xref: /linux/arch/powerpc/kexec/crash.c (revision ff2632d7d08edc11e8bd0629e9fcfebab25c78b4)
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 
45 static 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  */
52 static 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  */
61 int crash_wake_offline;
62 
63 #define CRASH_HANDLER_MAX 3
64 /* List of shutdown handles */
65 static crash_shutdown_t crash_shutdown_handles[CRASH_HANDLER_MAX];
66 static DEFINE_SPINLOCK(crash_handlers_lock);
67 
68 static unsigned long crash_shutdown_buf[JMP_BUF_LEN];
69 static int crash_shutdown_cpu = -1;
70 
handle_fault(struct pt_regs * regs)71 static 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 
80 static atomic_t cpus_in_crash;
crash_ipi_callback(struct pt_regs * regs)81 void 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 
crash_kexec_prepare_cpus(void)115 static 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 
138 again:
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  */
crash_kexec_secondary(struct pt_regs * regs)201 void 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 
crash_kexec_prepare_cpus(void)224 static 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 
crash_kexec_secondary(struct pt_regs * regs)239 void 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)
crash_kexec_wait_realmode(int cpu)246 noinstr 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
crash_kexec_wait_realmode(int cpu)267 static inline void crash_kexec_wait_realmode(int cpu) {}
268 #endif	/* CONFIG_SMP && CONFIG_PPC64 */
269 
crash_kexec_prepare(void)270 void 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  */
crash_shutdown_register(crash_shutdown_t handler)300 int 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 }
322 EXPORT_SYMBOL(crash_shutdown_register);
323 
crash_shutdown_unregister(crash_shutdown_t handler)324 int 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 }
352 EXPORT_SYMBOL(crash_shutdown_unregister);
353 
default_machine_crash_shutdown(struct pt_regs * regs)354 void 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 	crash_smp_send_stop();
363 
364 	crash_save_cpu(regs, crashing_cpu);
365 
366 	time_to_dump = 1;
367 
368 	crash_kexec_wait_realmode(crashing_cpu);
369 
370 	machine_kexec_mask_interrupts();
371 
372 	/*
373 	 * Call registered shutdown routines safely.  Swap out
374 	 * __debugger_fault_handler, and replace on exit.
375 	 */
376 	old_handler = __debugger_fault_handler;
377 	__debugger_fault_handler = handle_fault;
378 	crash_shutdown_cpu = smp_processor_id();
379 	for (i = 0; i < CRASH_HANDLER_MAX && crash_shutdown_handles[i]; i++) {
380 		if (setjmp(crash_shutdown_buf) == 0) {
381 			/*
382 			 * Insert syncs and delay to ensure
383 			 * instructions in the dangerous region don't
384 			 * leak away from this protected region.
385 			 */
386 			asm volatile("sync; isync");
387 			/* dangerous region */
388 			crash_shutdown_handles[i]();
389 			asm volatile("sync; isync");
390 		}
391 	}
392 	crash_shutdown_cpu = -1;
393 	__debugger_fault_handler = old_handler;
394 
395 	if (ppc_md.kexec_cpu_down)
396 		ppc_md.kexec_cpu_down(1, 0);
397 }
398 
399 #ifdef CONFIG_CRASH_HOTPLUG
400 #undef pr_fmt
401 #define pr_fmt(fmt) "crash hp: " fmt
402 
403 /*
404  * Advertise preferred elfcorehdr size to userspace via
405  * /sys/kernel/crash_elfcorehdr_size sysfs interface.
406  */
arch_crash_get_elfcorehdr_size(void)407 unsigned int arch_crash_get_elfcorehdr_size(void)
408 {
409 	unsigned long phdr_cnt;
410 
411 	/* A program header for possible CPUs + vmcoreinfo */
412 	phdr_cnt = num_possible_cpus() + 1;
413 	if (IS_ENABLED(CONFIG_MEMORY_HOTPLUG))
414 		phdr_cnt += CONFIG_CRASH_MAX_MEMORY_RANGES;
415 
416 	return sizeof(struct elfhdr) + (phdr_cnt * sizeof(Elf64_Phdr));
417 }
418 
419 /**
420  * update_crash_elfcorehdr() - Recreate the elfcorehdr and replace it with old
421  *			       elfcorehdr in the kexec segment array.
422  * @image: the active struct kimage
423  * @mn: struct memory_notify data handler
424  */
update_crash_elfcorehdr(struct kimage * image,struct memory_notify * mn)425 static void update_crash_elfcorehdr(struct kimage *image, struct memory_notify *mn)
426 {
427 	int ret;
428 	struct crash_mem *cmem = NULL;
429 	struct kexec_segment *ksegment;
430 	void *ptr, *mem, *elfbuf = NULL;
431 	unsigned long elfsz, memsz, base_addr, size;
432 
433 	ksegment = &image->segment[image->elfcorehdr_index];
434 	mem = (void *) ksegment->mem;
435 	memsz = ksegment->memsz;
436 
437 	ret = get_crash_memory_ranges(&cmem);
438 	if (ret) {
439 		pr_err("Failed to get crash mem range\n");
440 		return;
441 	}
442 
443 	/*
444 	 * The hot unplugged memory is part of crash memory ranges,
445 	 * remove it here.
446 	 */
447 	if (image->hp_action == KEXEC_CRASH_HP_REMOVE_MEMORY) {
448 		base_addr = PFN_PHYS(mn->start_pfn);
449 		size = mn->nr_pages * PAGE_SIZE;
450 		ret = remove_mem_range(&cmem, base_addr, size);
451 		if (ret) {
452 			pr_err("Failed to remove hot-unplugged memory from crash memory ranges\n");
453 			goto out;
454 		}
455 	}
456 
457 	ret = crash_prepare_elf64_headers(cmem, false, &elfbuf, &elfsz);
458 	if (ret) {
459 		pr_err("Failed to prepare elf header\n");
460 		goto out;
461 	}
462 
463 	/*
464 	 * It is unlikely that kernel hit this because elfcorehdr kexec
465 	 * segment (memsz) is built with addition space to accommodate growing
466 	 * number of crash memory ranges while loading the kdump kernel. It is
467 	 * Just to avoid any unforeseen case.
468 	 */
469 	if (elfsz > memsz) {
470 		pr_err("Updated crash elfcorehdr elfsz %lu > memsz %lu", elfsz, memsz);
471 		goto out;
472 	}
473 
474 	ptr = __va(mem);
475 	if (ptr) {
476 		/* Temporarily invalidate the crash image while it is replaced */
477 		xchg(&kexec_crash_image, NULL);
478 
479 		/* Replace the old elfcorehdr with newly prepared elfcorehdr */
480 		memcpy((void *)ptr, elfbuf, elfsz);
481 
482 		/* The crash image is now valid once again */
483 		xchg(&kexec_crash_image, image);
484 	}
485 out:
486 	kvfree(cmem);
487 	kvfree(elfbuf);
488 }
489 
490 /**
491  * get_fdt_index - Loop through the kexec segment array and find
492  *		   the index of the FDT segment.
493  * @image: a pointer to kexec_crash_image
494  *
495  * Returns the index of FDT segment in the kexec segment array
496  * if found; otherwise -1.
497  */
get_fdt_index(struct kimage * image)498 static int get_fdt_index(struct kimage *image)
499 {
500 	void *ptr;
501 	unsigned long mem;
502 	int i, fdt_index = -1;
503 
504 	/* Find the FDT segment index in kexec segment array. */
505 	for (i = 0; i < image->nr_segments; i++) {
506 		mem = image->segment[i].mem;
507 		ptr = __va(mem);
508 
509 		if (ptr && fdt_magic(ptr) == FDT_MAGIC) {
510 			fdt_index = i;
511 			break;
512 		}
513 	}
514 
515 	return fdt_index;
516 }
517 
518 /**
519  * update_crash_fdt - updates the cpus node of the crash FDT.
520  *
521  * @image: a pointer to kexec_crash_image
522  */
update_crash_fdt(struct kimage * image)523 static void update_crash_fdt(struct kimage *image)
524 {
525 	void *fdt;
526 	int fdt_index;
527 
528 	fdt_index = get_fdt_index(image);
529 	if (fdt_index < 0) {
530 		pr_err("Unable to locate FDT segment.\n");
531 		return;
532 	}
533 
534 	fdt = __va((void *)image->segment[fdt_index].mem);
535 
536 	/* Temporarily invalidate the crash image while it is replaced */
537 	xchg(&kexec_crash_image, NULL);
538 
539 	/* update FDT to reflect changes in CPU resources */
540 	if (update_cpus_node(fdt))
541 		pr_err("Failed to update crash FDT");
542 
543 	/* The crash image is now valid once again */
544 	xchg(&kexec_crash_image, image);
545 }
546 
arch_crash_hotplug_support(struct kimage * image,unsigned long kexec_flags)547 int arch_crash_hotplug_support(struct kimage *image, unsigned long kexec_flags)
548 {
549 #ifdef CONFIG_KEXEC_FILE
550 	if (image->file_mode)
551 		return 1;
552 #endif
553 	return kexec_flags & KEXEC_CRASH_HOTPLUG_SUPPORT;
554 }
555 
556 /**
557  * arch_crash_handle_hotplug_event - Handle crash CPU/Memory hotplug events to update the
558  *				     necessary kexec segments based on the hotplug event.
559  * @image: a pointer to kexec_crash_image
560  * @arg: struct memory_notify handler for memory hotplug case and NULL for CPU hotplug case.
561  *
562  * Update the kdump image based on the type of hotplug event, represented by image->hp_action.
563  * CPU add: Update the FDT segment to include the newly added CPU.
564  * CPU remove: No action is needed, with the assumption that it's okay to have offline CPUs
565  *	       part of the FDT.
566  * Memory add/remove: No action is taken as this is not yet supported.
567  */
arch_crash_handle_hotplug_event(struct kimage * image,void * arg)568 void arch_crash_handle_hotplug_event(struct kimage *image, void *arg)
569 {
570 	struct memory_notify *mn;
571 
572 	switch (image->hp_action) {
573 	case KEXEC_CRASH_HP_REMOVE_CPU:
574 		return;
575 
576 	case KEXEC_CRASH_HP_ADD_CPU:
577 		update_crash_fdt(image);
578 		break;
579 
580 	case KEXEC_CRASH_HP_REMOVE_MEMORY:
581 	case KEXEC_CRASH_HP_ADD_MEMORY:
582 		mn = (struct memory_notify *)arg;
583 		update_crash_elfcorehdr(image, mn);
584 		return;
585 	default:
586 		pr_warn_once("Unknown hotplug action\n");
587 	}
588 }
589 #endif /* CONFIG_CRASH_HOTPLUG */
590