1 /*
2 * CDDL HEADER START
3 *
4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License (the "License").
6 * You may not use this file except in compliance with the License.
7 *
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
12 *
13 * When distributing Covered Code, include this CDDL HEADER in each
14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 * If applicable, add the following below this CDDL HEADER, with the
16 * fields enclosed by brackets "[]" replaced with your own identifying
17 * information: Portions Copyright [yyyy] [name of copyright owner]
18 *
19 * CDDL HEADER END
20 */
21
22 /*
23 * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
24 * Copyright 2014 Nexenta Systems, Inc.
25 */
26
27 #include <string.h>
28 #include <stdio.h>
29 #include <sys/types.h>
30 #include <sgs.h>
31 #include <debug.h>
32 #include <_libld.h>
33 #include <dwarf.h>
34 #include <stdlib.h>
35
36 /*
37 * A EH_FRAME_HDR consists of the following:
38 *
39 * Encoding Field
40 * --------------------------------
41 * unsigned byte version
42 * unsigned byte eh_frame_ptr_enc
43 * unsigned byte fde_count_enc
44 * unsigned byte table_enc
45 * encoded eh_frame_ptr
46 * encoded fde_count
47 * [ binary search table ]
48 *
49 * The binary search table entries each consists of:
50 *
51 * encoded initial_func_loc
52 * encoded FDE_address
53 *
54 * The entries in the binary search table are sorted
55 * in a increasing order by the initial location.
56 *
57 *
58 * version
59 *
60 * Version of the .eh_frame_hdr format. This value shall be 1.
61 *
62 * eh_frame_ptr_enc
63 *
64 * The encoding format of the eh_frame_ptr field. For shared
65 * libraries the encoding must be
66 * DW_EH_PE_sdata4|DW_EH_PE_pcrel or
67 * DW_EH_PE_sdata4|DW_EH_PE_datarel.
68 *
69 *
70 * fde_count_enc
71 *
72 * The encoding format of the fde_count field. A value of
73 * DW_EH_PE_omit indicates the binary search table is not
74 * present.
75 *
76 * table_enc
77 *
78 * The encoding format of the entries in the binary search
79 * table. A value of DW_EH_PE_omit indicates the binary search
80 * table is not present. For shared libraries the encoding
81 * must be DW_EH_PE_sdata4|DW_EH_PE_pcrel or
82 * DW_EH_PE_sdata4|DW_EH_PE_datarel.
83 *
84 *
85 * eh_frame_ptr
86 *
87 * The encoded value of the pointer to the start of the
88 * .eh_frame section.
89 *
90 * fde_count
91 *
92 * The encoded value of the count of entries in the binary
93 * search table.
94 *
95 * binary search table
96 *
97 * A binary search table containing fde_count entries. Each
98 * entry of the table consist of two encoded values, the
99 * initial location of the function to which an FDE applies,
100 * and the address of the FDE. The entries are sorted in an
101 * increasing order by the initial location value.
102 *
103 */
104
105
106 /*
107 * EH_FRAME sections
108 * =================
109 *
110 * The call frame information needed for unwinding the stack is output in
111 * an ELF section(s) of type SHT_AMD64_UNWIND (amd64) or SHT_PROGBITS (other).
112 * In the simplest case there will be one such section per object file and it
113 * will be named ".eh_frame". An .eh_frame section consists of one or more
114 * subsections. Each subsection contains a CIE (Common Information Entry)
115 * followed by varying number of FDEs (Frame Descriptor Entry). A FDE
116 * corresponds to an explicit or compiler generated function in a
117 * compilation unit, all FDEs can access the CIE that begins their
118 * subsection for data.
119 *
120 * If an object file contains C++ template instantiations, there shall be
121 * a separate CIE immediately preceding each FDE corresponding to an
122 * instantiation.
123 *
124 * Using the preferred encoding specified below, the .eh_frame section can
125 * be entirely resolved at link time and thus can become part of the
126 * text segment.
127 *
128 * .eh_frame Section Layout
129 * ------------------------
130 *
131 * EH_PE encoding below refers to the pointer encoding as specified in the
132 * enhanced LSB Chapter 7 for Eh_Frame_Hdr.
133 *
134 * Common Information Entry (CIE)
135 * ------------------------------
136 * CIE has the following format:
137 *
138 * Length
139 * in
140 * Field Byte Description
141 * ----- ------ -----------
142 * 1. Length 4 Length of CIE (not including
143 * this 4-byte field).
144 *
145 * 2. CIE id 4 Value Zero (0) for .eh_frame
146 * (used to distinguish CIEs and
147 * FDEs when scanning the section)
148 *
149 * 3. Version 1 Value One (1)
150 *
151 * 4. CIE Augmentation string Null-terminated string with legal
152 * values being "" or 'z' optionally
153 * followed by single occurrences of
154 * 'P', 'L', or 'R' in any order.
155 * String The presence of character(s) in the
156 * string dictates the content of
157 * field 8, the Augmentation Section.
158 * Each character has one or two
159 * associated operands in the AS.
160 * Operand order depends on
161 * position in the string ('z' must
162 * be first).
163 *
164 * 5. Code Align Factor uleb128 To be multiplied with the
165 * "Advance Location" instructions in
166 * the Call Frame Instructions
167 *
168 * 6. Data Align Factor sleb128 To be multiplied with all offset
169 * in the Call Frame Instructions
170 *
171 * 7. Ret Address Reg 1 A "virtual" register representation
172 * of the return address. In Dwarf V2,
173 * this is a byte, otherwise it is
174 * uleb128. It is a byte in gcc 3.3.x
175 *
176 * 8. Optional CIE varying Present if Augmentation String in
177 * Augmentation Section field 4 is not 0.
178 *
179 * z:
180 * size uleb128 Length of the remainder of the
181 * Augmentation Section
182 *
183 * P:
184 * personality_enc 1 Encoding specifier - preferred
185 * value is a pc-relative, signed
186 * 4-byte
187 *
188 *
189 * personality routine (encoded) Encoded pointer to personality
190 * routine (actually to the PLT
191 * entry for the personality
192 * routine)
193 * R:
194 * code_enc 1 Non-default encoding for the
195 * code-pointers (FDE members
196 * "initial_location" and "address_range"
197 * and the operand for DW_CFA_set_loc)
198 * - preferred value is pc-relative,
199 * signed 4-byte.
200 * L:
201 * lsda_enc 1 FDE augmentation bodies may contain
202 * LSDA pointers. If so they are
203 * encoded as specified here -
204 * preferred value is pc-relative,
205 * signed 4-byte possibly indirect
206 * thru a GOT entry.
207 *
208 *
209 * 9. Optional Call Frame varying
210 * Instructions
211 *
212 * The size of the optional call frame instruction area must be computed
213 * based on the overall size and the offset reached while scanning the
214 * preceding fields of the CIE.
215 *
216 *
217 * Frame Descriptor Entry (FDE)
218 * ----------------------------
219 * FDE has the following format:
220 *
221 * Length
222 * in
223 * Field Byte Description
224 * ----- ------ -----------
225 * 1. Length 4 Length of remainder of this FDE
226 *
227 * 2. CIE Pointer 4 Distance from this field to the
228 * nearest preceding CIE
229 * (uthe value is subtracted from the
230 * current address). This value
231 * can never be zero and thus can
232 * be used to distinguish CIE's and
233 * FDE's when scanning the
234 * .eh_frame section
235 *
236 * 3. Initial Location varying Reference to the function code
237 * corresponding to this FDE.
238 * If 'R' is missing from the CIE
239 * Augmentation String, the field is an
240 * 8-byte absolute pointer. Otherwise,
241 * the corresponding EH_PE encoding in the
242 * CIE Augmentation Section is used to
243 * interpret the reference.
244 *
245 * 4. Address Range varying Size of the function code corresponding
246 * to this FDE.
247 * If 'R' is missing from the CIE
248 * Augmentation String, the field is an
249 * 8-byte unsigned number. Otherwise,
250 * the size is determined by the
251 * corresponding EH_PE encoding in the
252 * CIE Augmentation Section (the
253 * value is always absolute).
254 *
255 * 5. Optional FDE varying present if CIE augmentation
256 * Augmentation Section string is non-empty.
257 *
258 *
259 * 'z':
260 * length uleb128 length of the remainder of the
261 * FDE augmentation section
262 *
263 *
264 * 'L' (and length > 0):
265 * LSDA varying LSDA pointer, encoded in the
266 * format specified by the
267 * corresponding operand in the CIE's
268 * augmentation body.
269 *
270 * 6. Optional Call varying
271 * Frame Instructions
272 *
273 * The size of the optional call frame instruction area must be computed
274 * based on the overall size and the offset reached while scanning the
275 * preceding fields of the FDE.
276 *
277 * The overall size of a .eh_frame section is given in the ELF section
278 * header. The only way to determine the number of entries is to scan
279 * the section till the end and count.
280 *
281 */
282
283
284
285
286 static uint_t
287 extract_uint(const uchar_t *data, uint64_t *ndx, int do_swap)
288 {
289 uint_t r;
290 uchar_t *p = (uchar_t *)&r;
291
292 data += *ndx;
293 if (do_swap)
294 UL_ASSIGN_BSWAP_WORD(p, data);
295 else
296 UL_ASSIGN_WORD(p, data);
297
298 (*ndx) += 4;
299 return (r);
300 }
301
302 /*
303 * Create an unwind header (.eh_frame_hdr) output section.
304 * The section is created and space reserved, but the data
305 * is not copied into place. That is done by a later call
306 * to ld_unwind_populate(), after active relocations have been
307 * processed.
308 *
309 * When GNU linkonce processing is in effect, we can end up in a situation
310 * where the FDEs related to discarded sections remain in the eh_frame
311 * section. Ideally, we would remove these dead entries from eh_frame.
312 * However, that optimization has not yet been implemented. In the current
313 * implementation, the number of dead FDEs cannot be determined until
314 * active relocations are processed, and that processing follows the
315 * call to this function. This means that we are unable to detect dead FDEs
316 * here, and the section created by this routine is sized for maximum case
317 * where all FDEs are valid.
318 */
319 uintptr_t
320 ld_unwind_make_hdr(Ofl_desc *ofl)
321 {
322 int bswap = (ofl->ofl_flags1 & FLG_OF1_ENCDIFF) != 0;
323 Shdr *shdr;
324 Elf_Data *elfdata;
325 Is_desc *isp;
326 size_t size;
327 Xword fde_cnt;
328 Aliste idx1;
329 Os_desc *osp;
330
331 /*
332 * we only build a unwind header if we have
333 * some unwind information in the file.
334 */
335 if (ofl->ofl_unwind == NULL)
336 return (1);
337
338 /*
339 * Allocate and initialize the Elf_Data structure.
340 */
341 if ((elfdata = libld_calloc(sizeof (Elf_Data), 1)) == NULL)
342 return (S_ERROR);
343 elfdata->d_type = ELF_T_BYTE;
344 elfdata->d_align = ld_targ.t_m.m_word_align;
345 elfdata->d_version = ofl->ofl_dehdr->e_version;
346
347 /*
348 * Allocate and initialize the Shdr structure.
349 */
350 if ((shdr = libld_calloc(sizeof (Shdr), 1)) == NULL)
351 return (S_ERROR);
352 shdr->sh_type = ld_targ.t_m.m_sht_unwind;
353 shdr->sh_flags = SHF_ALLOC;
354 shdr->sh_addralign = ld_targ.t_m.m_word_align;
355 shdr->sh_entsize = 0;
356
357 /*
358 * Allocate and initialize the Is_desc structure.
359 */
360 if ((isp = libld_calloc(1, sizeof (Is_desc))) == NULL)
361 return (S_ERROR);
362 isp->is_name = MSG_ORIG(MSG_SCN_UNWINDHDR);
363 isp->is_shdr = shdr;
364 isp->is_indata = elfdata;
365
366 if ((ofl->ofl_unwindhdr = ld_place_section(ofl, isp, NULL,
367 ld_targ.t_id.id_unwindhdr, NULL)) == (Os_desc *)S_ERROR)
368 return (S_ERROR);
369
370 /*
371 * Scan through all of the input Frame information, counting each FDE
372 * that requires an index. Each fde_entry gets a corresponding entry
373 * in the binary search table.
374 */
375 fde_cnt = 0;
376 for (APLIST_TRAVERSE(ofl->ofl_unwind, idx1, osp)) {
377 Aliste idx2;
378 int os_isdescs_idx;
379
380 OS_ISDESCS_TRAVERSE(os_isdescs_idx, osp, idx2, isp) {
381 uchar_t *data;
382 uint64_t off = 0;
383
384 data = isp->is_indata->d_buf;
385 size = isp->is_indata->d_size;
386
387 while (off < size) {
388 uint_t length, id;
389 uint64_t ndx = 0;
390
391 /*
392 * Extract length in lsb format. A zero length
393 * indicates that this CIE is a terminator and
394 * that processing for unwind information is
395 * complete.
396 */
397 length = extract_uint(data + off, &ndx, bswap);
398 if (length == 0)
399 break;
400
401 /*
402 * Extract CIE id in lsb format.
403 */
404 id = extract_uint(data + off, &ndx, bswap);
405
406 /*
407 * A CIE record has a id of '0', otherwise
408 * this is a FDE entry and the 'id' is the
409 * CIE pointer.
410 */
411 if (id == 0) {
412 uint_t cieversion;
413 cieversion = data[off + ndx];
414 ndx += 1;
415 /* BEGIN CSTYLED */
416 if (cieversion != 1 && cieversion != 3) {
417 ld_eprintf(ofl, ERR_FATAL,
418 MSG_INTL(MSG_UNW_BADCIEVERS),
419 isp->is_file->ifl_name,
420 isp->is_name, off);
421 return (S_ERROR);
422 }
423 /* END CSTYLED */
424 } else {
425 fde_cnt++;
426 }
427 off += length + 4;
428 }
429 }
430 }
431
432 /*
433 * section size:
434 * byte version +1
435 * byte eh_frame_ptr_enc +1
436 * byte fde_count_enc +1
437 * byte table_enc +1
438 * 4 bytes eh_frame_ptr +4
439 * 4 bytes fde_count +4
440 * [4 bytes] [4bytes] * fde_count ...
441 */
442 size = 12 + (8 * fde_cnt);
443
444 if ((elfdata->d_buf = libld_calloc(size, 1)) == NULL)
445 return (S_ERROR);
446 elfdata->d_size = size;
447 shdr->sh_size = (Xword)size;
448
449 return (1);
450 }
451
452 /*
453 * the comparator function needs to calculate
454 * the actual 'initloc' of a bintab entry - to
455 * do this we initialize the following global to point
456 * to it.
457 */
458 static Addr framehdr_addr;
459
460 static int
461 bintabcompare(const void *p1, const void *p2)
462 {
463 uint_t *bintab1, *bintab2;
464 uint_t ent1, ent2;
465
466 bintab1 = (uint_t *)p1;
467 bintab2 = (uint_t *)p2;
468
469 assert(bintab1 != 0);
470 assert(bintab2 != 0);
471
472 ent1 = *bintab1 + framehdr_addr;
473 ent2 = *bintab2 + framehdr_addr;
474
475 if (ent1 > ent2)
476 return (1);
477 if (ent1 < ent2)
478 return (-1);
479 return (0);
480 }
481
482 uintptr_t
483 ld_unwind_populate_hdr(Ofl_desc *ofl)
484 {
485 uchar_t *hdrdata;
486 uint_t *binarytable;
487 uint_t hdroff;
488 Aliste idx;
489 Addr hdraddr;
490 Os_desc *hdrosp;
491 Os_desc *osp;
492 Os_desc *first_unwind;
493 uint_t fde_count;
494 uint_t *uint_ptr;
495 int bswap = (ofl->ofl_flags1 & FLG_OF1_ENCDIFF) != 0;
496
497 /*
498 * Are we building the unwind hdr?
499 */
500 if ((hdrosp = ofl->ofl_unwindhdr) == 0)
501 return (1);
502
503 hdrdata = hdrosp->os_outdata->d_buf;
504 hdraddr = hdrosp->os_shdr->sh_addr;
505 hdroff = 0;
506
507 /*
508 * version == 1
509 */
510 hdrdata[hdroff++] = 1;
511 /*
512 * The encodings are:
513 *
514 * eh_frameptr_enc sdata4 | pcrel
515 * fde_count_enc udata4
516 * table_enc sdata4 | datarel
517 */
518 hdrdata[hdroff++] = DW_EH_PE_sdata4 | DW_EH_PE_pcrel;
519 hdrdata[hdroff++] = DW_EH_PE_udata4;
520 hdrdata[hdroff++] = DW_EH_PE_sdata4 | DW_EH_PE_datarel;
521
522 /*
523 * Header Offsets
524 * -----------------------------------
525 * byte version +1
526 * byte eh_frame_ptr_enc +1
527 * byte fde_count_enc +1
528 * byte table_enc +1
529 * 4 bytes eh_frame_ptr +4
530 * 4 bytes fde_count +4
531 */
532 /* LINTED */
533 binarytable = (uint_t *)(hdrdata + 12);
534 first_unwind = 0;
535 fde_count = 0;
536
537 for (APLIST_TRAVERSE(ofl->ofl_unwind, idx, osp)) {
538 uchar_t *data;
539 size_t size;
540 uint64_t off = 0;
541 uint_t cieRflag = 0, ciePflag = 0;
542 Shdr *shdr;
543
544 /*
545 * remember first UNWIND section to
546 * point to in the frame_ptr entry.
547 */
548 if (first_unwind == 0)
549 first_unwind = osp;
550
551 data = osp->os_outdata->d_buf;
552 shdr = osp->os_shdr;
553 size = shdr->sh_size;
554
555 while (off < size) {
556 uint_t length, id;
557 uint64_t ndx = 0;
558
559 /*
560 * Extract length in lsb format. A zero length
561 * indicates that this CIE is a terminator and that
562 * processing of unwind information is complete.
563 */
564 length = extract_uint(data + off, &ndx, bswap);
565 if (length == 0)
566 goto done;
567
568 /*
569 * Extract CIE id in lsb format.
570 */
571 id = extract_uint(data + off, &ndx, bswap);
572
573 /*
574 * A CIE record has a id of '0'; otherwise
575 * this is a FDE entry and the 'id' is the
576 * CIE pointer.
577 */
578 if (id == 0) {
579 char *cieaugstr;
580 uint_t cieaugndx;
581 uint_t cieversion;
582
583 ciePflag = 0;
584 cieRflag = 0;
585 /*
586 * We need to drill through the CIE
587 * to find the Rflag. It's the Rflag
588 * which describes how the FDE code-pointers
589 * are encoded.
590 */
591
592 cieversion = data[off + ndx];
593 ndx += 1;
594
595 /*
596 * augstr
597 */
598 cieaugstr = (char *)(&data[off + ndx]);
599 ndx += strlen(cieaugstr) + 1;
600
601 /*
602 * calign & dalign
603 */
604 (void) uleb_extract(&data[off], &ndx);
605 (void) sleb_extract(&data[off], &ndx);
606
607 /*
608 * retreg
609 */
610 if (cieversion == 1)
611 ndx++;
612 else
613 (void) uleb_extract(&data[off], &ndx);
614 /*
615 * we walk through the augmentation
616 * section now looking for the Rflag
617 */
618 for (cieaugndx = 0; cieaugstr[cieaugndx];
619 cieaugndx++) {
620 /* BEGIN CSTYLED */
621 switch (cieaugstr[cieaugndx]) {
622 case 'z':
623 /* size */
624 (void) uleb_extract(&data[off],
625 &ndx);
626 break;
627 case 'P':
628 /* personality */
629 ciePflag = data[off + ndx];
630 ndx++;
631 /*
632 * Just need to extract the
633 * value to move on to the next
634 * field.
635 */
636 (void) dwarf_ehe_extract(
637 &data[off + ndx],
638 &ndx, ciePflag,
639 ofl->ofl_dehdr->e_ident, B_FALSE,
640 shdr->sh_addr, off + ndx, 0);
641 break;
642 case 'R':
643 /* code encoding */
644 cieRflag = data[off + ndx];
645 ndx++;
646 break;
647 case 'L':
648 /* lsda encoding */
649 ndx++;
650 break;
651 }
652 /* END CSTYLED */
653 }
654 } else {
655 uint_t bintabndx;
656 uint64_t initloc;
657 uint64_t fdeaddr;
658 uint64_t gotaddr = 0;
659
660 if (ofl->ofl_osgot != NULL)
661 gotaddr =
662 ofl->ofl_osgot->os_shdr->sh_addr;
663
664 initloc = dwarf_ehe_extract(&data[off],
665 &ndx, cieRflag, ofl->ofl_dehdr->e_ident,
666 B_FALSE,
667 shdr->sh_addr, off + ndx,
668 gotaddr);
669
670 /*
671 * Ignore FDEs with initloc set to 0.
672 * initloc will not be 0 unless this FDE was
673 * abandoned due to GNU linkonce processing.
674 * The 0 value occurs because we don't resolve
675 * sloppy relocations for unwind header target
676 * sections.
677 */
678 if (initloc != 0) {
679 bintabndx = fde_count * 2;
680 fde_count++;
681
682 /*
683 * FDEaddr is adjusted
684 * to account for the length & id which
685 * have already been consumed.
686 */
687 fdeaddr = shdr->sh_addr + off;
688
689 binarytable[bintabndx] =
690 (uint_t)(initloc - hdraddr);
691 binarytable[bintabndx + 1] =
692 (uint_t)(fdeaddr - hdraddr);
693 }
694 }
695
696 /*
697 * the length does not include the length
698 * itself - so account for that too.
699 */
700 off += length + 4;
701 }
702 }
703
704 done:
705 /*
706 * Do a quicksort on the binary table. If this is a cross
707 * link from a system with the opposite byte order, xlate
708 * the resulting values into LSB order.
709 */
710 framehdr_addr = hdraddr;
711 qsort((void *)binarytable, (size_t)fde_count,
712 (size_t)(sizeof (uint_t) * 2), bintabcompare);
713 if (bswap) {
714 uint_t *btable = binarytable;
715 uint_t cnt;
716
717 for (cnt = fde_count * 2; cnt-- > 0; btable++)
718 *btable = ld_bswap_Word(*btable);
719 }
720
721 /*
722 * Fill in:
723 * first_frame_ptr
724 * fde_count
725 */
726 hdroff = 4;
727 /* LINTED */
728 uint_ptr = (uint_t *)(&hdrdata[hdroff]);
729 *uint_ptr = first_unwind->os_shdr->sh_addr -
730 (hdrosp->os_shdr->sh_addr + hdroff);
731 if (bswap)
732 *uint_ptr = ld_bswap_Word(*uint_ptr);
733
734 hdroff += 4;
735 /* LINTED */
736 uint_ptr = (uint_t *)&hdrdata[hdroff];
737 *uint_ptr = fde_count;
738 if (bswap)
739 *uint_ptr = ld_bswap_Word(*uint_ptr);
740
741 /*
742 * If relaxed relocations are active, then there is a chance
743 * that we didn't use all the space reserved for this section.
744 * For details, see the note at head of ld_unwind_make_hdr() above.
745 *
746 * Find the PT_SUNW_UNWIND program header, and change the size values
747 * to the size of the subset of the section that was actually used.
748 */
749 if (ofl->ofl_flags1 & FLG_OF1_RLXREL) {
750 Word phnum = ofl->ofl_nehdr->e_phnum;
751 Phdr *phdr = ofl->ofl_phdr;
752
753 for (; phnum-- > 0; phdr++) {
754 if (phdr->p_type == PT_SUNW_UNWIND) {
755 phdr->p_memsz = 12 + (8 * fde_count);
756 phdr->p_filesz = phdr->p_memsz;
757 break;
758 }
759 }
760 }
761
762 return (1);
763 }
764
765 /*
766 * Append an .eh_frame section to our output list if not already present.
767 *
768 * Usually, there is a single .eh_frame output section. However, there can
769 * be more if there are incompatible section flags on incoming sections.
770 * If this does happen, the frame_ptr field of the eh_frame_hdr section
771 * will point at the base of the first output section, and the other
772 * sections will not be accessible via frame_ptr. However, the .eh_frame_hdr
773 * will be able to access all the data in the different .eh_frame sections,
774 * because the entries in sorted table are all encoded as DW_EH_PE_datarel.
775 */
776 uintptr_t
777 ld_unwind_register(Os_desc *osp, Ofl_desc * ofl)
778 {
779 Aliste idx;
780 Os_desc *_osp;
781 /*
782 * Check to see if this output section is already
783 * on the list.
784 */
785 for (APLIST_TRAVERSE(ofl->ofl_unwind, idx, _osp))
786 if (osp == _osp)
787 return (1);
788
789 /*
790 * Append output section to unwind list
791 */
792 if (aplist_append(&ofl->ofl_unwind, osp, AL_CNT_OFL_UNWIND) == NULL)
793 return (S_ERROR);
794
795 return (1);
796 }