crash.c

  1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * Architecture specific (PPC64) functions for kexec based crash dumps.
  4 *
  5 * Copyright (C) 2005, IBM Corp.
  6 *
  7 * Created by: Haren Myneni
  8 */
  9
 10#include <linux/kernel.h>
 11#include <linux/smp.h>
 12#include <linux/reboot.h>
 13#include <linux/kexec.h>
 14#include <linux/export.h>
 15#include <linux/crash_dump.h>
 16#include <linux/delay.h>
 17#include <linux/irq.h>
 18#include <linux/types.h>
 19#include <linux/libfdt.h>
 20#include <linux/memory.h>
 21
 22#include <asm/processor.h>
 23#include <asm/machdep.h>
 24#include <asm/kexec.h>
 25#include <asm/smp.h>
 26#include <asm/setjmp.h>
 27#include <asm/debug.h>
 28#include <asm/interrupt.h>
 29#include <asm/kexec_ranges.h>
 30
 31/*
 32 * The primary CPU waits a while for all secondary CPUs to enter. This is to
 33 * avoid sending an IPI if the secondary CPUs are entering
 34 * crash_kexec_secondary on their own (eg via a system reset).
 35 *
 36 * The secondary timeout has to be longer than the primary. Both timeouts are
 37 * in milliseconds.
 38 */
 39#define PRIMARY_TIMEOUT		500
 40#define SECONDARY_TIMEOUT	1000
 41
 42#define IPI_TIMEOUT		10000
 43#define REAL_MODE_TIMEOUT	10000
 44
 45static int time_to_dump;
 46
 47/*
 48 * In case of system reset, secondary CPUs enter crash_kexec_secondary with out
 49 * having to send an IPI explicitly. So, indicate if the crash is via
 50 * system reset to avoid sending another IPI.
 51 */
 52static int is_via_system_reset;
 53
 54/*
 55 * crash_wake_offline should be set to 1 by platforms that intend to wake
 56 * up offline cpus prior to jumping to a kdump kernel. Currently powernv
 57 * sets it to 1, since we want to avoid things from happening when an
 58 * offline CPU wakes up due to something like an HMI (malfunction error),
 59 * which propagates to all threads.
 60 */
 61int crash_wake_offline;
 62
 63#define CRASH_HANDLER_MAX 3
 64/* List of shutdown handles */
 65static crash_shutdown_t crash_shutdown_handles[CRASH_HANDLER_MAX];
 66static DEFINE_SPINLOCK(crash_handlers_lock);
 67
 68static unsigned long crash_shutdown_buf[JMP_BUF_LEN];
 69static int crash_shutdown_cpu = -1;
 70
 71static int handle_fault(struct pt_regs *regs)
 72{
 73	if (crash_shutdown_cpu == smp_processor_id())
 74		longjmp(crash_shutdown_buf, 1);
 75	return 0;
 76}
 77
 78#ifdef CONFIG_SMP
 79
 80static atomic_t cpus_in_crash;
 81void crash_ipi_callback(struct pt_regs *regs)
 82{
 83	static cpumask_t cpus_state_saved = CPU_MASK_NONE;
 84
 85	int cpu = smp_processor_id();
 86
 87	hard_irq_disable();
 88	if (!cpumask_test_cpu(cpu, &cpus_state_saved)) {
 89		crash_save_cpu(regs, cpu);
 90		cpumask_set_cpu(cpu, &cpus_state_saved);
 91	}
 92
 93	atomic_inc(&cpus_in_crash);
 94	smp_mb__after_atomic();
 95
 96	/*
 97	 * Starting the kdump boot.
 98	 * This barrier is needed to make sure that all CPUs are stopped.
 99	 */
100	while (!time_to_dump)
101		cpu_relax();
102
103	if (ppc_md.kexec_cpu_down)
104		ppc_md.kexec_cpu_down(1, 1);
105
106#ifdef CONFIG_PPC64
107	kexec_smp_wait();
108#else
109	for (;;);	/* FIXME */
110#endif
111
112	/* NOTREACHED */
113}
114
115static void crash_kexec_prepare_cpus(void)
116{
117	unsigned int msecs;
118	volatile unsigned int ncpus = num_online_cpus() - 1;/* Excluding the panic cpu */
119	volatile int tries = 0;
120	int (*old_handler)(struct pt_regs *regs);
121
122	printk(KERN_EMERG "Sending IPI to other CPUs\n");
123
124	if (crash_wake_offline)
125		ncpus = num_present_cpus() - 1;
126
127	/*
128	 * If we came in via system reset, secondaries enter via crash_kexec_secondary().
129	 * So, wait a while for the secondary CPUs to enter for that case.
130	 * Else, send IPI to all other CPUs.
131	 */
132	if (is_via_system_reset)
133		mdelay(PRIMARY_TIMEOUT);
134	else
135		crash_send_ipi(crash_ipi_callback);
136	smp_wmb();
137
138again:
139	/*
140	 * FIXME: Until we will have the way to stop other CPUs reliably,
141	 * the crash CPU will send an IPI and wait for other CPUs to
142	 * respond.
143	 */
144	msecs = IPI_TIMEOUT;
145	while ((atomic_read(&cpus_in_crash) < ncpus) && (--msecs > 0))
146		mdelay(1);
147
148	/* Would it be better to replace the trap vector here? */
149
150	if (atomic_read(&cpus_in_crash) >= ncpus) {
151		printk(KERN_EMERG "IPI complete\n");
152		return;
153	}
154
155	printk(KERN_EMERG "ERROR: %d cpu(s) not responding\n",
156		ncpus - atomic_read(&cpus_in_crash));
157
158	/*
159	 * If we have a panic timeout set then we can't wait indefinitely
160	 * for someone to activate system reset. We also give up on the
161	 * second time through if system reset fail to work.
162	 */
163	if ((panic_timeout > 0) || (tries > 0))
164		return;
165
166	/*
167	 * A system reset will cause all CPUs to take an 0x100 exception.
168	 * The primary CPU returns here via setjmp, and the secondary
169	 * CPUs reexecute the crash_kexec_secondary path.
170	 */
171	old_handler = __debugger;
172	__debugger = handle_fault;
173	crash_shutdown_cpu = smp_processor_id();
174
175	if (setjmp(crash_shutdown_buf) == 0) {
176		printk(KERN_EMERG "Activate system reset (dumprestart) "
177				  "to stop other cpu(s)\n");
178
179		/*
180		 * A system reset will force all CPUs to execute the
181		 * crash code again. We need to reset cpus_in_crash so we
182		 * wait for everyone to do this.
183		 */
184		atomic_set(&cpus_in_crash, 0);
185		smp_mb();
186
187		while (atomic_read(&cpus_in_crash) < ncpus)
188			cpu_relax();
189	}
190
191	crash_shutdown_cpu = -1;
192	__debugger = old_handler;
193
194	tries++;
195	goto again;
196}
197
198/*
199 * This function will be called by secondary cpus.
200 */
201void crash_kexec_secondary(struct pt_regs *regs)
202{
203	unsigned long flags;
204	int msecs = SECONDARY_TIMEOUT;
205
206	local_irq_save(flags);
207
208	/* Wait for the primary crash CPU to signal its progress */
209	while (crashing_cpu < 0) {
210		if (--msecs < 0) {
211			/* No response, kdump image may not have been loaded */
212			local_irq_restore(flags);
213			return;
214		}
215
216		mdelay(1);
217	}
218
219	crash_ipi_callback(regs);
220}
221
222#else	/* ! CONFIG_SMP */
223
224static void crash_kexec_prepare_cpus(void)
225{
226	/*
227	 * move the secondaries to us so that we can copy
228	 * the new kernel 0-0x100 safely
229	 *
230	 * do this if kexec in setup.c ?
231	 */
232#ifdef CONFIG_PPC64
233	smp_release_cpus();
234#else
235	/* FIXME */
236#endif
237}
238
239void crash_kexec_secondary(struct pt_regs *regs)
240{
241}
242#endif	/* CONFIG_SMP */
243
244/* wait for all the CPUs to hit real mode but timeout if they don't come in */
245#if defined(CONFIG_SMP) && defined(CONFIG_PPC64)
246noinstr static void __maybe_unused crash_kexec_wait_realmode(int cpu)
247{
248	unsigned int msecs;
249	int i;
250
251	msecs = REAL_MODE_TIMEOUT;
252	for (i=0; i < nr_cpu_ids && msecs > 0; i++) {
253		if (i == cpu)
254			continue;
255
256		while (paca_ptrs[i]->kexec_state < KEXEC_STATE_REAL_MODE) {
257			barrier();
258			if (!cpu_possible(i) || !cpu_online(i) || (msecs <= 0))
259				break;
260			msecs--;
261			mdelay(1);
262		}
263	}
264	mb();
265}
266#else
267static inline void crash_kexec_wait_realmode(int cpu) {}
268#endif	/* CONFIG_SMP && CONFIG_PPC64 */
269
270void crash_kexec_prepare(void)
271{
272	/* Avoid hardlocking with irresponsive CPU holding logbuf_lock */
273	printk_deferred_enter();
274
275	/*
276	 * This function is only called after the system
277	 * has panicked or is otherwise in a critical state.
278	 * The minimum amount of code to allow a kexec'd kernel
279	 * to run successfully needs to happen here.
280	 *
281	 * In practice this means stopping other cpus in
282	 * an SMP system.
283	 * The kernel is broken so disable interrupts.
284	 */
285	hard_irq_disable();
286
287	/*
288	 * Make a note of crashing cpu. Will be used in machine_kexec
289	 * such that another IPI will not be sent.
290	 */
291	crashing_cpu = smp_processor_id();
292
293	crash_kexec_prepare_cpus();
294}
295
296/*
297 * Register a function to be called on shutdown.  Only use this if you
298 * can't reset your device in the second kernel.
299 */
300int crash_shutdown_register(crash_shutdown_t handler)
301{
302	unsigned int i, rc;
303
304	spin_lock(&crash_handlers_lock);
305	for (i = 0 ; i < CRASH_HANDLER_MAX; i++)
306		if (!crash_shutdown_handles[i]) {
307			/* Insert handle at first empty entry */
308			crash_shutdown_handles[i] = handler;
309			rc = 0;
310			break;
311		}
312
313	if (i == CRASH_HANDLER_MAX) {
314		printk(KERN_ERR "Crash shutdown handles full, "
315		       "not registered.\n");
316		rc = 1;
317	}
318
319	spin_unlock(&crash_handlers_lock);
320	return rc;
321}
322EXPORT_SYMBOL(crash_shutdown_register);
323
324int crash_shutdown_unregister(crash_shutdown_t handler)
325{
326	unsigned int i, rc;
327
328	spin_lock(&crash_handlers_lock);
329	for (i = 0 ; i < CRASH_HANDLER_MAX; i++)
330		if (crash_shutdown_handles[i] == handler)
331			break;
332
333	if (i == CRASH_HANDLER_MAX) {
334		printk(KERN_ERR "Crash shutdown handle not found\n");
335		rc = 1;
336	} else {
337		/* Shift handles down */
338		for (; i < (CRASH_HANDLER_MAX - 1); i++)
339			crash_shutdown_handles[i] =
340				crash_shutdown_handles[i+1];
341		/*
342		 * Reset last entry to NULL now that it has been shifted down,
343		 * this will allow new handles to be added here.
344		 */
345		crash_shutdown_handles[i] = NULL;
346		rc = 0;
347	}
348
349	spin_unlock(&crash_handlers_lock);
350	return rc;
351}
352EXPORT_SYMBOL(crash_shutdown_unregister);
353
354void default_machine_crash_shutdown(struct pt_regs *regs)
355{
356	volatile unsigned int i;
357	int (*old_handler)(struct pt_regs *regs);
358
359	if (TRAP(regs) == INTERRUPT_SYSTEM_RESET)
360		is_via_system_reset = 1;
361
362	if (IS_ENABLED(CONFIG_SMP))
363		crash_smp_send_stop();
364	else
365		crash_kexec_prepare();
366
367	crash_save_cpu(regs, crashing_cpu);
368
369	time_to_dump = 1;
370
371	crash_kexec_wait_realmode(crashing_cpu);
372
373	machine_kexec_mask_interrupts();
374
375	/*
376	 * Call registered shutdown routines safely.  Swap out
377	 * __debugger_fault_handler, and replace on exit.
378	 */
379	old_handler = __debugger_fault_handler;
380	__debugger_fault_handler = handle_fault;
381	crash_shutdown_cpu = smp_processor_id();
382	for (i = 0; i < CRASH_HANDLER_MAX && crash_shutdown_handles[i]; i++) {
383		if (setjmp(crash_shutdown_buf) == 0) {
384			/*
385			 * Insert syncs and delay to ensure
386			 * instructions in the dangerous region don't
387			 * leak away from this protected region.
388			 */
389			asm volatile("sync; isync");
390			/* dangerous region */
391			crash_shutdown_handles[i]();
392			asm volatile("sync; isync");
393		}
394	}
395	crash_shutdown_cpu = -1;
396	__debugger_fault_handler = old_handler;
397
398	if (ppc_md.kexec_cpu_down)
399		ppc_md.kexec_cpu_down(1, 0);
400}
401
402#ifdef CONFIG_CRASH_HOTPLUG
403#undef pr_fmt
404#define pr_fmt(fmt) "crash hp: " fmt
405
406/*
407 * Advertise preferred elfcorehdr size to userspace via
408 * /sys/kernel/crash_elfcorehdr_size sysfs interface.
409 */
410unsigned int arch_crash_get_elfcorehdr_size(void)
411{
412	unsigned long phdr_cnt;
413
414	/* A program header for possible CPUs + vmcoreinfo */
415	phdr_cnt = num_possible_cpus() + 1;
416	if (IS_ENABLED(CONFIG_MEMORY_HOTPLUG))
417		phdr_cnt += CONFIG_CRASH_MAX_MEMORY_RANGES;
418
419	return sizeof(struct elfhdr) + (phdr_cnt * sizeof(Elf64_Phdr));
420}
421
422/**
423 * update_crash_elfcorehdr() - Recreate the elfcorehdr and replace it with old
424 *			       elfcorehdr in the kexec segment array.
425 * @image: the active struct kimage
426 * @mn: struct memory_notify data handler
427 */
428static void update_crash_elfcorehdr(struct kimage *image, struct memory_notify *mn)
429{
430	int ret;
431	struct crash_mem *cmem = NULL;
432	struct kexec_segment *ksegment;
433	void *ptr, *mem, *elfbuf = NULL;
434	unsigned long elfsz, memsz, base_addr, size;
435
436	ksegment = &image->segment[image->elfcorehdr_index];
437	mem = (void *) ksegment->mem;
438	memsz = ksegment->memsz;
439
440	ret = get_crash_memory_ranges(&cmem);
441	if (ret) {
442		pr_err("Failed to get crash mem range\n");
443		return;
444	}
445
446	/*
447	 * The hot unplugged memory is part of crash memory ranges,
448	 * remove it here.
449	 */
450	if (image->hp_action == KEXEC_CRASH_HP_REMOVE_MEMORY) {
451		base_addr = PFN_PHYS(mn->start_pfn);
452		size = mn->nr_pages * PAGE_SIZE;
453		ret = remove_mem_range(&cmem, base_addr, size);
454		if (ret) {
455			pr_err("Failed to remove hot-unplugged memory from crash memory ranges\n");
456			goto out;
457		}
458	}
459
460	ret = crash_prepare_elf64_headers(cmem, false, &elfbuf, &elfsz);
461	if (ret) {
462		pr_err("Failed to prepare elf header\n");
463		goto out;
464	}
465
466	/*
467	 * It is unlikely that kernel hit this because elfcorehdr kexec
468	 * segment (memsz) is built with addition space to accommodate growing
469	 * number of crash memory ranges while loading the kdump kernel. It is
470	 * Just to avoid any unforeseen case.
471	 */
472	if (elfsz > memsz) {
473		pr_err("Updated crash elfcorehdr elfsz %lu > memsz %lu", elfsz, memsz);
474		goto out;
475	}
476
477	ptr = __va(mem);
478	if (ptr) {
479		/* Temporarily invalidate the crash image while it is replaced */
480		xchg(&kexec_crash_image, NULL);
481
482		/* Replace the old elfcorehdr with newly prepared elfcorehdr */
483		memcpy((void *)ptr, elfbuf, elfsz);
484
485		/* The crash image is now valid once again */
486		xchg(&kexec_crash_image, image);
487	}
488out:
489	kvfree(cmem);
490	kvfree(elfbuf);
491}
492
493/**
494 * get_fdt_index - Loop through the kexec segment array and find
495 *		   the index of the FDT segment.
496 * @image: a pointer to kexec_crash_image
497 *
498 * Returns the index of FDT segment in the kexec segment array
499 * if found; otherwise -1.
500 */
501static int get_fdt_index(struct kimage *image)
502{
503	void *ptr;
504	unsigned long mem;
505	int i, fdt_index = -1;
506
507	/* Find the FDT segment index in kexec segment array. */
508	for (i = 0; i < image->nr_segments; i++) {
509		mem = image->segment[i].mem;
510		ptr = __va(mem);
511
512		if (ptr && fdt_magic(ptr) == FDT_MAGIC) {
513			fdt_index = i;
514			break;
515		}
516	}
517
518	return fdt_index;
519}
520
521/**
522 * update_crash_fdt - updates the cpus node of the crash FDT.
523 *
524 * @image: a pointer to kexec_crash_image
525 */
526static void update_crash_fdt(struct kimage *image)
527{
528	void *fdt;
529	int fdt_index;
530
531	fdt_index = get_fdt_index(image);
532	if (fdt_index < 0) {
533		pr_err("Unable to locate FDT segment.\n");
534		return;
535	}
536
537	fdt = __va((void *)image->segment[fdt_index].mem);
538
539	/* Temporarily invalidate the crash image while it is replaced */
540	xchg(&kexec_crash_image, NULL);
541
542	/* update FDT to reflect changes in CPU resources */
543	if (update_cpus_node(fdt))
544		pr_err("Failed to update crash FDT");
545
546	/* The crash image is now valid once again */
547	xchg(&kexec_crash_image, image);
548}
549
550int arch_crash_hotplug_support(struct kimage *image, unsigned long kexec_flags)
551{
552#ifdef CONFIG_KEXEC_FILE
553	if (image->file_mode)
554		return 1;
555#endif
556	return kexec_flags & KEXEC_CRASH_HOTPLUG_SUPPORT;
557}
558
559/**
560 * arch_crash_handle_hotplug_event - Handle crash CPU/Memory hotplug events to update the
561 *				     necessary kexec segments based on the hotplug event.
562 * @image: a pointer to kexec_crash_image
563 * @arg: struct memory_notify handler for memory hotplug case and NULL for CPU hotplug case.
564 *
565 * Update the kdump image based on the type of hotplug event, represented by image->hp_action.
566 * CPU add: Update the FDT segment to include the newly added CPU.
567 * CPU remove: No action is needed, with the assumption that it's okay to have offline CPUs
568 *	       part of the FDT.
569 * Memory add/remove: No action is taken as this is not yet supported.
570 */
571void arch_crash_handle_hotplug_event(struct kimage *image, void *arg)
572{
573	struct memory_notify *mn;
574
575	switch (image->hp_action) {
576	case KEXEC_CRASH_HP_REMOVE_CPU:
577		return;
578
579	case KEXEC_CRASH_HP_ADD_CPU:
580		update_crash_fdt(image);
581		break;
582
583	case KEXEC_CRASH_HP_REMOVE_MEMORY:
584	case KEXEC_CRASH_HP_ADD_MEMORY:
585		mn = (struct memory_notify *)arg;
586		update_crash_elfcorehdr(image, mn);
587		return;
588	default:
589		pr_warn_once("Unknown hotplug action\n");
590	}
591}
592#endif /* CONFIG_CRASH_HOTPLUG */