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Linux/kernel/kexec_file.c

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  1 /*
  2  * kexec: kexec_file_load system call
  3  *
  4  * Copyright (C) 2014 Red Hat Inc.
  5  * Authors:
  6  *      Vivek Goyal <vgoyal@redhat.com>
  7  *
  8  * This source code is licensed under the GNU General Public License,
  9  * Version 2.  See the file COPYING for more details.
 10  */
 11 
 12 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 13 
 14 #include <linux/capability.h>
 15 #include <linux/mm.h>
 16 #include <linux/file.h>
 17 #include <linux/slab.h>
 18 #include <linux/kexec.h>
 19 #include <linux/mutex.h>
 20 #include <linux/list.h>
 21 #include <linux/fs.h>
 22 #include <crypto/hash.h>
 23 #include <crypto/sha.h>
 24 #include <linux/syscalls.h>
 25 #include <linux/vmalloc.h>
 26 #include "kexec_internal.h"
 27 
 28 /*
 29  * Declare these symbols weak so that if architecture provides a purgatory,
 30  * these will be overridden.
 31  */
 32 char __weak kexec_purgatory[0];
 33 size_t __weak kexec_purgatory_size = 0;
 34 
 35 static int kexec_calculate_store_digests(struct kimage *image);
 36 
 37 /* Architectures can provide this probe function */
 38 int __weak arch_kexec_kernel_image_probe(struct kimage *image, void *buf,
 39                                          unsigned long buf_len)
 40 {
 41         return -ENOEXEC;
 42 }
 43 
 44 void * __weak arch_kexec_kernel_image_load(struct kimage *image)
 45 {
 46         return ERR_PTR(-ENOEXEC);
 47 }
 48 
 49 int __weak arch_kimage_file_post_load_cleanup(struct kimage *image)
 50 {
 51         return -EINVAL;
 52 }
 53 
 54 #ifdef CONFIG_KEXEC_VERIFY_SIG
 55 int __weak arch_kexec_kernel_verify_sig(struct kimage *image, void *buf,
 56                                         unsigned long buf_len)
 57 {
 58         return -EKEYREJECTED;
 59 }
 60 #endif
 61 
 62 /* Apply relocations of type RELA */
 63 int __weak
 64 arch_kexec_apply_relocations_add(const Elf_Ehdr *ehdr, Elf_Shdr *sechdrs,
 65                                  unsigned int relsec)
 66 {
 67         pr_err("RELA relocation unsupported.\n");
 68         return -ENOEXEC;
 69 }
 70 
 71 /* Apply relocations of type REL */
 72 int __weak
 73 arch_kexec_apply_relocations(const Elf_Ehdr *ehdr, Elf_Shdr *sechdrs,
 74                              unsigned int relsec)
 75 {
 76         pr_err("REL relocation unsupported.\n");
 77         return -ENOEXEC;
 78 }
 79 
 80 /*
 81  * Free up memory used by kernel, initrd, and command line. This is temporary
 82  * memory allocation which is not needed any more after these buffers have
 83  * been loaded into separate segments and have been copied elsewhere.
 84  */
 85 void kimage_file_post_load_cleanup(struct kimage *image)
 86 {
 87         struct purgatory_info *pi = &image->purgatory_info;
 88 
 89         vfree(image->kernel_buf);
 90         image->kernel_buf = NULL;
 91 
 92         vfree(image->initrd_buf);
 93         image->initrd_buf = NULL;
 94 
 95         kfree(image->cmdline_buf);
 96         image->cmdline_buf = NULL;
 97 
 98         vfree(pi->purgatory_buf);
 99         pi->purgatory_buf = NULL;
100 
101         vfree(pi->sechdrs);
102         pi->sechdrs = NULL;
103 
104         /* See if architecture has anything to cleanup post load */
105         arch_kimage_file_post_load_cleanup(image);
106 
107         /*
108          * Above call should have called into bootloader to free up
109          * any data stored in kimage->image_loader_data. It should
110          * be ok now to free it up.
111          */
112         kfree(image->image_loader_data);
113         image->image_loader_data = NULL;
114 }
115 
116 /*
117  * In file mode list of segments is prepared by kernel. Copy relevant
118  * data from user space, do error checking, prepare segment list
119  */
120 static int
121 kimage_file_prepare_segments(struct kimage *image, int kernel_fd, int initrd_fd,
122                              const char __user *cmdline_ptr,
123                              unsigned long cmdline_len, unsigned flags)
124 {
125         int ret = 0;
126         void *ldata;
127         loff_t size;
128 
129         ret = kernel_read_file_from_fd(kernel_fd, &image->kernel_buf,
130                                        &size, INT_MAX, READING_KEXEC_IMAGE);
131         if (ret)
132                 return ret;
133         image->kernel_buf_len = size;
134 
135         /* Call arch image probe handlers */
136         ret = arch_kexec_kernel_image_probe(image, image->kernel_buf,
137                                             image->kernel_buf_len);
138         if (ret)
139                 goto out;
140 
141 #ifdef CONFIG_KEXEC_VERIFY_SIG
142         ret = arch_kexec_kernel_verify_sig(image, image->kernel_buf,
143                                            image->kernel_buf_len);
144         if (ret) {
145                 pr_debug("kernel signature verification failed.\n");
146                 goto out;
147         }
148         pr_debug("kernel signature verification successful.\n");
149 #endif
150         /* It is possible that there no initramfs is being loaded */
151         if (!(flags & KEXEC_FILE_NO_INITRAMFS)) {
152                 ret = kernel_read_file_from_fd(initrd_fd, &image->initrd_buf,
153                                                &size, INT_MAX,
154                                                READING_KEXEC_INITRAMFS);
155                 if (ret)
156                         goto out;
157                 image->initrd_buf_len = size;
158         }
159 
160         if (cmdline_len) {
161                 image->cmdline_buf = kzalloc(cmdline_len, GFP_KERNEL);
162                 if (!image->cmdline_buf) {
163                         ret = -ENOMEM;
164                         goto out;
165                 }
166 
167                 ret = copy_from_user(image->cmdline_buf, cmdline_ptr,
168                                      cmdline_len);
169                 if (ret) {
170                         ret = -EFAULT;
171                         goto out;
172                 }
173 
174                 image->cmdline_buf_len = cmdline_len;
175 
176                 /* command line should be a string with last byte null */
177                 if (image->cmdline_buf[cmdline_len - 1] != '\0') {
178                         ret = -EINVAL;
179                         goto out;
180                 }
181         }
182 
183         /* Call arch image load handlers */
184         ldata = arch_kexec_kernel_image_load(image);
185 
186         if (IS_ERR(ldata)) {
187                 ret = PTR_ERR(ldata);
188                 goto out;
189         }
190 
191         image->image_loader_data = ldata;
192 out:
193         /* In case of error, free up all allocated memory in this function */
194         if (ret)
195                 kimage_file_post_load_cleanup(image);
196         return ret;
197 }
198 
199 static int
200 kimage_file_alloc_init(struct kimage **rimage, int kernel_fd,
201                        int initrd_fd, const char __user *cmdline_ptr,
202                        unsigned long cmdline_len, unsigned long flags)
203 {
204         int ret;
205         struct kimage *image;
206         bool kexec_on_panic = flags & KEXEC_FILE_ON_CRASH;
207 
208         image = do_kimage_alloc_init();
209         if (!image)
210                 return -ENOMEM;
211 
212         image->file_mode = 1;
213 
214         if (kexec_on_panic) {
215                 /* Enable special crash kernel control page alloc policy. */
216                 image->control_page = crashk_res.start;
217                 image->type = KEXEC_TYPE_CRASH;
218         }
219 
220         ret = kimage_file_prepare_segments(image, kernel_fd, initrd_fd,
221                                            cmdline_ptr, cmdline_len, flags);
222         if (ret)
223                 goto out_free_image;
224 
225         ret = sanity_check_segment_list(image);
226         if (ret)
227                 goto out_free_post_load_bufs;
228 
229         ret = -ENOMEM;
230         image->control_code_page = kimage_alloc_control_pages(image,
231                                            get_order(KEXEC_CONTROL_PAGE_SIZE));
232         if (!image->control_code_page) {
233                 pr_err("Could not allocate control_code_buffer\n");
234                 goto out_free_post_load_bufs;
235         }
236 
237         if (!kexec_on_panic) {
238                 image->swap_page = kimage_alloc_control_pages(image, 0);
239                 if (!image->swap_page) {
240                         pr_err("Could not allocate swap buffer\n");
241                         goto out_free_control_pages;
242                 }
243         }
244 
245         *rimage = image;
246         return 0;
247 out_free_control_pages:
248         kimage_free_page_list(&image->control_pages);
249 out_free_post_load_bufs:
250         kimage_file_post_load_cleanup(image);
251 out_free_image:
252         kfree(image);
253         return ret;
254 }
255 
256 SYSCALL_DEFINE5(kexec_file_load, int, kernel_fd, int, initrd_fd,
257                 unsigned long, cmdline_len, const char __user *, cmdline_ptr,
258                 unsigned long, flags)
259 {
260         int ret = 0, i;
261         struct kimage **dest_image, *image;
262 
263         /* We only trust the superuser with rebooting the system. */
264         if (!capable(CAP_SYS_BOOT) || kexec_load_disabled)
265                 return -EPERM;
266 
267         /* Make sure we have a legal set of flags */
268         if (flags != (flags & KEXEC_FILE_FLAGS))
269                 return -EINVAL;
270 
271         image = NULL;
272 
273         if (!mutex_trylock(&kexec_mutex))
274                 return -EBUSY;
275 
276         dest_image = &kexec_image;
277         if (flags & KEXEC_FILE_ON_CRASH)
278                 dest_image = &kexec_crash_image;
279 
280         if (flags & KEXEC_FILE_UNLOAD)
281                 goto exchange;
282 
283         /*
284          * In case of crash, new kernel gets loaded in reserved region. It is
285          * same memory where old crash kernel might be loaded. Free any
286          * current crash dump kernel before we corrupt it.
287          */
288         if (flags & KEXEC_FILE_ON_CRASH)
289                 kimage_free(xchg(&kexec_crash_image, NULL));
290 
291         ret = kimage_file_alloc_init(&image, kernel_fd, initrd_fd, cmdline_ptr,
292                                      cmdline_len, flags);
293         if (ret)
294                 goto out;
295 
296         ret = machine_kexec_prepare(image);
297         if (ret)
298                 goto out;
299 
300         ret = kexec_calculate_store_digests(image);
301         if (ret)
302                 goto out;
303 
304         for (i = 0; i < image->nr_segments; i++) {
305                 struct kexec_segment *ksegment;
306 
307                 ksegment = &image->segment[i];
308                 pr_debug("Loading segment %d: buf=0x%p bufsz=0x%zx mem=0x%lx memsz=0x%zx\n",
309                          i, ksegment->buf, ksegment->bufsz, ksegment->mem,
310                          ksegment->memsz);
311 
312                 ret = kimage_load_segment(image, &image->segment[i]);
313                 if (ret)
314                         goto out;
315         }
316 
317         kimage_terminate(image);
318 
319         /*
320          * Free up any temporary buffers allocated which are not needed
321          * after image has been loaded
322          */
323         kimage_file_post_load_cleanup(image);
324 exchange:
325         image = xchg(dest_image, image);
326 out:
327         mutex_unlock(&kexec_mutex);
328         kimage_free(image);
329         return ret;
330 }
331 
332 static int locate_mem_hole_top_down(unsigned long start, unsigned long end,
333                                     struct kexec_buf *kbuf)
334 {
335         struct kimage *image = kbuf->image;
336         unsigned long temp_start, temp_end;
337 
338         temp_end = min(end, kbuf->buf_max);
339         temp_start = temp_end - kbuf->memsz;
340 
341         do {
342                 /* align down start */
343                 temp_start = temp_start & (~(kbuf->buf_align - 1));
344 
345                 if (temp_start < start || temp_start < kbuf->buf_min)
346                         return 0;
347 
348                 temp_end = temp_start + kbuf->memsz - 1;
349 
350                 /*
351                  * Make sure this does not conflict with any of existing
352                  * segments
353                  */
354                 if (kimage_is_destination_range(image, temp_start, temp_end)) {
355                         temp_start = temp_start - PAGE_SIZE;
356                         continue;
357                 }
358 
359                 /* We found a suitable memory range */
360                 break;
361         } while (1);
362 
363         /* If we are here, we found a suitable memory range */
364         kbuf->mem = temp_start;
365 
366         /* Success, stop navigating through remaining System RAM ranges */
367         return 1;
368 }
369 
370 static int locate_mem_hole_bottom_up(unsigned long start, unsigned long end,
371                                      struct kexec_buf *kbuf)
372 {
373         struct kimage *image = kbuf->image;
374         unsigned long temp_start, temp_end;
375 
376         temp_start = max(start, kbuf->buf_min);
377 
378         do {
379                 temp_start = ALIGN(temp_start, kbuf->buf_align);
380                 temp_end = temp_start + kbuf->memsz - 1;
381 
382                 if (temp_end > end || temp_end > kbuf->buf_max)
383                         return 0;
384                 /*
385                  * Make sure this does not conflict with any of existing
386                  * segments
387                  */
388                 if (kimage_is_destination_range(image, temp_start, temp_end)) {
389                         temp_start = temp_start + PAGE_SIZE;
390                         continue;
391                 }
392 
393                 /* We found a suitable memory range */
394                 break;
395         } while (1);
396 
397         /* If we are here, we found a suitable memory range */
398         kbuf->mem = temp_start;
399 
400         /* Success, stop navigating through remaining System RAM ranges */
401         return 1;
402 }
403 
404 static int locate_mem_hole_callback(u64 start, u64 end, void *arg)
405 {
406         struct kexec_buf *kbuf = (struct kexec_buf *)arg;
407         unsigned long sz = end - start + 1;
408 
409         /* Returning 0 will take to next memory range */
410         if (sz < kbuf->memsz)
411                 return 0;
412 
413         if (end < kbuf->buf_min || start > kbuf->buf_max)
414                 return 0;
415 
416         /*
417          * Allocate memory top down with-in ram range. Otherwise bottom up
418          * allocation.
419          */
420         if (kbuf->top_down)
421                 return locate_mem_hole_top_down(start, end, kbuf);
422         return locate_mem_hole_bottom_up(start, end, kbuf);
423 }
424 
425 /*
426  * Helper function for placing a buffer in a kexec segment. This assumes
427  * that kexec_mutex is held.
428  */
429 int kexec_add_buffer(struct kimage *image, char *buffer, unsigned long bufsz,
430                      unsigned long memsz, unsigned long buf_align,
431                      unsigned long buf_min, unsigned long buf_max,
432                      bool top_down, unsigned long *load_addr)
433 {
434 
435         struct kexec_segment *ksegment;
436         struct kexec_buf buf, *kbuf;
437         int ret;
438 
439         /* Currently adding segment this way is allowed only in file mode */
440         if (!image->file_mode)
441                 return -EINVAL;
442 
443         if (image->nr_segments >= KEXEC_SEGMENT_MAX)
444                 return -EINVAL;
445 
446         /*
447          * Make sure we are not trying to add buffer after allocating
448          * control pages. All segments need to be placed first before
449          * any control pages are allocated. As control page allocation
450          * logic goes through list of segments to make sure there are
451          * no destination overlaps.
452          */
453         if (!list_empty(&image->control_pages)) {
454                 WARN_ON(1);
455                 return -EINVAL;
456         }
457 
458         memset(&buf, 0, sizeof(struct kexec_buf));
459         kbuf = &buf;
460         kbuf->image = image;
461         kbuf->buffer = buffer;
462         kbuf->bufsz = bufsz;
463 
464         kbuf->memsz = ALIGN(memsz, PAGE_SIZE);
465         kbuf->buf_align = max(buf_align, PAGE_SIZE);
466         kbuf->buf_min = buf_min;
467         kbuf->buf_max = buf_max;
468         kbuf->top_down = top_down;
469 
470         /* Walk the RAM ranges and allocate a suitable range for the buffer */
471         if (image->type == KEXEC_TYPE_CRASH)
472                 ret = walk_iomem_res_desc(crashk_res.desc,
473                                 IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY,
474                                 crashk_res.start, crashk_res.end, kbuf,
475                                 locate_mem_hole_callback);
476         else
477                 ret = walk_system_ram_res(0, -1, kbuf,
478                                           locate_mem_hole_callback);
479         if (ret != 1) {
480                 /* A suitable memory range could not be found for buffer */
481                 return -EADDRNOTAVAIL;
482         }
483 
484         /* Found a suitable memory range */
485         ksegment = &image->segment[image->nr_segments];
486         ksegment->kbuf = kbuf->buffer;
487         ksegment->bufsz = kbuf->bufsz;
488         ksegment->mem = kbuf->mem;
489         ksegment->memsz = kbuf->memsz;
490         image->nr_segments++;
491         *load_addr = ksegment->mem;
492         return 0;
493 }
494 
495 /* Calculate and store the digest of segments */
496 static int kexec_calculate_store_digests(struct kimage *image)
497 {
498         struct crypto_shash *tfm;
499         struct shash_desc *desc;
500         int ret = 0, i, j, zero_buf_sz, sha_region_sz;
501         size_t desc_size, nullsz;
502         char *digest;
503         void *zero_buf;
504         struct kexec_sha_region *sha_regions;
505         struct purgatory_info *pi = &image->purgatory_info;
506 
507         zero_buf = __va(page_to_pfn(ZERO_PAGE(0)) << PAGE_SHIFT);
508         zero_buf_sz = PAGE_SIZE;
509 
510         tfm = crypto_alloc_shash("sha256", 0, 0);
511         if (IS_ERR(tfm)) {
512                 ret = PTR_ERR(tfm);
513                 goto out;
514         }
515 
516         desc_size = crypto_shash_descsize(tfm) + sizeof(*desc);
517         desc = kzalloc(desc_size, GFP_KERNEL);
518         if (!desc) {
519                 ret = -ENOMEM;
520                 goto out_free_tfm;
521         }
522 
523         sha_region_sz = KEXEC_SEGMENT_MAX * sizeof(struct kexec_sha_region);
524         sha_regions = vzalloc(sha_region_sz);
525         if (!sha_regions)
526                 goto out_free_desc;
527 
528         desc->tfm   = tfm;
529         desc->flags = 0;
530 
531         ret = crypto_shash_init(desc);
532         if (ret < 0)
533                 goto out_free_sha_regions;
534 
535         digest = kzalloc(SHA256_DIGEST_SIZE, GFP_KERNEL);
536         if (!digest) {
537                 ret = -ENOMEM;
538                 goto out_free_sha_regions;
539         }
540 
541         for (j = i = 0; i < image->nr_segments; i++) {
542                 struct kexec_segment *ksegment;
543 
544                 ksegment = &image->segment[i];
545                 /*
546                  * Skip purgatory as it will be modified once we put digest
547                  * info in purgatory.
548                  */
549                 if (ksegment->kbuf == pi->purgatory_buf)
550                         continue;
551 
552                 ret = crypto_shash_update(desc, ksegment->kbuf,
553                                           ksegment->bufsz);
554                 if (ret)
555                         break;
556 
557                 /*
558                  * Assume rest of the buffer is filled with zero and
559                  * update digest accordingly.
560                  */
561                 nullsz = ksegment->memsz - ksegment->bufsz;
562                 while (nullsz) {
563                         unsigned long bytes = nullsz;
564 
565                         if (bytes > zero_buf_sz)
566                                 bytes = zero_buf_sz;
567                         ret = crypto_shash_update(desc, zero_buf, bytes);
568                         if (ret)
569                                 break;
570                         nullsz -= bytes;
571                 }
572 
573                 if (ret)
574                         break;
575 
576                 sha_regions[j].start = ksegment->mem;
577                 sha_regions[j].len = ksegment->memsz;
578                 j++;
579         }
580 
581         if (!ret) {
582                 ret = crypto_shash_final(desc, digest);
583                 if (ret)
584                         goto out_free_digest;
585                 ret = kexec_purgatory_get_set_symbol(image, "sha_regions",
586                                                 sha_regions, sha_region_sz, 0);
587                 if (ret)
588                         goto out_free_digest;
589 
590                 ret = kexec_purgatory_get_set_symbol(image, "sha256_digest",
591                                                 digest, SHA256_DIGEST_SIZE, 0);
592                 if (ret)
593                         goto out_free_digest;
594         }
595 
596 out_free_digest:
597         kfree(digest);
598 out_free_sha_regions:
599         vfree(sha_regions);
600 out_free_desc:
601         kfree(desc);
602 out_free_tfm:
603         kfree(tfm);
604 out:
605         return ret;
606 }
607 
608 /* Actually load purgatory. Lot of code taken from kexec-tools */
609 static int __kexec_load_purgatory(struct kimage *image, unsigned long min,
610                                   unsigned long max, int top_down)
611 {
612         struct purgatory_info *pi = &image->purgatory_info;
613         unsigned long align, buf_align, bss_align, buf_sz, bss_sz, bss_pad;
614         unsigned long memsz, entry, load_addr, curr_load_addr, bss_addr, offset;
615         unsigned char *buf_addr, *src;
616         int i, ret = 0, entry_sidx = -1;
617         const Elf_Shdr *sechdrs_c;
618         Elf_Shdr *sechdrs = NULL;
619         void *purgatory_buf = NULL;
620 
621         /*
622          * sechdrs_c points to section headers in purgatory and are read
623          * only. No modifications allowed.
624          */
625         sechdrs_c = (void *)pi->ehdr + pi->ehdr->e_shoff;
626 
627         /*
628          * We can not modify sechdrs_c[] and its fields. It is read only.
629          * Copy it over to a local copy where one can store some temporary
630          * data and free it at the end. We need to modify ->sh_addr and
631          * ->sh_offset fields to keep track of permanent and temporary
632          * locations of sections.
633          */
634         sechdrs = vzalloc(pi->ehdr->e_shnum * sizeof(Elf_Shdr));
635         if (!sechdrs)
636                 return -ENOMEM;
637 
638         memcpy(sechdrs, sechdrs_c, pi->ehdr->e_shnum * sizeof(Elf_Shdr));
639 
640         /*
641          * We seem to have multiple copies of sections. First copy is which
642          * is embedded in kernel in read only section. Some of these sections
643          * will be copied to a temporary buffer and relocated. And these
644          * sections will finally be copied to their final destination at
645          * segment load time.
646          *
647          * Use ->sh_offset to reflect section address in memory. It will
648          * point to original read only copy if section is not allocatable.
649          * Otherwise it will point to temporary copy which will be relocated.
650          *
651          * Use ->sh_addr to contain final address of the section where it
652          * will go during execution time.
653          */
654         for (i = 0; i < pi->ehdr->e_shnum; i++) {
655                 if (sechdrs[i].sh_type == SHT_NOBITS)
656                         continue;
657 
658                 sechdrs[i].sh_offset = (unsigned long)pi->ehdr +
659                                                 sechdrs[i].sh_offset;
660         }
661 
662         /*
663          * Identify entry point section and make entry relative to section
664          * start.
665          */
666         entry = pi->ehdr->e_entry;
667         for (i = 0; i < pi->ehdr->e_shnum; i++) {
668                 if (!(sechdrs[i].sh_flags & SHF_ALLOC))
669                         continue;
670 
671                 if (!(sechdrs[i].sh_flags & SHF_EXECINSTR))
672                         continue;
673 
674                 /* Make entry section relative */
675                 if (sechdrs[i].sh_addr <= pi->ehdr->e_entry &&
676                     ((sechdrs[i].sh_addr + sechdrs[i].sh_size) >
677                      pi->ehdr->e_entry)) {
678                         entry_sidx = i;
679                         entry -= sechdrs[i].sh_addr;
680                         break;
681                 }
682         }
683 
684         /* Determine how much memory is needed to load relocatable object. */
685         buf_align = 1;
686         bss_align = 1;
687         buf_sz = 0;
688         bss_sz = 0;
689 
690         for (i = 0; i < pi->ehdr->e_shnum; i++) {
691                 if (!(sechdrs[i].sh_flags & SHF_ALLOC))
692                         continue;
693 
694                 align = sechdrs[i].sh_addralign;
695                 if (sechdrs[i].sh_type != SHT_NOBITS) {
696                         if (buf_align < align)
697                                 buf_align = align;
698                         buf_sz = ALIGN(buf_sz, align);
699                         buf_sz += sechdrs[i].sh_size;
700                 } else {
701                         /* bss section */
702                         if (bss_align < align)
703                                 bss_align = align;
704                         bss_sz = ALIGN(bss_sz, align);
705                         bss_sz += sechdrs[i].sh_size;
706                 }
707         }
708 
709         /* Determine the bss padding required to align bss properly */
710         bss_pad = 0;
711         if (buf_sz & (bss_align - 1))
712                 bss_pad = bss_align - (buf_sz & (bss_align - 1));
713 
714         memsz = buf_sz + bss_pad + bss_sz;
715 
716         /* Allocate buffer for purgatory */
717         purgatory_buf = vzalloc(buf_sz);
718         if (!purgatory_buf) {
719                 ret = -ENOMEM;
720                 goto out;
721         }
722 
723         if (buf_align < bss_align)
724                 buf_align = bss_align;
725 
726         /* Add buffer to segment list */
727         ret = kexec_add_buffer(image, purgatory_buf, buf_sz, memsz,
728                                 buf_align, min, max, top_down,
729                                 &pi->purgatory_load_addr);
730         if (ret)
731                 goto out;
732 
733         /* Load SHF_ALLOC sections */
734         buf_addr = purgatory_buf;
735         load_addr = curr_load_addr = pi->purgatory_load_addr;
736         bss_addr = load_addr + buf_sz + bss_pad;
737 
738         for (i = 0; i < pi->ehdr->e_shnum; i++) {
739                 if (!(sechdrs[i].sh_flags & SHF_ALLOC))
740                         continue;
741 
742                 align = sechdrs[i].sh_addralign;
743                 if (sechdrs[i].sh_type != SHT_NOBITS) {
744                         curr_load_addr = ALIGN(curr_load_addr, align);
745                         offset = curr_load_addr - load_addr;
746                         /* We already modifed ->sh_offset to keep src addr */
747                         src = (char *) sechdrs[i].sh_offset;
748                         memcpy(buf_addr + offset, src, sechdrs[i].sh_size);
749 
750                         /* Store load address and source address of section */
751                         sechdrs[i].sh_addr = curr_load_addr;
752 
753                         /*
754                          * This section got copied to temporary buffer. Update
755                          * ->sh_offset accordingly.
756                          */
757                         sechdrs[i].sh_offset = (unsigned long)(buf_addr + offset);
758 
759                         /* Advance to the next address */
760                         curr_load_addr += sechdrs[i].sh_size;
761                 } else {
762                         bss_addr = ALIGN(bss_addr, align);
763                         sechdrs[i].sh_addr = bss_addr;
764                         bss_addr += sechdrs[i].sh_size;
765                 }
766         }
767 
768         /* Update entry point based on load address of text section */
769         if (entry_sidx >= 0)
770                 entry += sechdrs[entry_sidx].sh_addr;
771 
772         /* Make kernel jump to purgatory after shutdown */
773         image->start = entry;
774 
775         /* Used later to get/set symbol values */
776         pi->sechdrs = sechdrs;
777 
778         /*
779          * Used later to identify which section is purgatory and skip it
780          * from checksumming.
781          */
782         pi->purgatory_buf = purgatory_buf;
783         return ret;
784 out:
785         vfree(sechdrs);
786         vfree(purgatory_buf);
787         return ret;
788 }
789 
790 static int kexec_apply_relocations(struct kimage *image)
791 {
792         int i, ret;
793         struct purgatory_info *pi = &image->purgatory_info;
794         Elf_Shdr *sechdrs = pi->sechdrs;
795 
796         /* Apply relocations */
797         for (i = 0; i < pi->ehdr->e_shnum; i++) {
798                 Elf_Shdr *section, *symtab;
799 
800                 if (sechdrs[i].sh_type != SHT_RELA &&
801                     sechdrs[i].sh_type != SHT_REL)
802                         continue;
803 
804                 /*
805                  * For section of type SHT_RELA/SHT_REL,
806                  * ->sh_link contains section header index of associated
807                  * symbol table. And ->sh_info contains section header
808                  * index of section to which relocations apply.
809                  */
810                 if (sechdrs[i].sh_info >= pi->ehdr->e_shnum ||
811                     sechdrs[i].sh_link >= pi->ehdr->e_shnum)
812                         return -ENOEXEC;
813 
814                 section = &sechdrs[sechdrs[i].sh_info];
815                 symtab = &sechdrs[sechdrs[i].sh_link];
816 
817                 if (!(section->sh_flags & SHF_ALLOC))
818                         continue;
819 
820                 /*
821                  * symtab->sh_link contain section header index of associated
822                  * string table.
823                  */
824                 if (symtab->sh_link >= pi->ehdr->e_shnum)
825                         /* Invalid section number? */
826                         continue;
827 
828                 /*
829                  * Respective architecture needs to provide support for applying
830                  * relocations of type SHT_RELA/SHT_REL.
831                  */
832                 if (sechdrs[i].sh_type == SHT_RELA)
833                         ret = arch_kexec_apply_relocations_add(pi->ehdr,
834                                                                sechdrs, i);
835                 else if (sechdrs[i].sh_type == SHT_REL)
836                         ret = arch_kexec_apply_relocations(pi->ehdr,
837                                                            sechdrs, i);
838                 if (ret)
839                         return ret;
840         }
841 
842         return 0;
843 }
844 
845 /* Load relocatable purgatory object and relocate it appropriately */
846 int kexec_load_purgatory(struct kimage *image, unsigned long min,
847                          unsigned long max, int top_down,
848                          unsigned long *load_addr)
849 {
850         struct purgatory_info *pi = &image->purgatory_info;
851         int ret;
852 
853         if (kexec_purgatory_size <= 0)
854                 return -EINVAL;
855 
856         if (kexec_purgatory_size < sizeof(Elf_Ehdr))
857                 return -ENOEXEC;
858 
859         pi->ehdr = (Elf_Ehdr *)kexec_purgatory;
860 
861         if (memcmp(pi->ehdr->e_ident, ELFMAG, SELFMAG) != 0
862             || pi->ehdr->e_type != ET_REL
863             || !elf_check_arch(pi->ehdr)
864             || pi->ehdr->e_shentsize != sizeof(Elf_Shdr))
865                 return -ENOEXEC;
866 
867         if (pi->ehdr->e_shoff >= kexec_purgatory_size
868             || (pi->ehdr->e_shnum * sizeof(Elf_Shdr) >
869             kexec_purgatory_size - pi->ehdr->e_shoff))
870                 return -ENOEXEC;
871 
872         ret = __kexec_load_purgatory(image, min, max, top_down);
873         if (ret)
874                 return ret;
875 
876         ret = kexec_apply_relocations(image);
877         if (ret)
878                 goto out;
879 
880         *load_addr = pi->purgatory_load_addr;
881         return 0;
882 out:
883         vfree(pi->sechdrs);
884         vfree(pi->purgatory_buf);
885         return ret;
886 }
887 
888 static Elf_Sym *kexec_purgatory_find_symbol(struct purgatory_info *pi,
889                                             const char *name)
890 {
891         Elf_Sym *syms;
892         Elf_Shdr *sechdrs;
893         Elf_Ehdr *ehdr;
894         int i, k;
895         const char *strtab;
896 
897         if (!pi->sechdrs || !pi->ehdr)
898                 return NULL;
899 
900         sechdrs = pi->sechdrs;
901         ehdr = pi->ehdr;
902 
903         for (i = 0; i < ehdr->e_shnum; i++) {
904                 if (sechdrs[i].sh_type != SHT_SYMTAB)
905                         continue;
906 
907                 if (sechdrs[i].sh_link >= ehdr->e_shnum)
908                         /* Invalid strtab section number */
909                         continue;
910                 strtab = (char *)sechdrs[sechdrs[i].sh_link].sh_offset;
911                 syms = (Elf_Sym *)sechdrs[i].sh_offset;
912 
913                 /* Go through symbols for a match */
914                 for (k = 0; k < sechdrs[i].sh_size/sizeof(Elf_Sym); k++) {
915                         if (ELF_ST_BIND(syms[k].st_info) != STB_GLOBAL)
916                                 continue;
917 
918                         if (strcmp(strtab + syms[k].st_name, name) != 0)
919                                 continue;
920 
921                         if (syms[k].st_shndx == SHN_UNDEF ||
922                             syms[k].st_shndx >= ehdr->e_shnum) {
923                                 pr_debug("Symbol: %s has bad section index %d.\n",
924                                                 name, syms[k].st_shndx);
925                                 return NULL;
926                         }
927 
928                         /* Found the symbol we are looking for */
929                         return &syms[k];
930                 }
931         }
932 
933         return NULL;
934 }
935 
936 void *kexec_purgatory_get_symbol_addr(struct kimage *image, const char *name)
937 {
938         struct purgatory_info *pi = &image->purgatory_info;
939         Elf_Sym *sym;
940         Elf_Shdr *sechdr;
941 
942         sym = kexec_purgatory_find_symbol(pi, name);
943         if (!sym)
944                 return ERR_PTR(-EINVAL);
945 
946         sechdr = &pi->sechdrs[sym->st_shndx];
947 
948         /*
949          * Returns the address where symbol will finally be loaded after
950          * kexec_load_segment()
951          */
952         return (void *)(sechdr->sh_addr + sym->st_value);
953 }
954 
955 /*
956  * Get or set value of a symbol. If "get_value" is true, symbol value is
957  * returned in buf otherwise symbol value is set based on value in buf.
958  */
959 int kexec_purgatory_get_set_symbol(struct kimage *image, const char *name,
960                                    void *buf, unsigned int size, bool get_value)
961 {
962         Elf_Sym *sym;
963         Elf_Shdr *sechdrs;
964         struct purgatory_info *pi = &image->purgatory_info;
965         char *sym_buf;
966 
967         sym = kexec_purgatory_find_symbol(pi, name);
968         if (!sym)
969                 return -EINVAL;
970 
971         if (sym->st_size != size) {
972                 pr_err("symbol %s size mismatch: expected %lu actual %u\n",
973                        name, (unsigned long)sym->st_size, size);
974                 return -EINVAL;
975         }
976 
977         sechdrs = pi->sechdrs;
978 
979         if (sechdrs[sym->st_shndx].sh_type == SHT_NOBITS) {
980                 pr_err("symbol %s is in a bss section. Cannot %s\n", name,
981                        get_value ? "get" : "set");
982                 return -EINVAL;
983         }
984 
985         sym_buf = (unsigned char *)sechdrs[sym->st_shndx].sh_offset +
986                                         sym->st_value;
987 
988         if (get_value)
989                 memcpy((void *)buf, sym_buf, size);
990         else
991                 memcpy((void *)sym_buf, buf, size);
992 
993         return 0;
994 }
995 

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