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
 20#include <asm/processor.h>
 21#include <asm/machdep.h>
 22#include <asm/kexec.h>
 23#include <asm/prom.h>
 24#include <asm/smp.h>
 25#include <asm/setjmp.h>
 26#include <asm/debug.h>
 27
 28/*
 29 * The primary CPU waits a while for all secondary CPUs to enter. This is to
 30 * avoid sending an IPI if the secondary CPUs are entering
 31 * crash_kexec_secondary on their own (eg via a system reset).
 32 *
 33 * The secondary timeout has to be longer than the primary. Both timeouts are
 34 * in milliseconds.
 35 */
 36#define PRIMARY_TIMEOUT		500
 37#define SECONDARY_TIMEOUT	1000
 38
 39#define IPI_TIMEOUT		10000
 40#define REAL_MODE_TIMEOUT	10000
 41
 42static int time_to_dump;
 43/*
 44 * crash_wake_offline should be set to 1 by platforms that intend to wake
 45 * up offline cpus prior to jumping to a kdump kernel. Currently powernv
 46 * sets it to 1, since we want to avoid things from happening when an
 47 * offline CPU wakes up due to something like an HMI (malfunction error),
 48 * which propagates to all threads.
 49 */
 50int crash_wake_offline;
 51
 52#define CRASH_HANDLER_MAX 3
 53/* List of shutdown handles */
 54static crash_shutdown_t crash_shutdown_handles[CRASH_HANDLER_MAX];
 55static DEFINE_SPINLOCK(crash_handlers_lock);
 56
 57static unsigned long crash_shutdown_buf[JMP_BUF_LEN];
 58static int crash_shutdown_cpu = -1;
 59
 60static int handle_fault(struct pt_regs *regs)
 61{
 62	if (crash_shutdown_cpu == smp_processor_id())
 63		longjmp(crash_shutdown_buf, 1);
 64	return 0;
 65}
 66
 67#ifdef CONFIG_SMP
 68
 69static atomic_t cpus_in_crash;
 70void crash_ipi_callback(struct pt_regs *regs)
 71{
 72	static cpumask_t cpus_state_saved = CPU_MASK_NONE;
 73
 74	int cpu = smp_processor_id();
 75
 76	hard_irq_disable();
 77	if (!cpumask_test_cpu(cpu, &cpus_state_saved)) {
 78		crash_save_cpu(regs, cpu);
 79		cpumask_set_cpu(cpu, &cpus_state_saved);
 80	}
 81
 82	atomic_inc(&cpus_in_crash);
 83	smp_mb__after_atomic();
 84
 85	/*
 86	 * Starting the kdump boot.
 87	 * This barrier is needed to make sure that all CPUs are stopped.
 88	 */
 89	while (!time_to_dump)
 90		cpu_relax();
 91
 92	if (ppc_md.kexec_cpu_down)
 93		ppc_md.kexec_cpu_down(1, 1);
 94
 95#ifdef CONFIG_PPC64
 96	kexec_smp_wait();
 97#else
 98	for (;;);	/* FIXME */
 99#endif
100
101	/* NOTREACHED */
102}
103
104static void crash_kexec_prepare_cpus(int cpu)
105{
106	unsigned int msecs;
107	unsigned int ncpus = num_online_cpus() - 1;/* Excluding the panic cpu */
108	int tries = 0;
109	int (*old_handler)(struct pt_regs *regs);
110
111	printk(KERN_EMERG "Sending IPI to other CPUs\n");
112
113	if (crash_wake_offline)
114		ncpus = num_present_cpus() - 1;
115
116	crash_send_ipi(crash_ipi_callback);
117	smp_wmb();
118
119again:
120	/*
121	 * FIXME: Until we will have the way to stop other CPUs reliably,
122	 * the crash CPU will send an IPI and wait for other CPUs to
123	 * respond.
124	 */
125	msecs = IPI_TIMEOUT;
126	while ((atomic_read(&cpus_in_crash) < ncpus) && (--msecs > 0))
127		mdelay(1);
128
129	/* Would it be better to replace the trap vector here? */
130
131	if (atomic_read(&cpus_in_crash) >= ncpus) {
132		printk(KERN_EMERG "IPI complete\n");
133		return;
134	}
135
136	printk(KERN_EMERG "ERROR: %d cpu(s) not responding\n",
137		ncpus - atomic_read(&cpus_in_crash));
138
139	/*
140	 * If we have a panic timeout set then we can't wait indefinitely
141	 * for someone to activate system reset. We also give up on the
142	 * second time through if system reset fail to work.
143	 */
144	if ((panic_timeout > 0) || (tries > 0))
145		return;
146
147	/*
148	 * A system reset will cause all CPUs to take an 0x100 exception.
149	 * The primary CPU returns here via setjmp, and the secondary
150	 * CPUs reexecute the crash_kexec_secondary path.
151	 */
152	old_handler = __debugger;
153	__debugger = handle_fault;
154	crash_shutdown_cpu = smp_processor_id();
155
156	if (setjmp(crash_shutdown_buf) == 0) {
157		printk(KERN_EMERG "Activate system reset (dumprestart) "
158				  "to stop other cpu(s)\n");
159
160		/*
161		 * A system reset will force all CPUs to execute the
162		 * crash code again. We need to reset cpus_in_crash so we
163		 * wait for everyone to do this.
164		 */
165		atomic_set(&cpus_in_crash, 0);
166		smp_mb();
167
168		while (atomic_read(&cpus_in_crash) < ncpus)
169			cpu_relax();
170	}
171
172	crash_shutdown_cpu = -1;
173	__debugger = old_handler;
174
175	tries++;
176	goto again;
177}
178
179/*
180 * This function will be called by secondary cpus.
181 */
182void crash_kexec_secondary(struct pt_regs *regs)
183{
184	unsigned long flags;
185	int msecs = SECONDARY_TIMEOUT;
186
187	local_irq_save(flags);
188
189	/* Wait for the primary crash CPU to signal its progress */
190	while (crashing_cpu < 0) {
191		if (--msecs < 0) {
192			/* No response, kdump image may not have been loaded */
193			local_irq_restore(flags);
194			return;
195		}
196
197		mdelay(1);
198	}
199
200	crash_ipi_callback(regs);
201}
202
203#else	/* ! CONFIG_SMP */
204
205static void crash_kexec_prepare_cpus(int cpu)
206{
207	/*
208	 * move the secondaries to us so that we can copy
209	 * the new kernel 0-0x100 safely
210	 *
211	 * do this if kexec in setup.c ?
212	 */
213#ifdef CONFIG_PPC64
214	smp_release_cpus();
215#else
216	/* FIXME */
217#endif
218}
219
220void crash_kexec_secondary(struct pt_regs *regs)
221{
222}
223#endif	/* CONFIG_SMP */
224
225/* wait for all the CPUs to hit real mode but timeout if they don't come in */
226#if defined(CONFIG_SMP) && defined(CONFIG_PPC64)
227static void __maybe_unused crash_kexec_wait_realmode(int cpu)
228{
229	unsigned int msecs;
230	int i;
231
232	msecs = REAL_MODE_TIMEOUT;
233	for (i=0; i < nr_cpu_ids && msecs > 0; i++) {
234		if (i == cpu)
235			continue;
236
237		while (paca_ptrs[i]->kexec_state < KEXEC_STATE_REAL_MODE) {
238			barrier();
239			if (!cpu_possible(i) || !cpu_online(i) || (msecs <= 0))
240				break;
241			msecs--;
242			mdelay(1);
243		}
244	}
245	mb();
246}
247#else
248static inline void crash_kexec_wait_realmode(int cpu) {}
249#endif	/* CONFIG_SMP && CONFIG_PPC64 */
250
251/*
252 * Register a function to be called on shutdown.  Only use this if you
253 * can't reset your device in the second kernel.
254 */
255int crash_shutdown_register(crash_shutdown_t handler)
256{
257	unsigned int i, rc;
258
259	spin_lock(&crash_handlers_lock);
260	for (i = 0 ; i < CRASH_HANDLER_MAX; i++)
261		if (!crash_shutdown_handles[i]) {
262			/* Insert handle at first empty entry */
263			crash_shutdown_handles[i] = handler;
264			rc = 0;
265			break;
266		}
267
268	if (i == CRASH_HANDLER_MAX) {
269		printk(KERN_ERR "Crash shutdown handles full, "
270		       "not registered.\n");
271		rc = 1;
272	}
273
274	spin_unlock(&crash_handlers_lock);
275	return rc;
276}
277EXPORT_SYMBOL(crash_shutdown_register);
278
279int crash_shutdown_unregister(crash_shutdown_t handler)
280{
281	unsigned int i, rc;
282
283	spin_lock(&crash_handlers_lock);
284	for (i = 0 ; i < CRASH_HANDLER_MAX; i++)
285		if (crash_shutdown_handles[i] == handler)
286			break;
287
288	if (i == CRASH_HANDLER_MAX) {
289		printk(KERN_ERR "Crash shutdown handle not found\n");
290		rc = 1;
291	} else {
292		/* Shift handles down */
293		for (; i < (CRASH_HANDLER_MAX - 1); i++)
294			crash_shutdown_handles[i] =
295				crash_shutdown_handles[i+1];
296		/*
297		 * Reset last entry to NULL now that it has been shifted down,
298		 * this will allow new handles to be added here.
299		 */
300		crash_shutdown_handles[i] = NULL;
301		rc = 0;
302	}
303
304	spin_unlock(&crash_handlers_lock);
305	return rc;
306}
307EXPORT_SYMBOL(crash_shutdown_unregister);
308
309void default_machine_crash_shutdown(struct pt_regs *regs)
310{
311	unsigned int i;
312	int (*old_handler)(struct pt_regs *regs);
313
314	/*
315	 * This function is only called after the system
316	 * has panicked or is otherwise in a critical state.
317	 * The minimum amount of code to allow a kexec'd kernel
318	 * to run successfully needs to happen here.
319	 *
320	 * In practice this means stopping other cpus in
321	 * an SMP system.
322	 * The kernel is broken so disable interrupts.
323	 */
324	hard_irq_disable();
325
326	/*
327	 * Make a note of crashing cpu. Will be used in machine_kexec
328	 * such that another IPI will not be sent.
329	 */
330	crashing_cpu = smp_processor_id();
331
332	/*
333	 * If we came in via system reset, wait a while for the secondary
334	 * CPUs to enter.
335	 */
336	if (TRAP(regs) == 0x100)
337		mdelay(PRIMARY_TIMEOUT);
338
339	crash_kexec_prepare_cpus(crashing_cpu);
340
341	crash_save_cpu(regs, crashing_cpu);
342
343	time_to_dump = 1;
344
345	crash_kexec_wait_realmode(crashing_cpu);
346
347	machine_kexec_mask_interrupts();
348
349	/*
350	 * Call registered shutdown routines safely.  Swap out
351	 * __debugger_fault_handler, and replace on exit.
352	 */
353	old_handler = __debugger_fault_handler;
354	__debugger_fault_handler = handle_fault;
355	crash_shutdown_cpu = smp_processor_id();
356	for (i = 0; i < CRASH_HANDLER_MAX && crash_shutdown_handles[i]; i++) {
357		if (setjmp(crash_shutdown_buf) == 0) {
358			/*
359			 * Insert syncs and delay to ensure
360			 * instructions in the dangerous region don't
361			 * leak away from this protected region.
362			 */
363			asm volatile("sync; isync");
364			/* dangerous region */
365			crash_shutdown_handles[i]();
366			asm volatile("sync; isync");
367		}
368	}
369	crash_shutdown_cpu = -1;
370	__debugger_fault_handler = old_handler;
371
372	if (ppc_md.kexec_cpu_down)
373		ppc_md.kexec_cpu_down(1, 0);
374}