bfd/reloc16.c

   1 /* 8 and 16 bit COFF relocation functions, for BFD.
   2    Copyright (C) 1990-2018 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           (*link_info->callbacks->undefined_symbol)
  84             (link_info, bfd_asymbol_name (symbol),
  85              input_section->owner, input_section, reloc->address, TRUE);
  86           value = 0;
  87         }
  88     }
  89   else
  90     {
  91       value = symbol->value
  92         + symbol->section->output_offset
  93         + symbol->section->output_section->vma;
  94     }
  95
  96   /* Add the value contained in the relocation.  */
  97   value += reloc->addend;
  98
  99   return value;
 100 }
 101
 102 void
 103 bfd_perform_slip (bfd *abfd,
 104                   unsigned int slip,
 105                   asection *input_section,
 106                   bfd_vma value)
 107 {
 108   asymbol **s;
 109
 110   s = _bfd_generic_link_get_symbols (abfd);
 111   BFD_ASSERT (s != (asymbol **) NULL);
 112
 113   /* Find all symbols past this point, and make them know
 114      what's happened.  */
 115   while (*s)
 116     {
 117       asymbol *p = *s;
 118       if (p->section == input_section)
 119         {
 120           /* This was pointing into this section, so mangle it.  */
 121           if (p->value > value)
 122             {
 123               p->value -= slip;
 124               if (p->udata.p != NULL)
 125                 {
 126                   struct generic_link_hash_entry *h;
 127
 128                   h = (struct generic_link_hash_entry *) p->udata.p;
 129                   BFD_ASSERT (h->root.type == bfd_link_hash_defined
 130                               || h->root.type == bfd_link_hash_defweak);
 131                   h->root.u.def.value -= slip;
 132                   BFD_ASSERT (h->root.u.def.value == p->value);
 133                 }
 134             }
 135         }
 136       s++;
 137     }
 138 }
 139
 140 bfd_boolean
 141 bfd_coff_reloc16_relax_section (bfd *abfd,
 142                                 asection *input_section,
 143                                 struct bfd_link_info *link_info,
 144                                 bfd_boolean *again)
 145 {
 146   /* Get enough memory to hold the stuff.  */
 147   bfd *input_bfd = input_section->owner;
 148   unsigned *shrinks;
 149   unsigned shrink = 0;
 150   long reloc_size = bfd_get_reloc_upper_bound (input_bfd, input_section);
 151   arelent **reloc_vector = NULL;
 152   long reloc_count;
 153
 154   if (bfd_link_relocatable (link_info))
 155     (*link_info->callbacks->einfo)
 156       (_("%P%F: --relax and -r may not be used together\n"));
 157
 158   /* We only do global relaxation once.  It is not safe to do it multiple
 159      times (see discussion of the "shrinks" array below).  */
 160   *again = FALSE;
 161
 162   if (reloc_size < 0)
 163     return FALSE;
 164
 165   reloc_vector = (arelent **) bfd_malloc ((bfd_size_type) reloc_size);
 166   if (!reloc_vector && reloc_size > 0)
 167     return FALSE;
 168
 169   /* Get the relocs and think about them.  */
 170   reloc_count =
 171     bfd_canonicalize_reloc (input_bfd, input_section, reloc_vector,
 172                             _bfd_generic_link_get_symbols (input_bfd));
 173   if (reloc_count < 0)
 174     {
 175       free (reloc_vector);
 176       return FALSE;
 177     }
 178
 179   /* The reloc16.c and related relaxing code is very simple, the price
 180      for that simplicity is we can only call this function once for
 181      each section.
 182
 183      So, to get the best results within that limitation, we do multiple
 184      relaxing passes over each section here.  That involves keeping track
 185      of the "shrink" at each reloc in the section.  This allows us to
 186      accurately determine the relative location of two relocs within
 187      this section.
 188
 189      In theory, if we kept the "shrinks" array for each section for the
 190      entire link, we could use the generic relaxing code in the linker
 191      and get better results, particularly for jsr->bsr and 24->16 bit
 192      memory reference relaxations.  */
 193
 194   if (reloc_count > 0)
 195     {
 196       int another_pass = 0;
 197       bfd_size_type amt;
 198
 199       /* Allocate and initialize the shrinks array for this section.
 200          The last element is used as an accumulator of shrinks.  */
 201       amt = reloc_count + 1;
 202       amt *= sizeof (unsigned);
 203       shrinks = (unsigned *) bfd_zmalloc (amt);
 204
 205       /* Loop until nothing changes in this section.  */
 206       do
 207         {
 208           arelent **parent;
 209           unsigned int i;
 210           long j;
 211
 212           another_pass = 0;
 213
 214           for (i = 0, parent = reloc_vector; *parent; parent++, i++)
 215             {
 216               /* Let the target/machine dependent code examine each reloc
 217                  in this section and attempt to shrink it.  */
 218               shrink = bfd_coff_reloc16_estimate (abfd, input_section, *parent,
 219                                                   shrinks[i], link_info);
 220
 221               /* If it shrunk, note it in the shrinks array and set up for
 222                  another pass.  */
 223               if (shrink != shrinks[i])
 224                 {
 225                   another_pass = 1;
 226                   for (j = i + 1; j <= reloc_count; j++)
 227                     shrinks[j] += shrink - shrinks[i];
 228                 }
 229             }
 230         }
 231       while (another_pass);
 232
 233       shrink = shrinks[reloc_count];
 234       free ((char *) shrinks);
 235     }
 236
 237   input_section->rawsize = input_section->size;
 238   input_section->size -= shrink;
 239   free ((char *) reloc_vector);
 240   return TRUE;
 241 }
 242
 243 bfd_byte *
 244 bfd_coff_reloc16_get_relocated_section_contents
 245   (bfd *in_abfd,
 246    struct bfd_link_info *link_info,
 247    struct bfd_link_order *link_order,
 248    bfd_byte *data,
 249    bfd_boolean relocatable,
 250    asymbol **symbols)
 251 {
 252   /* Get enough memory to hold the stuff.  */
 253   bfd *input_bfd = link_order->u.indirect.section->owner;
 254   asection *input_section = link_order->u.indirect.section;
 255   long reloc_size = bfd_get_reloc_upper_bound (input_bfd, input_section);
 256   arelent **reloc_vector;
 257   long reloc_count;
 258   bfd_size_type sz;
 259
 260   if (reloc_size < 0)
 261     return NULL;
 262
 263   /* If producing relocatable output, don't bother to relax.  */
 264   if (relocatable)
 265     return bfd_generic_get_relocated_section_contents (in_abfd, link_info,
 266                                                        link_order,
 267                                                        data, relocatable,
 268                                                        symbols);
 269
 270   /* Read in the section.  */
 271   sz = input_section->rawsize ? input_section->rawsize : input_section->size;
 272   if (!bfd_get_section_contents (input_bfd, input_section, data, 0, sz))
 273     return NULL;
 274
 275   reloc_vector = (arelent **) bfd_malloc ((bfd_size_type) reloc_size);
 276   if (!reloc_vector && reloc_size != 0)
 277     return NULL;
 278
 279   reloc_count = bfd_canonicalize_reloc (input_bfd,
 280                                         input_section,
 281                                         reloc_vector,
 282                                         symbols);
 283   if (reloc_count < 0)
 284     {
 285       free (reloc_vector);
 286       return NULL;
 287     }
 288
 289   if (reloc_count > 0)
 290     {
 291       arelent **parent = reloc_vector;
 292       arelent *reloc;
 293       unsigned int dst_address = 0;
 294       unsigned int src_address = 0;
 295       unsigned int run;
 296       unsigned int idx;
 297
 298       /* Find how long a run we can do.  */
 299       while (dst_address < link_order->size)
 300         {
 301           reloc = *parent;
 302           if (reloc)
 303             {
 304               /* Note that the relaxing didn't tie up the addresses in the
 305                  relocation, so we use the original address to work out the
 306                  run of non-relocated data.  */
 307               run = reloc->address - src_address;
 308               parent++;
 309             }
 310           else
 311             {
 312               run = link_order->size - dst_address;
 313             }
 314
 315           /* Copy the bytes.  */
 316           for (idx = 0; idx < run; idx++)
 317             data[dst_address++] = data[src_address++];
 318
 319           /* Now do the relocation.  */
 320           if (reloc)
 321             {
 322               bfd_coff_reloc16_extra_cases (input_bfd, link_info, link_order,
 323                                             reloc, data, &src_address,
 324                                             &dst_address);
 325             }
 326         }
 327     }
 328   free ((char *) reloc_vector);
 329   return data;
 330 }