1/* ELF string table handling.
2   Copyright (C) 2000, 2001, 2002, 2005 Red Hat, Inc.
3   This file is part of elfutils.
4   Written by Ulrich Drepper <drepper@redhat.com>, 2000.
5
6   This file is free software; you can redistribute it and/or modify
7   it under the terms of either
8
9     * the GNU Lesser General Public License as published by the Free
10       Software Foundation; either version 3 of the License, or (at
11       your option) any later version
12
13   or
14
15     * the GNU General Public License as published by the Free
16       Software Foundation; either version 2 of the License, or (at
17       your option) any later version
18
19   or both in parallel, as here.
20
21   elfutils is distributed in the hope that it will be useful, but
22   WITHOUT ANY WARRANTY; without even the implied warranty of
23   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
24   General Public License for more details.
25
26   You should have received copies of the GNU General Public License and
27   the GNU Lesser General Public License along with this program.  If
28   not, see <http://www.gnu.org/licenses/>.  */
29
30#ifdef HAVE_CONFIG_H
31# include <config.h>
32#endif
33
34#include <assert.h>
35#include <inttypes.h>
36#include <libelf.h>
37#include <stddef.h>
38#include <stdlib.h>
39#include <string.h>
40#include <unistd.h>
41#include <sys/param.h>
42
43#include "libebl.h"
44#include <system.h>
45
46#ifndef MIN
47# define MIN(a, b) ((a) < (b) ? (a) : (b))
48#endif
49
50
51struct Ebl_Strent
52{
53  const char *string;
54  size_t len;
55  struct Ebl_Strent *next;
56  struct Ebl_Strent *left;
57  struct Ebl_Strent *right;
58  size_t offset;
59  char reverse[0];
60};
61
62
63struct memoryblock
64{
65  struct memoryblock *next;
66  char memory[0];
67};
68
69
70struct Ebl_Strtab
71{
72  struct Ebl_Strent *root;
73  struct memoryblock *memory;
74  char *backp;
75  size_t left;
76  size_t total;
77  bool nullstr;
78
79  struct Ebl_Strent null;
80};
81
82
83/* Cache for the pagesize.  */
84static size_t ps;
85/* We correct this value a bit so that `malloc' is not allocating more
86   than a page. */
87#define MALLOC_OVERHEAD (2 * sizeof (void *))
88
89
90struct Ebl_Strtab *
91ebl_strtabinit (bool nullstr)
92{
93  if (ps == 0)
94    {
95      ps = sysconf (_SC_PAGESIZE);
96      assert (sizeof (struct memoryblock) < ps - MALLOC_OVERHEAD);
97    }
98
99  struct Ebl_Strtab *ret
100    = (struct Ebl_Strtab *) calloc (1, sizeof (struct Ebl_Strtab));
101  if (ret != NULL)
102    {
103      ret->nullstr = nullstr;
104
105      if (nullstr)
106	{
107	  ret->null.len = 1;
108	  ret->null.string = "";
109	}
110    }
111
112  return ret;
113}
114
115
116static int
117morememory (struct Ebl_Strtab *st, size_t len)
118{
119  size_t overhead = offsetof (struct memoryblock, memory);
120  len += overhead + MALLOC_OVERHEAD;
121
122  /* Allocate nearest multiple of pagesize >= len.  */
123  len = ((len / ps) + (len % ps != 0)) * ps - MALLOC_OVERHEAD;
124
125  struct memoryblock *newmem = (struct memoryblock *) malloc (len);
126  if (newmem == NULL)
127    return 1;
128
129  newmem->next = st->memory;
130  st->memory = newmem;
131  st->backp = newmem->memory;
132  st->left = len - overhead;
133
134  return 0;
135}
136
137
138void
139ebl_strtabfree (struct Ebl_Strtab *st)
140{
141  struct memoryblock *mb = st->memory;
142
143  while (mb != NULL)
144    {
145      void *old = mb;
146      mb = mb->next;
147      free (old);
148    }
149
150  free (st);
151}
152
153
154static struct Ebl_Strent *
155newstring (struct Ebl_Strtab *st, const char *str, size_t len)
156{
157  /* Compute the amount of padding needed to make the structure aligned.  */
158  size_t align = ((__alignof__ (struct Ebl_Strent)
159		   - (((uintptr_t) st->backp)
160		      & (__alignof__ (struct Ebl_Strent) - 1)))
161		  & (__alignof__ (struct Ebl_Strent) - 1));
162
163  /* Make sure there is enough room in the memory block.  */
164  if (st->left < align + sizeof (struct Ebl_Strent) + len)
165    {
166      if (morememory (st, sizeof (struct Ebl_Strent) + len))
167	return NULL;
168
169      align = 0;
170    }
171
172  /* Create the reserved string.  */
173  struct Ebl_Strent *newstr = (struct Ebl_Strent *) (st->backp + align);
174  newstr->string = str;
175  newstr->len = len;
176  newstr->next = NULL;
177  newstr->left = NULL;
178  newstr->right = NULL;
179  newstr->offset = 0;
180  for (int i = len - 2; i >= 0; --i)
181    newstr->reverse[i] = str[len - 2 - i];
182  newstr->reverse[len - 1] = '\0';
183  st->backp += align + sizeof (struct Ebl_Strent) + len;
184  st->left -= align + sizeof (struct Ebl_Strent) + len;
185
186  return newstr;
187}
188
189
190/* XXX This function should definitely be rewritten to use a balancing
191   tree algorith (AVL, red-black trees).  For now a simple, correct
192   implementation is enough.  */
193static struct Ebl_Strent **
194searchstring (struct Ebl_Strent **sep, struct Ebl_Strent *newstr)
195{
196  /* More strings?  */
197  if (*sep == NULL)
198    {
199      *sep = newstr;
200      return sep;
201    }
202
203  /* Compare the strings.  */
204  int cmpres = memcmp ((*sep)->reverse, newstr->reverse,
205		       MIN ((*sep)->len, newstr->len) - 1);
206  if (cmpres == 0)
207    /* We found a matching string.  */
208    return sep;
209  else if (cmpres > 0)
210    return searchstring (&(*sep)->left, newstr);
211  else
212    return searchstring (&(*sep)->right, newstr);
213}
214
215
216/* Add new string.  The actual string is assumed to be permanent.  */
217struct Ebl_Strent *
218ebl_strtabadd (struct Ebl_Strtab *st, const char *str, size_t len)
219{
220  /* Compute the string length if the caller doesn't know it.  */
221  if (len == 0)
222    len = strlen (str) + 1;
223
224  /* Make sure all "" strings get offset 0 but only if the table was
225     created with a special null entry in mind.  */
226  if (len == 1 && st->null.string != NULL)
227    return &st->null;
228
229  /* Allocate memory for the new string and its associated information.  */
230  struct Ebl_Strent *newstr = newstring (st, str, len);
231  if (newstr == NULL)
232    return NULL;
233
234  /* Search in the array for the place to insert the string.  If there
235     is no string with matching prefix and no string with matching
236     leading substring, create a new entry.  */
237  struct Ebl_Strent **sep = searchstring (&st->root, newstr);
238  if (*sep != newstr)
239    {
240      /* This is not the same entry.  This means we have a prefix match.  */
241      if ((*sep)->len > newstr->len)
242	{
243	  /* Check whether we already know this string.  */
244	  for (struct Ebl_Strent *subs = (*sep)->next; subs != NULL;
245	       subs = subs->next)
246	    if (subs->len == newstr->len)
247	      {
248		/* We have an exact match with a substring.  Free the memory
249		   we allocated.  */
250		st->left += st->backp - (char *) newstr;
251		st->backp = (char *) newstr;
252
253		return subs;
254	      }
255
256	  /* We have a new substring.  This means we don't need the reverse
257	     string of this entry anymore.  */
258	  st->backp -= newstr->len;
259	  st->left += newstr->len;
260
261	  newstr->next = (*sep)->next;
262	  (*sep)->next = newstr;
263	}
264      else if ((*sep)->len != newstr->len)
265	{
266	  /* When we get here it means that the string we are about to
267	     add has a common prefix with a string we already have but
268	     it is longer.  In this case we have to put it first.  */
269	  st->total += newstr->len - (*sep)->len;
270	  newstr->next = *sep;
271	  newstr->left = (*sep)->left;
272	  newstr->right = (*sep)->right;
273	  *sep = newstr;
274	}
275      else
276	{
277	  /* We have an exact match.  Free the memory we allocated.  */
278	  st->left += st->backp - (char *) newstr;
279	  st->backp = (char *) newstr;
280
281	  newstr = *sep;
282	}
283    }
284  else
285    st->total += newstr->len;
286
287  return newstr;
288}
289
290
291static void
292copystrings (struct Ebl_Strent *nodep, char **freep, size_t *offsetp)
293{
294  if (nodep->left != NULL)
295    copystrings (nodep->left, freep, offsetp);
296
297  /* Process the current node.  */
298  nodep->offset = *offsetp;
299  *freep = (char *) mempcpy (*freep, nodep->string, nodep->len);
300  *offsetp += nodep->len;
301
302  for (struct Ebl_Strent *subs = nodep->next; subs != NULL; subs = subs->next)
303    {
304      assert (subs->len < nodep->len);
305      subs->offset = nodep->offset + nodep->len - subs->len;
306      assert (subs->offset != 0 || subs->string[0] == '\0');
307    }
308
309  if (nodep->right != NULL)
310    copystrings (nodep->right, freep, offsetp);
311}
312
313
314void
315ebl_strtabfinalize (struct Ebl_Strtab *st, Elf_Data *data)
316{
317  size_t nulllen = st->nullstr ? 1 : 0;
318
319  /* Fill in the information.  */
320  data->d_buf = malloc (st->total + nulllen);
321  if (data->d_buf == NULL)
322    abort ();
323
324  /* The first byte must always be zero if we created the table with a
325     null string.  */
326  if (st->nullstr)
327    *((char *) data->d_buf) = '\0';
328
329  data->d_type = ELF_T_BYTE;
330  data->d_size = st->total + nulllen;
331  data->d_off = 0;
332  data->d_align = 1;
333  data->d_version = EV_CURRENT;
334
335  /* Now run through the tree and add all the string while also updating
336     the offset members of the elfstrent records.  */
337  char *endp = (char *) data->d_buf + nulllen;
338  size_t copylen = nulllen;
339  if (st->root)
340    copystrings (st->root, &endp, &copylen);
341  assert (copylen == st->total + nulllen);
342}
343
344
345size_t
346ebl_strtaboffset (struct Ebl_Strent *se)
347{
348  return se->offset;
349}
350
351
352const char *
353ebl_string (struct Ebl_Strent *se)
354{
355  assert (se->string != NULL);
356
357  return se->string;
358}
359