Re: [RFC PATCH, binutils, ARM 3/11, ping] Allow stubs without associated input section in ARM backend

[Thomas Preudhomme <thomas dot preudhomme at foss dot arm dot com>]

Ping?

On Wednesday 23 December 2015 15:56:33 Thomas Preud'homme wrote:
> Hi,
> 
> [Posting patch series as RFC]
> 
> This patch is part of a patch series to add support for ARMv8-M security
> extension[1] to GNU ld. This specific patch allows stubs to not be
> associated by an input section, as required for creating Secure Gateway
> veneers. This is achieved by letting the bfd ARM backend specify the output
> section for a veneer input section.
> 
> 
> [1] Software requirements for ARMv8-M security extension are described in
> document ARM-ECM-0359818 [2] [2] Available on http://infocenter.arm.com in
> Developer guides and articles > Software development > ARMÂv8-M Security
> Extensions: Requirements on Development Tools
> 
> ChangeLog entries are as follow:
> 
> 
> *** bfd/ChangeLog ***
> 
> 2015-12-16  Thomas Preud'homme  <thomas.preudhomme@arm.com>
> 
>         * bfd-in.h (elf32_arm_size_stubs): Add an output section parameter.
>         * bfd-in2.h: Regenerated.
>         * elf32-arm.c (struct elf32_arm_link_hash_table): Add an output
> section parameter to add_stub_section callback.
>         (elf32_arm_create_or_find_stub_sec): Get output section from
> link_sec and pass it down to add_stub_section.
>         (elf32_arm_add_stub): Set section to stub_sec if NULL before using
> it for error message.
>         (elf32_arm_size_stubs): Add output section parameter to
>         add_stub_section function pointer parameter.
> 
> 
> *** ld/ChangeLog ***
> 
> 2015-12-16  Thomas Preud'homme  <thomas.preudhomme@arm.com>
> 
>         * emultempl/armelf.em (elf32_arm_add_stub_section): Add
> output_section parameter and rename input_section parameter to
> after_input_section. Append input stub section to the output section if
> after_input_section is NULL.
> 
> 
> diff --git a/bfd/bfd-in.h b/bfd/bfd-in.h
> index
> 1721ce7003d4a76953793b002583997e438e3cb0..7abc05878789788bc9d5a9329dc92d80a
> 0346935 100644 --- a/bfd/bfd-in.h
> +++ b/bfd/bfd-in.h
> @@ -934,7 +934,8 @@ extern void elf32_arm_next_input_section
>    (struct bfd_link_info *, struct bfd_section *);
>  extern bfd_boolean elf32_arm_size_stubs
>    (bfd *, bfd *, struct bfd_link_info *, bfd_signed_vma,
> -   struct bfd_section * (*) (const char *, struct bfd_section *, unsigned
> int), +   struct bfd_section * (*) (const char *, struct bfd_section *,
> +			     struct bfd_section *, unsigned int),
>     void (*) (void));
>  extern bfd_boolean elf32_arm_build_stubs
>    (struct bfd_link_info *);
> diff --git a/bfd/bfd-in2.h b/bfd/bfd-in2.h
> index
> 606d11b73c783ae54728e7f9f2fd90c00f7617b7..87ee56b80b2a1a0ae785ff4cb2495e2c7
> fd23a47 100644 --- a/bfd/bfd-in2.h
> +++ b/bfd/bfd-in2.h
> @@ -941,7 +941,8 @@ extern void elf32_arm_next_input_section
>    (struct bfd_link_info *, struct bfd_section *);
>  extern bfd_boolean elf32_arm_size_stubs
>    (bfd *, bfd *, struct bfd_link_info *, bfd_signed_vma,
> -   struct bfd_section * (*) (const char *, struct bfd_section *, unsigned
> int), +   struct bfd_section * (*) (const char *, struct bfd_section *,
> +			     struct bfd_section *, unsigned int),
>     void (*) (void));
>  extern bfd_boolean elf32_arm_build_stubs
>    (struct bfd_link_info *);
> diff --git a/bfd/elf32-arm.c b/bfd/elf32-arm.c
> index
> e6afb99512524ac26c0e3842e8dbe293c58bacad..8450733016a496ec34533e8aad4900be1
> 6dc5849 100644 --- a/bfd/elf32-arm.c
> +++ b/bfd/elf32-arm.c
> @@ -3103,7 +3103,8 @@ struct elf32_arm_link_hash_table
>    bfd *stub_bfd;
> 
>    /* Linker call-backs.  */
> -  asection * (*add_stub_section) (const char *, asection *, unsigned int);
> +  asection * (*add_stub_section) (const char *, asection *, asection *,
> +				  unsigned int);
>    void (*layout_sections_again) (void);
> 
>    /* Array to keep track of which stub sections have been created, and
> @@ -4068,6 +4069,7 @@ elf32_arm_create_or_find_stub_sec (asection
> **link_sec_p, asection *section, {
>    asection *link_sec;
>    asection *stub_sec;
> +  asection *out_sec;
> 
>    link_sec = htab->stub_group[section->id].link_sec;
>    BFD_ASSERT (link_sec != NULL);
> @@ -4090,7 +4092,8 @@ elf32_arm_create_or_find_stub_sec (asection
> **link_sec_p, asection *section,
> 
>  	  memcpy (s_name, link_sec->name, namelen);
>  	  memcpy (s_name + namelen, STUB_SUFFIX, sizeof (STUB_SUFFIX));
> -	  stub_sec = (*htab->add_stub_section) (s_name, link_sec,
> +	  out_sec = link_sec->output_section;
> +	  stub_sec = (*htab->add_stub_section) (s_name, out_sec, link_sec,
>  						htab->nacl_p ? 4 : 3);
>  	  if (stub_sec == NULL)
>  	    return NULL;
> @@ -4126,6 +4129,8 @@ elf32_arm_add_stub (const char *stub_name,
>  				     TRUE, FALSE);
>    if (stub_entry == NULL)
>      {
> +      if (section == NULL)
> +	section = stub_sec;
>        (*_bfd_error_handler) (_("%s: cannot create stub entry %s"),
>  			     section->owner,
>  			     stub_name);
> @@ -5140,6 +5145,7 @@ elf32_arm_size_stubs (bfd *output_bfd,
>  		      struct bfd_link_info *info,
>  		      bfd_signed_vma group_size,
>  		      asection * (*add_stub_section) (const char *, asection *,
> +						      asection *,
>  						      unsigned int),
>  		      void (*layout_sections_again) (void))
>  {
> diff --git a/ld/emultempl/armelf.em b/ld/emultempl/armelf.em
> index
> 2931a49f3fb0fee2a035d0788ead7726eab83d10..a3b52e685fcd2d415737f3ee9ed461978
> a2419f6 100644 --- a/ld/emultempl/armelf.em
> +++ b/ld/emultempl/armelf.em
> @@ -203,12 +203,12 @@ hook_in_stub (struct hook_stub_info *info,
> lang_statement_union_type **lp)
> 
>  static asection *
>  elf32_arm_add_stub_section (const char * stub_sec_name,
> -			    asection *   input_section,
> +			    asection *   output_section,
> +			    asection *   after_input_section,
>  			    unsigned int alignment_power)
>  {
>    asection *stub_sec;
>    flagword flags;
> -  asection *output_section;
>    lang_output_section_statement_type *os;
>    struct hook_stub_info info;
> 
> @@ -221,18 +221,34 @@ elf32_arm_add_stub_section (const char *
> stub_sec_name,
> 
>    bfd_set_section_alignment (stub_file->the_bfd, stub_sec,
> alignment_power);
> 
> -  output_section = input_section->output_section;
>    os = lang_output_section_get (output_section);
> 
> -  info.input_section = input_section;
> +  info.input_section = after_input_section;
>    lang_list_init (&info.add);
>    lang_add_section (&info.add, stub_sec, NULL, os);
> 
>    if (info.add.head == NULL)
>      goto err_ret;
> 
> -  if (hook_in_stub (&info, &os->children.head))
> -    return stub_sec;
> +  if (after_input_section == NULL)
> +    {
> +      lang_statement_union_type **lp = &os->children.head;
> +      lang_statement_union_type *l, *lprev = NULL;
> +
> +      for (; (l = *lp) != NULL; lp = &l->header.next, lprev = l);
> +
> +      if (lprev)
> +	lprev->header.next = info.add.head;
> +      else
> +	os->children.head = info.add.head;
> +
> +      return stub_sec;
> +    }
> +  else
> +    {
> +      if (hook_in_stub (&info, &os->children.head))
> +	return stub_sec;
> +    }
> 
>   err_ret:
>    einfo ("%X%P: can not make stub section: %E\n");
> 
> 
> The patch doesn't show any regression when running the binutils-gdb
> testsuite for the arm-none-eabi target.
> 
> Any comments?
> 
> Best regards,
> 
> Thomas