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	/* Avoid hardlocking with irresponsive CPU holding logbuf_lock */
315	printk_nmi_enter();
316
317	/*
318	 * This function is only called after the system
319	 * has panicked or is otherwise in a critical state.
320	 * The minimum amount of code to allow a kexec'd kernel
321	 * to run successfully needs to happen here.
322	 *
323	 * In practice this means stopping other cpus in
324	 * an SMP system.
325	 * The kernel is broken so disable interrupts.
326	 */
327	hard_irq_disable();
328
329	/*
330	 * Make a note of crashing cpu. Will be used in machine_kexec
331	 * such that another IPI will not be sent.
332	 */
333	crashing_cpu = smp_processor_id();
334
335	/*
336	 * If we came in via system reset, wait a while for the secondary
337	 * CPUs to enter.
338	 */
339	if (TRAP(regs) == 0x100)
340		mdelay(PRIMARY_TIMEOUT);
341
342	crash_kexec_prepare_cpus(crashing_cpu);
343
344	crash_save_cpu(regs, crashing_cpu);
345
346	time_to_dump = 1;
347
348	crash_kexec_wait_realmode(crashing_cpu);
349
350	machine_kexec_mask_interrupts();
351
352	/*
353	 * Call registered shutdown routines safely.  Swap out
354	 * __debugger_fault_handler, and replace on exit.
355	 */
356	old_handler = __debugger_fault_handler;
357	__debugger_fault_handler = handle_fault;
358	crash_shutdown_cpu = smp_processor_id();
359	for (i = 0; i < CRASH_HANDLER_MAX && crash_shutdown_handles[i]; i++) {
360		if (setjmp(crash_shutdown_buf) == 0) {
361			/*
362			 * Insert syncs and delay to ensure
363			 * instructions in the dangerous region don't
364			 * leak away from this protected region.
365			 */
366			asm volatile("sync; isync");
367			/* dangerous region */
368			crash_shutdown_handles[i]();
369			asm volatile("sync; isync");
370		}
371	}
372	crash_shutdown_cpu = -1;
373	__debugger_fault_handler = old_handler;
374
375	if (ppc_md.kexec_cpu_down)
376		ppc_md.kexec_cpu_down(1, 0);
377}
378