2 Copyright 2001, 2002, 2003, 2004, 2005 Free Software Foundation, Inc.
3 Written by Jakub Jelinek <jakub@redhat.com>.
5 This file is part of BFD, the Binary File Descriptor library.
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.
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.
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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
21 /* This file contains support for merging duplicate entities within sections,
22 as used in ELF SHF_MERGE. */
28 #include "libiberty.h"
30 struct sec_merge_sec_info;
32 /* An entry in the section merge hash table. */
34 struct sec_merge_hash_entry
36 struct bfd_hash_entry root;
37 /* Length of this entry. This includes the zero terminator. */
39 /* Start of this string needs to be aligned to
40 alignment octets (not 1 << align). */
41 unsigned int alignment;
44 /* Index within the merged section. */
46 /* Entry this is a suffix of (if alignment is 0). */
47 struct sec_merge_hash_entry *suffix;
49 /* Which section is it in. */
50 struct sec_merge_sec_info *secinfo;
51 /* Next entity in the hash table. */
52 struct sec_merge_hash_entry *next;
55 /* The section merge hash table. */
59 struct bfd_hash_table table;
60 /* Next available index. */
62 /* First entity in the SEC_MERGE sections of this type. */
63 struct sec_merge_hash_entry *first;
64 /* Last entity in the SEC_MERGE sections of this type. */
65 struct sec_merge_hash_entry *last;
68 /* Are entries fixed size or zero terminated strings? */
74 /* Chain of sec_merge_infos. */
75 struct sec_merge_info *next;
76 /* Chain of sec_merge_sec_infos. */
77 struct sec_merge_sec_info *chain;
78 /* A hash table used to hold section content. */
79 struct sec_merge_hash *htab;
82 struct sec_merge_sec_info
84 /* Chain of sec_merge_sec_infos. */
85 struct sec_merge_sec_info *next;
86 /* The corresponding section. */
88 /* Pointer to merge_info pointing to us. */
90 /* A hash table used to hold section content. */
91 struct sec_merge_hash *htab;
92 /* First string in this section. */
93 struct sec_merge_hash_entry *first_str;
94 /* Original section content. */
95 unsigned char contents[1];
99 /* Routine to create an entry in a section merge hashtab. */
101 static struct bfd_hash_entry *
102 sec_merge_hash_newfunc (struct bfd_hash_entry *entry,
103 struct bfd_hash_table *table, const char *string)
105 /* Allocate the structure if it has not already been allocated by a
108 entry = bfd_hash_allocate (table, sizeof (struct sec_merge_hash_entry));
112 /* Call the allocation method of the superclass. */
113 entry = bfd_hash_newfunc (entry, table, string);
117 /* Initialize the local fields. */
118 struct sec_merge_hash_entry *ret = (struct sec_merge_hash_entry *) entry;
120 ret->u.suffix = NULL;
129 /* Look up an entry in a section merge hash table. */
131 static struct sec_merge_hash_entry *
132 sec_merge_hash_lookup (struct sec_merge_hash *table, const char *string,
133 unsigned int alignment, bfd_boolean create)
135 register const unsigned char *s;
136 register unsigned long hash;
137 register unsigned int c;
138 struct sec_merge_hash_entry *hashp;
144 s = (const unsigned char *) string;
147 if (table->entsize == 1)
149 while ((c = *s++) != '\0')
151 hash += c + (c << 17);
155 hash += len + (len << 17);
161 for (i = 0; i < table->entsize; ++i)
164 if (i == table->entsize)
166 for (i = 0; i < table->entsize; ++i)
169 hash += c + (c << 17);
174 hash += len + (len << 17);
175 len *= table->entsize;
178 len += table->entsize;
182 for (i = 0; i < table->entsize; ++i)
185 hash += c + (c << 17);
188 len = table->entsize;
191 index = hash % table->table.size;
192 for (hashp = (struct sec_merge_hash_entry *) table->table.table[index];
194 hashp = (struct sec_merge_hash_entry *) hashp->root.next)
196 if (hashp->root.hash == hash
198 && memcmp (hashp->root.string, string, len) == 0)
200 /* If the string we found does not have at least the required
201 alignment, we need to insert another copy. */
202 if (hashp->alignment < alignment)
206 /* Mark the less aligned copy as deleted. */
208 hashp->alignment = 0;
219 hashp = ((struct sec_merge_hash_entry *)
220 sec_merge_hash_newfunc (NULL, &table->table, string));
223 hashp->root.string = string;
224 hashp->root.hash = hash;
226 hashp->alignment = alignment;
227 hashp->root.next = table->table.table[index];
228 table->table.table[index] = (struct bfd_hash_entry *) hashp;
233 /* Create a new hash table. */
235 static struct sec_merge_hash *
236 sec_merge_init (unsigned int entsize, bfd_boolean strings)
238 struct sec_merge_hash *table;
240 table = bfd_malloc (sizeof (struct sec_merge_hash));
244 if (! bfd_hash_table_init (&table->table, sec_merge_hash_newfunc))
253 table->entsize = entsize;
254 table->strings = strings;
259 /* Get the index of an entity in a hash table, adding it if it is not
262 static struct sec_merge_hash_entry *
263 sec_merge_add (struct sec_merge_hash *tab, const char *str,
264 unsigned int alignment, struct sec_merge_sec_info *secinfo)
266 register struct sec_merge_hash_entry *entry;
268 entry = sec_merge_hash_lookup (tab, str, alignment, TRUE);
272 if (entry->secinfo == NULL)
275 entry->secinfo = secinfo;
276 if (tab->first == NULL)
279 tab->last->next = entry;
287 sec_merge_emit (bfd *abfd, struct sec_merge_hash_entry *entry)
289 struct sec_merge_sec_info *secinfo = entry->secinfo;
290 asection *sec = secinfo->sec;
292 bfd_size_type off = 0;
293 int alignment_power = sec->output_section->alignment_power;
297 pad = bfd_zmalloc ((bfd_size_type) 1 << alignment_power);
302 for (; entry != NULL && entry->secinfo == secinfo; entry = entry->next)
307 len = -off & (entry->alignment - 1);
310 if (bfd_bwrite (pad, len, abfd) != len)
315 str = entry->root.string;
318 if (bfd_bwrite (str, len, abfd) != len)
324 /* Trailing alignment needed? */
325 off = sec->size - off;
327 && bfd_bwrite (pad, off, abfd) != off)
340 /* Register a SEC_MERGE section as a candidate for merging.
341 This function is called for all non-dynamic SEC_MERGE input sections. */
344 _bfd_add_merge_section (bfd *abfd, void **psinfo, asection *sec,
347 struct sec_merge_info *sinfo;
348 struct sec_merge_sec_info *secinfo;
352 if ((abfd->flags & DYNAMIC) != 0
353 || (sec->flags & SEC_MERGE) == 0)
357 || (sec->flags & SEC_EXCLUDE) != 0
358 || sec->entsize == 0)
361 if ((sec->flags & SEC_RELOC) != 0)
363 /* We aren't prepared to handle relocations in merged sections. */
367 align = sec->alignment_power;
368 if ((sec->entsize < (unsigned) 1 << align
369 && ((sec->entsize & (sec->entsize - 1))
370 || !(sec->flags & SEC_STRINGS)))
371 || (sec->entsize > (unsigned) 1 << align
372 && (sec->entsize & (((unsigned) 1 << align) - 1))))
374 /* Sanity check. If string character size is smaller than
375 alignment, then we require character size to be a power
376 of 2, otherwise character size must be integer multiple
377 of alignment. For non-string constants, alignment must
378 be smaller than or equal to entity size and entity size
379 must be integer multiple of alignment. */
383 for (sinfo = (struct sec_merge_info *) *psinfo; sinfo; sinfo = sinfo->next)
384 if ((secinfo = sinfo->chain)
385 && ! ((secinfo->sec->flags ^ sec->flags) & (SEC_MERGE | SEC_STRINGS))
386 && secinfo->sec->entsize == sec->entsize
387 && secinfo->sec->alignment_power == sec->alignment_power
388 && secinfo->sec->output_section == sec->output_section)
393 /* Initialize the information we need to keep track of. */
394 sinfo = bfd_alloc (abfd, sizeof (struct sec_merge_info));
397 sinfo->next = (struct sec_merge_info *) *psinfo;
400 sinfo->htab = sec_merge_init (sec->entsize, (sec->flags & SEC_STRINGS));
401 if (sinfo->htab == NULL)
405 /* Read the section from abfd. */
407 amt = sizeof (struct sec_merge_sec_info) + sec->size - 1;
408 *psecinfo = bfd_alloc (abfd, amt);
409 if (*psecinfo == NULL)
412 secinfo = (struct sec_merge_sec_info *) *psecinfo;
415 secinfo->next = sinfo->chain->next;
416 sinfo->chain->next = secinfo;
419 secinfo->next = secinfo;
420 sinfo->chain = secinfo;
422 secinfo->psecinfo = psecinfo;
423 secinfo->htab = sinfo->htab;
424 secinfo->first_str = NULL;
426 sec->rawsize = sec->size;
427 if (! bfd_get_section_contents (sec->owner, sec, secinfo->contents,
438 /* Record one section into the hash table. */
440 record_section (struct sec_merge_info *sinfo,
441 struct sec_merge_sec_info *secinfo)
443 asection *sec = secinfo->sec;
444 struct sec_merge_hash_entry *entry;
446 unsigned char *p, *end;
447 bfd_vma mask, eltalign;
448 unsigned int align, i;
450 align = sec->alignment_power;
451 end = secinfo->contents + sec->size;
453 mask = ((bfd_vma) 1 << align) - 1;
454 if (sec->flags & SEC_STRINGS)
456 for (p = secinfo->contents; p < end; )
458 eltalign = p - secinfo->contents;
459 eltalign = ((eltalign ^ (eltalign - 1)) + 1) >> 1;
460 if (!eltalign || eltalign > mask)
462 entry = sec_merge_add (sinfo->htab, (char *) p, (unsigned) eltalign,
467 if (sec->entsize == 1)
469 while (p < end && *p == 0)
471 if (!nul && !((p - secinfo->contents) & mask))
474 entry = sec_merge_add (sinfo->htab, "",
475 (unsigned) mask + 1, secinfo);
486 for (i = 0; i < sec->entsize; i++)
489 if (i != sec->entsize)
491 if (!nul && !((p - secinfo->contents) & mask))
494 entry = sec_merge_add (sinfo->htab, (char *) p,
495 (unsigned) mask + 1, secinfo);
506 for (p = secinfo->contents; p < end; p += sec->entsize)
508 entry = sec_merge_add (sinfo->htab, (char *) p, 1, secinfo);
517 for (secinfo = sinfo->chain; secinfo; secinfo = secinfo->next)
518 *secinfo->psecinfo = NULL;
523 strrevcmp (const void *a, const void *b)
525 struct sec_merge_hash_entry *A = *(struct sec_merge_hash_entry **) a;
526 struct sec_merge_hash_entry *B = *(struct sec_merge_hash_entry **) b;
527 unsigned int lenA = A->len;
528 unsigned int lenB = B->len;
529 const unsigned char *s = (const unsigned char *) A->root.string + lenA - 1;
530 const unsigned char *t = (const unsigned char *) B->root.string + lenB - 1;
531 int l = lenA < lenB ? lenA : lenB;
536 return (int) *s - (int) *t;
544 /* Like strrevcmp, but for the case where all strings have the same
545 alignment > entsize. */
548 strrevcmp_align (const void *a, const void *b)
550 struct sec_merge_hash_entry *A = *(struct sec_merge_hash_entry **) a;
551 struct sec_merge_hash_entry *B = *(struct sec_merge_hash_entry **) b;
552 unsigned int lenA = A->len;
553 unsigned int lenB = B->len;
554 const unsigned char *s = (const unsigned char *) A->root.string + lenA - 1;
555 const unsigned char *t = (const unsigned char *) B->root.string + lenB - 1;
556 int l = lenA < lenB ? lenA : lenB;
557 int tail_align = (lenA & (A->alignment - 1)) - (lenB & (A->alignment - 1));
565 return (int) *s - (int) *t;
574 is_suffix (const struct sec_merge_hash_entry *A,
575 const struct sec_merge_hash_entry *B)
577 if (A->len <= B->len)
578 /* B cannot be a suffix of A unless A is equal to B, which is guaranteed
579 not to be equal by the hash table. */
582 return memcmp (A->root.string + (A->len - B->len),
583 B->root.string, B->len) == 0;
586 /* This is a helper function for _bfd_merge_sections. It attempts to
587 merge strings matching suffixes of longer strings. */
589 merge_strings (struct sec_merge_info *sinfo)
591 struct sec_merge_hash_entry **array, **a, *e;
592 struct sec_merge_sec_info *secinfo;
593 bfd_size_type size, amt;
594 unsigned int alignment = 0;
596 /* Now sort the strings */
597 amt = sinfo->htab->size * sizeof (struct sec_merge_hash_entry *);
598 array = bfd_malloc (amt);
602 for (e = sinfo->htab->first, a = array; e; e = e->next)
606 /* Adjust the length to not include the zero terminator. */
607 e->len -= sinfo->htab->entsize;
608 if (alignment != e->alignment)
611 alignment = e->alignment;
613 alignment = (unsigned) -1;
617 sinfo->htab->size = a - array;
618 if (sinfo->htab->size != 0)
620 qsort (array, (size_t) sinfo->htab->size,
621 sizeof (struct sec_merge_hash_entry *),
622 (alignment != (unsigned) -1 && alignment > sinfo->htab->entsize
623 ? strrevcmp_align : strrevcmp));
625 /* Loop over the sorted array and merge suffixes */
627 e->len += sinfo->htab->entsize;
630 struct sec_merge_hash_entry *cmp = *a;
632 cmp->len += sinfo->htab->entsize;
633 if (e->alignment >= cmp->alignment
634 && !((e->len - cmp->len) & (cmp->alignment - 1))
635 && is_suffix (e, cmp))
649 /* Now assign positions to the strings we want to keep. */
651 secinfo = sinfo->htab->first->secinfo;
652 for (e = sinfo->htab->first; e; e = e->next)
654 if (e->secinfo != secinfo)
656 secinfo->sec->size = size;
657 secinfo = e->secinfo;
661 if (e->secinfo->first_str == NULL)
663 e->secinfo->first_str = e;
666 size = (size + e->alignment - 1) & ~((bfd_vma) e->alignment - 1);
671 secinfo->sec->size = size;
672 if (secinfo->sec->alignment_power != 0)
674 bfd_size_type align = (bfd_size_type) 1 << secinfo->sec->alignment_power;
675 secinfo->sec->size = (secinfo->sec->size + align - 1) & -align;
678 /* And now adjust the rest, removing them from the chain (but not hashtable)
680 for (a = &sinfo->htab->first, e = *a; e; e = e->next)
688 e->secinfo = e->u.suffix->secinfo;
689 e->alignment = e->u.suffix->alignment;
690 e->u.index = e->u.suffix->u.index + (e->u.suffix->len - e->len);
695 /* This function is called once after all SEC_MERGE sections are registered
696 with _bfd_merge_section. */
699 _bfd_merge_sections (bfd *abfd ATTRIBUTE_UNUSED, struct bfd_link_info *info,
700 void *xsinfo, void (*remove_hook) (bfd *, asection *))
702 struct sec_merge_info *sinfo;
704 for (sinfo = (struct sec_merge_info *) xsinfo; sinfo; sinfo = sinfo->next)
706 struct sec_merge_sec_info * secinfo;
711 /* Move sinfo->chain to head of the chain, terminate it. */
712 secinfo = sinfo->chain;
713 sinfo->chain = secinfo->next;
714 secinfo->next = NULL;
716 /* Record the sections into the hash table. */
717 for (secinfo = sinfo->chain; secinfo; secinfo = secinfo->next)
718 if (secinfo->sec->flags & SEC_EXCLUDE)
720 *secinfo->psecinfo = NULL;
722 (*remove_hook) (abfd, secinfo->sec);
724 else if (! record_section (sinfo, secinfo))
730 if (sinfo->htab->first == NULL)
733 if (sinfo->htab->strings)
734 merge_strings (sinfo);
737 struct sec_merge_hash_entry *e;
738 bfd_size_type size = 0;
740 /* Things are much simpler for non-strings.
741 Just assign them slots in the section. */
743 for (e = sinfo->htab->first; e; e = e->next)
745 if (e->secinfo->first_str == NULL)
748 secinfo->sec->size = size;
749 e->secinfo->first_str = e;
752 size = (size + e->alignment - 1)
753 & ~((bfd_vma) e->alignment - 1);
756 secinfo = e->secinfo;
758 secinfo->sec->size = size;
761 /* Finally remove all input sections which have not made it into
762 the hash table at all. */
763 for (secinfo = sinfo->chain; secinfo; secinfo = secinfo->next)
764 if (secinfo->first_str == NULL)
765 _bfd_strip_section_from_output (info, secinfo->sec);
771 /* Write out the merged section. */
774 _bfd_write_merged_section (bfd *output_bfd, asection *sec, void *psecinfo)
776 struct sec_merge_sec_info *secinfo;
779 secinfo = (struct sec_merge_sec_info *) psecinfo;
781 if (secinfo->first_str == NULL)
784 pos = sec->output_section->filepos + sec->output_offset;
785 if (bfd_seek (output_bfd, pos, SEEK_SET) != 0)
788 if (! sec_merge_emit (output_bfd, secinfo->first_str))
794 /* Adjust an address in the SEC_MERGE section. Given OFFSET within
795 *PSEC, this returns the new offset in the adjusted SEC_MERGE
796 section and writes the new section back into *PSEC. */
799 _bfd_merged_section_offset (bfd *output_bfd ATTRIBUTE_UNUSED, asection **psec,
800 void *psecinfo, bfd_vma offset)
802 struct sec_merge_sec_info *secinfo;
803 struct sec_merge_hash_entry *entry;
805 asection *sec = *psec;
807 secinfo = (struct sec_merge_sec_info *) psecinfo;
809 if (offset >= sec->rawsize)
811 if (offset > sec->rawsize)
813 (*_bfd_error_handler)
814 (_("%s: access beyond end of merged section (%ld)"),
815 bfd_get_filename (sec->owner), (long) offset);
817 return secinfo->first_str ? sec->size : 0;
820 if (secinfo->htab->strings)
822 if (sec->entsize == 1)
824 p = secinfo->contents + offset - 1;
825 while (p >= secinfo->contents && *p)
831 p = secinfo->contents + (offset / sec->entsize) * sec->entsize;
833 while (p >= secinfo->contents)
837 for (i = 0; i < sec->entsize; ++i)
840 if (i == sec->entsize)
849 p = secinfo->contents + (offset / sec->entsize) * sec->entsize;
851 entry = sec_merge_hash_lookup (secinfo->htab, (char *) p, 0, FALSE);
854 if (! secinfo->htab->strings)
856 /* This should only happen if somebody points into the padding
857 after a NUL character but before next entity. */
860 if (! secinfo->htab->first)
862 entry = secinfo->htab->first;
863 p = (secinfo->contents + (offset / sec->entsize + 1) * sec->entsize
867 *psec = entry->secinfo->sec;
868 return entry->u.index + (secinfo->contents + offset - p);