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Re: [PATCH] static-PIE: Update DT_DEBUG for debugger [BZ #23206]
- From: Carlos O'Donell <carlos at redhat dot com>
- To: "H.J. Lu" <hjl dot tools at gmail dot com>, GNU C Library <libc-alpha at sourceware dot org>
- Date: Tue, 29 May 2018 09:21:10 -0400
- Subject: Re: [PATCH] static-PIE: Update DT_DEBUG for debugger [BZ #23206]
- References: <20180529120848.GA13734@intel.com>
On 05/29/2018 08:08 AM, H.J. Lu wrote:
> This is needed to support debugging dlopened shared libraries in static
> PIE.
>
> OK for master?
>
This looks good. We always need to setup r_debug properly and this looks
like the right solution to me. IIUC we set RT_CONSISTENT at this point because
we are consistent (not doing anything with the link map the debugger needs to
be aware of).
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
> H.J.
> [BZ #23206]
> * elf/dl-reloc-static-pie.c (_dl_relocate_static_pie): Initialize
> _r_debug and update DT_DEBUG for debugger.
> ---
> elf/dl-reloc-static-pie.c | 16 ++++++++++++++++
> 1 file changed, 16 insertions(+)
>
> diff --git a/elf/dl-reloc-static-pie.c b/elf/dl-reloc-static-pie.c
> index bd2d516e5d..ab1ce0eacc 100644
> --- a/elf/dl-reloc-static-pie.c
> +++ b/elf/dl-reloc-static-pie.c
> @@ -48,5 +48,21 @@ _dl_relocate_static_pie (void)
> data access using the global offset table. */
> ELF_DYNAMIC_RELOCATE (main_map, 0, 0, 0);
> main_map->l_relocated = 1;
> +
> + /* Initialize _r_debug. */
> + struct r_debug *r = _dl_debug_initialize (0, LM_ID_BASE);
> + r->r_state = RT_CONSISTENT;
> +
> + /* Set up debugging before the debugger is notified for the first
> + time. */
> +# ifdef ELF_MACHINE_DEBUG_SETUP
> + /* Some machines (e.g. MIPS) don't use DT_DEBUG in this way. */
> + ELF_MACHINE_DEBUG_SETUP (main_map, r);
> +# else
> + if (main_map->l_info[DT_DEBUG] != NULL)
> + /* There is a DT_DEBUG entry in the dynamic section. Fill it in
> + with the run-time address of the r_debug structure */
> + main_map->l_info[DT_DEBUG]->d_un.d_ptr = (ElfW(Addr)) r;
> +# endif
> }
> #endif
>