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Linux/arch/powerpc/kexec/crash.c

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  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 
 42 static 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  */
 50 int crash_wake_offline;
 51 
 52 #define CRASH_HANDLER_MAX 3
 53 /* List of shutdown handles */
 54 static crash_shutdown_t crash_shutdown_handles[CRASH_HANDLER_MAX];
 55 static DEFINE_SPINLOCK(crash_handlers_lock);
 56 
 57 static unsigned long crash_shutdown_buf[JMP_BUF_LEN];
 58 static int crash_shutdown_cpu = -1;
 59 
 60 static 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 
 69 static atomic_t cpus_in_crash;
 70 void 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 
104 static 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 
119 again:
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  */
182 void 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 
205 static 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 
220 void 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)
227 static 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
248 static 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  */
255 int 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 }
277 EXPORT_SYMBOL(crash_shutdown_register);
278 
279 int 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 }
307 EXPORT_SYMBOL(crash_shutdown_unregister);
308 
309 void 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 }
375 

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