2 Copyright (C) 2001-2018 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 3 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., 51 Franklin Street - Fifth Floor, Boston,
20 MA 02110-1301, USA. */
23 /* This file contains support for merging duplicate entities within sections,
24 as used in ELF SHF_MERGE. */
31 #include "libiberty.h"
33 struct sec_merge_sec_info;
35 /* An entry in the section merge hash table. */
37 struct sec_merge_hash_entry
39 struct bfd_hash_entry root;
40 /* Length of this entry. This includes the zero terminator. */
42 /* Start of this string needs to be aligned to
43 alignment octets (not 1 << align). */
44 unsigned int alignment;
47 /* Index within the merged section. */
49 /* Entry this is a suffix of (if alignment is 0). */
50 struct sec_merge_hash_entry *suffix;
52 /* Which section is it in. */
53 struct sec_merge_sec_info *secinfo;
54 /* Next entity in the hash table. */
55 struct sec_merge_hash_entry *next;
58 /* The section merge hash table. */
62 struct bfd_hash_table table;
63 /* Next available index. */
65 /* First entity in the SEC_MERGE sections of this type. */
66 struct sec_merge_hash_entry *first;
67 /* Last entity in the SEC_MERGE sections of this type. */
68 struct sec_merge_hash_entry *last;
71 /* Are entries fixed size or zero terminated strings? */
77 /* Chain of sec_merge_infos. */
78 struct sec_merge_info *next;
79 /* Chain of sec_merge_sec_infos. */
80 struct sec_merge_sec_info *chain;
81 /* A hash table used to hold section content. */
82 struct sec_merge_hash *htab;
85 struct sec_merge_sec_info
87 /* Chain of sec_merge_sec_infos. */
88 struct sec_merge_sec_info *next;
89 /* The corresponding section. */
91 /* Pointer to merge_info pointing to us. */
93 /* A hash table used to hold section content. */
94 struct sec_merge_hash *htab;
95 /* First string in this section. */
96 struct sec_merge_hash_entry *first_str;
97 /* Original section content. */
98 unsigned char contents[1];
102 /* Routine to create an entry in a section merge hashtab. */
104 static struct bfd_hash_entry *
105 sec_merge_hash_newfunc (struct bfd_hash_entry *entry,
106 struct bfd_hash_table *table, const char *string)
108 /* Allocate the structure if it has not already been allocated by a
111 entry = (struct bfd_hash_entry *)
112 bfd_hash_allocate (table, sizeof (struct sec_merge_hash_entry));
116 /* Call the allocation method of the superclass. */
117 entry = bfd_hash_newfunc (entry, table, string);
121 /* Initialize the local fields. */
122 struct sec_merge_hash_entry *ret = (struct sec_merge_hash_entry *) entry;
124 ret->u.suffix = NULL;
133 /* Look up an entry in a section merge hash table. */
135 static struct sec_merge_hash_entry *
136 sec_merge_hash_lookup (struct sec_merge_hash *table, const char *string,
137 unsigned int alignment, bfd_boolean create)
139 const unsigned char *s;
142 struct sec_merge_hash_entry *hashp;
148 s = (const unsigned char *) string;
151 if (table->entsize == 1)
153 while ((c = *s++) != '\0')
155 hash += c + (c << 17);
159 hash += len + (len << 17);
165 for (i = 0; i < table->entsize; ++i)
168 if (i == table->entsize)
170 for (i = 0; i < table->entsize; ++i)
173 hash += c + (c << 17);
178 hash += len + (len << 17);
179 len *= table->entsize;
182 len += table->entsize;
186 for (i = 0; i < table->entsize; ++i)
189 hash += c + (c << 17);
192 len = table->entsize;
195 _index = hash % table->table.size;
196 for (hashp = (struct sec_merge_hash_entry *) table->table.table[_index];
198 hashp = (struct sec_merge_hash_entry *) hashp->root.next)
200 if (hashp->root.hash == hash
202 && memcmp (hashp->root.string, string, len) == 0)
204 /* If the string we found does not have at least the required
205 alignment, we need to insert another copy. */
206 if (hashp->alignment < alignment)
210 /* Mark the less aligned copy as deleted. */
212 hashp->alignment = 0;
223 hashp = ((struct sec_merge_hash_entry *)
224 bfd_hash_insert (&table->table, string, hash));
228 hashp->alignment = alignment;
232 /* Create a new hash table. */
234 static struct sec_merge_hash *
235 sec_merge_init (unsigned int entsize, bfd_boolean strings)
237 struct sec_merge_hash *table;
239 table = (struct sec_merge_hash *) bfd_malloc (sizeof (struct sec_merge_hash));
243 if (! bfd_hash_table_init_n (&table->table, sec_merge_hash_newfunc,
244 sizeof (struct sec_merge_hash_entry), 16699))
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 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,
288 unsigned char *contents, file_ptr offset)
290 struct sec_merge_sec_info *secinfo = entry->secinfo;
291 asection *sec = secinfo->sec;
293 bfd_size_type off = 0;
294 int alignment_power = sec->output_section->alignment_power;
295 bfd_size_type pad_len;
297 /* FIXME: If alignment_power is 0 then really we should scan the
298 entry list for the largest required alignment and use that. */
299 pad_len = alignment_power ? ((bfd_size_type) 1 << alignment_power) : 16;
301 pad = (char *) bfd_zmalloc (pad_len);
305 for (; entry != NULL && entry->secinfo == secinfo; entry = entry->next)
310 len = -off & (entry->alignment - 1);
313 BFD_ASSERT (len <= pad_len);
316 memcpy (contents + offset, pad, len);
319 else if (bfd_bwrite (pad, len, abfd) != len)
324 str = entry->root.string;
329 memcpy (contents + offset, str, len);
332 else if (bfd_bwrite (str, len, abfd) != len)
338 /* Trailing alignment needed? */
339 off = sec->size - off;
342 BFD_ASSERT (off <= pad_len);
344 memcpy (contents + offset, pad, off);
345 else if (bfd_bwrite (pad, off, abfd) != off)
357 /* Register a SEC_MERGE section as a candidate for merging.
358 This function is called for all non-dynamic SEC_MERGE input sections. */
361 _bfd_add_merge_section (bfd *abfd, void **psinfo, asection *sec,
364 struct sec_merge_info *sinfo;
365 struct sec_merge_sec_info *secinfo;
370 if ((abfd->flags & DYNAMIC) != 0
371 || (sec->flags & SEC_MERGE) == 0)
375 || (sec->flags & SEC_EXCLUDE) != 0
376 || sec->entsize == 0)
379 if (sec->size % sec->entsize != 0)
382 if ((sec->flags & SEC_RELOC) != 0)
384 /* We aren't prepared to handle relocations in merged sections. */
388 align = sec->alignment_power;
389 if ((sec->entsize < (unsigned) 1 << align
390 && ((sec->entsize & (sec->entsize - 1))
391 || !(sec->flags & SEC_STRINGS)))
392 || (sec->entsize > (unsigned) 1 << align
393 && (sec->entsize & (((unsigned) 1 << align) - 1))))
395 /* Sanity check. If string character size is smaller than
396 alignment, then we require character size to be a power
397 of 2, otherwise character size must be integer multiple
398 of alignment. For non-string constants, alignment must
399 be smaller than or equal to entity size and entity size
400 must be integer multiple of alignment. */
404 for (sinfo = (struct sec_merge_info *) *psinfo; sinfo; sinfo = sinfo->next)
405 if ((secinfo = sinfo->chain)
406 && ! ((secinfo->sec->flags ^ sec->flags) & (SEC_MERGE | SEC_STRINGS))
407 && secinfo->sec->entsize == sec->entsize
408 && secinfo->sec->alignment_power == sec->alignment_power
409 && secinfo->sec->output_section == sec->output_section)
414 /* Initialize the information we need to keep track of. */
415 sinfo = (struct sec_merge_info *)
416 bfd_alloc (abfd, sizeof (struct sec_merge_info));
419 sinfo->next = (struct sec_merge_info *) *psinfo;
422 sinfo->htab = sec_merge_init (sec->entsize, (sec->flags & SEC_STRINGS));
423 if (sinfo->htab == NULL)
427 /* Read the section from abfd. */
429 amt = sizeof (struct sec_merge_sec_info) - 1 + sec->size;
430 if (sec->flags & SEC_STRINGS)
431 /* Some versions of gcc may emit a string without a zero terminator.
432 See http://gcc.gnu.org/ml/gcc-patches/2006-06/msg01004.html
433 Allocate space for an extra zero. */
435 *psecinfo = bfd_alloc (abfd, amt);
436 if (*psecinfo == NULL)
439 secinfo = (struct sec_merge_sec_info *) *psecinfo;
442 secinfo->next = sinfo->chain->next;
443 sinfo->chain->next = secinfo;
446 secinfo->next = secinfo;
447 sinfo->chain = secinfo;
449 secinfo->psecinfo = psecinfo;
450 secinfo->htab = sinfo->htab;
451 secinfo->first_str = NULL;
453 sec->rawsize = sec->size;
454 if (sec->flags & SEC_STRINGS)
455 memset (secinfo->contents + sec->size, 0, sec->entsize);
456 contents = secinfo->contents;
457 if (! bfd_get_full_section_contents (sec->owner, sec, &contents))
467 /* Record one section into the hash table. */
469 record_section (struct sec_merge_info *sinfo,
470 struct sec_merge_sec_info *secinfo)
472 asection *sec = secinfo->sec;
473 struct sec_merge_hash_entry *entry;
475 unsigned char *p, *end;
476 bfd_vma mask, eltalign;
477 unsigned int align, i;
479 align = sec->alignment_power;
480 end = secinfo->contents + sec->size;
482 mask = ((bfd_vma) 1 << align) - 1;
483 if (sec->flags & SEC_STRINGS)
485 for (p = secinfo->contents; p < end; )
487 eltalign = p - secinfo->contents;
488 eltalign = ((eltalign ^ (eltalign - 1)) + 1) >> 1;
489 if (!eltalign || eltalign > mask)
491 entry = sec_merge_add (sinfo->htab, (char *) p, (unsigned) eltalign,
496 if (sec->entsize == 1)
498 while (p < end && *p == 0)
500 if (!nul && !((p - secinfo->contents) & mask))
503 entry = sec_merge_add (sinfo->htab, "",
504 (unsigned) mask + 1, secinfo);
515 for (i = 0; i < sec->entsize; i++)
518 if (i != sec->entsize)
520 if (!nul && !((p - secinfo->contents) & mask))
523 entry = sec_merge_add (sinfo->htab, (char *) p,
524 (unsigned) mask + 1, secinfo);
535 for (p = secinfo->contents; p < end; p += sec->entsize)
537 entry = sec_merge_add (sinfo->htab, (char *) p, 1, secinfo);
546 for (secinfo = sinfo->chain; secinfo; secinfo = secinfo->next)
547 *secinfo->psecinfo = NULL;
552 strrevcmp (const void *a, const void *b)
554 struct sec_merge_hash_entry *A = *(struct sec_merge_hash_entry **) a;
555 struct sec_merge_hash_entry *B = *(struct sec_merge_hash_entry **) b;
556 unsigned int lenA = A->len;
557 unsigned int lenB = B->len;
558 const unsigned char *s = (const unsigned char *) A->root.string + lenA - 1;
559 const unsigned char *t = (const unsigned char *) B->root.string + lenB - 1;
560 int l = lenA < lenB ? lenA : lenB;
565 return (int) *s - (int) *t;
573 /* Like strrevcmp, but for the case where all strings have the same
574 alignment > entsize. */
577 strrevcmp_align (const void *a, const void *b)
579 struct sec_merge_hash_entry *A = *(struct sec_merge_hash_entry **) a;
580 struct sec_merge_hash_entry *B = *(struct sec_merge_hash_entry **) b;
581 unsigned int lenA = A->len;
582 unsigned int lenB = B->len;
583 const unsigned char *s = (const unsigned char *) A->root.string + lenA - 1;
584 const unsigned char *t = (const unsigned char *) B->root.string + lenB - 1;
585 int l = lenA < lenB ? lenA : lenB;
586 int tail_align = (lenA & (A->alignment - 1)) - (lenB & (A->alignment - 1));
594 return (int) *s - (int) *t;
603 is_suffix (const struct sec_merge_hash_entry *A,
604 const struct sec_merge_hash_entry *B)
606 if (A->len <= B->len)
607 /* B cannot be a suffix of A unless A is equal to B, which is guaranteed
608 not to be equal by the hash table. */
611 return memcmp (A->root.string + (A->len - B->len),
612 B->root.string, B->len) == 0;
615 /* This is a helper function for _bfd_merge_sections. It attempts to
616 merge strings matching suffixes of longer strings. */
618 merge_strings (struct sec_merge_info *sinfo)
620 struct sec_merge_hash_entry **array, **a, *e;
621 struct sec_merge_sec_info *secinfo;
622 bfd_size_type size, amt;
623 unsigned int alignment = 0;
625 /* Now sort the strings */
626 amt = sinfo->htab->size * sizeof (struct sec_merge_hash_entry *);
627 array = (struct sec_merge_hash_entry **) bfd_malloc (amt);
631 for (e = sinfo->htab->first, a = array; e; e = e->next)
635 /* Adjust the length to not include the zero terminator. */
636 e->len -= sinfo->htab->entsize;
637 if (alignment != e->alignment)
640 alignment = e->alignment;
642 alignment = (unsigned) -1;
646 sinfo->htab->size = a - array;
647 if (sinfo->htab->size != 0)
649 qsort (array, (size_t) sinfo->htab->size,
650 sizeof (struct sec_merge_hash_entry *),
651 (alignment != (unsigned) -1 && alignment > sinfo->htab->entsize
652 ? strrevcmp_align : strrevcmp));
654 /* Loop over the sorted array and merge suffixes */
656 e->len += sinfo->htab->entsize;
659 struct sec_merge_hash_entry *cmp = *a;
661 cmp->len += sinfo->htab->entsize;
662 if (e->alignment >= cmp->alignment
663 && !((e->len - cmp->len) & (cmp->alignment - 1))
664 && is_suffix (e, cmp))
676 /* Now assign positions to the strings we want to keep. */
678 secinfo = sinfo->htab->first->secinfo;
679 for (e = sinfo->htab->first; e; e = e->next)
681 if (e->secinfo != secinfo)
683 secinfo->sec->size = size;
684 secinfo = e->secinfo;
688 if (e->secinfo->first_str == NULL)
690 e->secinfo->first_str = e;
693 size = (size + e->alignment - 1) & ~((bfd_vma) e->alignment - 1);
698 secinfo->sec->size = size;
699 if (secinfo->sec->alignment_power != 0)
701 bfd_size_type align = (bfd_size_type) 1 << secinfo->sec->alignment_power;
702 secinfo->sec->size = (secinfo->sec->size + align - 1) & -align;
705 /* And now adjust the rest, removing them from the chain (but not hashtable)
707 for (a = &sinfo->htab->first, e = *a; e; e = e->next)
715 e->secinfo = e->u.suffix->secinfo;
716 e->alignment = e->u.suffix->alignment;
717 e->u.index = e->u.suffix->u.index + (e->u.suffix->len - e->len);
723 /* This function is called once after all SEC_MERGE sections are registered
724 with _bfd_merge_section. */
727 _bfd_merge_sections (bfd *abfd,
728 struct bfd_link_info *info ATTRIBUTE_UNUSED,
730 void (*remove_hook) (bfd *, asection *))
732 struct sec_merge_info *sinfo;
734 for (sinfo = (struct sec_merge_info *) xsinfo; sinfo; sinfo = sinfo->next)
736 struct sec_merge_sec_info * secinfo;
741 /* Move sinfo->chain to head of the chain, terminate it. */
742 secinfo = sinfo->chain;
743 sinfo->chain = secinfo->next;
744 secinfo->next = NULL;
746 /* Record the sections into the hash table. */
747 for (secinfo = sinfo->chain; secinfo; secinfo = secinfo->next)
748 if (secinfo->sec->flags & SEC_EXCLUDE)
750 *secinfo->psecinfo = NULL;
752 (*remove_hook) (abfd, secinfo->sec);
754 else if (! record_section (sinfo, secinfo))
760 if (sinfo->htab->first == NULL)
763 if (sinfo->htab->strings)
765 if (!merge_strings (sinfo))
770 struct sec_merge_hash_entry *e;
771 bfd_size_type size = 0;
773 /* Things are much simpler for non-strings.
774 Just assign them slots in the section. */
776 for (e = sinfo->htab->first; e; e = e->next)
778 if (e->secinfo->first_str == NULL)
781 secinfo->sec->size = size;
782 e->secinfo->first_str = e;
785 size = (size + e->alignment - 1)
786 & ~((bfd_vma) e->alignment - 1);
789 secinfo = e->secinfo;
791 secinfo->sec->size = size;
794 /* Finally remove all input sections which have not made it into
795 the hash table at all. */
796 for (secinfo = sinfo->chain; secinfo; secinfo = secinfo->next)
797 if (secinfo->first_str == NULL)
798 secinfo->sec->flags |= SEC_EXCLUDE | SEC_KEEP;
804 /* Write out the merged section. */
807 _bfd_write_merged_section (bfd *output_bfd, asection *sec, void *psecinfo)
809 struct sec_merge_sec_info *secinfo;
811 unsigned char *contents;
812 Elf_Internal_Shdr *hdr;
814 secinfo = (struct sec_merge_sec_info *) psecinfo;
819 if (secinfo->first_str == NULL)
822 /* FIXME: octets_per_byte. */
823 hdr = &elf_section_data (sec->output_section)->this_hdr;
824 if (hdr->sh_offset == (file_ptr) -1)
826 /* We must compress this section. Write output to the
828 contents = hdr->contents;
829 if ((sec->output_section->flags & SEC_ELF_COMPRESS) == 0
836 pos = sec->output_section->filepos + sec->output_offset;
837 if (bfd_seek (output_bfd, pos, SEEK_SET) != 0)
841 if (! sec_merge_emit (output_bfd, secinfo->first_str, contents,
848 /* Adjust an address in the SEC_MERGE section. Given OFFSET within
849 *PSEC, this returns the new offset in the adjusted SEC_MERGE
850 section and writes the new section back into *PSEC. */
853 _bfd_merged_section_offset (bfd *output_bfd ATTRIBUTE_UNUSED, asection **psec,
854 void *psecinfo, bfd_vma offset)
856 struct sec_merge_sec_info *secinfo;
857 struct sec_merge_hash_entry *entry;
859 asection *sec = *psec;
861 secinfo = (struct sec_merge_sec_info *) psecinfo;
866 if (offset >= sec->rawsize)
868 if (offset > sec->rawsize)
870 /* xgettext:c-format */
871 (_("%pB: access beyond end of merged section (%" PRId64 ")"),
872 sec->owner, (int64_t) offset);
873 return secinfo->first_str ? sec->size : 0;
876 if (secinfo->htab->strings)
878 if (sec->entsize == 1)
880 p = secinfo->contents + offset - 1;
881 while (p >= secinfo->contents && *p)
887 p = secinfo->contents + (offset / sec->entsize) * sec->entsize;
889 while (p >= secinfo->contents)
893 for (i = 0; i < sec->entsize; ++i)
896 if (i == sec->entsize)
905 p = secinfo->contents + (offset / sec->entsize) * sec->entsize;
907 entry = sec_merge_hash_lookup (secinfo->htab, (char *) p, 0, FALSE);
910 if (! secinfo->htab->strings)
912 /* This should only happen if somebody points into the padding
913 after a NUL character but before next entity. */
916 if (! secinfo->htab->first)
918 entry = secinfo->htab->first;
919 p = (secinfo->contents + (offset / sec->entsize + 1) * sec->entsize
923 *psec = entry->secinfo->sec;
924 return entry->u.index + (secinfo->contents + offset - p);
927 /* Tidy up when done. */
930 _bfd_merge_sections_free (void *xsinfo)
932 struct sec_merge_info *sinfo;
934 for (sinfo = (struct sec_merge_info *) xsinfo; sinfo; sinfo = sinfo->next)
936 bfd_hash_table_free (&sinfo->htab->table);