6 ++++++
 NEWS                     |    2 +-
 sysdeps/arm/dl-tlsdesc.S |   27 ++++++++++++++++++---------
 3 files changed, 25 insertions(+), 10 deletions(-)

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