Re: [Patch gas/mach-o 2/2] implement mach-o subsections-via-symbols.

[Tristan Gingold <gingold at adacore dot com>]

On Feb 17, 2012, at 6:21 PM, Iain Sandoe wrote:

> This is the bulk of the 'work' associated with the implementation.
> 
> I've re-named a couple of routines to keep to "obj_mach_o_xxx" and tried to ensure that the order of routines in the main file and header match up.  Our code is growing quite fast and maybe they got a little out of synch (new culpa, I'm sure ;)).
> 
> OK for trunk?

Ok.  (You need a global maintainer OK for part 1/2)

I think we have to add some comments to :-)

Tristan.

> Iain
> 
> gas:
> 
> 	* config/obj-macho.c (obj_mach_o_frob_colon): New.
> 	(obj_mach_o_frob_label): Record sub-section labels.
> 	(obj_mach_o_frob_symbol): Rename from obj_macho_frob_symbol.
> 	(obj_mach_o_set_subsections): New.
> 	(obj_mach_o_pre_relax_hook): New.
> 	(obj_mach_o_in_different_subsection): New.
> 	(obj_mach_o_force_reloc_sub_same): New.
> 	(obj_mach_o_force_reloc_sub_local): New.
> 	(obj_mach_o_force_reloc): New.
> 	* config/obj-macho.h (OBJ_SYMFIELD_TYPE): New.
> 	(obj_frob_colon): New Define.
> 	(obj_mach_o_frob_label): Renamed.
> 	(obj_mach_o_frob_symbol): Renamed.
> 	(OBJ_FRAG_TYPE): New.
> 	(obj_mach_o_in_different_subsection, obj_mach_o_force_reloc,
> 	 obj_mach_o_force_reloc_sub_same,
> 	 obj_mach_o_force_reloc_sub_local): New declarations.
> 
> gas/config/obj-macho.c |  199 ++++++++++++++++++++++++++++++++++++++++--------
> gas/config/obj-macho.h |   49 ++++++++++---
> 2 files changed, 205 insertions(+), 43 deletions(-)
> 
> diff --git a/gas/config/obj-macho.c b/gas/config/obj-macho.c
> index 2a2e47d..632eafa 100644
> --- a/gas/config/obj-macho.c
> +++ b/gas/config/obj-macho.c
> @@ -1331,6 +1331,18 @@ obj_mach_o_type_for_symbol (bfd_mach_o_asymbol *s)
>     return BFD_MACH_O_N_SECT;
> }
> 
> +void
> +obj_mach_o_frob_colon (const char *name)
> +{
> +  if (!bfd_is_local_label_name (stdoutput, name))
> +    {
> +      /* A non-local label will create a new subsection, so start a new
> +         frag.  */
> +      frag_wane (frag_now);
> +      frag_new (0);
> +    }
> +}
> +
> /* We need to check the correspondence between some kinds of symbols and their
>    sections.  Common and BSS vars will seen via the obj_macho_comm() function.
> 
> @@ -1345,13 +1357,21 @@ obj_mach_o_type_for_symbol (bfd_mach_o_asymbol *s)
>    are possibly incompatible with the section etc. that the symbol is defined
>    in.  */
> 
> -void obj_macho_frob_label (struct symbol *sp)
> +void obj_mach_o_frob_label (struct symbol *sp)
> {
>   bfd_mach_o_asymbol *s;
>   unsigned base_type;
>   bfd_mach_o_section *sec;
>   int sectype = -1;
> 
> +  if (!bfd_is_local_label_name (stdoutput, S_GET_NAME (sp)))
> +    {
> +      /* If this is a non-local label, it should have started a new sub-
> +	 section.  */
> +      gas_assert (frag_now->obj_frag_data.subsection == NULL);
> +      frag_now->obj_frag_data.subsection = sp;
> +    }
> +
>   /* Leave local symbols alone.  */
> 
>   if (S_IS_LOCAL (sp))
> @@ -1392,7 +1412,7 @@ void obj_macho_frob_label (struct symbol *sp)
>    (e.g. global + weak_def).  */
> 
> int
> -obj_macho_frob_symbol (struct symbol *sp)
> +obj_mach_o_frob_symbol (struct symbol *sp)
> {
>   bfd_mach_o_asymbol *s;
>   unsigned base_type;
> @@ -1483,6 +1503,95 @@ obj_macho_frob_symbol (struct symbol *sp)
>   return 0;
> }
> 
> +/* Support stabs for mach-o.  */
> +
> +void
> +obj_mach_o_process_stab (int what, const char *string,
> +			 int type, int other, int desc)
> +{
> +  symbolS *symbolP;
> +  bfd_mach_o_asymbol *s;
> +
> +  switch (what)
> +    {
> +      case 'd':
> +	symbolP = symbol_new ("", now_seg, frag_now_fix (), frag_now);
> +	/* Special stabd NULL name indicator.  */
> +	S_SET_NAME (symbolP, NULL);
> +	break;
> +
> +      case 'n':
> +      case 's':
> +	symbolP = symbol_new (string, undefined_section, (valueT) 0,
> +			      &zero_address_frag);
> +	pseudo_set (symbolP);
> +	break;
> +
> +      default:
> +	as_bad(_("unrecognized stab type '%c'"), (char)what);
> +	abort ();
> +	break;
> +    }
> +
> +  s = (bfd_mach_o_asymbol *) symbol_get_bfdsym (symbolP);
> +  s->n_type = type;
> +  s->n_desc = desc;
> +  /* For stabd, this will eventually get overwritten by the section number.  */
> +  s->n_sect = other;
> +
> +  /* It's a debug symbol.  */
> +  s->symbol.flags |= BSF_DEBUGGING;
> +}
> +
> +/* Here we count up frags in each subsection (where a sub-section is defined
> +   as starting with a non-local symbol).
> +   Note that, if there are no non-local symbols in a section, all the frags will
> +   be attached as one anonymous subsection.  */
> +
> +static void
> +obj_mach_o_set_subsections (bfd *abfd ATTRIBUTE_UNUSED,
> +                            asection *sec,
> +                            void *unused ATTRIBUTE_UNUSED)
> +{
> +  segment_info_type *seginfo = seg_info (sec);
> +  symbolS *cur_subsection = NULL;
> +  struct obj_mach_o_symbol_data *cur_subsection_data = NULL;
> +  fragS *frag;
> +  frchainS *chain;
> +
> +  /* Protect against sections not created by gas.  */
> +  if (seginfo == NULL)
> +    return;
> +
> +  /* Attach every frag to a subsection.  */
> +  for (chain = seginfo->frchainP; chain != NULL; chain = chain->frch_next)
> +    for (frag = chain->frch_root; frag != NULL; frag = frag->fr_next)
> +      {
> +        if (frag->obj_frag_data.subsection == NULL)
> +          frag->obj_frag_data.subsection = cur_subsection;
> +        else
> +          {
> +            cur_subsection = frag->obj_frag_data.subsection;
> +            cur_subsection_data = symbol_get_obj (cur_subsection);
> +            cur_subsection_data->subsection_size = 0;
> +          }
> +        if (cur_subsection_data != NULL)
> +          {
> +            /* Update subsection size.  */
> +            cur_subsection_data->subsection_size += frag->fr_fix;
> +          }
> +      }
> +}
> +
> +/* Handle mach-o subsections-via-symbols counting up frags belonging to each
> +   sub-section.  */
> +
> +void
> +obj_mach_o_pre_relax_hook (void)
> +{
> +  bfd_map_over_sections (stdoutput, obj_mach_o_set_subsections, (char *) 0);
> +}
> +
> /* Zerofill and GB Zerofill sections must be sorted to follow all other
>    sections in their segments.
> 
> @@ -1706,42 +1815,66 @@ obj_mach_o_reorder_section_relocs (asection *sec, arelent **rels, unsigned int n
>   bfd_set_reloc (stdoutput, sec, rels, n);
> }
> 
> -/* Support stabs for mach-o.  */
> -
> -void
> -obj_mach_o_process_stab (int what, const char *string,
> -			 int type, int other, int desc)
> +int
> +obj_mach_o_in_different_subsection (symbolS *a, symbolS *b)
> {
> -  symbolS *symbolP;
> -  bfd_mach_o_asymbol *s;
> +  fragS *fa;
> +  fragS *fb;
> 
> -  switch (what)
> +  if (S_GET_SEGMENT (a) != S_GET_SEGMENT (b)
> +      || !S_IS_DEFINED (a)
> +      || !S_IS_DEFINED (b))
>     {
> -      case 'd':
> -	symbolP = symbol_new ("", now_seg, frag_now_fix (), frag_now);
> -	/* Special stabd NULL name indicator.  */
> -	S_SET_NAME (symbolP, NULL);
> -	break;
> -
> -      case 'n':
> -      case 's':
> -	symbolP = symbol_new (string, undefined_section, (valueT) 0,
> -			      &zero_address_frag);
> -	pseudo_set (symbolP);
> -	break;
> +      /* Not in the same segment, or undefined symbol.  */
> +      return 1;
> +    }
> 
> -      default:
> -	as_bad(_("unrecognized stab type '%c'"), (char)what);
> -	abort ();
> -	break;
> +  fa = symbol_get_frag (a);
> +  fb = symbol_get_frag (b);
> +  if (fa == NULL || fb == NULL)
> +    {
> +      /* One of the symbols is not in a subsection.  */
> +      return 1;
>     }
> 
> -  s = (bfd_mach_o_asymbol *) symbol_get_bfdsym (symbolP);
> -  s->n_type = type;
> -  s->n_desc = desc;
> -  /* For stabd, this will eventually get overwritten by the section number.  */
> -  s->n_sect = other;
> +  return fa->obj_frag_data.subsection != fb->obj_frag_data.subsection;
> +}
> 
> -  /* It's a debug symbol.  */
> -  s->symbol.flags |= BSF_DEBUGGING;
> +int
> +obj_mach_o_force_reloc_sub_same (fixS *fix, segT seg)
> +{
> +  if (! SEG_NORMAL (seg))
> +    return 1;
> +  return obj_mach_o_in_different_subsection (fix->fx_addsy, fix->fx_subsy);
> +}
> +
> +int
> +obj_mach_o_force_reloc_sub_local (fixS *fix, segT seg ATTRIBUTE_UNUSED)
> +{
> +  return obj_mach_o_in_different_subsection (fix->fx_addsy, fix->fx_subsy);
> +}
> +
> +int
> +obj_mach_o_force_reloc (fixS *fix)
> +{
> +  if (generic_force_reloc (fix))
> +    return 1;
> +
> +  /* Force a reloc if the target is not in the same subsection.
> +     FIXME: handle (a - b) where a and b belongs to the same subsection ?  */
> +  if (fix->fx_addsy != NULL)
> +    {
> +      symbolS *subsec = fix->fx_frag->obj_frag_data.subsection;
> +      symbolS *targ = fix->fx_addsy;
> +
> +      /* There might be no subsections at all.  */
> +      if (subsec == NULL)
> +        return 0;
> +
> +      if (S_GET_SEGMENT (targ) == absolute_section)
> +        return 0;
> +
> +      return obj_mach_o_in_different_subsection (targ, subsec);
> +    }
> +  return 0;
> }
> diff --git a/gas/config/obj-macho.h b/gas/config/obj-macho.h
> index bb8daf9..b49038c 100644
> --- a/gas/config/obj-macho.h
> +++ b/gas/config/obj-macho.h
> @@ -56,11 +56,36 @@ extern const pseudo_typeS mach_o_pseudo_table[];
> #define obj_read_begin_hook()	{;}
> #define obj_symbol_new_hook(s)	{;}
> 
> -#define obj_frob_label(s) obj_macho_frob_label(s)
> -extern void obj_macho_frob_label (struct symbol *);
> +#define EMIT_SECTION_SYMBOLS		0
> +
> +struct obj_mach_o_symbol_data
> +{
> +  /* If the symbol represents a subsection, this is the size of the subsection.
> +     This is used to check whether a local symbol belongs to a subsection.  */
> +  valueT subsection_size;
> +};
> +#define OBJ_SYMFIELD_TYPE struct obj_mach_o_symbol_data
> +
> +#define obj_frob_colon obj_mach_o_frob_colon
> +extern void obj_mach_o_frob_colon (const char *);
> +
> +/* Called when a label is defined.  Mach-O uses this to create subsections.  */
> +#define obj_frob_label obj_mach_o_frob_label
> +extern void obj_mach_o_frob_label (symbolS *);
> 
> -#define obj_frob_symbol(s, punt) punt = obj_macho_frob_symbol(s)
> -extern int obj_macho_frob_symbol (struct symbol *);
> +#define obj_frob_symbol(s, punt) punt = obj_mach_o_frob_symbol(s)
> +extern int obj_mach_o_frob_symbol (struct symbol *);
> +
> +struct obj_mach_o_frag_data
> +{
> +  /* Symbol that corresponds to the subsection.  */
> +  symbolS *subsection;
> +};
> +
> +#define OBJ_FRAG_TYPE struct obj_mach_o_frag_data
> +
> +#define md_pre_relax_hook obj_mach_o_pre_relax_hook()
> +extern void obj_mach_o_pre_relax_hook (void);
> 
> #define md_post_relax_hook obj_mach_o_post_relax_hook()
> void obj_mach_o_post_relax_hook (void);
> @@ -68,14 +93,18 @@ void obj_mach_o_post_relax_hook (void);
> #define obj_frob_file_after_relocs obj_mach_o_frob_file_after_relocs
> extern void obj_mach_o_frob_file_after_relocs (void);
> 
> -void obj_mach_o_reorder_section_relocs (asection *, arelent **, unsigned int);
> +#define OBJ_PROCESS_STAB(SEG,W,S,T,O,D)	obj_mach_o_process_stab(W,S,T,O,D)
> +extern void obj_mach_o_process_stab (int, const char *,int, int, int);
> 
> #define SET_SECTION_RELOCS(sec, relocs, n) \
>   obj_mach_o_reorder_section_relocs (sec, relocs, n)
> -
> -#define EMIT_SECTION_SYMBOLS		0
> -
> -#define OBJ_PROCESS_STAB(SEG,W,S,T,O,D)	obj_mach_o_process_stab(W,S,T,O,D)
> -extern void obj_mach_o_process_stab (int, const char *,int, int, int);
> +extern void obj_mach_o_reorder_section_relocs (asection *, arelent **,
> +					       unsigned int);
> +
> +struct fix;
> +int obj_mach_o_in_different_subsection (symbolS *a, symbolS *b);
> +int obj_mach_o_force_reloc (struct fix *fix);
> +int obj_mach_o_force_reloc_sub_same (struct fix *fix, segT seg);
> +int obj_mach_o_force_reloc_sub_local (struct fix *fix, segT seg);
> 
> #endif /* _OBJ_MACH_O_H */
>