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/smp.h>
24 #include <asm/setjmp.h>
25 #include <asm/debug.h>
26 #include <asm/interrupt.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
42 static int time_to_dump;
43
44 /*
45 * In case of system reset, secondary CPUs enter crash_kexec_secondary with out
46 * having to send an IPI explicitly. So, indicate if the crash is via
47 * system reset to avoid sending another IPI.
48 */
49 static int is_via_system_reset;
50
51 /*
52 * crash_wake_offline should be set to 1 by platforms that intend to wake
53 * up offline cpus prior to jumping to a kdump kernel. Currently powernv
54 * sets it to 1, since we want to avoid things from happening when an
55 * offline CPU wakes up due to something like an HMI (malfunction error),
56 * which propagates to all threads.
57 */
58 int crash_wake_offline;
59
60 #define CRASH_HANDLER_MAX 3
61 /* List of shutdown handles */
62 static crash_shutdown_t crash_shutdown_handles[CRASH_HANDLER_MAX];
63 static DEFINE_SPINLOCK(crash_handlers_lock);
64
65 static unsigned long crash_shutdown_buf[JMP_BUF_LEN];
66 static int crash_shutdown_cpu = -1;
67
handle_fault(struct pt_regs * regs)68 static int handle_fault(struct pt_regs *regs)
69 {
70 if (crash_shutdown_cpu == smp_processor_id())
71 longjmp(crash_shutdown_buf, 1);
72 return 0;
73 }
74
75 #ifdef CONFIG_SMP
76
77 static atomic_t cpus_in_crash;
crash_ipi_callback(struct pt_regs * regs)78 void crash_ipi_callback(struct pt_regs *regs)
79 {
80 static cpumask_t cpus_state_saved = CPU_MASK_NONE;
81
82 int cpu = smp_processor_id();
83
84 hard_irq_disable();
85 if (!cpumask_test_cpu(cpu, &cpus_state_saved)) {
86 crash_save_cpu(regs, cpu);
87 cpumask_set_cpu(cpu, &cpus_state_saved);
88 }
89
90 atomic_inc(&cpus_in_crash);
91 smp_mb__after_atomic();
92
93 /*
94 * Starting the kdump boot.
95 * This barrier is needed to make sure that all CPUs are stopped.
96 */
97 while (!time_to_dump)
98 cpu_relax();
99
100 if (ppc_md.kexec_cpu_down)
101 ppc_md.kexec_cpu_down(1, 1);
102
103 #ifdef CONFIG_PPC64
104 kexec_smp_wait();
105 #else
106 for (;;); /* FIXME */
107 #endif
108
109 /* NOTREACHED */
110 }
111
crash_kexec_prepare_cpus(void)112 static void crash_kexec_prepare_cpus(void)
113 {
114 unsigned int msecs;
115 volatile unsigned int ncpus = num_online_cpus() - 1;/* Excluding the panic cpu */
116 volatile int tries = 0;
117 int (*old_handler)(struct pt_regs *regs);
118
119 printk(KERN_EMERG "Sending IPI to other CPUs\n");
120
121 if (crash_wake_offline)
122 ncpus = num_present_cpus() - 1;
123
124 /*
125 * If we came in via system reset, secondaries enter via crash_kexec_secondary().
126 * So, wait a while for the secondary CPUs to enter for that case.
127 * Else, send IPI to all other CPUs.
128 */
129 if (is_via_system_reset)
130 mdelay(PRIMARY_TIMEOUT);
131 else
132 crash_send_ipi(crash_ipi_callback);
133 smp_wmb();
134
135 again:
136 /*
137 * FIXME: Until we will have the way to stop other CPUs reliably,
138 * the crash CPU will send an IPI and wait for other CPUs to
139 * respond.
140 */
141 msecs = IPI_TIMEOUT;
142 while ((atomic_read(&cpus_in_crash) < ncpus) && (--msecs > 0))
143 mdelay(1);
144
145 /* Would it be better to replace the trap vector here? */
146
147 if (atomic_read(&cpus_in_crash) >= ncpus) {
148 printk(KERN_EMERG "IPI complete\n");
149 return;
150 }
151
152 printk(KERN_EMERG "ERROR: %d cpu(s) not responding\n",
153 ncpus - atomic_read(&cpus_in_crash));
154
155 /*
156 * If we have a panic timeout set then we can't wait indefinitely
157 * for someone to activate system reset. We also give up on the
158 * second time through if system reset fail to work.
159 */
160 if ((panic_timeout > 0) || (tries > 0))
161 return;
162
163 /*
164 * A system reset will cause all CPUs to take an 0x100 exception.
165 * The primary CPU returns here via setjmp, and the secondary
166 * CPUs reexecute the crash_kexec_secondary path.
167 */
168 old_handler = __debugger;
169 __debugger = handle_fault;
170 crash_shutdown_cpu = smp_processor_id();
171
172 if (setjmp(crash_shutdown_buf) == 0) {
173 printk(KERN_EMERG "Activate system reset (dumprestart) "
174 "to stop other cpu(s)\n");
175
176 /*
177 * A system reset will force all CPUs to execute the
178 * crash code again. We need to reset cpus_in_crash so we
179 * wait for everyone to do this.
180 */
181 atomic_set(&cpus_in_crash, 0);
182 smp_mb();
183
184 while (atomic_read(&cpus_in_crash) < ncpus)
185 cpu_relax();
186 }
187
188 crash_shutdown_cpu = -1;
189 __debugger = old_handler;
190
191 tries++;
192 goto again;
193 }
194
195 /*
196 * This function will be called by secondary cpus.
197 */
crash_kexec_secondary(struct pt_regs * regs)198 void crash_kexec_secondary(struct pt_regs *regs)
199 {
200 unsigned long flags;
201 int msecs = SECONDARY_TIMEOUT;
202
203 local_irq_save(flags);
204
205 /* Wait for the primary crash CPU to signal its progress */
206 while (crashing_cpu < 0) {
207 if (--msecs < 0) {
208 /* No response, kdump image may not have been loaded */
209 local_irq_restore(flags);
210 return;
211 }
212
213 mdelay(1);
214 }
215
216 crash_ipi_callback(regs);
217 }
218
219 #else /* ! CONFIG_SMP */
220
crash_kexec_prepare_cpus(void)221 static void crash_kexec_prepare_cpus(void)
222 {
223 /*
224 * move the secondaries to us so that we can copy
225 * the new kernel 0-0x100 safely
226 *
227 * do this if kexec in setup.c ?
228 */
229 #ifdef CONFIG_PPC64
230 smp_release_cpus();
231 #else
232 /* FIXME */
233 #endif
234 }
235
crash_kexec_secondary(struct pt_regs * regs)236 void crash_kexec_secondary(struct pt_regs *regs)
237 {
238 }
239 #endif /* CONFIG_SMP */
240
241 /* wait for all the CPUs to hit real mode but timeout if they don't come in */
242 #if defined(CONFIG_SMP) && defined(CONFIG_PPC64)
crash_kexec_wait_realmode(int cpu)243 noinstr static void __maybe_unused crash_kexec_wait_realmode(int cpu)
244 {
245 unsigned int msecs;
246 int i;
247
248 msecs = REAL_MODE_TIMEOUT;
249 for (i=0; i < nr_cpu_ids && msecs > 0; i++) {
250 if (i == cpu)
251 continue;
252
253 while (paca_ptrs[i]->kexec_state < KEXEC_STATE_REAL_MODE) {
254 barrier();
255 if (!cpu_possible(i) || !cpu_online(i) || (msecs <= 0))
256 break;
257 msecs--;
258 mdelay(1);
259 }
260 }
261 mb();
262 }
263 #else
crash_kexec_wait_realmode(int cpu)264 static inline void crash_kexec_wait_realmode(int cpu) {}
265 #endif /* CONFIG_SMP && CONFIG_PPC64 */
266
crash_kexec_prepare(void)267 void crash_kexec_prepare(void)
268 {
269 /* Avoid hardlocking with irresponsive CPU holding logbuf_lock */
270 printk_deferred_enter();
271
272 /*
273 * This function is only called after the system
274 * has panicked or is otherwise in a critical state.
275 * The minimum amount of code to allow a kexec'd kernel
276 * to run successfully needs to happen here.
277 *
278 * In practice this means stopping other cpus in
279 * an SMP system.
280 * The kernel is broken so disable interrupts.
281 */
282 hard_irq_disable();
283
284 /*
285 * Make a note of crashing cpu. Will be used in machine_kexec
286 * such that another IPI will not be sent.
287 */
288 crashing_cpu = smp_processor_id();
289
290 crash_kexec_prepare_cpus();
291 }
292
293 /*
294 * Register a function to be called on shutdown. Only use this if you
295 * can't reset your device in the second kernel.
296 */
crash_shutdown_register(crash_shutdown_t handler)297 int crash_shutdown_register(crash_shutdown_t handler)
298 {
299 unsigned int i, rc;
300
301 spin_lock(&crash_handlers_lock);
302 for (i = 0 ; i < CRASH_HANDLER_MAX; i++)
303 if (!crash_shutdown_handles[i]) {
304 /* Insert handle at first empty entry */
305 crash_shutdown_handles[i] = handler;
306 rc = 0;
307 break;
308 }
309
310 if (i == CRASH_HANDLER_MAX) {
311 printk(KERN_ERR "Crash shutdown handles full, "
312 "not registered.\n");
313 rc = 1;
314 }
315
316 spin_unlock(&crash_handlers_lock);
317 return rc;
318 }
319 EXPORT_SYMBOL(crash_shutdown_register);
320
crash_shutdown_unregister(crash_shutdown_t handler)321 int crash_shutdown_unregister(crash_shutdown_t handler)
322 {
323 unsigned int i, rc;
324
325 spin_lock(&crash_handlers_lock);
326 for (i = 0 ; i < CRASH_HANDLER_MAX; i++)
327 if (crash_shutdown_handles[i] == handler)
328 break;
329
330 if (i == CRASH_HANDLER_MAX) {
331 printk(KERN_ERR "Crash shutdown handle not found\n");
332 rc = 1;
333 } else {
334 /* Shift handles down */
335 for (; i < (CRASH_HANDLER_MAX - 1); i++)
336 crash_shutdown_handles[i] =
337 crash_shutdown_handles[i+1];
338 /*
339 * Reset last entry to NULL now that it has been shifted down,
340 * this will allow new handles to be added here.
341 */
342 crash_shutdown_handles[i] = NULL;
343 rc = 0;
344 }
345
346 spin_unlock(&crash_handlers_lock);
347 return rc;
348 }
349 EXPORT_SYMBOL(crash_shutdown_unregister);
350
default_machine_crash_shutdown(struct pt_regs * regs)351 void default_machine_crash_shutdown(struct pt_regs *regs)
352 {
353 unsigned int i;
354 int (*old_handler)(struct pt_regs *regs);
355
356 if (TRAP(regs) == INTERRUPT_SYSTEM_RESET)
357 is_via_system_reset = 1;
358
359 crash_smp_send_stop();
360
361 crash_save_cpu(regs, crashing_cpu);
362
363 time_to_dump = 1;
364
365 crash_kexec_wait_realmode(crashing_cpu);
366
367 machine_kexec_mask_interrupts();
368
369 /*
370 * Call registered shutdown routines safely. Swap out
371 * __debugger_fault_handler, and replace on exit.
372 */
373 old_handler = __debugger_fault_handler;
374 __debugger_fault_handler = handle_fault;
375 crash_shutdown_cpu = smp_processor_id();
376 for (i = 0; i < CRASH_HANDLER_MAX && crash_shutdown_handles[i]; i++) {
377 if (setjmp(crash_shutdown_buf) == 0) {
378 /*
379 * Insert syncs and delay to ensure
380 * instructions in the dangerous region don't
381 * leak away from this protected region.
382 */
383 asm volatile("sync; isync");
384 /* dangerous region */
385 crash_shutdown_handles[i]();
386 asm volatile("sync; isync");
387 }
388 }
389 crash_shutdown_cpu = -1;
390 __debugger_fault_handler = old_handler;
391
392 if (ppc_md.kexec_cpu_down)
393 ppc_md.kexec_cpu_down(1, 0);
394 }
395