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Re: [PATCH] [BZ #19178] ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA conflict
- From: Mark Hatle <mark dot hatle at windriver dot com>
- To: "H.J. Lu" <hjl dot tools at gmail dot com>, GNU C Library <libc-alpha at sourceware dot org>
- Date: Wed, 28 Oct 2015 18:33:18 -0500
- Subject: Re: [PATCH] [BZ #19178] ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA conflict
- Authentication-results: sourceware.org; auth=none
- References: <20151028114906 dot GA7686 at gmail dot com> <CAMe9rOquOovFN=ZaD+6AFUm=XVer8nj+sQzu-6q+1mDC_CRjtw at mail dot gmail dot com> <CAMe9rOqtF_9qSfftHHSd22ig7FwsSM_pK_9dOPufHd6zChAjcg at mail dot gmail dot com> <CAMe9rOrJ71FK_x0mXtzas_pYM3x9rjsbrT_0FFNcjrocSboBDQ at mail dot gmail dot com>
I have verified the attached patch works with the prelinker.
Also the output of the ld.so when performing LD_TRACE_PRELINKING is now that
same as glibc-2.21.
Tested-by: Mark Hatle <mark.hatle@windriver.com>
On 10/28/15 6:18 PM, H.J. Lu wrote:
> On Wed, Oct 28, 2015 at 3:04 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
>> > On Wed, Oct 28, 2015 at 6:42 AM, H.J. Lu <hjl.tools@gmail.com> wrote:
>>> >> On Wed, Oct 28, 2015 at 4:49 AM, H.J. Lu <hjl.tools@gmail.com> wrote:
>>>> >>> _dl_debug_bindings updates relocation type class with 4 and 8. But
>>>> >>> ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA may be defined to 4. This patch
>>>> >>> adds ELF_RTYPE_CLASS_TLS/ELF_RTYPE_CLASS_IFUNC and use them in
>>>> >>> _dl_debug_bindings.
>>>> >>>
>>>> >>> Tested on i686 and x86-64. OK for master and 2.22 branch?
>>>> >>>
>>>> >>>
>>>> >>> H.J.
>>>> >>> --
>>>> >>> [BZ #19178]
>>>> >>> * dl-lookup.c (_dl_debug_bindings): Replace 4 and 8 with
>>>> >>> ELF_RTYPE_CLASS_TLS and ELF_RTYPE_CLASS_IFUNC.
>>>> >>> * sysdeps/generic/ldsodefs.h (ELF_RTYPE_CLASS_TLS): New.
>>>> >>> (ELF_RTYPE_CLASS_IFUNC): Likewise.
>>> >>
>>> >>
>>> >> It doesn't work with prelink.
>>> >>
>> >
>> > Here is the correct patch. Verified with prelink. OK for master
>> > and 2.22 branch?
> Here is the updated patch to keep only ELF_RTYPE_CLASS_PLT and
> ELF_RTYPE_CLASS_COPY bits for prelink.
>
> Mark, can you verify it with prelink?
>
> Thanks.
>
>
> -- H.J.
>
>
> 0001-Keep-only-ELF_RTYPE_CLASS_-PLT-COPY-bits-for-prelink.patch
>
>
> From 7f16bc353495e6c2ec101abeee4ba26525e6c725 Mon Sep 17 00:00:00 2001
> From: "H.J. Lu" <hjl.tools@gmail.com>
> Date: Wed, 28 Oct 2015 07:49:44 -0700
> Subject: [PATCH] Keep only ELF_RTYPE_CLASS_{PLT|COPY} bits for prelink
>
> prelink runs ld.so with the environment variable LD_TRACE_PRELINKING
> set to dump the relocation type class from _dl_debug_bindings. prelink
> has the following relocation type classes:
>
> #define RTYPE_CLASS_VALID 8
> #define RTYPE_CLASS_PLT (8|1)
> #define RTYPE_CLASS_COPY (8|2)
> #define RTYPE_CLASS_TLS (8|4)
>
> where ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA has a conflict with
> RTYPE_CLASS_TLS.
>
> Since prelink only uses ELF_RTYPE_CLASS_PLT and ELF_RTYPE_CLASS_COPY
> bits, we should clear the other bits when the DL_DEBUG_PRELINK bit is
> set.
>
> [BZ #19178]
> * elf/dl-lookup.c (RTYPE_CLASS_VALID): New.
> (RTYPE_CLASS_PLT): Likewise.
> (RTYPE_CLASS_COPY): Likewise.
> (RTYPE_CLASS_TLS): Likewise.
> (_dl_debug_bindings): Use RTYPE_CLASS_TLS and RTYPE_CLASS_VALID
> to set relocation type class for DL_DEBUG_PRELINK. Keep only
> ELF_RTYPE_CLASS_PLT and ELF_RTYPE_CLASS_COPY bits for
> DL_DEBUG_PRELINK.
> ---
> elf/dl-lookup.c | 21 +++++++++++++++++++--
> 1 file changed, 19 insertions(+), 2 deletions(-)
>
> diff --git a/elf/dl-lookup.c b/elf/dl-lookup.c
> index 581fb20..6ae6cc3 100644
> --- a/elf/dl-lookup.c
> +++ b/elf/dl-lookup.c
> @@ -1016,6 +1016,18 @@ _dl_debug_bindings (const char *undef_name, struct link_map *undef_map,
> #ifdef SHARED
> if (GLRO(dl_debug_mask) & DL_DEBUG_PRELINK)
> {
> +/* ELF_RTYPE_CLASS_XXX must match RTYPE_CLASS_XXX used by prelink with
> + LD_TRACE_PRELINKING. */
> +#define RTYPE_CLASS_VALID 8
> +#define RTYPE_CLASS_PLT (8|1)
> +#define RTYPE_CLASS_COPY (8|2)
> +#define RTYPE_CLASS_TLS (8|4)
> +#if ELF_RTYPE_CLASS_PLT != 0 && ELF_RTYPE_CLASS_PLT != 1
> +# error ELF_RTYPE_CLASS_PLT must be 0 or 1!
> +#endif
> +#if ELF_RTYPE_CLASS_COPY != 0 && ELF_RTYPE_CLASS_COPY != 2
> +# error ELF_RTYPE_CLASS_COPY must be 0 or 2!
> +#endif
> int conflict = 0;
> struct sym_val val = { NULL, NULL };
>
> @@ -1071,12 +1083,17 @@ _dl_debug_bindings (const char *undef_name, struct link_map *undef_map,
>
> if (value->s)
> {
> + /* Keep only ELF_RTYPE_CLASS_PLT and ELF_RTYPE_CLASS_COPY
> + bits since since prelink only uses them. */
> + type_class &= ELF_RTYPE_CLASS_PLT | ELF_RTYPE_CLASS_COPY;
> if (__glibc_unlikely (ELFW(ST_TYPE) (value->s->st_info)
> == STT_TLS))
> - type_class = 4;
> + /* Clear the RTYPE_CLASS_VALID bit in RTYPE_CLASS_TLS. */
> + type_class = RTYPE_CLASS_TLS & ~RTYPE_CLASS_VALID;
> else if (__glibc_unlikely (ELFW(ST_TYPE) (value->s->st_info)
> == STT_GNU_IFUNC))
> - type_class |= 8;
> + /* Set the RTYPE_CLASS_VALID bit. */
> + type_class |= RTYPE_CLASS_VALID;
> }
>
> if (conflict
> -- 2.4.3
>