Re: [PATCH v2] nptl_db: disable DT_RELR on libthread_db.so

[Carlos O'Donell <carlos@redhat.com>]

On 6/3/22 10:50, Paul E. Murphy via Libc-alpha wrote:
> Continued from
> 
> https://sourceware.org/pipermail/libc-alpha/2022-June/139357.html

LGTM.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>

> ---8<---
> 
> Some nptl tests inadvertently use the host's gdb to verify
> libthread_db.so, which is loaded with the host's runtime.  This causes
> a couple of test failures when the host glibc does not support DT_RELR.
> 
> The not correct, but simple, workaround is to build without DT_RELR
> as this library is otherwise likely to load on glibc 2.17 and newer
> today.
> 
> This allows tst-pthread-gdb-attach{,-static} to continue working
> when testing on a gdb loaded with an older glibc.

OK.

> 
> This avoids a failure in tst-pthread-gdb-attach similar to:
> 
>   Trying host libthread_db library: .../build/glibc/nptl_db/libthread_db.so.1.
>   dlopen failed: /lib64/libc.so.6: version `GLIBC_ABI_DT_RELR' not found (required by .../build/glibc/nptl_db/libthread_db.so.1).

OK.

> ---
>  nptl_db/Makefile | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/nptl_db/Makefile b/nptl_db/Makefile
> index ed923a41e5..2360e53c88 100644
> --- a/nptl_db/Makefile
> +++ b/nptl_db/Makefile
> @@ -49,6 +49,12 @@ libthread_db-inhibit-o = $(filter-out .os,$(object-suffixes))
>  # The ps_* callback functions are not defined.
>  libthread_db.so-no-z-defs = yes
>  
> +# This is a hack.  This is not the correct solution.  When this glibc
> +# is tested, the gdb used could be loaded by the host glibc, which
> +# may not support DT_RELR, and report a failure instead of unsupported.
> +# For now, build this without DT_RELR support to avoid this situation.

OK. *Great* comment :-)

> +libthread_db.so-no-dt-relr = yes
> +
>  tests-special += $(objpfx)db-symbols.out
>  
>  include ../Rules


-- 
Cheers,
Carlos.