xref: /illumos-gate/usr/src/cmd/sgs/libld/common/outfile.c (revision fb12490ab4d1e87e7a63e457dd4fba1ea34c402a)
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) 1988 AT&T
24  *	  All Rights Reserved
25  *
26  * Copyright (c) 1989, 2010, Oracle and/or its affiliates. All rights reserved.
27  *
28  * Copyright 2011, Richard Lowe.
29  */
30 
31 /*
32  * This file contains the functions responsible for opening the output file
33  * image, associating the appropriate input elf structures with the new image,
34  * and obtaining new elf structures to define the new image.
35  */
36 #include	<stdio.h>
37 #include	<sys/stat.h>
38 #include	<fcntl.h>
39 #include	<link.h>
40 #include	<errno.h>
41 #include	<string.h>
42 #include	<limits.h>
43 #include	<debug.h>
44 #include	<unistd.h>
45 #include	"msg.h"
46 #include	"_libld.h"
47 
48 /*
49  * Determine a least common multiplier.  Input sections contain an alignment
50  * requirement, which elf_update() uses to insure that the section is aligned
51  * correctly off of the base of the elf image.  We must also insure that the
52  * sections mapping is congruent with this alignment requirement.  For each
53  * input section associated with a loadable segment determine whether the
54  * segments alignment must be adjusted to compensate for a sections alignment
55  * requirements.
56  */
57 Xword
ld_lcm(Xword a,Xword b)58 ld_lcm(Xword a, Xword b)
59 {
60 	Xword	_r, _a, _b;
61 
62 	if ((_a = a) == 0)
63 		return (b);
64 	if ((_b = b) == 0)
65 		return (a);
66 
67 	if (_a > _b)
68 		_a = b, _b = a;
69 	while ((_r = _b % _a) != 0)
70 		_b = _a, _a = _r;
71 	return ((a / _a) * b);
72 }
73 
74 /*
75  * Open the output file and insure the correct access modes.
76  */
77 uintptr_t
ld_open_outfile(Ofl_desc * ofl)78 ld_open_outfile(Ofl_desc * ofl)
79 {
80 	mode_t		mode;
81 	struct stat	status;
82 
83 	/*
84 	 * Determine the required file mode from the type of output file we
85 	 * are creating.
86 	 */
87 	mode = (ofl->ofl_flags & (FLG_OF_EXEC | FLG_OF_SHAROBJ))
88 	    ? 0777 : 0666;
89 
90 	/* Determine if the output file already exists */
91 	if (stat(ofl->ofl_name, &status) == 0) {
92 		if ((status.st_mode & S_IFMT) != S_IFREG) {
93 			/*
94 			 * It is not a regular file, so don't delete it
95 			 * or allow it to be deleted.  This allows root
96 			 * users to specify /dev/null output file for
97 			 * verification links.
98 			 */
99 			ofl->ofl_flags1 |= FLG_OF1_NONREG;
100 		} else {
101 			/*
102 			 * It's a regular file, so unlink it. In standard
103 			 * Unix fashion, the old file will continue to
104 			 * exist until its link count drops to 0 and no
105 			 * process has the file open. In the meantime, we
106 			 * create a new file (inode) under the same name,
107 			 * available for new use.
108 			 *
109 			 * The advantage of this policy is that creating
110 			 * a new executable or sharable library does not
111 			 * corrupt existing processes using the old file.
112 			 * A possible disadvantage is that if the existing
113 			 * file has a (link_count > 1), the other names will
114 			 * continue to reference the old inode, thus
115 			 * breaking the link.
116 			 *
117 			 * A subtlety here is that POSIX says we are not
118 			 * supposed to replace a non-writable file, which
119 			 * is something that unlink() is happy to do. The
120 			 * only 100% reliable test against this is to open
121 			 * the file for non-destructive write access. If the
122 			 * open succeeds, we are clear to unlink it, and if
123 			 * not, then the error generated is the error we
124 			 * need to report.
125 			 */
126 			if ((ofl->ofl_fd = open(ofl->ofl_name, O_RDWR,
127 			    mode)) < 0) {
128 				int	err = errno;
129 
130 				if (err != ENOENT) {
131 					ld_eprintf(ofl, ERR_FATAL,
132 					    MSG_INTL(MSG_SYS_OPEN),
133 					    ofl->ofl_name, strerror(err));
134 					return (S_ERROR);
135 				}
136 			} else {
137 				(void) close(ofl->ofl_fd);
138 			}
139 
140 			if ((unlink(ofl->ofl_name) == -1) &&
141 			    (errno != ENOENT)) {
142 				int err = errno;
143 
144 				ld_eprintf(ofl, ERR_FATAL,
145 				    MSG_INTL(MSG_SYS_UNLINK),
146 				    ofl->ofl_name, strerror(err));
147 				return (S_ERROR);
148 			}
149 		}
150 	}
151 
152 	/*
153 	 * Open (or create) the output file name (ofl_fd acts as a global
154 	 * flag to ldexit() signifying whether the output file should be
155 	 * removed or not on error).
156 	 */
157 	if ((ofl->ofl_fd = open(ofl->ofl_name, O_RDWR | O_CREAT | O_TRUNC,
158 	    mode)) < 0) {
159 		int	err = errno;
160 
161 		ld_eprintf(ofl, ERR_FATAL, MSG_INTL(MSG_SYS_OPEN),
162 		    ofl->ofl_name, strerror(err));
163 		return (S_ERROR);
164 	}
165 
166 	return (1);
167 }
168 
169 
170 /*
171  * If we are creating a memory model we need to update the present memory image.
172  * Use elf_update(ELF_C_NULL) to calculate the offset of each section and their
173  * associated data buffers.  From this information determine what padding is
174  * required.
175  *
176  * Two actions are necessary to convert the present disc image into a memory
177  * image:
178  *
179  *  -	Loadable segments must be padded so that the next segment virtual
180  *	address and file offset are the same.
181  *
182  *  -	NOBITS sections must be converted into allocated, null filled sections.
183  */
184 static uintptr_t
pad_outfile(Ofl_desc * ofl)185 pad_outfile(Ofl_desc *ofl)
186 {
187 	Aliste		idx1;
188 	off_t		offset;
189 	Elf_Scn		*oscn = 0;
190 	Sg_desc		*sgp;
191 	Ehdr		*ehdr;
192 
193 	/*
194 	 * Update all the elf structures.  This will assign offsets to the
195 	 * section headers and data buffers as they relate to the new image.
196 	 */
197 	if (elf_update(ofl->ofl_welf, ELF_C_NULL) == -1) {
198 		ld_eprintf(ofl, ERR_ELF, MSG_INTL(MSG_ELF_UPDATE),
199 		    ofl->ofl_name);
200 		return (S_ERROR);
201 	}
202 	if ((ehdr = elf_getehdr(ofl->ofl_welf)) == NULL) {
203 		ld_eprintf(ofl, ERR_ELF, MSG_INTL(MSG_ELF_GETEHDR),
204 		    ofl->ofl_name);
205 		return (S_ERROR);
206 	}
207 
208 	/*
209 	 * Initialize the offset by skipping the Elf header and program
210 	 * headers.
211 	 */
212 	offset = ehdr->e_phoff + (ehdr->e_phnum * ehdr->e_phentsize);
213 
214 	/*
215 	 * Traverse the segment list looking for loadable segments.
216 	 */
217 	for (APLIST_TRAVERSE(ofl->ofl_segs, idx1, sgp)) {
218 		Phdr	*phdr = &(sgp->sg_phdr);
219 		Os_desc	*osp;
220 		Aliste	idx2;
221 
222 		/*
223 		 * If we've already processed a loadable segment, the `scn'
224 		 * variable will be initialized to the last section that was
225 		 * part of that segment.  Add sufficient padding to this section
226 		 * to cause the next segments virtual address and file offset to
227 		 * be the same.
228 		 */
229 		if (oscn && (phdr->p_type == PT_LOAD)) {
230 			Elf_Data *	data;
231 			size_t		size;
232 
233 			size = (size_t)(S_ROUND(offset, phdr->p_align) -
234 			    offset);
235 
236 			if ((data = elf_newdata(oscn)) == NULL) {
237 				ld_eprintf(ofl, ERR_ELF,
238 				    MSG_INTL(MSG_ELF_NEWDATA), ofl->ofl_name);
239 				return (S_ERROR);
240 			}
241 			if ((data->d_buf = libld_calloc(1, size)) == NULL)
242 				return (S_ERROR);
243 
244 			data->d_type = ELF_T_BYTE;
245 			data->d_size = size;
246 			data->d_align = 1;
247 			data->d_version = ofl->ofl_dehdr->e_version;
248 		}
249 
250 		/*
251 		 * Traverse the output sections for this segment calculating the
252 		 * offset of each section. Retain the final section descriptor
253 		 * as this will be where any padding buffer will be added.
254 		 */
255 		for (APLIST_TRAVERSE(sgp->sg_osdescs, idx2, osp)) {
256 			Shdr	*shdr = osp->os_shdr;
257 
258 			offset = (off_t)S_ROUND(offset, shdr->sh_addralign);
259 			offset += shdr->sh_size;
260 
261 			/*
262 			 * If this is a NOBITS output section convert all of
263 			 * its associated input sections into real, null filled,
264 			 * data buffers, and change the section to PROGBITS.
265 			 */
266 			if (shdr->sh_type == SHT_NOBITS)
267 				shdr->sh_type = SHT_PROGBITS;
268 		}
269 
270 		/*
271 		 * If this is a loadable segment retain the last output section
272 		 * descriptor.  This acts both as a flag that a loadable
273 		 * segment has been seen, and as the segment to which a padding
274 		 * buffer will be added.
275 		 */
276 		if (phdr->p_type == PT_LOAD)
277 			oscn = osp->os_scn;
278 	}
279 	return (1);
280 }
281 
282 /*
283  * Create an output section.  The first instance of an input section triggers
284  * the creation of a new output section.
285  */
286 static uintptr_t
create_outsec(Ofl_desc * ofl,Sg_desc * sgp,Os_desc * osp,Word ptype,int shidx,Boolean fixalign)287 create_outsec(Ofl_desc *ofl, Sg_desc *sgp, Os_desc *osp, Word ptype, int shidx,
288     Boolean fixalign)
289 {
290 	Elf_Scn	*scn;
291 	Shdr	*shdr;
292 
293 	/*
294 	 * Get a section descriptor for the section.
295 	 */
296 	if ((scn = elf_newscn(ofl->ofl_welf)) == NULL) {
297 		ld_eprintf(ofl, ERR_ELF, MSG_INTL(MSG_ELF_NEWSCN),
298 		    ofl->ofl_name);
299 		return (S_ERROR);
300 	}
301 	osp->os_scn = scn;
302 
303 	/*
304 	 * Get a new section header table entry and copy the pertinent
305 	 * information from the in-core descriptor.
306 	 */
307 	if ((shdr = elf_getshdr(scn)) == NULL) {
308 		ld_eprintf(ofl, ERR_ELF, MSG_INTL(MSG_ELF_GETSHDR),
309 		    ofl->ofl_name);
310 		return (S_ERROR);
311 	}
312 	*shdr = *(osp->os_shdr);
313 	osp->os_shdr = shdr;
314 
315 	/*
316 	 * If this is the first section within a loadable segment, and the
317 	 * alignment needs to be updated, record this section.
318 	 */
319 	if ((fixalign == TRUE) && (ptype == PT_LOAD) && (shidx == 1))
320 		sgp->sg_fscn = scn;
321 
322 	/*
323 	 * If not building a relocatable object, remove any of the
324 	 * following flags, as they have been acted upon and are not
325 	 * meaningful in the output:
326 	 *	SHF_ORDERED, SHF_LINK_ORDER, SHF_GROUP
327 	 * For relocatable objects, we allow them to propagate to
328 	 * the output object to be handled by the next linker that
329 	 * sees them.
330 	 */
331 	if ((ofl->ofl_flags & FLG_OF_RELOBJ) == 0)
332 		osp->os_shdr->sh_flags &= ~(ALL_SHF_ORDER|SHF_GROUP);
333 
334 	/*
335 	 * If this is a TLS section, save it so that the PT_TLS program header
336 	 * information can be established after the output image has been
337 	 * initially created.  At this point, all TLS input sections are ordered
338 	 * as they will appear in the output image.
339 	 */
340 	if ((ofl->ofl_flags & FLG_OF_TLSPHDR) &&
341 	    (osp->os_shdr->sh_flags & SHF_TLS) &&
342 	    (aplist_append(&ofl->ofl_ostlsseg, osp,
343 	    AL_CNT_OFL_OSTLSSEG) == NULL))
344 		return (S_ERROR);
345 
346 	return (0);
347 }
348 
349 /*
350  * Create the elf structures that allow the input data to be associated with the
351  * new image:
352  *
353  *  -	define the new elf image using elf_begin(),
354  *
355  *  -	obtain an elf header for the image,
356  *
357  *  -	traverse the input segments and create a program header array to define
358  *	the required segments,
359  *
360  *  -	traverse the output sections for each segment assigning a new section
361  *	descriptor and section header for each,
362  *
363  *  -	traverse the input sections associated with each output section and
364  *	assign a new data descriptor to each (each output section becomes a
365  *	linked list of input data buffers).
366  */
367 uintptr_t
ld_create_outfile(Ofl_desc * ofl)368 ld_create_outfile(Ofl_desc *ofl)
369 {
370 	Sg_desc		*sgp;
371 	Os_desc		*osp;
372 	Is_desc		*isp;
373 	Elf_Data	*tlsdata = 0;
374 	Aliste		idx1;
375 	ofl_flag_t	flags = ofl->ofl_flags;
376 	ofl_flag_t	flags1 = ofl->ofl_flags1;
377 	size_t		ndx;
378 	Elf_Cmd		cmd;
379 	Boolean		fixalign = FALSE;
380 	int		fd, nseg = 0, shidx, dataidx, ptloadidx = 0;
381 
382 	DBG_CALL(Dbg_basic_create(ofl->ofl_lml));
383 
384 	/*
385 	 * If DF_1_NOHDR or FLG_OF1_VADDR were set,
386 	 * we need to do alignment adjustment.
387 	 */
388 	if ((flags1 & FLG_OF1_VADDR) ||
389 	    (ofl->ofl_dtflags_1 & DF_1_NOHDR)) {
390 		fixalign = TRUE;
391 	}
392 
393 	if (flags1 & FLG_OF1_MEMORY) {
394 		cmd = ELF_C_IMAGE;
395 		fd = 0;
396 	} else {
397 		fd = ofl->ofl_fd;
398 		cmd = ELF_C_WRITE;
399 	}
400 
401 	/*
402 	 * If there are any ordered sections, handle them here.
403 	 */
404 	if ((ofl->ofl_ordered != NULL) &&
405 	    (ld_sort_ordered(ofl) == S_ERROR))
406 		return (S_ERROR);
407 
408 	/*
409 	 * Tell the access library about our new temporary file.
410 	 */
411 	if ((ofl->ofl_welf = elf_begin(fd, cmd, 0)) == NULL) {
412 		ld_eprintf(ofl, ERR_ELF, MSG_INTL(MSG_ELF_BEGIN),
413 		    ofl->ofl_name);
414 		return (S_ERROR);
415 	}
416 
417 	/*
418 	 * Obtain a new Elf header.
419 	 */
420 	if ((ofl->ofl_nehdr = elf_newehdr(ofl->ofl_welf)) == NULL) {
421 		ld_eprintf(ofl, ERR_ELF, MSG_INTL(MSG_ELF_NEWEHDR),
422 		    ofl->ofl_name);
423 		return (S_ERROR);
424 	}
425 	ofl->ofl_nehdr->e_machine = ofl->ofl_dehdr->e_machine;
426 
427 	DBG_CALL(Dbg_util_nl(ofl->ofl_lml, DBG_NL_STD));
428 	for (APLIST_TRAVERSE(ofl->ofl_segs, idx1, sgp)) {
429 		int	frst = 0;
430 		Phdr	*phdr = &(sgp->sg_phdr);
431 		Word	ptype = phdr->p_type;
432 		Aliste	idx2;
433 		Os_desc *nonempty = NULL; /* First non-empty section */
434 
435 		/*
436 		 * Count the number of segments that will go in the program
437 		 * header table. If a segment is empty, ignore it.
438 		 */
439 		if (!(flags & FLG_OF_RELOBJ)) {
440 			/*
441 			 * If the program header type belongs to the os range,
442 			 * the resulting object is ELFOSABI_SOLARIS.
443 			 */
444 			if ((ptype >= PT_LOOS) && (ptype <= PT_HIOS))
445 				ofl->ofl_flags |= FLG_OF_OSABI;
446 
447 			if (ptype == PT_PHDR) {
448 				/*
449 				 * If we are generating an interp section (and
450 				 * thus an associated PT_INTERP program header
451 				 * entry) also generate a PT_PHDR program header
452 				 * entry.  This allows the kernel to generate
453 				 * the appropriate aux vector entries to pass to
454 				 * the interpreter (refer to exec/elf/elf.c).
455 				 * Note that if an image was generated with an
456 				 * interp section, but no associated PT_PHDR
457 				 * program header entry, the kernel will simply
458 				 * pass the interpreter an open file descriptor
459 				 * when the image is executed).
460 				 */
461 				if (ofl->ofl_osinterp)
462 					nseg++;
463 			} else if (ptype == PT_INTERP) {
464 				if (ofl->ofl_osinterp)
465 					nseg++;
466 			} else if (ptype == PT_DYNAMIC) {
467 				if (flags & FLG_OF_DYNAMIC)
468 					nseg++;
469 			} else if (ptype == PT_TLS) {
470 				if (flags & FLG_OF_TLSPHDR)
471 					nseg++;
472 			} else if (ptype == PT_SUNW_UNWIND) {
473 				if (ofl->ofl_unwindhdr)
474 					nseg++;
475 			} else if (ptype == PT_SUNWDTRACE) {
476 				if (ofl->ofl_dtracesym)
477 					nseg++;
478 			} else if (ptype == PT_SUNWCAP) {
479 				if (ofl->ofl_oscap)
480 					nseg++;
481 			} else if (ptype == PT_SUNWSTACK) {
482 				if ((sgp->sg_flags & FLG_SG_DISABLED) == 0)
483 					nseg++;
484 			} else if (sgp->sg_flags & FLG_SG_EMPTY) {
485 					nseg++;
486 			} else if (aplist_nitems(sgp->sg_osdescs) != 0) {
487 				if ((sgp->sg_flags & FLG_SG_PHREQ) == 0) {
488 					/*
489 					 * If this is a segment for which
490 					 * we are not making a program header,
491 					 * don't increment nseg
492 					 */
493 					ptype = (sgp->sg_phdr).p_type = PT_NULL;
494 				} else if (ptype != PT_NULL)
495 					nseg++;
496 			}
497 		}
498 
499 		/*
500 		 * Establish any processing unique to the first loadable
501 		 * segment.
502 		 */
503 		if ((ptype == PT_LOAD) && (ptloadidx == 0)) {
504 			ptloadidx++;
505 
506 			/*
507 			 * If the first loadable segment is not supposed to
508 			 * include the ELF or program headers,  alignments
509 			 * of the following segments need to be fixed,
510 			 * plus a .dynamic FLAGS1 setting is required.
511 			 */
512 			if (ofl->ofl_dtflags_1 & DF_1_NOHDR)
513 				fixalign = TRUE;
514 		}
515 
516 		shidx = 0;
517 		for (APLIST_TRAVERSE(sgp->sg_osdescs, idx2, osp)) {
518 			Aliste	idx3;
519 			int	os_isdescs_idx;
520 
521 			dataidx = 0;
522 
523 			OS_ISDESCS_TRAVERSE(os_isdescs_idx, osp, idx3, isp) {
524 				Elf_Data	*data;
525 				Ifl_desc	*ifl = isp->is_file;
526 
527 				/*
528 				 * An input section in the list that has
529 				 * been previously marked to be discarded
530 				 * should be completely ignored.
531 				 */
532 				if (isp->is_flags & FLG_IS_DISCARD)
533 					continue;
534 
535 				/*
536 				 * At this point we know whether a section has
537 				 * been referenced.  If it hasn't, and the whole
538 				 * file hasn't been referenced (which would have
539 				 * been caught in ignore_section_processing()),
540 				 * give a diagnostic (-D unused,detail) or
541 				 * discard the section if -zignore is in effect.
542 				 */
543 				if (ifl &&
544 				    (((ifl->ifl_flags & FLG_IF_FILEREF) == 0) ||
545 				    ((ptype == PT_LOAD) &&
546 				    ((isp->is_flags & FLG_IS_SECTREF) == 0) &&
547 				    (isp->is_shdr->sh_size > 0)))) {
548 					Lm_list	*lml = ofl->ofl_lml;
549 
550 					if (ifl->ifl_flags & FLG_IF_IGNORE) {
551 						isp->is_flags |= FLG_IS_DISCARD;
552 						DBG_CALL(Dbg_unused_sec(lml,
553 						    isp));
554 						continue;
555 					} else {
556 						DBG_CALL(Dbg_unused_sec(lml,
557 						    isp));
558 					}
559 				}
560 
561 				/*
562 				 * If this section provides no data, and isn't
563 				 * referenced, then it can be discarded as well.
564 				 * Note, if this is the first input section
565 				 * associated to an output section, let it
566 				 * through, there may be a legitimate reason why
567 				 * the user wants a null section.  Discarding
568 				 * additional sections is intended to remove the
569 				 * empty clutter the compilers have a habit of
570 				 * creating.  Don't provide an unused diagnostic
571 				 * as these sections aren't typically the users
572 				 * creation.
573 				 */
574 				if (ifl && dataidx &&
575 				    ((isp->is_flags & FLG_IS_SECTREF) == 0) &&
576 				    (isp->is_shdr->sh_size == 0)) {
577 					isp->is_flags |= FLG_IS_DISCARD;
578 					continue;
579 				}
580 
581 				/*
582 				 * The first input section triggers the creation
583 				 * of the associated output section.
584 				 */
585 				if (osp->os_scn == NULL) {
586 					shidx++;
587 
588 					if (create_outsec(ofl, sgp, osp, ptype,
589 					    shidx, fixalign) == S_ERROR)
590 						return (S_ERROR);
591 				}
592 
593 				dataidx++;
594 
595 				/*
596 				 * Create a new output data buffer for each
597 				 * input data buffer, thus linking the new
598 				 * buffers to the new elf output structures.
599 				 * Simply make the new data buffers point to
600 				 * the old data.
601 				 */
602 				if ((data = elf_newdata(osp->os_scn)) == NULL) {
603 					ld_eprintf(ofl, ERR_ELF,
604 					    MSG_INTL(MSG_ELF_NEWDATA),
605 					    ofl->ofl_name);
606 					return (S_ERROR);
607 				}
608 				*data = *(isp->is_indata);
609 				isp->is_indata = data;
610 
611 				if ((fixalign == TRUE) && (ptype == PT_LOAD) &&
612 				    (shidx == 1) && (dataidx == 1))
613 					data->d_align = sgp->sg_align;
614 
615 				/*
616 				 * Save the first TLS data buffer, as this is
617 				 * the start of the TLS segment. Realign this
618 				 * buffer based on the alignment requirements
619 				 * of all the TLS input sections.
620 				 */
621 				if ((flags & FLG_OF_TLSPHDR) &&
622 				    (isp->is_shdr->sh_flags & SHF_TLS)) {
623 					if (tlsdata == 0)
624 						tlsdata = data;
625 					tlsdata->d_align =
626 					    ld_lcm(tlsdata->d_align,
627 					    isp->is_shdr->sh_addralign);
628 				}
629 
630 #if	defined(_ELF64) && defined(_ILP32)
631 				/*
632 				 * 4106312, the 32-bit ELF64 version of ld
633 				 * needs to be able to create large .bss
634 				 * sections.  The d_size member of Elf_Data
635 				 * only allows 32-bits in _ILP32, so we build
636 				 * multiple data-items that each fit into 32-
637 				 * bits.  libelf (4106398) can summ these up
638 				 * into a 64-bit quantity.  This only works
639 				 * for NOBITS sections which don't have any
640 				 * real data to maintain and don't require
641 				 * large file support.
642 				 */
643 				if (isp->is_shdr->sh_type == SHT_NOBITS) {
644 					Xword sz = isp->is_shdr->sh_size;
645 
646 					while (sz >> 32) {
647 						data->d_size = SIZE_MAX;
648 						sz -= (Xword)SIZE_MAX;
649 
650 						data = elf_newdata(osp->os_scn);
651 						if (data == NULL)
652 							return (S_ERROR);
653 					}
654 					data->d_size = (size_t)sz;
655 				}
656 #endif
657 
658 				/*
659 				 * If this segment requires rounding realign the
660 				 * first data buffer associated with the first
661 				 * section.
662 				 */
663 				if ((frst++ == 0) &&
664 				    (sgp->sg_flags & FLG_SG_ROUND)) {
665 					Xword    align;
666 
667 					if (data->d_align)
668 						align = (Xword)
669 						    S_ROUND(data->d_align,
670 						    sgp->sg_round);
671 					else
672 						align = sgp->sg_round;
673 
674 					data->d_align = (size_t)align;
675 				}
676 
677 				if ((data->d_size != 0) && (nonempty == NULL)) {
678 					nonempty = osp;
679 				}
680 			}
681 
682 			/*
683 			 * Clear the szoutrels counter so that it can be used
684 			 * again in the building of relocs.  See machrel.c.
685 			 */
686 			osp->os_szoutrels = 0;
687 		}
688 
689 		/*
690 		 * We need to raise the alignment of any empty sections at the
691 		 * start of a segment to be at least as aligned as the first
692 		 * non-empty section, such that the empty and first non-empty
693 		 * sections are placed at the same offset.
694 		 */
695 		if (nonempty != NULL) {
696 			Elf_Data	*ne = NULL;
697 			Xword		pad_align = 1;
698 
699 			ne = elf_getdata(nonempty->os_scn, NULL);
700 			assert(ne != NULL);
701 
702 			do {
703 				pad_align = ld_lcm(pad_align, ne->d_align);
704 				ne = elf_getdata(nonempty->os_scn, ne);
705 			} while (ne != NULL);
706 
707 			for (APLIST_TRAVERSE(sgp->sg_osdescs, idx2, osp)) {
708 				Elf_Data	*d = NULL;
709 
710 				/* Stop at the first non-empty section */
711 				if (osp == nonempty)
712 					break;
713 
714 				d = elf_getdata(osp->os_scn, NULL);
715 
716 				if (d != NULL)
717 					d->d_align = pad_align;
718 			}
719 		}
720 	}
721 
722 	/*
723 	 * Did we use ELF features from the osabi range? If so,
724 	 * update the ELF header osabi fields. If this doesn't happen,
725 	 * those fields remain 0, reflecting a generic System V ELF ABI.
726 	 */
727 	if (ofl->ofl_flags & FLG_OF_OSABI) {
728 		ofl->ofl_nehdr->e_ident[EI_OSABI] = ELFOSABI_SOLARIS;
729 		ofl->ofl_nehdr->e_ident[EI_ABIVERSION] = EAV_SUNW_CURRENT;
730 	}
731 
732 	/*
733 	 * Build an empty PHDR.
734 	 */
735 	if (nseg) {
736 		if ((ofl->ofl_phdr = elf_newphdr(ofl->ofl_welf,
737 		    nseg)) == NULL) {
738 			ld_eprintf(ofl, ERR_ELF, MSG_INTL(MSG_ELF_NEWPHDR),
739 			    ofl->ofl_name);
740 			return (S_ERROR);
741 		}
742 	}
743 
744 	/*
745 	 * If we need to generate a memory model, pad the image.
746 	 */
747 	if (flags1 & FLG_OF1_MEMORY) {
748 		if (pad_outfile(ofl) == S_ERROR)
749 			return (S_ERROR);
750 	}
751 
752 	/*
753 	 * After all the basic input file processing, all data pointers are
754 	 * referencing two types of memory:
755 	 *
756 	 *  -	allocated memory, ie. elf structures, internal link editor
757 	 *	structures, and any new sections that have been created.
758 	 *
759 	 *  -	original input file mmap'ed memory, ie. the actual data
760 	 *	sections of the input file images.
761 	 *
762 	 * Up until now, the only memory modifications have been carried out on
763 	 * the allocated memory.  Before carrying out any relocations, write the
764 	 * new output file image and reassign any necessary data pointers to the
765 	 * output files memory image.  This insures that any relocation
766 	 * modifications are made to the output file image and not to the input
767 	 * file image, thus preventing the creation of dirty pages and reducing
768 	 * the overall swap space requirement.
769 	 *
770 	 * Write out the elf structure so as to create the new file image.
771 	 */
772 	if ((ofl->ofl_size = (size_t)elf_update(ofl->ofl_welf,
773 	    ELF_C_WRIMAGE)) == (size_t)-1) {
774 		ld_eprintf(ofl, ERR_ELF, MSG_INTL(MSG_ELF_UPDATE),
775 		    ofl->ofl_name);
776 		return (S_ERROR);
777 	}
778 
779 	/*
780 	 * Initialize the true `ofl' information with the memory images address
781 	 * and size.  This will be used to write() out the image once any
782 	 * relocation processing has been completed.  We also use this image
783 	 * information to setup a new Elf descriptor, which is used to obtain
784 	 * all the necessary elf pointers within the new output image.
785 	 */
786 	if ((ofl->ofl_elf = elf_begin(0, ELF_C_IMAGE,
787 	    ofl->ofl_welf)) == NULL) {
788 		ld_eprintf(ofl, ERR_ELF, MSG_INTL(MSG_ELF_BEGIN),
789 		    ofl->ofl_name);
790 		return (S_ERROR);
791 	}
792 	if ((ofl->ofl_nehdr = elf_getehdr(ofl->ofl_elf)) == NULL) {
793 		ld_eprintf(ofl, ERR_ELF, MSG_INTL(MSG_ELF_GETEHDR),
794 		    ofl->ofl_name);
795 		return (S_ERROR);
796 	}
797 	if (!(flags & FLG_OF_RELOBJ))
798 		if ((ofl->ofl_phdr = elf_getphdr(ofl->ofl_elf)) == NULL) {
799 			ld_eprintf(ofl, ERR_ELF, MSG_INTL(MSG_ELF_GETPHDR),
800 			    ofl->ofl_name);
801 			return (S_ERROR);
802 		}
803 
804 	/*
805 	 * Reinitialize the section descriptors, section headers and obtain new
806 	 * output data buffer pointers (these will be used to perform any
807 	 * relocations).
808 	 */
809 	ndx = 0;
810 	for (APLIST_TRAVERSE(ofl->ofl_segs, idx1, sgp)) {
811 		Phdr	*_phdr = &(sgp->sg_phdr);
812 		Os_desc	*osp;
813 		Aliste	idx2;
814 		Boolean	recorded = FALSE;
815 
816 		for (APLIST_TRAVERSE(sgp->sg_osdescs, idx2, osp)) {
817 			/*
818 			 * Make sure that an output section was originally
819 			 * created.  Input sections that had been marked as
820 			 * discarded may have made an output section
821 			 * unnecessary.  Remove this alist entry so that
822 			 * future output section descriptor processing doesn't
823 			 * have to compensate for this empty section.
824 			 */
825 			if (osp->os_scn == NULL) {
826 				aplist_delete(sgp->sg_osdescs, &idx2);
827 				continue;
828 			}
829 			if ((osp->os_scn =
830 			    elf_getscn(ofl->ofl_elf, ++ndx)) == NULL) {
831 				ld_eprintf(ofl, ERR_ELF,
832 				    MSG_INTL(MSG_ELF_GETSCN), ofl->ofl_name,
833 				    ndx);
834 				return (S_ERROR);
835 			}
836 			if ((osp->os_shdr =
837 			    elf_getshdr(osp->os_scn)) == NULL) {
838 				ld_eprintf(ofl, ERR_ELF,
839 				    MSG_INTL(MSG_ELF_GETSHDR), ofl->ofl_name);
840 				return (S_ERROR);
841 			}
842 			if ((fixalign == TRUE) && sgp->sg_fscn &&
843 			    (recorded == FALSE)) {
844 				size_t	fndx;
845 				Elf_Scn *scn;
846 
847 				scn = sgp->sg_fscn;
848 				if ((fndx = elf_ndxscn(scn)) == SHN_UNDEF) {
849 					ld_eprintf(ofl, ERR_ELF,
850 					    MSG_INTL(MSG_ELF_NDXSCN),
851 					    ofl->ofl_name);
852 					return (S_ERROR);
853 				}
854 				if (ndx == fndx) {
855 					sgp->sg_fscn = osp->os_scn;
856 					recorded = TRUE;
857 				}
858 			}
859 
860 			if ((osp->os_outdata =
861 			    elf_getdata(osp->os_scn, NULL)) == NULL) {
862 				ld_eprintf(ofl, ERR_ELF,
863 				    MSG_INTL(MSG_ELF_GETDATA), ofl->ofl_name);
864 				return (S_ERROR);
865 			}
866 
867 			/*
868 			 * If this section is part of a loadable segment insure
869 			 * that the segments alignment is appropriate.
870 			 */
871 			if (_phdr->p_type == PT_LOAD) {
872 				_phdr->p_align = ld_lcm(_phdr->p_align,
873 				    osp->os_shdr->sh_addralign);
874 			}
875 		}
876 	}
877 	return (1);
878 }
879