1 /* 8 and 16 bit COFF relocation functions, for BFD.
2    Copyright (C) 1990-2016 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
bfd_coff_reloc16_get_value(arelent * reloc,struct bfd_link_info * link_info,asection * input_section)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
bfd_perform_slip(bfd * abfd,unsigned int slip,asection * input_section,bfd_vma value)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
bfd_coff_reloc16_relax_section(bfd * abfd,asection * input_section,struct bfd_link_info * link_info,bfd_boolean * again)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 *
bfd_coff_reloc16_get_relocated_section_contents(bfd * in_abfd,struct bfd_link_info * link_info,struct bfd_link_order * link_order,bfd_byte * data,bfd_boolean relocatable,asymbol ** symbols)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 }
331