1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * crash.c - kernel crash support code.
4 * Copyright (C) 2002-2004 Eric Biederman <ebiederm@xmission.com>
5 */
6
7#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
8
9#include <linux/buildid.h>
10#include <linux/init.h>
11#include <linux/utsname.h>
12#include <linux/vmalloc.h>
13#include <linux/sizes.h>
14#include <linux/kexec.h>
15#include <linux/memory.h>
16#include <linux/mm.h>
17#include <linux/cpuhotplug.h>
18#include <linux/memblock.h>
19#include <linux/kmemleak.h>
20#include <linux/crash_core.h>
21#include <linux/reboot.h>
22#include <linux/btf.h>
23#include <linux/objtool.h>
24#include <linux/delay.h>
25#include <linux/panic.h>
26
27#include <asm/page.h>
28#include <asm/sections.h>
29
30#include <crypto/sha1.h>
31
32#include "kallsyms_internal.h"
33#include "kexec_internal.h"
34
35/* Per cpu memory for storing cpu states in case of system crash. */
36note_buf_t __percpu *crash_notes;
37
38/* time to wait for possible DMA to finish before starting the kdump kernel
39 * when a CMA reservation is used
40 */
41#define CMA_DMA_TIMEOUT_SEC 10
42
43#ifdef CONFIG_CRASH_DUMP
44
45int kimage_crash_copy_vmcoreinfo(struct kimage *image)
46{
47 struct page *vmcoreinfo_page;
48 void *safecopy;
49
50 if (!IS_ENABLED(CONFIG_CRASH_DUMP))
51 return 0;
52 if (image->type != KEXEC_TYPE_CRASH)
53 return 0;
54
55 /*
56 * For kdump, allocate one vmcoreinfo safe copy from the
57 * crash memory. as we have arch_kexec_protect_crashkres()
58 * after kexec syscall, we naturally protect it from write
59 * (even read) access under kernel direct mapping. But on
60 * the other hand, we still need to operate it when crash
61 * happens to generate vmcoreinfo note, hereby we rely on
62 * vmap for this purpose.
63 */
64 vmcoreinfo_page = kimage_alloc_control_pages(image, order: 0);
65 if (!vmcoreinfo_page) {
66 pr_warn("Could not allocate vmcoreinfo buffer\n");
67 return -ENOMEM;
68 }
69 safecopy = vmap(pages: &vmcoreinfo_page, count: 1, VM_MAP, PAGE_KERNEL);
70 if (!safecopy) {
71 pr_warn("Could not vmap vmcoreinfo buffer\n");
72 return -ENOMEM;
73 }
74
75 image->vmcoreinfo_data_copy = safecopy;
76 crash_update_vmcoreinfo_safecopy(ptr: safecopy);
77
78 return 0;
79}
80
81
82
83int kexec_should_crash(struct task_struct *p)
84{
85 /*
86 * If crash_kexec_post_notifiers is enabled, don't run
87 * crash_kexec() here yet, which must be run after panic
88 * notifiers in panic().
89 */
90 if (crash_kexec_post_notifiers)
91 return 0;
92 /*
93 * There are 4 panic() calls in make_task_dead() path, each of which
94 * corresponds to each of these 4 conditions.
95 */
96 if (in_interrupt() || !p->pid || is_global_init(tsk: p) || panic_on_oops)
97 return 1;
98 return 0;
99}
100
101int kexec_crash_loaded(void)
102{
103 return !!kexec_crash_image;
104}
105EXPORT_SYMBOL_GPL(kexec_crash_loaded);
106
107static void crash_cma_clear_pending_dma(void)
108{
109 if (!crashk_cma_cnt)
110 return;
111
112 mdelay(CMA_DMA_TIMEOUT_SEC * 1000);
113}
114
115/*
116 * No panic_cpu check version of crash_kexec(). This function is called
117 * only when panic_cpu holds the current CPU number; this is the only CPU
118 * which processes crash_kexec routines.
119 */
120void __noclone __crash_kexec(struct pt_regs *regs)
121{
122 /* Take the kexec_lock here to prevent sys_kexec_load
123 * running on one cpu from replacing the crash kernel
124 * we are using after a panic on a different cpu.
125 *
126 * If the crash kernel was not located in a fixed area
127 * of memory the xchg(&kexec_crash_image) would be
128 * sufficient. But since I reuse the memory...
129 */
130 if (kexec_trylock()) {
131 if (kexec_crash_image) {
132 struct pt_regs fixed_regs;
133
134 crash_setup_regs(newregs: &fixed_regs, oldregs: regs);
135 crash_save_vmcoreinfo();
136 machine_crash_shutdown(&fixed_regs);
137 crash_cma_clear_pending_dma();
138 machine_kexec(image: kexec_crash_image);
139 }
140 kexec_unlock();
141 }
142}
143STACK_FRAME_NON_STANDARD(__crash_kexec);
144
145__bpf_kfunc void crash_kexec(struct pt_regs *regs)
146{
147 if (panic_try_start()) {
148 /* This is the 1st CPU which comes here, so go ahead. */
149 __crash_kexec(regs);
150
151 /*
152 * Reset panic_cpu to allow another panic()/crash_kexec()
153 * call.
154 */
155 panic_reset();
156 }
157}
158
159static inline resource_size_t crash_resource_size(const struct resource *res)
160{
161 return !res->end ? 0 : resource_size(res);
162}
163
164
165
166
167int crash_prepare_elf64_headers(struct crash_mem *mem, int need_kernel_map,
168 void **addr, unsigned long *sz)
169{
170 Elf64_Ehdr *ehdr;
171 Elf64_Phdr *phdr;
172 unsigned long nr_cpus = num_possible_cpus(), nr_phdr, elf_sz;
173 unsigned char *buf;
174 unsigned int cpu, i;
175 unsigned long long notes_addr;
176 unsigned long mstart, mend;
177
178 /* extra phdr for vmcoreinfo ELF note */
179 nr_phdr = nr_cpus + 1;
180 nr_phdr += mem->nr_ranges;
181
182 /*
183 * kexec-tools creates an extra PT_LOAD phdr for kernel text mapping
184 * area (for example, ffffffff80000000 - ffffffffa0000000 on x86_64).
185 * I think this is required by tools like gdb. So same physical
186 * memory will be mapped in two ELF headers. One will contain kernel
187 * text virtual addresses and other will have __va(physical) addresses.
188 */
189
190 nr_phdr++;
191 elf_sz = sizeof(Elf64_Ehdr) + nr_phdr * sizeof(Elf64_Phdr);
192 elf_sz = ALIGN(elf_sz, ELF_CORE_HEADER_ALIGN);
193
194 buf = vzalloc(elf_sz);
195 if (!buf)
196 return -ENOMEM;
197
198 ehdr = (Elf64_Ehdr *)buf;
199 phdr = (Elf64_Phdr *)(ehdr + 1);
200 memcpy(to: ehdr->e_ident, ELFMAG, SELFMAG);
201 ehdr->e_ident[EI_CLASS] = ELFCLASS64;
202 ehdr->e_ident[EI_DATA] = ELFDATA2LSB;
203 ehdr->e_ident[EI_VERSION] = EV_CURRENT;
204 ehdr->e_ident[EI_OSABI] = ELF_OSABI;
205 memset(s: ehdr->e_ident + EI_PAD, c: 0, EI_NIDENT - EI_PAD);
206 ehdr->e_type = ET_CORE;
207 ehdr->e_machine = ELF_ARCH;
208 ehdr->e_version = EV_CURRENT;
209 ehdr->e_phoff = sizeof(Elf64_Ehdr);
210 ehdr->e_ehsize = sizeof(Elf64_Ehdr);
211 ehdr->e_phentsize = sizeof(Elf64_Phdr);
212
213 /* Prepare one phdr of type PT_NOTE for each possible CPU */
214 for_each_possible_cpu(cpu) {
215 phdr->p_type = PT_NOTE;
216 notes_addr = per_cpu_ptr_to_phys(per_cpu_ptr(crash_notes, cpu));
217 phdr->p_offset = phdr->p_paddr = notes_addr;
218 phdr->p_filesz = phdr->p_memsz = sizeof(note_buf_t);
219 (ehdr->e_phnum)++;
220 phdr++;
221 }
222
223 /* Prepare one PT_NOTE header for vmcoreinfo */
224 phdr->p_type = PT_NOTE;
225 phdr->p_offset = phdr->p_paddr = paddr_vmcoreinfo_note();
226 phdr->p_filesz = phdr->p_memsz = VMCOREINFO_NOTE_SIZE;
227 (ehdr->e_phnum)++;
228 phdr++;
229
230 /* Prepare PT_LOAD type program header for kernel text region */
231 if (need_kernel_map) {
232 phdr->p_type = PT_LOAD;
233 phdr->p_flags = PF_R|PF_W|PF_X;
234 phdr->p_vaddr = (unsigned long) _text;
235 phdr->p_filesz = phdr->p_memsz = _end - _text;
236 phdr->p_offset = phdr->p_paddr = __pa_symbol(_text);
237 ehdr->e_phnum++;
238 phdr++;
239 }
240
241 /* Go through all the ranges in mem->ranges[] and prepare phdr */
242 for (i = 0; i < mem->nr_ranges; i++) {
243 mstart = mem->ranges[i].start;
244 mend = mem->ranges[i].end;
245
246 phdr->p_type = PT_LOAD;
247 phdr->p_flags = PF_R|PF_W|PF_X;
248 phdr->p_offset = mstart;
249
250 phdr->p_paddr = mstart;
251 phdr->p_vaddr = (unsigned long) __va(mstart);
252 phdr->p_filesz = phdr->p_memsz = mend - mstart + 1;
253 phdr->p_align = 0;
254 ehdr->e_phnum++;
255#ifdef CONFIG_KEXEC_FILE
256 kexec_dprintk("Crash PT_LOAD ELF header. phdr=%p vaddr=0x%llx, paddr=0x%llx, sz=0x%llx e_phnum=%d p_offset=0x%llx\n",
257 phdr, phdr->p_vaddr, phdr->p_paddr, phdr->p_filesz,
258 ehdr->e_phnum, phdr->p_offset);
259#endif
260 phdr++;
261 }
262
263 *addr = buf;
264 *sz = elf_sz;
265 return 0;
266}
267
268/**
269 * crash_exclude_mem_range - exclude a mem range for existing ranges
270 * @mem: mem->range contains an array of ranges sorted in ascending order
271 * @mstart: the start of to-be-excluded range
272 * @mend: the start of to-be-excluded range
273 *
274 * If you are unsure if a range split will happen, to avoid function call
275 * failure because of -ENOMEM, always make sure
276 * mem->max_nr_ranges == mem->nr_ranges + 1
277 * before calling the function each time.
278 *
279 * returns 0 if a memory range is excluded successfully
280 * return -ENOMEM if mem->ranges doesn't have space to hold split ranges
281 */
282int crash_exclude_mem_range(struct crash_mem *mem,
283 unsigned long long mstart, unsigned long long mend)
284{
285 int i;
286 unsigned long long start, end, p_start, p_end;
287
288 for (i = 0; i < mem->nr_ranges; i++) {
289 start = mem->ranges[i].start;
290 end = mem->ranges[i].end;
291 p_start = mstart;
292 p_end = mend;
293
294 if (p_start > end)
295 continue;
296
297 /*
298 * Because the memory ranges in mem->ranges are stored in
299 * ascending order, when we detect `p_end < start`, we can
300 * immediately exit the for loop, as the subsequent memory
301 * ranges will definitely be outside the range we are looking
302 * for.
303 */
304 if (p_end < start)
305 break;
306
307 /* Truncate any area outside of range */
308 if (p_start < start)
309 p_start = start;
310 if (p_end > end)
311 p_end = end;
312
313 /* Found completely overlapping range */
314 if (p_start == start && p_end == end) {
315 memmove(dest: &mem->ranges[i], src: &mem->ranges[i + 1],
316 count: (mem->nr_ranges - (i + 1)) * sizeof(mem->ranges[i]));
317 i--;
318 mem->nr_ranges--;
319 } else if (p_start > start && p_end < end) {
320 /* Split original range */
321 if (mem->nr_ranges >= mem->max_nr_ranges)
322 return -ENOMEM;
323
324 memmove(dest: &mem->ranges[i + 2], src: &mem->ranges[i + 1],
325 count: (mem->nr_ranges - (i + 1)) * sizeof(mem->ranges[i]));
326
327 mem->ranges[i].end = p_start - 1;
328 mem->ranges[i + 1].start = p_end + 1;
329 mem->ranges[i + 1].end = end;
330
331 i++;
332 mem->nr_ranges++;
333 } else if (p_start != start)
334 mem->ranges[i].end = p_start - 1;
335 else
336 mem->ranges[i].start = p_end + 1;
337 }
338
339 return 0;
340}
341EXPORT_SYMBOL_GPL(crash_exclude_mem_range);
342
343ssize_t crash_get_memory_size(void)
344{
345 ssize_t size = 0;
346
347 if (!kexec_trylock())
348 return -EBUSY;
349
350 size += crash_resource_size(res: &crashk_res);
351 size += crash_resource_size(res: &crashk_low_res);
352
353 kexec_unlock();
354 return size;
355}
356
357static int __crash_shrink_memory(struct resource *old_res,
358 unsigned long new_size)
359{
360 struct resource *ram_res;
361
362 ram_res = kzalloc(sizeof(*ram_res), GFP_KERNEL);
363 if (!ram_res)
364 return -ENOMEM;
365
366 ram_res->start = old_res->start + new_size;
367 ram_res->end = old_res->end;
368 ram_res->flags = IORESOURCE_BUSY | IORESOURCE_SYSTEM_RAM;
369 ram_res->name = "System RAM";
370
371 if (!new_size) {
372 release_resource(new: old_res);
373 old_res->start = 0;
374 old_res->end = 0;
375 } else {
376 crashk_res.end = ram_res->start - 1;
377 }
378
379 crash_free_reserved_phys_range(begin: ram_res->start, end: ram_res->end);
380 insert_resource(parent: &iomem_resource, new: ram_res);
381
382 return 0;
383}
384
385int crash_shrink_memory(unsigned long new_size)
386{
387 int ret = 0;
388 unsigned long old_size, low_size;
389
390 if (!kexec_trylock())
391 return -EBUSY;
392
393 if (kexec_crash_image) {
394 ret = -ENOENT;
395 goto unlock;
396 }
397
398 low_size = crash_resource_size(res: &crashk_low_res);
399 old_size = crash_resource_size(res: &crashk_res) + low_size;
400 new_size = roundup(new_size, KEXEC_CRASH_MEM_ALIGN);
401 if (new_size >= old_size) {
402 ret = (new_size == old_size) ? 0 : -EINVAL;
403 goto unlock;
404 }
405
406 /*
407 * (low_size > new_size) implies that low_size is greater than zero.
408 * This also means that if low_size is zero, the else branch is taken.
409 *
410 * If low_size is greater than 0, (low_size > new_size) indicates that
411 * crashk_low_res also needs to be shrunken. Otherwise, only crashk_res
412 * needs to be shrunken.
413 */
414 if (low_size > new_size) {
415 ret = __crash_shrink_memory(old_res: &crashk_res, new_size: 0);
416 if (ret)
417 goto unlock;
418
419 ret = __crash_shrink_memory(old_res: &crashk_low_res, new_size);
420 } else {
421 ret = __crash_shrink_memory(old_res: &crashk_res, new_size: new_size - low_size);
422 }
423
424 /* Swap crashk_res and crashk_low_res if needed */
425 if (!crashk_res.end && crashk_low_res.end) {
426 crashk_res.start = crashk_low_res.start;
427 crashk_res.end = crashk_low_res.end;
428 release_resource(new: &crashk_low_res);
429 crashk_low_res.start = 0;
430 crashk_low_res.end = 0;
431 insert_resource(parent: &iomem_resource, new: &crashk_res);
432 }
433
434unlock:
435 kexec_unlock();
436 return ret;
437}
438
439void crash_save_cpu(struct pt_regs *regs, int cpu)
440{
441 struct elf_prstatus prstatus;
442 u32 *buf;
443
444 if ((cpu < 0) || (cpu >= nr_cpu_ids))
445 return;
446
447 /* Using ELF notes here is opportunistic.
448 * I need a well defined structure format
449 * for the data I pass, and I need tags
450 * on the data to indicate what information I have
451 * squirrelled away. ELF notes happen to provide
452 * all of that, so there is no need to invent something new.
453 */
454 buf = (u32 *)per_cpu_ptr(crash_notes, cpu);
455 if (!buf)
456 return;
457 memset(s: &prstatus, c: 0, n: sizeof(prstatus));
458 prstatus.common.pr_pid = current->pid;
459 elf_core_copy_regs(elfregs: &prstatus.pr_reg, regs);
460 buf = append_elf_note(buf, NN_PRSTATUS, NT_PRSTATUS,
461 data: &prstatus, data_len: sizeof(prstatus));
462 final_note(buf);
463}
464
465
466
467static int __init crash_notes_memory_init(void)
468{
469 /* Allocate memory for saving cpu registers. */
470 size_t size, align;
471
472 /*
473 * crash_notes could be allocated across 2 vmalloc pages when percpu
474 * is vmalloc based . vmalloc doesn't guarantee 2 continuous vmalloc
475 * pages are also on 2 continuous physical pages. In this case the
476 * 2nd part of crash_notes in 2nd page could be lost since only the
477 * starting address and size of crash_notes are exported through sysfs.
478 * Here round up the size of crash_notes to the nearest power of two
479 * and pass it to __alloc_percpu as align value. This can make sure
480 * crash_notes is allocated inside one physical page.
481 */
482 size = sizeof(note_buf_t);
483 align = min(roundup_pow_of_two(sizeof(note_buf_t)), PAGE_SIZE);
484
485 /*
486 * Break compile if size is bigger than PAGE_SIZE since crash_notes
487 * definitely will be in 2 pages with that.
488 */
489 BUILD_BUG_ON(size > PAGE_SIZE);
490
491 crash_notes = __alloc_percpu(size, align);
492 if (!crash_notes) {
493 pr_warn("Memory allocation for saving cpu register states failed\n");
494 return -ENOMEM;
495 }
496 return 0;
497}
498subsys_initcall(crash_notes_memory_init);
499
500#endif /*CONFIG_CRASH_DUMP*/
501
502#ifdef CONFIG_CRASH_HOTPLUG
503#undef pr_fmt
504#define pr_fmt(fmt) "crash hp: " fmt
505
506/*
507 * Different than kexec/kdump loading/unloading/jumping/shrinking which
508 * usually rarely happen, there will be many crash hotplug events notified
509 * during one short period, e.g one memory board is hot added and memory
510 * regions are online. So mutex lock __crash_hotplug_lock is used to
511 * serialize the crash hotplug handling specifically.
512 */
513static DEFINE_MUTEX(__crash_hotplug_lock);
514#define crash_hotplug_lock() mutex_lock(&__crash_hotplug_lock)
515#define crash_hotplug_unlock() mutex_unlock(&__crash_hotplug_lock)
516
517/*
518 * This routine utilized when the crash_hotplug sysfs node is read.
519 * It reflects the kernel's ability/permission to update the kdump
520 * image directly.
521 */
522int crash_check_hotplug_support(void)
523{
524 int rc = 0;
525
526 crash_hotplug_lock();
527 /* Obtain lock while reading crash information */
528 if (!kexec_trylock()) {
529 if (!kexec_in_progress)
530 pr_info("kexec_trylock() failed, kdump image may be inaccurate\n");
531 crash_hotplug_unlock();
532 return 0;
533 }
534 if (kexec_crash_image) {
535 rc = kexec_crash_image->hotplug_support;
536 }
537 /* Release lock now that update complete */
538 kexec_unlock();
539 crash_hotplug_unlock();
540
541 return rc;
542}
543
544/*
545 * To accurately reflect hot un/plug changes of CPU and Memory resources
546 * (including onling and offlining of those resources), the relevant
547 * kexec segments must be updated with latest CPU and Memory resources.
548 *
549 * Architectures must ensure two things for all segments that need
550 * updating during hotplug events:
551 *
552 * 1. Segments must be large enough to accommodate a growing number of
553 * resources.
554 * 2. Exclude the segments from SHA verification.
555 *
556 * For example, on most architectures, the elfcorehdr (which is passed
557 * to the crash kernel via the elfcorehdr= parameter) must include the
558 * new list of CPUs and memory. To make changes to the elfcorehdr, it
559 * should be large enough to permit a growing number of CPU and Memory
560 * resources. One can estimate the elfcorehdr memory size based on
561 * NR_CPUS_DEFAULT and CRASH_MAX_MEMORY_RANGES. The elfcorehdr is
562 * excluded from SHA verification by default if the architecture
563 * supports crash hotplug.
564 */
565static void crash_handle_hotplug_event(unsigned int hp_action, unsigned int cpu, void *arg)
566{
567 struct kimage *image;
568
569 crash_hotplug_lock();
570 /* Obtain lock while changing crash information */
571 if (!kexec_trylock()) {
572 if (!kexec_in_progress)
573 pr_info("kexec_trylock() failed, kdump image may be inaccurate\n");
574 crash_hotplug_unlock();
575 return;
576 }
577
578 /* Check kdump is not loaded */
579 if (!kexec_crash_image)
580 goto out;
581
582 image = kexec_crash_image;
583
584 /* Check that kexec segments update is permitted */
585 if (!image->hotplug_support)
586 goto out;
587
588 if (hp_action == KEXEC_CRASH_HP_ADD_CPU ||
589 hp_action == KEXEC_CRASH_HP_REMOVE_CPU)
590 pr_debug("hp_action %u, cpu %u\n", hp_action, cpu);
591 else
592 pr_debug("hp_action %u\n", hp_action);
593
594 /*
595 * The elfcorehdr_index is set to -1 when the struct kimage
596 * is allocated. Find the segment containing the elfcorehdr,
597 * if not already found.
598 */
599 if (image->elfcorehdr_index < 0) {
600 unsigned long mem;
601 unsigned char *ptr;
602 unsigned int n;
603
604 for (n = 0; n < image->nr_segments; n++) {
605 mem = image->segment[n].mem;
606 ptr = kmap_local_page(pfn_to_page(mem >> PAGE_SHIFT));
607 if (ptr) {
608 /* The segment containing elfcorehdr */
609 if (memcmp(ptr, ELFMAG, SELFMAG) == 0)
610 image->elfcorehdr_index = (int)n;
611 kunmap_local(ptr);
612 }
613 }
614 }
615
616 if (image->elfcorehdr_index < 0) {
617 pr_err("unable to locate elfcorehdr segment");
618 goto out;
619 }
620
621 /* Needed in order for the segments to be updated */
622 arch_kexec_unprotect_crashkres();
623
624 /* Differentiate between normal load and hotplug update */
625 image->hp_action = hp_action;
626
627 /* Now invoke arch-specific update handler */
628 arch_crash_handle_hotplug_event(image, arg);
629
630 /* No longer handling a hotplug event */
631 image->hp_action = KEXEC_CRASH_HP_NONE;
632 image->elfcorehdr_updated = true;
633
634 /* Change back to read-only */
635 arch_kexec_protect_crashkres();
636
637 /* Errors in the callback is not a reason to rollback state */
638out:
639 /* Release lock now that update complete */
640 kexec_unlock();
641 crash_hotplug_unlock();
642}
643
644static int crash_memhp_notifier(struct notifier_block *nb, unsigned long val, void *arg)
645{
646 switch (val) {
647 case MEM_ONLINE:
648 crash_handle_hotplug_event(KEXEC_CRASH_HP_ADD_MEMORY,
649 KEXEC_CRASH_HP_INVALID_CPU, arg);
650 break;
651
652 case MEM_OFFLINE:
653 crash_handle_hotplug_event(KEXEC_CRASH_HP_REMOVE_MEMORY,
654 KEXEC_CRASH_HP_INVALID_CPU, arg);
655 break;
656 }
657 return NOTIFY_OK;
658}
659
660static struct notifier_block crash_memhp_nb = {
661 .notifier_call = crash_memhp_notifier,
662 .priority = 0
663};
664
665static int crash_cpuhp_online(unsigned int cpu)
666{
667 crash_handle_hotplug_event(KEXEC_CRASH_HP_ADD_CPU, cpu, NULL);
668 return 0;
669}
670
671static int crash_cpuhp_offline(unsigned int cpu)
672{
673 crash_handle_hotplug_event(KEXEC_CRASH_HP_REMOVE_CPU, cpu, NULL);
674 return 0;
675}
676
677static int __init crash_hotplug_init(void)
678{
679 int result = 0;
680
681 if (IS_ENABLED(CONFIG_MEMORY_HOTPLUG))
682 register_memory_notifier(nb: &crash_memhp_nb);
683
684 if (IS_ENABLED(CONFIG_HOTPLUG_CPU)) {
685 result = cpuhp_setup_state_nocalls(state: CPUHP_BP_PREPARE_DYN,
686 name: "crash/cpuhp", startup: crash_cpuhp_online, teardown: crash_cpuhp_offline);
687 }
688
689 return result;
690}
691
692subsys_initcall(crash_hotplug_init);
693#endif
694