bfd/reloc16.c

   1 /* 8 and 16 bit COFF relocation functions, for BFD.
   2    Copyright (C) 1990-2015 Free Software Foundation, Inc.
   3    Written by Cygnus Support.
   4
   5    This file is part of BFD, the Binary File Descriptor library.
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program; if not, write to the Free Software
  19    Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
  20    MA 02110-1301, USA.  */
  21
  22
  23 /* Most of this hacked by Steve Chamberlain <sac@cygnus.com>.  */
  24
  25 /* These routines are used by coff-h8300 and coff-z8k to do
  26    relocation.
  27
  28    FIXME: This code should be rewritten to support the new COFF
  29    linker.  Basically, they need to deal with COFF relocs rather than
  30    BFD generic relocs.  They should store the relocs in some location
  31    where coff_link_input_bfd can find them (and coff_link_input_bfd
  32    should be changed to use this location rather than rereading the
  33    file) (unless info->keep_memory is FALSE, in which case they should
  34    free up the relocs after dealing with them).  */
  35
  36 #include "sysdep.h"
  37 #include "bfd.h"
  38 #include "libbfd.h"
  39 #include "bfdlink.h"
  40 #include "genlink.h"
  41 #include "coff/internal.h"
  42 #include "libcoff.h"
  43
  44 bfd_vma
  45 bfd_coff_reloc16_get_value (arelent *reloc,
  46                             struct bfd_link_info *link_info,
  47                             asection *input_section)
  48 {
  49   bfd_vma value;
  50   asymbol *symbol = *(reloc->sym_ptr_ptr);
  51   /* A symbol holds a pointer to a section, and an offset from the
  52      base of the section.  To relocate, we find where the section will
  53      live in the output and add that in.  */
  54
  55   if (bfd_is_und_section (symbol->section)
  56       || bfd_is_com_section (symbol->section))
  57     {
  58       struct bfd_link_hash_entry *h;
  59
  60       /* The symbol is undefined in this BFD.  Look it up in the
  61          global linker hash table.  FIXME: This should be changed when
  62          we convert this stuff to use a specific final_link function
  63          and change the interface to bfd_relax_section to not require
  64          the generic symbols.  */
  65       h = bfd_wrapped_link_hash_lookup (input_section->owner, link_info,
  66                                         bfd_asymbol_name (symbol),
  67                                         FALSE, FALSE, TRUE);
  68       if (h != (struct bfd_link_hash_entry *) NULL
  69           && (h->type == bfd_link_hash_defined
  70               || h->type == bfd_link_hash_defweak))
  71         value = (h->u.def.value
  72                  + h->u.def.section->output_section->vma
  73                  + h->u.def.section->output_offset);
  74       else if (h != (struct bfd_link_hash_entry *) NULL
  75                && h->type == bfd_link_hash_common)
  76         value = h->u.c.size;
  77       else if (h != (struct bfd_link_hash_entry *) NULL
  78                && h->type == bfd_link_hash_undefweak)
  79         /* This is a GNU extension.  */
  80         value = 0;
  81       else
  82         {
  83           if (!((*link_info->callbacks->undefined_symbol)
  84                 (link_info, bfd_asymbol_name (symbol),
  85                  input_section->owner, input_section, reloc->address,
  86                  TRUE)))
  87             abort ();
  88           value = 0;
  89         }
  90     }
  91   else
  92     {
  93       value = symbol->value
  94         + symbol->section->output_offset
  95         + symbol->section->output_section->vma;
  96     }
  97
  98   /* Add the value contained in the relocation.  */
  99   value += reloc->addend;
 100
 101   return value;
 102 }
 103
 104 void
 105 bfd_perform_slip (bfd *abfd,
 106                   unsigned int slip,
 107                   asection *input_section,
 108                   bfd_vma value)
 109 {
 110   asymbol **s;
 111
 112   s = _bfd_generic_link_get_symbols (abfd);
 113   BFD_ASSERT (s != (asymbol **) NULL);
 114
 115   /* Find all symbols past this point, and make them know
 116      what's happened.  */
 117   while (*s)
 118     {
 119       asymbol *p = *s;
 120       if (p->section == input_section)
 121         {
 122           /* This was pointing into this section, so mangle it.  */
 123           if (p->value > value)
 124             {
 125               p->value -= slip;
 126               if (p->udata.p != NULL)
 127                 {
 128                   struct generic_link_hash_entry *h;
 129
 130                   h = (struct generic_link_hash_entry *) p->udata.p;
 131                   BFD_ASSERT (h->root.type == bfd_link_hash_defined
 132                               || h->root.type == bfd_link_hash_defweak);
 133                   h->root.u.def.value -= slip;
 134                   BFD_ASSERT (h->root.u.def.value == p->value);
 135                 }
 136             }
 137         }
 138       s++;
 139     }
 140 }
 141
 142 bfd_boolean
 143 bfd_coff_reloc16_relax_section (bfd *abfd,
 144                                 asection *input_section,
 145                                 struct bfd_link_info *link_info,
 146                                 bfd_boolean *again)
 147 {
 148   /* Get enough memory to hold the stuff.  */
 149   bfd *input_bfd = input_section->owner;
 150   unsigned *shrinks;
 151   unsigned shrink = 0;
 152   long reloc_size = bfd_get_reloc_upper_bound (input_bfd, input_section);
 153   arelent **reloc_vector = NULL;
 154   long reloc_count;
 155
 156   if (bfd_link_relocatable (link_info))
 157     (*link_info->callbacks->einfo)
 158       (_("%P%F: --relax and -r may not be used together\n"));
 159
 160   /* We only do global relaxation once.  It is not safe to do it multiple
 161      times (see discussion of the "shrinks" array below).  */
 162   *again = FALSE;
 163
 164   if (reloc_size < 0)
 165     return FALSE;
 166
 167   reloc_vector = (arelent **) bfd_malloc ((bfd_size_type) reloc_size);
 168   if (!reloc_vector && reloc_size > 0)
 169     return FALSE;
 170
 171   /* Get the relocs and think about them.  */
 172   reloc_count =
 173     bfd_canonicalize_reloc (input_bfd, input_section, reloc_vector,
 174                             _bfd_generic_link_get_symbols (input_bfd));
 175   if (reloc_count < 0)
 176     {
 177       free (reloc_vector);
 178       return FALSE;
 179     }
 180
 181   /* The reloc16.c and related relaxing code is very simple, the price
 182      for that simplicity is we can only call this function once for
 183      each section.
 184
 185      So, to get the best results within that limitation, we do multiple
 186      relaxing passes over each section here.  That involves keeping track
 187      of the "shrink" at each reloc in the section.  This allows us to
 188      accurately determine the relative location of two relocs within
 189      this section.
 190
 191      In theory, if we kept the "shrinks" array for each section for the
 192      entire link, we could use the generic relaxing code in the linker
 193      and get better results, particularly for jsr->bsr and 24->16 bit
 194      memory reference relaxations.  */
 195
 196   if (reloc_count > 0)
 197     {
 198       int another_pass = 0;
 199       bfd_size_type amt;
 200
 201       /* Allocate and initialize the shrinks array for this section.
 202          The last element is used as an accumulator of shrinks.  */
 203       amt = reloc_count + 1;
 204       amt *= sizeof (unsigned);
 205       shrinks = (unsigned *) bfd_zmalloc (amt);
 206
 207       /* Loop until nothing changes in this section.  */
 208       do
 209         {
 210           arelent **parent;
 211           unsigned int i;
 212           long j;
 213
 214           another_pass = 0;
 215
 216           for (i = 0, parent = reloc_vector; *parent; parent++, i++)
 217             {
 218               /* Let the target/machine dependent code examine each reloc
 219                  in this section and attempt to shrink it.  */
 220               shrink = bfd_coff_reloc16_estimate (abfd, input_section, *parent,
 221                                                   shrinks[i], link_info);
 222
 223               /* If it shrunk, note it in the shrinks array and set up for
 224                  another pass.  */
 225               if (shrink != shrinks[i])
 226                 {
 227                   another_pass = 1;
 228                   for (j = i + 1; j <= reloc_count; j++)
 229                     shrinks[j] += shrink - shrinks[i];
 230                 }
 231             }
 232         }
 233       while (another_pass);
 234
 235       shrink = shrinks[reloc_count];
 236       free ((char *) shrinks);
 237     }
 238
 239   input_section->rawsize = input_section->size;
 240   input_section->size -= shrink;
 241   free ((char *) reloc_vector);
 242   return TRUE;
 243 }
 244
 245 bfd_byte *
 246 bfd_coff_reloc16_get_relocated_section_contents
 247   (bfd *in_abfd,
 248    struct bfd_link_info *link_info,
 249    struct bfd_link_order *link_order,
 250    bfd_byte *data,
 251    bfd_boolean relocatable,
 252    asymbol **symbols)
 253 {
 254   /* Get enough memory to hold the stuff.  */
 255   bfd *input_bfd = link_order->u.indirect.section->owner;
 256   asection *input_section = link_order->u.indirect.section;
 257   long reloc_size = bfd_get_reloc_upper_bound (input_bfd, input_section);
 258   arelent **reloc_vector;
 259   long reloc_count;
 260   bfd_size_type sz;
 261
 262   if (reloc_size < 0)
 263     return NULL;
 264
 265   /* If producing relocatable output, don't bother to relax.  */
 266   if (relocatable)
 267     return bfd_generic_get_relocated_section_contents (in_abfd, link_info,
 268                                                        link_order,
 269                                                        data, relocatable,
 270                                                        symbols);
 271
 272   /* Read in the section.  */
 273   sz = input_section->rawsize ? input_section->rawsize : input_section->size;
 274   if (!bfd_get_section_contents (input_bfd, input_section, data, 0, sz))
 275     return NULL;
 276
 277   reloc_vector = (arelent **) bfd_malloc ((bfd_size_type) reloc_size);
 278   if (!reloc_vector && reloc_size != 0)
 279     return NULL;
 280
 281   reloc_count = bfd_canonicalize_reloc (input_bfd,
 282                                         input_section,
 283                                         reloc_vector,
 284                                         symbols);
 285   if (reloc_count < 0)
 286     {
 287       free (reloc_vector);
 288       return NULL;
 289     }
 290
 291   if (reloc_count > 0)
 292     {
 293       arelent **parent = reloc_vector;
 294       arelent *reloc;
 295       unsigned int dst_address = 0;
 296       unsigned int src_address = 0;
 297       unsigned int run;
 298       unsigned int idx;
 299
 300       /* Find how long a run we can do.  */
 301       while (dst_address < link_order->size)
 302         {
 303           reloc = *parent;
 304           if (reloc)
 305             {
 306               /* Note that the relaxing didn't tie up the addresses in the
 307                  relocation, so we use the original address to work out the
 308                  run of non-relocated data.  */
 309               run = reloc->address - src_address;
 310               parent++;
 311             }
 312           else
 313             {
 314               run = link_order->size - dst_address;
 315             }
 316
 317           /* Copy the bytes.  */
 318           for (idx = 0; idx < run; idx++)
 319             data[dst_address++] = data[src_address++];
 320
 321           /* Now do the relocation.  */
 322           if (reloc)
 323             {
 324               bfd_coff_reloc16_extra_cases (input_bfd, link_info, link_order,
 325                                             reloc, data, &src_address,
 326                                             &dst_address);
 327             }
 328         }
 329     }
 330   free ((char *) reloc_vector);
 331   return data;
 332 }