This is the mail archive of the
mailing list for the glibc project.
Re: [PATCH 1/2] Add ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA to x86
- From: "H.J. Lu" <hjl dot tools at gmail dot com>
- To: GNU C Library <libc-alpha at sourceware dot org>
- Date: Fri, 6 Mar 2015 06:54:00 -0800
- Subject: Re: [PATCH 1/2] Add ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA to x86
- Authentication-results: sourceware.org; auth=none
- References: <20150306001923 dot GA11077 at intel dot com>
On Thu, Mar 5, 2015 at 4:19 PM, H.J. Lu <firstname.lastname@example.org> wrote:
> With copy relocation, address of protected data defined in the shared
> library may be external. When there is a relocation against the
> protected data symbol within the shared library, we need to check if we
> should skip the definition in the executable copied from the protected
> data. This patch adds ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA and defines
> it for x86. If ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA isn't 0, do_lookup_x
> will skip the data definition in the executable from copy reloc.
> I only defined DL_EXTERN_PROTECTED_DATA for x86. Other targets can
> define DL_EXTERN_PROTECTED_DATA and update elf_machine_type_class to
> support copy relocation on protected data.
> I will submit a testcase in a separate email.
> Tested on x86-32 and x86-64. OK for master?
> [BZ #17711]
> * elf/dl-lookup.c (do_lookup_x): When UNDEF_MAP is NULL, which
> indicates it is called from do_lookup_x on relocation against
> protected data, skip the data definion in the executable from
> copy reloc.
> (_dl_lookup_symbol_x): Pass ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA,
> instead of ELF_RTYPE_CLASS_PLT, to do_lookup_x for
> EXTERN_PROTECTED_DATA relocation against STT_OBJECT symbol.
> * sysdeps/generic/ldsodefs.h * (ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA):
> New. Defined to 4 if DL_EXTERN_PROTECTED_DATA is defined,
> otherwise to 0.
> * sysdeps/i386/dl-lookupcfg.h (DL_EXTERN_PROTECTED_DATA): New.
> * sysdeps/i386/dl-machine.h (elf_machine_type_class): Set class
> to ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA for R_386_GLOB_DAT.
> * sysdeps/x86_64/dl-lookupcfg.h (DL_EXTERN_PROTECTED_DATA): New.
> * sysdeps/x86_64/dl-machine.h (elf_machine_type_class): Set class
> to ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA for R_X86_64_GLOB_DAT.
FWIW, If a target doesn't define DL_NO_COPY_RELOCS, its elf_machine_type_class
should properly handle ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA. Fix it
should be very much straight forward by adding
| (((type) == R_XXX_GLOB_DAT) * ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA))
to elf_machine_type_class. Target maintainer should give it a try.