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->flags & SEC_RELOC) != 0)
381 /* We aren't prepared to handle relocations in merged sections. */
385 align = sec->alignment_power;
386 if ((sec->entsize < (unsigned) 1 << align
387 && ((sec->entsize & (sec->entsize - 1))
388 || !(sec->flags & SEC_STRINGS)))
389 || (sec->entsize > (unsigned) 1 << align
390 && (sec->entsize & (((unsigned) 1 << align) - 1))))
392 /* Sanity check. If string character size is smaller than
393 alignment, then we require character size to be a power
394 of 2, otherwise character size must be integer multiple
395 of alignment. For non-string constants, alignment must
396 be smaller than or equal to entity size and entity size
397 must be integer multiple of alignment. */
401 for (sinfo = (struct sec_merge_info *) *psinfo; sinfo; sinfo = sinfo->next)
402 if ((secinfo = sinfo->chain)
403 && ! ((secinfo->sec->flags ^ sec->flags) & (SEC_MERGE | SEC_STRINGS))
404 && secinfo->sec->entsize == sec->entsize
405 && secinfo->sec->alignment_power == sec->alignment_power
406 && secinfo->sec->output_section == sec->output_section)
411 /* Initialize the information we need to keep track of. */
412 sinfo = (struct sec_merge_info *)
413 bfd_alloc (abfd, sizeof (struct sec_merge_info));
416 sinfo->next = (struct sec_merge_info *) *psinfo;
419 sinfo->htab = sec_merge_init (sec->entsize, (sec->flags & SEC_STRINGS));
420 if (sinfo->htab == NULL)
424 /* Read the section from abfd. */
426 amt = sizeof (struct sec_merge_sec_info) - 1 + sec->size;
427 if (sec->flags & SEC_STRINGS)
428 /* Some versions of gcc may emit a string without a zero terminator.
429 See http://gcc.gnu.org/ml/gcc-patches/2006-06/msg01004.html
430 Allocate space for an extra zero. */
432 *psecinfo = bfd_alloc (abfd, amt);
433 if (*psecinfo == NULL)
436 secinfo = (struct sec_merge_sec_info *) *psecinfo;
439 secinfo->next = sinfo->chain->next;
440 sinfo->chain->next = secinfo;
443 secinfo->next = secinfo;
444 sinfo->chain = secinfo;
446 secinfo->psecinfo = psecinfo;
447 secinfo->htab = sinfo->htab;
448 secinfo->first_str = NULL;
450 sec->rawsize = sec->size;
451 if (sec->flags & SEC_STRINGS)
452 memset (secinfo->contents + sec->size, 0, sec->entsize);
453 contents = secinfo->contents;
454 if (! bfd_get_full_section_contents (sec->owner, sec, &contents))
464 /* Record one section into the hash table. */
466 record_section (struct sec_merge_info *sinfo,
467 struct sec_merge_sec_info *secinfo)
469 asection *sec = secinfo->sec;
470 struct sec_merge_hash_entry *entry;
472 unsigned char *p, *end;
473 bfd_vma mask, eltalign;
474 unsigned int align, i;
476 align = sec->alignment_power;
477 end = secinfo->contents + sec->size;
479 mask = ((bfd_vma) 1 << align) - 1;
480 if (sec->flags & SEC_STRINGS)
482 for (p = secinfo->contents; p < end; )
484 eltalign = p - secinfo->contents;
485 eltalign = ((eltalign ^ (eltalign - 1)) + 1) >> 1;
486 if (!eltalign || eltalign > mask)
488 entry = sec_merge_add (sinfo->htab, (char *) p, (unsigned) eltalign,
493 if (sec->entsize == 1)
495 while (p < end && *p == 0)
497 if (!nul && !((p - secinfo->contents) & mask))
500 entry = sec_merge_add (sinfo->htab, "",
501 (unsigned) mask + 1, secinfo);
512 for (i = 0; i < sec->entsize; i++)
515 if (i != sec->entsize)
517 if (!nul && !((p - secinfo->contents) & mask))
520 entry = sec_merge_add (sinfo->htab, (char *) p,
521 (unsigned) mask + 1, secinfo);
532 for (p = secinfo->contents; p < end; p += sec->entsize)
534 entry = sec_merge_add (sinfo->htab, (char *) p, 1, secinfo);
543 for (secinfo = sinfo->chain; secinfo; secinfo = secinfo->next)
544 *secinfo->psecinfo = NULL;
549 strrevcmp (const void *a, const void *b)
551 struct sec_merge_hash_entry *A = *(struct sec_merge_hash_entry **) a;
552 struct sec_merge_hash_entry *B = *(struct sec_merge_hash_entry **) b;
553 unsigned int lenA = A->len;
554 unsigned int lenB = B->len;
555 const unsigned char *s = (const unsigned char *) A->root.string + lenA - 1;
556 const unsigned char *t = (const unsigned char *) B->root.string + lenB - 1;
557 int l = lenA < lenB ? lenA : lenB;
562 return (int) *s - (int) *t;
570 /* Like strrevcmp, but for the case where all strings have the same
571 alignment > entsize. */
574 strrevcmp_align (const void *a, const void *b)
576 struct sec_merge_hash_entry *A = *(struct sec_merge_hash_entry **) a;
577 struct sec_merge_hash_entry *B = *(struct sec_merge_hash_entry **) b;
578 unsigned int lenA = A->len;
579 unsigned int lenB = B->len;
580 const unsigned char *s = (const unsigned char *) A->root.string + lenA - 1;
581 const unsigned char *t = (const unsigned char *) B->root.string + lenB - 1;
582 int l = lenA < lenB ? lenA : lenB;
583 int tail_align = (lenA & (A->alignment - 1)) - (lenB & (A->alignment - 1));
591 return (int) *s - (int) *t;
600 is_suffix (const struct sec_merge_hash_entry *A,
601 const struct sec_merge_hash_entry *B)
603 if (A->len <= B->len)
604 /* B cannot be a suffix of A unless A is equal to B, which is guaranteed
605 not to be equal by the hash table. */
608 return memcmp (A->root.string + (A->len - B->len),
609 B->root.string, B->len) == 0;
612 /* This is a helper function for _bfd_merge_sections. It attempts to
613 merge strings matching suffixes of longer strings. */
615 merge_strings (struct sec_merge_info *sinfo)
617 struct sec_merge_hash_entry **array, **a, *e;
618 struct sec_merge_sec_info *secinfo;
619 bfd_size_type size, amt;
620 unsigned int alignment = 0;
622 /* Now sort the strings */
623 amt = sinfo->htab->size * sizeof (struct sec_merge_hash_entry *);
624 array = (struct sec_merge_hash_entry **) bfd_malloc (amt);
628 for (e = sinfo->htab->first, a = array; e; e = e->next)
632 /* Adjust the length to not include the zero terminator. */
633 e->len -= sinfo->htab->entsize;
634 if (alignment != e->alignment)
637 alignment = e->alignment;
639 alignment = (unsigned) -1;
643 sinfo->htab->size = a - array;
644 if (sinfo->htab->size != 0)
646 qsort (array, (size_t) sinfo->htab->size,
647 sizeof (struct sec_merge_hash_entry *),
648 (alignment != (unsigned) -1 && alignment > sinfo->htab->entsize
649 ? strrevcmp_align : strrevcmp));
651 /* Loop over the sorted array and merge suffixes */
653 e->len += sinfo->htab->entsize;
656 struct sec_merge_hash_entry *cmp = *a;
658 cmp->len += sinfo->htab->entsize;
659 if (e->alignment >= cmp->alignment
660 && !((e->len - cmp->len) & (cmp->alignment - 1))
661 && is_suffix (e, cmp))
673 /* Now assign positions to the strings we want to keep. */
675 secinfo = sinfo->htab->first->secinfo;
676 for (e = sinfo->htab->first; e; e = e->next)
678 if (e->secinfo != secinfo)
680 secinfo->sec->size = size;
681 secinfo = e->secinfo;
685 if (e->secinfo->first_str == NULL)
687 e->secinfo->first_str = e;
690 size = (size + e->alignment - 1) & ~((bfd_vma) e->alignment - 1);
695 secinfo->sec->size = size;
696 if (secinfo->sec->alignment_power != 0)
698 bfd_size_type align = (bfd_size_type) 1 << secinfo->sec->alignment_power;
699 secinfo->sec->size = (secinfo->sec->size + align - 1) & -align;
702 /* And now adjust the rest, removing them from the chain (but not hashtable)
704 for (a = &sinfo->htab->first, e = *a; e; e = e->next)
712 e->secinfo = e->u.suffix->secinfo;
713 e->alignment = e->u.suffix->alignment;
714 e->u.index = e->u.suffix->u.index + (e->u.suffix->len - e->len);
720 /* This function is called once after all SEC_MERGE sections are registered
721 with _bfd_merge_section. */
724 _bfd_merge_sections (bfd *abfd,
725 struct bfd_link_info *info ATTRIBUTE_UNUSED,
727 void (*remove_hook) (bfd *, asection *))
729 struct sec_merge_info *sinfo;
731 for (sinfo = (struct sec_merge_info *) xsinfo; sinfo; sinfo = sinfo->next)
733 struct sec_merge_sec_info * secinfo;
738 /* Move sinfo->chain to head of the chain, terminate it. */
739 secinfo = sinfo->chain;
740 sinfo->chain = secinfo->next;
741 secinfo->next = NULL;
743 /* Record the sections into the hash table. */
744 for (secinfo = sinfo->chain; secinfo; secinfo = secinfo->next)
745 if (secinfo->sec->flags & SEC_EXCLUDE)
747 *secinfo->psecinfo = NULL;
749 (*remove_hook) (abfd, secinfo->sec);
751 else if (! record_section (sinfo, secinfo))
757 if (sinfo->htab->first == NULL)
760 if (sinfo->htab->strings)
762 if (!merge_strings (sinfo))
767 struct sec_merge_hash_entry *e;
768 bfd_size_type size = 0;
770 /* Things are much simpler for non-strings.
771 Just assign them slots in the section. */
773 for (e = sinfo->htab->first; e; e = e->next)
775 if (e->secinfo->first_str == NULL)
778 secinfo->sec->size = size;
779 e->secinfo->first_str = e;
782 size = (size + e->alignment - 1)
783 & ~((bfd_vma) e->alignment - 1);
786 secinfo = e->secinfo;
788 secinfo->sec->size = size;
791 /* Finally remove all input sections which have not made it into
792 the hash table at all. */
793 for (secinfo = sinfo->chain; secinfo; secinfo = secinfo->next)
794 if (secinfo->first_str == NULL)
795 secinfo->sec->flags |= SEC_EXCLUDE | SEC_KEEP;
801 /* Write out the merged section. */
804 _bfd_write_merged_section (bfd *output_bfd, asection *sec, void *psecinfo)
806 struct sec_merge_sec_info *secinfo;
808 unsigned char *contents;
809 Elf_Internal_Shdr *hdr;
811 secinfo = (struct sec_merge_sec_info *) psecinfo;
816 if (secinfo->first_str == NULL)
819 /* FIXME: octets_per_byte. */
820 hdr = &elf_section_data (sec->output_section)->this_hdr;
821 if (hdr->sh_offset == (file_ptr) -1)
823 /* We must compress this section. Write output to the
825 contents = hdr->contents;
826 if ((sec->output_section->flags & SEC_ELF_COMPRESS) == 0
833 pos = sec->output_section->filepos + sec->output_offset;
834 if (bfd_seek (output_bfd, pos, SEEK_SET) != 0)
838 if (! sec_merge_emit (output_bfd, secinfo->first_str, contents,
845 /* Adjust an address in the SEC_MERGE section. Given OFFSET within
846 *PSEC, this returns the new offset in the adjusted SEC_MERGE
847 section and writes the new section back into *PSEC. */
850 _bfd_merged_section_offset (bfd *output_bfd ATTRIBUTE_UNUSED, asection **psec,
851 void *psecinfo, bfd_vma offset)
853 struct sec_merge_sec_info *secinfo;
854 struct sec_merge_hash_entry *entry;
856 asection *sec = *psec;
858 secinfo = (struct sec_merge_sec_info *) psecinfo;
863 if (offset >= sec->rawsize)
865 if (offset > sec->rawsize)
867 /* xgettext:c-format */
868 (_("%pB: access beyond end of merged section (%Ld)"),
870 return secinfo->first_str ? sec->size : 0;
873 if (secinfo->htab->strings)
875 if (sec->entsize == 1)
877 p = secinfo->contents + offset - 1;
878 while (p >= secinfo->contents && *p)
884 p = secinfo->contents + (offset / sec->entsize) * sec->entsize;
886 while (p >= secinfo->contents)
890 for (i = 0; i < sec->entsize; ++i)
893 if (i == sec->entsize)
902 p = secinfo->contents + (offset / sec->entsize) * sec->entsize;
904 entry = sec_merge_hash_lookup (secinfo->htab, (char *) p, 0, FALSE);
907 if (! secinfo->htab->strings)
909 /* This should only happen if somebody points into the padding
910 after a NUL character but before next entity. */
913 if (! secinfo->htab->first)
915 entry = secinfo->htab->first;
916 p = (secinfo->contents + (offset / sec->entsize + 1) * sec->entsize
920 *psec = entry->secinfo->sec;
921 return entry->u.index + (secinfo->contents + offset - p);
924 /* Tidy up when done. */
927 _bfd_merge_sections_free (void *xsinfo)
929 struct sec_merge_info *sinfo;
931 for (sinfo = (struct sec_merge_info *) xsinfo; sinfo; sinfo = sinfo->next)
933 bfd_hash_table_free (&sinfo->htab->table);