Re: [PATCH 2/2] x86: Add elf_x86_backend_data

["H.J. Lu" <hjl dot tools at gmail dot com>]

On Thu, Sep 14, 2017 at 8:26 AM, H.J. Lu <hongjiu.lu@intel.com> wrote:
> Add plt0_pad_byte and target_os fields to elf_x86_link_hash_table.
> Replace elf_i386_backend_data and elf_x86_64_backend_data with
> elf_x86_backend_data.
>
>         * elf32-i386.c (elf_i386_backend_data): Removed.
>         (get_elf_i386_backend_data): Likewise.
>         (elf_i386_arch_bed): Replace elf_i386_backend_data with
>         elf_x86_backend_data.
>         (elf_i386_get_synthetic_symtab): Likewise.
>         (elf_i386_nacl_arch_bed): Likewise.
>         (elf_i386_vxworks_arch_bed): Likewise.
>         (elf_i386_relocate_section): Check target_os instead of
>         is_vxworks.
>         (elf_i386_finish_dynamic_symbol): Likewise.
>         (elf_i386_finish_dynamic_sections): Use htab->plt0_pad_byte.
>         Check target_os instead of is_vxworks.
>         (elf_i386_link_setup_gnu_properties): Remove normal_target and
>         is_vxworks.  Initialize plt0_pad_byte.
>         * elf64-x86-64.c (elf_x86_64_backend_data); Removed.
>         (get_elf_x86_64_arch_data): Likewise.
>         (get_elf_x86_64_backend_data): Likewise.
>         (elf_x86_64_arch_bed): Replace elf_x86_64_backend_data with
>         elf_x86_backend_data.
>         (elf_x86_64_get_synthetic_symtab): Likewise.
>         (elf_x86_64_nacl_arch_bed): Likewise.
>         (elf_x86_64_link_setup_gnu_properties): Remove is_vxworks and
>         normal_target.  Initialize plt0_pad_byte.
>         * elfxx-x86.c (elf_x86_allocate_dynrelocs): Check target_os
>         instead of is_vxworks.
>         (_bfd_x86_elf_size_dynamic_sections): Likewise.
>         (_bfd_x86_elf_finish_dynamic_sections): Likewise.
>         (_bfd_x86_elf_adjust_dynamic_symbol): Likewise.
>         (_bfd_x86_elf_link_hash_table_create): Initialize target_os.
>         (_bfd_x86_elf_link_setup_gnu_properties): Remove is_vxworks.
>         Update normal_target.  Set up plt0_pad_byte.  Check target_os
>         instead of is_vxworks.
>         * elfxx-x86.h (elf_x86_target_os): New.
>         (elf_x86_backend_data): Likewise.
>         (get_elf_x86_backend_data): Likewise.
>         (elf_x86_link_hash_table): Remove is_vxworks.  Add plt0_pad_byte
>         and target_os.
>         (elf_x86_init_table): Remove normal_target and is_vxworks.  Add
>         plt0_pad_byte.
> ---
>  bfd/elf32-i386.c   | 53 +++++++++++++----------------------------------------
>  bfd/elf64-x86-64.c | 35 +++++++++--------------------------
>  bfd/elfxx-x86.c    | 28 +++++++++++++++-------------
>  bfd/elfxx-x86.h    | 34 +++++++++++++++++++++++++---------
>  4 files changed, 62 insertions(+), 88 deletions(-)
>
> diff --git a/bfd/elf32-i386.c b/bfd/elf32-i386.c
> index 2daa163cbf..f11db44f0d 100644
> --- a/bfd/elf32-i386.c
> +++ b/bfd/elf32-i386.c
> @@ -820,30 +820,9 @@ static const struct elf_x86_non_lazy_plt_layout elf_i386_non_lazy_ibt_plt =
>  #define PLTRESOLVE_RELOCS 2
>  #define PLT_NON_JUMP_SLOT_RELOCS 2
>
> -/* Architecture-specific backend data for i386.  */
> -
> -struct elf_i386_backend_data
> -{
> -  /* Value used to fill the unused bytes of the first PLT entry.  */
> -  bfd_byte plt0_pad_byte;
> -
> -  /* Target system.  */
> -  enum
> -    {
> -      is_normal,
> -      is_vxworks,
> -      is_nacl
> -    } os;
> -};
> -
> -#define get_elf_i386_backend_data(abfd) \
> -  ((const struct elf_i386_backend_data *) \
> -   get_elf_backend_data (abfd)->arch_data)
> -
>  /* These are the standard parameters.  */
> -static const struct elf_i386_backend_data elf_i386_arch_bed =
> +static const struct elf_x86_backend_data elf_i386_arch_bed =
>    {
> -    0,                                  /* plt0_pad_byte */
>      is_normal                           /* os */
>    };
>
> @@ -2047,7 +2026,7 @@ elf_i386_relocate_section (bfd *output_bfd,
>    local_tlsdesc_gotents = elf_x86_local_tlsdesc_gotent (input_bfd);
>    /* We have to handle relocations in vxworks .tls_vars sections
>       specially, because the dynamic loader is 'weird'.  */
> -  is_vxworks_tls = (htab->is_vxworks
> +  is_vxworks_tls = (htab->target_os == is_vxworks
>                      && bfd_link_pic (info)
>                     && !strcmp (input_section->output_section->name,
>                                 ".tls_vars"));
> @@ -3714,7 +3693,7 @@ elf_i386_finish_dynamic_symbol (bfd *output_bfd,
>                       resolved_plt->contents + plt_offset
>                        + htab->plt.plt_got_offset);
>
> -         if (htab->is_vxworks)
> +         if (htab->target_os == is_vxworks)
>             {
>               int s, k, reloc_index;
>
> @@ -4120,13 +4099,10 @@ elf_i386_finish_dynamic_sections (bfd *output_bfd,
>         {
>           /* Fill in the special first entry in the procedure linkage
>              table.  */
> -         const struct elf_i386_backend_data *abed
> -           = get_elf_i386_backend_data (output_bfd);
> -
>           memcpy (htab->elf.splt->contents, htab->plt.plt0_entry,
>                   htab->lazy_plt->plt0_entry_size);
>           memset (htab->elf.splt->contents + htab->lazy_plt->plt0_entry_size,
> -                 abed->plt0_pad_byte,
> +                 htab->plt0_pad_byte,
>                   htab->plt.plt_entry_size - htab->lazy_plt->plt0_entry_size);
>           if (!bfd_link_pic (info))
>             {
> @@ -4143,7 +4119,7 @@ elf_i386_finish_dynamic_sections (bfd *output_bfd,
>                           htab->elf.splt->contents
>                           + htab->lazy_plt->plt0_got2_offset);
>
> -             if (htab->is_vxworks)
> +             if (htab->target_os == is_vxworks)
>                 {
>                   Elf_Internal_Rela rel;
>                   int num_plts = (htab->elf.splt->size
> @@ -4284,7 +4260,7 @@ elf_i386_get_synthetic_symtab (bfd *abfd,
>    lazy_plt = NULL;
>    non_lazy_ibt_plt = NULL;
>    lazy_ibt_plt = NULL;
> -  switch (get_elf_i386_backend_data (abfd)->os)
> +  switch (get_elf_x86_backend_data (abfd)->target_os)
>      {
>      case is_normal:
>        non_lazy_plt = &elf_i386_non_lazy_plt;
> @@ -4443,25 +4419,24 @@ elf_i386_link_setup_gnu_properties (struct bfd_link_info *info)
>  {
>    struct elf_x86_init_table init_table;
>
> -  init_table.normal_target = FALSE;
> -  init_table.is_vxworks = FALSE;
> -  switch (get_elf_i386_backend_data (info->output_bfd)->os)
> +  switch (get_elf_x86_backend_data (info->output_bfd)->target_os)
>      {
>      case is_normal:
> +      init_table.plt0_pad_byte = 0x0;
>        init_table.lazy_plt = &elf_i386_lazy_plt;
>        init_table.non_lazy_plt = &elf_i386_non_lazy_plt;
>        init_table.lazy_ibt_plt = &elf_i386_lazy_ibt_plt;
>        init_table.non_lazy_ibt_plt = &elf_i386_non_lazy_ibt_plt;
> -      init_table.normal_target = TRUE;
>        break;
>      case is_vxworks:
> +      init_table.plt0_pad_byte = 0x90;
>        init_table.lazy_plt = &elf_i386_lazy_plt;
>        init_table.non_lazy_plt = NULL;
>        init_table.lazy_ibt_plt = NULL;
>        init_table.non_lazy_ibt_plt = NULL;
> -      init_table.is_vxworks = TRUE;
>        break;
>      case is_nacl:
> +      init_table.plt0_pad_byte = 0x90;
>        init_table.lazy_plt = &elf_i386_nacl_plt;
>        init_table.non_lazy_plt = NULL;
>        init_table.lazy_ibt_plt = NULL;
> @@ -4814,7 +4789,7 @@ static const bfd_byte elf_i386_nacl_eh_frame_plt[] =
>       || PLT_FDE_LENGTH != 36                            \
>       || PLT_FDE_START_OFFSET != 4 + PLT_CIE_LENGTH + 8  \
>       || PLT_FDE_LEN_OFFSET != 4 + PLT_CIE_LENGTH + 12)
> -# error "Need elf_i386_backend_data parameters for eh_frame_plt offsets!"
> +# error "Need elf_x86_backend_data parameters for eh_frame_plt offsets!"
>  #endif
>      PLT_CIE_LENGTH, 0, 0, 0,           /* CIE length */
>      0, 0, 0, 0,                         /* CIE ID */
> @@ -4868,9 +4843,8 @@ static const struct elf_x86_lazy_plt_layout elf_i386_nacl_plt =
>      sizeof (elf_i386_nacl_eh_frame_plt) /* eh_frame_plt_size */
>    };
>
> -static const struct elf_i386_backend_data elf_i386_nacl_arch_bed =
> +static const struct elf_x86_backend_data elf_i386_nacl_arch_bed =
>    {
> -    0x90,                               /* plt0_pad_byte: nop insn */
>      is_nacl                             /* os */
>    };
>
> @@ -4914,9 +4888,8 @@ elf32_i386_nacl_elf_object_p (bfd *abfd)
>  #undef elf_backend_plt_alignment
>  #define elf_backend_plt_alignment      4
>
> -static const struct elf_i386_backend_data elf_i386_vxworks_arch_bed =
> +static const struct elf_x86_backend_data elf_i386_vxworks_arch_bed =
>    {
> -    0x90,                               /* plt0_pad_byte */
>      is_vxworks                          /* os */
>    };
>
> diff --git a/bfd/elf64-x86-64.c b/bfd/elf64-x86-64.c
> index fd58bd7139..188a24265a 100644
> --- a/bfd/elf64-x86-64.c
> +++ b/bfd/elf64-x86-64.c
> @@ -816,24 +816,6 @@ static const bfd_byte elf_x86_64_eh_frame_non_lazy_plt[] =
>    DW_CFA_nop, DW_CFA_nop, DW_CFA_nop
>  };
>
> -/* Architecture-specific backend data for x86-64.  */
> -
> -struct elf_x86_64_backend_data
> -{
> -  /* Target system.  */
> -  enum
> -    {
> -      is_normal,
> -      is_nacl
> -    } os;
> -};
> -
> -#define get_elf_x86_64_arch_data(bed) \
> -  ((const struct elf_x86_64_backend_data *) (bed)->arch_data)
> -
> -#define get_elf_x86_64_backend_data(abfd) \
> -  get_elf_x86_64_arch_data (get_elf_backend_data (abfd))
> -
>  /* These are the standard parameters.  */
>  static const struct elf_x86_lazy_plt_layout elf_x86_64_lazy_plt =
>    {
> @@ -963,7 +945,7 @@ static const struct elf_x86_non_lazy_plt_layout elf_x32_non_lazy_ibt_plt =
>      sizeof (elf_x86_64_eh_frame_non_lazy_plt) /* eh_frame_plt_size */
>    };
>
> -static const struct elf_x86_64_backend_data elf_x86_64_arch_bed =
> +static const struct elf_x86_backend_data elf_x86_64_arch_bed =
>    {
>      is_normal                            /* os */
>    };
> @@ -4620,7 +4602,7 @@ elf_x86_64_get_synthetic_symtab (bfd *abfd,
>    if (relsize <= 0)
>      return -1;
>
> -  if (get_elf_x86_64_backend_data (abfd)->os == is_normal)
> +  if (get_elf_x86_backend_data (abfd)->target_os == is_normal)
>      {
>        lazy_plt = &elf_x86_64_lazy_plt;
>        non_lazy_plt = &elf_x86_64_non_lazy_plt;
> @@ -4968,8 +4950,11 @@ elf_x86_64_link_setup_gnu_properties (struct bfd_link_info *info)
>           != (int) R_X86_64_GNU_VTENTRY))
>      abort ();
>
> -  init_table.is_vxworks = FALSE;
> -  if (get_elf_x86_64_backend_data (info->output_bfd)->os == is_normal)
> +  /* This is unused for x86-64.  */
> +  init_table.plt0_pad_byte = 0x90;
> +
> +  if (get_elf_x86_backend_data (info->output_bfd)->target_os
> +      == is_normal)
>      {
>        if (info->bndplt)
>         {
> @@ -4992,7 +4977,6 @@ elf_x86_64_link_setup_gnu_properties (struct bfd_link_info *info)
>           init_table.lazy_ibt_plt = &elf_x32_lazy_ibt_plt;
>           init_table.non_lazy_ibt_plt = &elf_x32_non_lazy_ibt_plt;
>         }
> -      init_table.normal_target = TRUE;
>      }
>    else
>      {
> @@ -5000,7 +4984,6 @@ elf_x86_64_link_setup_gnu_properties (struct bfd_link_info *info)
>        init_table.non_lazy_plt = NULL;
>        init_table.lazy_ibt_plt = NULL;
>        init_table.non_lazy_ibt_plt = NULL;
> -      init_table.normal_target = FALSE;
>      }
>
>    if (ABI_64_P (info->output_bfd))
> @@ -5265,7 +5248,7 @@ static const bfd_byte elf_x86_64_nacl_eh_frame_plt[] =
>       || PLT_FDE_LENGTH != 36                            \
>       || PLT_FDE_START_OFFSET != 4 + PLT_CIE_LENGTH + 8  \
>       || PLT_FDE_LEN_OFFSET != 4 + PLT_CIE_LENGTH + 12)
> -# error "Need elf_x86_64_backend_data parameters for eh_frame_plt offsets!"
> +# error "Need elf_x86_backend_data parameters for eh_frame_plt offsets!"
>  #endif
>      PLT_CIE_LENGTH, 0, 0, 0,   /* CIE length */
>      0, 0, 0, 0,                        /* CIE ID */
> @@ -5319,7 +5302,7 @@ static const struct elf_x86_lazy_plt_layout elf_x86_64_nacl_plt =
>      sizeof (elf_x86_64_nacl_eh_frame_plt)    /* eh_frame_plt_size */
>    };
>
> -static const struct elf_x86_64_backend_data elf_x86_64_nacl_arch_bed =
> +static const struct elf_x86_backend_data elf_x86_64_nacl_arch_bed =
>    {
>      is_nacl                                  /* os */
>    };
> diff --git a/bfd/elfxx-x86.c b/bfd/elfxx-x86.c
> index a0fe9d19ff..d78c1e485f 100644
> --- a/bfd/elfxx-x86.c
> +++ b/bfd/elfxx-x86.c
> @@ -262,7 +262,7 @@ elf_x86_allocate_dynrelocs (struct elf_link_hash_entry *h,
>                 }
>             }
>
> -         if (htab->is_vxworks && !bfd_link_pic (info))
> +         if (htab->target_os == is_vxworks && !bfd_link_pic (info))
>             {
>               /* VxWorks has a second set of relocations for each PLT entry
>                  in executables.  They go in a separate relocation section,
> @@ -406,7 +406,7 @@ elf_x86_allocate_dynrelocs (struct elf_link_hash_entry *h,
>             }
>         }
>
> -      if (htab->is_vxworks)
> +      if (htab->target_os == is_vxworks)
>         {
>           struct elf_dyn_relocs **pp;
>           for (pp = &eh->dyn_relocs; (p = *pp) != NULL; )
> @@ -799,6 +799,7 @@ _bfd_x86_elf_link_hash_table_create (bfd *abfd)
>         }
>      }
>    ret->target_id = bed->target_id;
> +  ret->target_os = get_elf_x86_backend_data (abfd)->target_os;
>
>    ret->loc_hash_table = htab_try_create (1024,
>                                          _bfd_x86_elf_local_htab_hash,
> @@ -924,7 +925,7 @@ _bfd_x86_elf_size_dynamic_sections (bfd *output_bfd,
>                      linker script /DISCARD/, so we'll be discarding
>                      the relocs too.  */
>                 }
> -             else if (htab->is_vxworks
> +             else if (htab->target_os == is_vxworks
>                        && strcmp (p->sec->output_section->name,
>                                   ".tls_vars") == 0)
>                 {
> @@ -1285,7 +1286,7 @@ _bfd_x86_elf_size_dynamic_sections (bfd *output_bfd,
>                 return FALSE;
>             }
>         }
> -      if (htab->is_vxworks
> +      if (htab->target_os == is_vxworks
>           && !elf_vxworks_add_dynamic_entries (output_bfd, info))
>         return FALSE;
>      }
> @@ -1377,7 +1378,7 @@ _bfd_x86_elf_finish_dynamic_sections (bfd *output_bfd,
>        switch (dyn.d_tag)
>         {
>         default:
> -         if (htab->is_vxworks
> +         if (htab->target_os == is_vxworks
>               && elf_vxworks_finish_dynamic_entry (output_bfd, &dyn))
>             break;
>           continue;
> @@ -1836,7 +1837,7 @@ _bfd_x86_elf_adjust_dynamic_symbol (struct bfd_link_info *info,
>    if (ELIMINATE_COPY_RELOCS
>        && (bed->target_id == X86_64_ELF_DATA
>           || (!eh->gotoff_ref
> -             && !htab->is_vxworks)))
> +             && htab->target_os != is_vxworks)))
>      {
>        for (p = eh->dyn_relocs; p != NULL; p = p->next)
>         {
> @@ -2414,13 +2415,14 @@ error_alignment:
>    if (htab == NULL)
>      return pbfd;
>
> -  htab->is_vxworks = init_table->is_vxworks;
>    htab->r_info = init_table->r_info;
>    htab->r_sym = init_table->r_sym;
>
>    if (bfd_link_relocatable (info))
>      return pbfd;
>
> +  htab->plt0_pad_byte = init_table->plt0_pad_byte;
> +
>    use_ibt_plt = info->ibtplt || info->ibt;
>    if (!use_ibt_plt && pbfd != NULL)
>      {
> @@ -2472,11 +2474,15 @@ error_alignment:
>         }
>      }
>
> +  /* Return if there are no normal input files.  */
> +  if (dynobj == NULL)
> +    return pbfd;
> +
>    /* Even when lazy binding is disabled by "-z now", the PLT0 entry may
>       still be used with LD_AUDIT or LD_PROFILE if PLT entry is used for
>       canonical function address.  */
>    htab->plt.has_plt0 = 1;
> -  normal_target = init_table->normal_target;
> +  normal_target = htab->target_os == is_normal;
>
>    if (normal_target)
>      {
> @@ -2539,11 +2545,7 @@ error_alignment:
>        htab->plt.eh_frame_plt = htab->lazy_plt->eh_frame_plt;
>      }
>
> -  /* Return if there are no normal input files.  */
> -  if (dynobj == NULL)
> -    return pbfd;
> -
> -  if (htab->is_vxworks
> +  if (htab->target_os == is_vxworks
>        && !elf_vxworks_create_dynamic_sections (dynobj, info,
>                                                &htab->srelplt2))
>      {
> diff --git a/bfd/elfxx-x86.h b/bfd/elfxx-x86.h
> index 3d6366f16b..5e33cdd1ba 100644
> --- a/bfd/elfxx-x86.h
> +++ b/bfd/elfxx-x86.h
> @@ -256,6 +256,13 @@ struct elf_x86_plt_layout
>  #define elf_x86_hash_entry(ent) \
>    ((struct elf_x86_link_hash_entry *)(ent))
>
> +enum elf_x86_target_os
> +{
> +  is_normal,
> +  is_vxworks,
> +  is_nacl
> +};
> +
>  /* x86 ELF linker hash table.  */
>
>  struct elf_x86_link_hash_table
> @@ -311,10 +318,6 @@ struct elf_x86_link_hash_table
>       to read-only sections.  */
>    bfd_boolean readonly_dynrelocs_against_ifunc;
>
> -  /* TRUE if this is a VxWorks x86 target.  This is only used for
> -     i386.  */
> -  bfd_boolean is_vxworks;
> -
>    /* The (unloaded but important) .rel.plt.unloaded section on VxWorks.
>       This is used for i386 only.  */
>    asection *srelplt2;
> @@ -329,10 +332,15 @@ struct elf_x86_link_hash_table
>       yet.  This is only used for x86-64.  */
>    bfd_vma tlsdesc_plt;
>
> +   /* Value used to fill the unused bytes of the first PLT entry.  This
> +      is only used for i386.  */
> +  bfd_byte plt0_pad_byte;
> +
>    bfd_vma (*r_info) (bfd_vma, bfd_vma);
>    bfd_vma (*r_sym) (bfd_vma);
>    bfd_boolean (*is_reloc_section) (const char *);
>    enum elf_target_id target_id;
> +  enum elf_x86_target_os target_os;
>    unsigned int sizeof_reloc;
>    unsigned int dt_reloc;
>    unsigned int dt_reloc_sz;
> @@ -344,6 +352,18 @@ struct elf_x86_link_hash_table
>    const char *tls_get_addr;
>  };
>
> +/* Architecture-specific backend data for x86.  */
> +
> +struct elf_x86_backend_data
> +{
> +  /* Target system.  */
> +  enum elf_x86_target_os target_os;
> +};
> +
> +#define get_elf_x86_backend_data(abfd) \
> +  ((const struct elf_x86_backend_data *) \
> +   get_elf_backend_data (abfd)->arch_data)
> +
>  struct elf_x86_init_table
>  {
>    /* The lazy PLT layout.  */
> @@ -358,11 +378,7 @@ struct elf_x86_init_table
>    /* The non-lazy PLT layout for IBT.  */
>    const struct elf_x86_non_lazy_plt_layout *non_lazy_ibt_plt;
>
> -  /* TRUE if this is a normal x86 target.  */
> -  bfd_boolean normal_target;
> -
> -  /* TRUE if this is a VxWorks x86 target.  */
> -  bfd_boolean is_vxworks;
> +  bfd_byte plt0_pad_byte;
>
>    bfd_vma (*r_info) (bfd_vma, bfd_vma);
>    bfd_vma (*r_sym) (bfd_vma);
> --
> 2.13.5
>

I am checking it in.


-- 
H.J.