1/* ELF strtab with GC and suffix merging support.
2   Copyright 2001, 2002, 2003, 2005, 2006 Free Software Foundation, Inc.
3   Written by Jakub Jelinek <jakub@redhat.com>.
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 2 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, MA 02110-1301, USA.  */
20
21#include "bfd.h"
22#include "sysdep.h"
23#include "libbfd.h"
24#include "elf-bfd.h"
25#include "hashtab.h"
26#include "libiberty.h"
27
28/* An entry in the strtab hash table.  */
29
30struct elf_strtab_hash_entry
31{
32  struct bfd_hash_entry root;
33  /* Length of this entry.  This includes the zero terminator.  */
34  int len;
35  unsigned int refcount;
36  union {
37    /* Index within the merged section.  */
38    bfd_size_type index;
39    /* Entry this is a suffix of (if len < 0).  */
40    struct elf_strtab_hash_entry *suffix;
41  } u;
42};
43
44/* The strtab hash table.  */
45
46struct elf_strtab_hash
47{
48  struct bfd_hash_table table;
49  /* Next available index.  */
50  bfd_size_type size;
51  /* Number of array entries alloced.  */
52  bfd_size_type alloced;
53  /* Final strtab size.  */
54  bfd_size_type sec_size;
55  /* Array of pointers to strtab entries.  */
56  struct elf_strtab_hash_entry **array;
57};
58
59/* Routine to create an entry in a section merge hashtab.  */
60
61static struct bfd_hash_entry *
62elf_strtab_hash_newfunc (struct bfd_hash_entry *entry,
63			 struct bfd_hash_table *table,
64			 const char *string)
65{
66  /* Allocate the structure if it has not already been allocated by a
67     subclass.  */
68  if (entry == NULL)
69    entry = bfd_hash_allocate (table, sizeof (struct elf_strtab_hash_entry));
70  if (entry == NULL)
71    return NULL;
72
73  /* Call the allocation method of the superclass.  */
74  entry = bfd_hash_newfunc (entry, table, string);
75
76  if (entry)
77    {
78      /* Initialize the local fields.  */
79      struct elf_strtab_hash_entry *ret;
80
81      ret = (struct elf_strtab_hash_entry *) entry;
82      ret->u.index = -1;
83      ret->refcount = 0;
84      ret->len = 0;
85    }
86
87  return entry;
88}
89
90/* Create a new hash table.  */
91
92struct elf_strtab_hash *
93_bfd_elf_strtab_init (void)
94{
95  struct elf_strtab_hash *table;
96  bfd_size_type amt = sizeof (struct elf_strtab_hash);
97
98  table = bfd_malloc (amt);
99  if (table == NULL)
100    return NULL;
101
102  if (!bfd_hash_table_init (&table->table, elf_strtab_hash_newfunc,
103			    sizeof (struct elf_strtab_hash_entry)))
104    {
105      free (table);
106      return NULL;
107    }
108
109  table->sec_size = 0;
110  table->size = 1;
111  table->alloced = 64;
112  amt = sizeof (struct elf_strtab_hasn_entry *);
113  table->array = bfd_malloc (table->alloced * amt);
114  if (table->array == NULL)
115    {
116      free (table);
117      return NULL;
118    }
119
120  table->array[0] = NULL;
121
122  return table;
123}
124
125/* Free a strtab.  */
126
127void
128_bfd_elf_strtab_free (struct elf_strtab_hash *tab)
129{
130  bfd_hash_table_free (&tab->table);
131  free (tab->array);
132  free (tab);
133}
134
135/* Get the index of an entity in a hash table, adding it if it is not
136   already present.  */
137
138bfd_size_type
139_bfd_elf_strtab_add (struct elf_strtab_hash *tab,
140		     const char *str,
141		     bfd_boolean copy)
142{
143  register struct elf_strtab_hash_entry *entry;
144
145  /* We handle this specially, since we don't want to do refcounting
146     on it.  */
147  if (*str == '\0')
148    return 0;
149
150  BFD_ASSERT (tab->sec_size == 0);
151  entry = (struct elf_strtab_hash_entry *)
152	  bfd_hash_lookup (&tab->table, str, TRUE, copy);
153
154  if (entry == NULL)
155    return (bfd_size_type) -1;
156
157  entry->refcount++;
158  if (entry->len == 0)
159    {
160      entry->len = strlen (str) + 1;
161      /* 2G strings lose.  */
162      BFD_ASSERT (entry->len > 0);
163      if (tab->size == tab->alloced)
164	{
165	  bfd_size_type amt = sizeof (struct elf_strtab_hash_entry *);
166	  tab->alloced *= 2;
167	  tab->array = bfd_realloc (tab->array, tab->alloced * amt);
168	  if (tab->array == NULL)
169	    return (bfd_size_type) -1;
170	}
171
172      entry->u.index = tab->size++;
173      tab->array[entry->u.index] = entry;
174    }
175  return entry->u.index;
176}
177
178void
179_bfd_elf_strtab_addref (struct elf_strtab_hash *tab, bfd_size_type idx)
180{
181  if (idx == 0 || idx == (bfd_size_type) -1)
182    return;
183  BFD_ASSERT (tab->sec_size == 0);
184  BFD_ASSERT (idx < tab->size);
185  ++tab->array[idx]->refcount;
186}
187
188void
189_bfd_elf_strtab_delref (struct elf_strtab_hash *tab, bfd_size_type idx)
190{
191  if (idx == 0 || idx == (bfd_size_type) -1)
192    return;
193  BFD_ASSERT (tab->sec_size == 0);
194  BFD_ASSERT (idx < tab->size);
195  BFD_ASSERT (tab->array[idx]->refcount > 0);
196  --tab->array[idx]->refcount;
197}
198
199void
200_bfd_elf_strtab_clear_all_refs (struct elf_strtab_hash *tab)
201{
202  bfd_size_type idx;
203
204  for (idx = 1; idx < tab->size; ++idx)
205    tab->array[idx]->refcount = 0;
206}
207
208bfd_size_type
209_bfd_elf_strtab_size (struct elf_strtab_hash *tab)
210{
211  return tab->sec_size ? tab->sec_size : tab->size;
212}
213
214bfd_size_type
215_bfd_elf_strtab_offset (struct elf_strtab_hash *tab, bfd_size_type idx)
216{
217  struct elf_strtab_hash_entry *entry;
218
219  if (idx == 0)
220    return 0;
221  BFD_ASSERT (idx < tab->size);
222  BFD_ASSERT (tab->sec_size);
223  entry = tab->array[idx];
224  BFD_ASSERT (entry->refcount > 0);
225  entry->refcount--;
226  return tab->array[idx]->u.index;
227}
228
229bfd_boolean
230_bfd_elf_strtab_emit (register bfd *abfd, struct elf_strtab_hash *tab)
231{
232  bfd_size_type off = 1, i;
233
234  if (bfd_bwrite ("", 1, abfd) != 1)
235    return FALSE;
236
237  for (i = 1; i < tab->size; ++i)
238    {
239      register const char *str;
240      register unsigned int len;
241
242      BFD_ASSERT (tab->array[i]->refcount == 0);
243      len = tab->array[i]->len;
244      if ((int) len < 0)
245	continue;
246
247      str = tab->array[i]->root.string;
248      if (bfd_bwrite (str, len, abfd) != len)
249	return FALSE;
250
251      off += len;
252    }
253
254  BFD_ASSERT (off == tab->sec_size);
255  return TRUE;
256}
257
258/* Compare two elf_strtab_hash_entry structures.  Called via qsort.  */
259
260static int
261strrevcmp (const void *a, const void *b)
262{
263  struct elf_strtab_hash_entry *A = *(struct elf_strtab_hash_entry **) a;
264  struct elf_strtab_hash_entry *B = *(struct elf_strtab_hash_entry **) b;
265  unsigned int lenA = A->len;
266  unsigned int lenB = B->len;
267  const unsigned char *s = (const unsigned char *) A->root.string + lenA - 1;
268  const unsigned char *t = (const unsigned char *) B->root.string + lenB - 1;
269  int l = lenA < lenB ? lenA : lenB;
270
271  while (l)
272    {
273      if (*s != *t)
274	return (int) *s - (int) *t;
275      s--;
276      t--;
277      l--;
278    }
279  return lenA - lenB;
280}
281
282static inline int
283is_suffix (const struct elf_strtab_hash_entry *A,
284	   const struct elf_strtab_hash_entry *B)
285{
286  if (A->len <= B->len)
287    /* B cannot be a suffix of A unless A is equal to B, which is guaranteed
288       not to be equal by the hash table.  */
289    return 0;
290
291  return memcmp (A->root.string + (A->len - B->len),
292		 B->root.string, B->len - 1) == 0;
293}
294
295/* This function assigns final string table offsets for used strings,
296   merging strings matching suffixes of longer strings if possible.  */
297
298void
299_bfd_elf_strtab_finalize (struct elf_strtab_hash *tab)
300{
301  struct elf_strtab_hash_entry **array, **a, *e;
302  bfd_size_type size, amt;
303
304  /* GCC 2.91.66 (egcs-1.1.2) on i386 miscompiles this function when i is
305     a 64-bit bfd_size_type: a 64-bit target or --enable-64-bit-bfd.
306     Besides, indexing with a long long wouldn't give anything but extra
307     cycles.  */
308  size_t i;
309
310  /* Sort the strings by suffix and length.  */
311  amt = tab->size * sizeof (struct elf_strtab_hash_entry *);
312  array = bfd_malloc (amt);
313  if (array == NULL)
314    goto alloc_failure;
315
316  for (i = 1, a = array; i < tab->size; ++i)
317    {
318      e = tab->array[i];
319      if (e->refcount)
320	{
321	  *a++ = e;
322	  /* Adjust the length to not include the zero terminator.  */
323	  e->len -= 1;
324	}
325      else
326	e->len = 0;
327    }
328
329  size = a - array;
330  if (size != 0)
331    {
332      qsort (array, size, sizeof (struct elf_strtab_hash_entry *), strrevcmp);
333
334      /* Loop over the sorted array and merge suffixes.  Start from the
335	 end because we want eg.
336
337	 s1 -> "d"
338	 s2 -> "bcd"
339	 s3 -> "abcd"
340
341	 to end up as
342
343	 s3 -> "abcd"
344	 s2 _____^
345	 s1 _______^
346
347	 ie. we don't want s1 pointing into the old s2.  */
348      e = *--a;
349      e->len += 1;
350      while (--a >= array)
351	{
352	  struct elf_strtab_hash_entry *cmp = *a;
353
354	  cmp->len += 1;
355	  if (is_suffix (e, cmp))
356	    {
357	      cmp->u.suffix = e;
358	      cmp->len = -cmp->len;
359	    }
360	  else
361	    e = cmp;
362	}
363    }
364
365alloc_failure:
366  if (array)
367    free (array);
368
369  /* Assign positions to the strings we want to keep.  */
370  size = 1;
371  for (i = 1; i < tab->size; ++i)
372    {
373      e = tab->array[i];
374      if (e->refcount && e->len > 0)
375	{
376	  e->u.index = size;
377	  size += e->len;
378	}
379    }
380
381  tab->sec_size = size;
382
383  /* Adjust the rest.  */
384  for (i = 1; i < tab->size; ++i)
385    {
386      e = tab->array[i];
387      if (e->refcount && e->len < 0)
388	e->u.index = e->u.suffix->u.index + (e->u.suffix->len + e->len);
389    }
390}
391