crash_core.c

  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, 0);
 65	if (!vmcoreinfo_page) {
 66		pr_warn("Could not allocate vmcoreinfo buffer\n");
 67		return -ENOMEM;
 68	}
 69	safecopy = vmap(&vmcoreinfo_page, 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(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(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(&fixed_regs, regs);
135			crash_save_vmcoreinfo();
136			machine_crash_shutdown(&fixed_regs);
137			crash_cma_clear_pending_dma();
138			machine_kexec(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(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(ehdr->e_ident + EI_PAD, 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(&mem->ranges[i], &mem->ranges[i + 1],
316				(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(&mem->ranges[i + 2], &mem->ranges[i + 1],
325				(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(&crashk_res);
351	size += crash_resource_size(&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(old_res);
373		old_res->start = 0;
374		old_res->end   = 0;
375	} else {
376		old_res->end = ram_res->start - 1;
377	}
378
379	crash_free_reserved_phys_range(ram_res->start, ram_res->end);
380	insert_resource(&iomem_resource, 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(&crashk_low_res);
399	old_size = crash_resource_size(&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(&crashk_res, 0);
416		if (ret)
417			goto unlock;
418
419		ret = __crash_shrink_memory(&crashk_low_res, new_size);
420	} else {
421		ret = __crash_shrink_memory(&crashk_res, 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(&crashk_low_res);
429		crashk_low_res.start = 0;
430		crashk_low_res.end   = 0;
431		insert_resource(&iomem_resource, &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(&prstatus, 0, sizeof(prstatus));
458	prstatus.common.pr_pid = current->pid;
459	elf_core_copy_regs(&prstatus.pr_reg, regs);
460	buf = append_elf_note(buf, NN_PRSTATUS, NT_PRSTATUS,
461			      &prstatus, 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(&crash_memhp_nb);
683
684	if (IS_ENABLED(CONFIG_HOTPLUG_CPU)) {
685		result = cpuhp_setup_state_nocalls(CPUHP_BP_PREPARE_DYN,
686			"crash/cpuhp", crash_cpuhp_online, crash_cpuhp_offline);
687	}
688
689	return result;
690}
691
692subsys_initcall(crash_hotplug_init);
693#endif