bfd/reloc16.c

   1 /* 8 and 16 bit COFF relocation functions, for BFD.
   2    Copyright (C) 1990-2022 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-z8k to do relocation.
  26
  27    FIXME: This code should be rewritten to support the new COFF
  28    linker.  Basically, they need to deal with COFF relocs rather than
  29    BFD generic relocs.  They should store the relocs in some location
  30    where coff_link_input_bfd can find them (and coff_link_input_bfd
  31    should be changed to use this location rather than rereading the
  32    file) (unless info->keep_memory is FALSE, in which case they should
  33    free up the relocs after dealing with them).  */
  34
  35 #include "sysdep.h"
  36 #include "bfd.h"
  37 #include "libbfd.h"
  38 #include "bfdlink.h"
  39 #include "genlink.h"
  40 #include "coff/internal.h"
  41 #include "libcoff.h"
  42
  43 bfd_vma
  44 bfd_coff_reloc16_get_value (arelent *reloc,
  45                             struct bfd_link_info *link_info,
  46                             asection *input_section)
  47 {
  48   bfd_vma value;
  49   asymbol *symbol = *(reloc->sym_ptr_ptr);
  50   /* A symbol holds a pointer to a section, and an offset from the
  51      base of the section.  To relocate, we find where the section will
  52      live in the output and add that in.  */
  53
  54   if (bfd_is_und_section (symbol->section)
  55       || bfd_is_com_section (symbol->section))
  56     {
  57       struct bfd_link_hash_entry *h;
  58
  59       /* The symbol is undefined in this BFD.  Look it up in the
  60          global linker hash table.  FIXME: This should be changed when
  61          we convert this stuff to use a specific final_link function
  62          and change the interface to bfd_relax_section to not require
  63          the generic symbols.  */
  64       h = bfd_wrapped_link_hash_lookup (input_section->owner, link_info,
  65                                         bfd_asymbol_name (symbol),
  66                                         false, false, true);
  67       if (h != (struct bfd_link_hash_entry *) NULL
  68           && (h->type == bfd_link_hash_defined
  69               || h->type == bfd_link_hash_defweak))
  70         value = (h->u.def.value
  71                  + h->u.def.section->output_section->vma
  72                  + h->u.def.section->output_offset);
  73       else if (h != (struct bfd_link_hash_entry *) NULL
  74                && h->type == bfd_link_hash_common)
  75         value = h->u.c.size;
  76       else if (h != (struct bfd_link_hash_entry *) NULL
  77                && h->type == bfd_link_hash_undefweak)
  78         /* This is a GNU extension.  */
  79         value = 0;
  80       else
  81         {
  82           (*link_info->callbacks->undefined_symbol)
  83             (link_info, bfd_asymbol_name (symbol),
  84              input_section->owner, input_section, reloc->address, true);
  85           value = 0;
  86         }
  87     }
  88   else
  89     {
  90       value = symbol->value
  91         + symbol->section->output_offset
  92         + symbol->section->output_section->vma;
  93     }
  94
  95   /* Add the value contained in the relocation.  */
  96   value += reloc->addend;
  97
  98   return value;
  99 }
 100
 101 void
 102 bfd_perform_slip (bfd *abfd,
 103                   unsigned int slip,
 104                   asection *input_section,
 105                   bfd_vma value)
 106 {
 107   asymbol **s;
 108
 109   s = _bfd_generic_link_get_symbols (abfd);
 110   BFD_ASSERT (s != (asymbol **) NULL);
 111
 112   /* Find all symbols past this point, and make them know
 113      what's happened.  */
 114   while (*s)
 115     {
 116       asymbol *p = *s;
 117       if (p->section == input_section)
 118         {
 119           /* This was pointing into this section, so mangle it.  */
 120           if (p->value > value)
 121             {
 122               p->value -= slip;
 123               if (p->udata.p != NULL)
 124                 {
 125                   struct generic_link_hash_entry *h;
 126
 127                   h = (struct generic_link_hash_entry *) p->udata.p;
 128                   BFD_ASSERT (h->root.type == bfd_link_hash_defined
 129                               || h->root.type == bfd_link_hash_defweak);
 130                   h->root.u.def.value -= slip;
 131                   BFD_ASSERT (h->root.u.def.value == p->value);
 132                 }
 133             }
 134         }
 135       s++;
 136     }
 137 }
 138
 139 bool
 140 bfd_coff_reloc16_relax_section (bfd *abfd,
 141                                 asection *input_section,
 142                                 struct bfd_link_info *link_info,
 143                                 bool *again)
 144 {
 145   /* Get enough memory to hold the stuff.  */
 146   bfd *input_bfd = input_section->owner;
 147   unsigned *shrinks;
 148   unsigned shrink = 0;
 149   long reloc_size = bfd_get_reloc_upper_bound (input_bfd, input_section);
 150   arelent **reloc_vector = NULL;
 151   long reloc_count;
 152
 153   if (bfd_link_relocatable (link_info))
 154     (*link_info->callbacks->einfo)
 155       (_("%P%F: --relax and -r may not be used together\n"));
 156
 157   /* We only do global relaxation once.  It is not safe to do it multiple
 158      times (see discussion of the "shrinks" array below).  */
 159   *again = false;
 160
 161   if (reloc_size < 0)
 162     return false;
 163
 164   reloc_vector = (arelent **) bfd_malloc ((bfd_size_type) reloc_size);
 165   if (!reloc_vector && reloc_size > 0)
 166     return false;
 167
 168   /* Get the relocs and think about them.  */
 169   reloc_count =
 170     bfd_canonicalize_reloc (input_bfd, input_section, reloc_vector,
 171                             _bfd_generic_link_get_symbols (input_bfd));
 172   if (reloc_count < 0)
 173     {
 174       free (reloc_vector);
 175       return false;
 176     }
 177
 178   /* The reloc16.c and related relaxing code is very simple, the price
 179      for that simplicity is we can only call this function once for
 180      each section.
 181
 182      So, to get the best results within that limitation, we do multiple
 183      relaxing passes over each section here.  That involves keeping track
 184      of the "shrink" at each reloc in the section.  This allows us to
 185      accurately determine the relative location of two relocs within
 186      this section.
 187
 188      In theory, if we kept the "shrinks" array for each section for the
 189      entire link, we could use the generic relaxing code in the linker
 190      and get better results, particularly for jsr->bsr and 24->16 bit
 191      memory reference relaxations.  */
 192
 193   if (reloc_count > 0)
 194     {
 195       int another_pass = 0;
 196       bfd_size_type amt;
 197
 198       /* Allocate and initialize the shrinks array for this section.
 199          The last element is used as an accumulator of shrinks.  */
 200       amt = reloc_count + 1;
 201       amt *= sizeof (unsigned);
 202       shrinks = (unsigned *) bfd_zmalloc (amt);
 203
 204       /* Loop until nothing changes in this section.  */
 205       do
 206         {
 207           arelent **parent;
 208           unsigned int i;
 209           long j;
 210
 211           another_pass = 0;
 212
 213           for (i = 0, parent = reloc_vector; *parent; parent++, i++)
 214             {
 215               /* Let the target/machine dependent code examine each reloc
 216                  in this section and attempt to shrink it.  */
 217               shrink = bfd_coff_reloc16_estimate (abfd, input_section, *parent,
 218                                                   shrinks[i], link_info);
 219
 220               /* If it shrunk, note it in the shrinks array and set up for
 221                  another pass.  */
 222               if (shrink != shrinks[i])
 223                 {
 224                   another_pass = 1;
 225                   for (j = i + 1; j <= reloc_count; j++)
 226                     shrinks[j] += shrink - shrinks[i];
 227                 }
 228             }
 229         }
 230       while (another_pass);
 231
 232       shrink = shrinks[reloc_count];
 233       free ((char *) shrinks);
 234     }
 235
 236   input_section->rawsize = input_section->size;
 237   input_section->size -= shrink;
 238   free ((char *) reloc_vector);
 239   return true;
 240 }
 241
 242 bfd_byte *
 243 bfd_coff_reloc16_get_relocated_section_contents
 244   (bfd *in_abfd,
 245    struct bfd_link_info *link_info,
 246    struct bfd_link_order *link_order,
 247    bfd_byte *data,
 248    bool relocatable,
 249    asymbol **symbols)
 250 {
 251   /* Get enough memory to hold the stuff.  */
 252   bfd *input_bfd = link_order->u.indirect.section->owner;
 253   asection *input_section = link_order->u.indirect.section;
 254   long reloc_size = bfd_get_reloc_upper_bound (input_bfd, input_section);
 255   arelent **reloc_vector;
 256   long reloc_count;
 257   bfd_size_type sz;
 258
 259   if (reloc_size < 0)
 260     return NULL;
 261
 262   /* If producing relocatable output, don't bother to relax.  */
 263   if (relocatable)
 264     return bfd_generic_get_relocated_section_contents (in_abfd, link_info,
 265                                                        link_order,
 266                                                        data, relocatable,
 267                                                        symbols);
 268
 269   /* Read in the section.  */
 270   sz = input_section->rawsize ? input_section->rawsize : input_section->size;
 271   if (!bfd_get_section_contents (input_bfd, input_section, data, 0, sz))
 272     return NULL;
 273
 274   reloc_vector = (arelent **) bfd_malloc ((bfd_size_type) reloc_size);
 275   if (!reloc_vector && reloc_size != 0)
 276     return NULL;
 277
 278   reloc_count = bfd_canonicalize_reloc (input_bfd,
 279                                         input_section,
 280                                         reloc_vector,
 281                                         symbols);
 282   if (reloc_count < 0)
 283     {
 284       free (reloc_vector);
 285       return NULL;
 286     }
 287
 288   if (reloc_count > 0)
 289     {
 290       arelent **parent = reloc_vector;
 291       arelent *reloc;
 292       unsigned int dst_address = 0;
 293       unsigned int src_address = 0;
 294       unsigned int run;
 295       unsigned int idx;
 296
 297       /* Find how long a run we can do.  */
 298       while (dst_address < link_order->size)
 299         {
 300           reloc = *parent;
 301           if (reloc)
 302             {
 303               /* Note that the relaxing didn't tie up the addresses in the
 304                  relocation, so we use the original address to work out the
 305                  run of non-relocated data.  */
 306               run = reloc->address - src_address;
 307               parent++;
 308             }
 309           else
 310             {
 311               run = link_order->size - dst_address;
 312             }
 313
 314           /* Copy the bytes.  */
 315           for (idx = 0; idx < run; idx++)
 316             data[dst_address++] = data[src_address++];
 317
 318           /* Now do the relocation.  */
 319           if (reloc)
 320             {
 321               bfd_coff_reloc16_extra_cases (input_bfd, link_info, link_order,
 322                                             reloc, data, &src_address,
 323                                             &dst_address);
 324             }
 325         }
 326     }
 327   free ((char *) reloc_vector);
 328   return data;
 329 }