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Linux/arch/powerpc/kernel/crash.c

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  1 /*
  2  * Architecture specific (PPC64) functions for kexec based crash dumps.
  3  *
  4  * Copyright (C) 2005, IBM Corp.
  5  *
  6  * Created by: Haren Myneni
  7  *
  8  * This source code is licensed under the GNU General Public License,
  9  * Version 2.  See the file COPYING for more details.
 10  *
 11  */
 12 
 13 #include <linux/kernel.h>
 14 #include <linux/smp.h>
 15 #include <linux/reboot.h>
 16 #include <linux/kexec.h>
 17 #include <linux/export.h>
 18 #include <linux/crash_dump.h>
 19 #include <linux/delay.h>
 20 #include <linux/init.h>
 21 #include <linux/irq.h>
 22 #include <linux/types.h>
 23 
 24 #include <asm/processor.h>
 25 #include <asm/machdep.h>
 26 #include <asm/kexec.h>
 27 #include <asm/kdump.h>
 28 #include <asm/prom.h>
 29 #include <asm/smp.h>
 30 #include <asm/setjmp.h>
 31 #include <asm/debug.h>
 32 
 33 /*
 34  * The primary CPU waits a while for all secondary CPUs to enter. This is to
 35  * avoid sending an IPI if the secondary CPUs are entering
 36  * crash_kexec_secondary on their own (eg via a system reset).
 37  *
 38  * The secondary timeout has to be longer than the primary. Both timeouts are
 39  * in milliseconds.
 40  */
 41 #define PRIMARY_TIMEOUT         500
 42 #define SECONDARY_TIMEOUT       1000
 43 
 44 #define IPI_TIMEOUT             10000
 45 #define REAL_MODE_TIMEOUT       10000
 46 
 47 /* This keeps a track of which one is the crashing cpu. */
 48 int crashing_cpu = -1;
 49 static int time_to_dump;
 50 
 51 #define CRASH_HANDLER_MAX 3
 52 /* NULL terminated list of shutdown handles */
 53 static crash_shutdown_t crash_shutdown_handles[CRASH_HANDLER_MAX+1];
 54 static DEFINE_SPINLOCK(crash_handlers_lock);
 55 
 56 static unsigned long crash_shutdown_buf[JMP_BUF_LEN];
 57 static int crash_shutdown_cpu = -1;
 58 
 59 static int handle_fault(struct pt_regs *regs)
 60 {
 61         if (crash_shutdown_cpu == smp_processor_id())
 62                 longjmp(crash_shutdown_buf, 1);
 63         return 0;
 64 }
 65 
 66 #ifdef CONFIG_SMP
 67 
 68 static atomic_t cpus_in_crash;
 69 void crash_ipi_callback(struct pt_regs *regs)
 70 {
 71         static cpumask_t cpus_state_saved = CPU_MASK_NONE;
 72 
 73         int cpu = smp_processor_id();
 74 
 75         if (!cpu_online(cpu))
 76                 return;
 77 
 78         hard_irq_disable();
 79         if (!cpumask_test_cpu(cpu, &cpus_state_saved)) {
 80                 crash_save_cpu(regs, cpu);
 81                 cpumask_set_cpu(cpu, &cpus_state_saved);
 82         }
 83 
 84         atomic_inc(&cpus_in_crash);
 85         smp_mb__after_atomic_inc();
 86 
 87         /*
 88          * Starting the kdump boot.
 89          * This barrier is needed to make sure that all CPUs are stopped.
 90          */
 91         while (!time_to_dump)
 92                 cpu_relax();
 93 
 94         if (ppc_md.kexec_cpu_down)
 95                 ppc_md.kexec_cpu_down(1, 1);
 96 
 97 #ifdef CONFIG_PPC64
 98         kexec_smp_wait();
 99 #else
100         for (;;);       /* FIXME */
101 #endif
102 
103         /* NOTREACHED */
104 }
105 
106 static void crash_kexec_prepare_cpus(int cpu)
107 {
108         unsigned int msecs;
109         unsigned int ncpus = num_online_cpus() - 1;/* Excluding the panic cpu */
110         int tries = 0;
111         int (*old_handler)(struct pt_regs *regs);
112 
113         printk(KERN_EMERG "Sending IPI to other CPUs\n");
114 
115         crash_send_ipi(crash_ipi_callback);
116         smp_wmb();
117 
118 again:
119         /*
120          * FIXME: Until we will have the way to stop other CPUs reliably,
121          * the crash CPU will send an IPI and wait for other CPUs to
122          * respond.
123          */
124         msecs = IPI_TIMEOUT;
125         while ((atomic_read(&cpus_in_crash) < ncpus) && (--msecs > 0))
126                 mdelay(1);
127 
128         /* Would it be better to replace the trap vector here? */
129 
130         if (atomic_read(&cpus_in_crash) >= ncpus) {
131                 printk(KERN_EMERG "IPI complete\n");
132                 return;
133         }
134 
135         printk(KERN_EMERG "ERROR: %d cpu(s) not responding\n",
136                 ncpus - atomic_read(&cpus_in_crash));
137 
138         /*
139          * If we have a panic timeout set then we can't wait indefinitely
140          * for someone to activate system reset. We also give up on the
141          * second time through if system reset fail to work.
142          */
143         if ((panic_timeout > 0) || (tries > 0))
144                 return;
145 
146         /*
147          * A system reset will cause all CPUs to take an 0x100 exception.
148          * The primary CPU returns here via setjmp, and the secondary
149          * CPUs reexecute the crash_kexec_secondary path.
150          */
151         old_handler = __debugger;
152         __debugger = handle_fault;
153         crash_shutdown_cpu = smp_processor_id();
154 
155         if (setjmp(crash_shutdown_buf) == 0) {
156                 printk(KERN_EMERG "Activate system reset (dumprestart) "
157                                   "to stop other cpu(s)\n");
158 
159                 /*
160                  * A system reset will force all CPUs to execute the
161                  * crash code again. We need to reset cpus_in_crash so we
162                  * wait for everyone to do this.
163                  */
164                 atomic_set(&cpus_in_crash, 0);
165                 smp_mb();
166 
167                 while (atomic_read(&cpus_in_crash) < ncpus)
168                         cpu_relax();
169         }
170 
171         crash_shutdown_cpu = -1;
172         __debugger = old_handler;
173 
174         tries++;
175         goto again;
176 }
177 
178 /*
179  * This function will be called by secondary cpus.
180  */
181 void crash_kexec_secondary(struct pt_regs *regs)
182 {
183         unsigned long flags;
184         int msecs = SECONDARY_TIMEOUT;
185 
186         local_irq_save(flags);
187 
188         /* Wait for the primary crash CPU to signal its progress */
189         while (crashing_cpu < 0) {
190                 if (--msecs < 0) {
191                         /* No response, kdump image may not have been loaded */
192                         local_irq_restore(flags);
193                         return;
194                 }
195 
196                 mdelay(1);
197         }
198 
199         crash_ipi_callback(regs);
200 }
201 
202 #else   /* ! CONFIG_SMP */
203 
204 static void crash_kexec_prepare_cpus(int cpu)
205 {
206         /*
207          * move the secondaries to us so that we can copy
208          * the new kernel 0-0x100 safely
209          *
210          * do this if kexec in setup.c ?
211          */
212 #ifdef CONFIG_PPC64
213         smp_release_cpus();
214 #else
215         /* FIXME */
216 #endif
217 }
218 
219 void crash_kexec_secondary(struct pt_regs *regs)
220 {
221 }
222 #endif  /* CONFIG_SMP */
223 
224 /* wait for all the CPUs to hit real mode but timeout if they don't come in */
225 #if defined(CONFIG_SMP) && defined(CONFIG_PPC_STD_MMU_64)
226 static void crash_kexec_wait_realmode(int cpu)
227 {
228         unsigned int msecs;
229         int i;
230 
231         msecs = REAL_MODE_TIMEOUT;
232         for (i=0; i < nr_cpu_ids && msecs > 0; i++) {
233                 if (i == cpu)
234                         continue;
235 
236                 while (paca[i].kexec_state < KEXEC_STATE_REAL_MODE) {
237                         barrier();
238                         if (!cpu_possible(i) || !cpu_online(i) || (msecs <= 0))
239                                 break;
240                         msecs--;
241                         mdelay(1);
242                 }
243         }
244         mb();
245 }
246 #else
247 static inline void crash_kexec_wait_realmode(int cpu) {}
248 #endif  /* CONFIG_SMP && CONFIG_PPC_STD_MMU_64 */
249 
250 /*
251  * Register a function to be called on shutdown.  Only use this if you
252  * can't reset your device in the second kernel.
253  */
254 int crash_shutdown_register(crash_shutdown_t handler)
255 {
256         unsigned int i, rc;
257 
258         spin_lock(&crash_handlers_lock);
259         for (i = 0 ; i < CRASH_HANDLER_MAX; i++)
260                 if (!crash_shutdown_handles[i]) {
261                         /* Insert handle at first empty entry */
262                         crash_shutdown_handles[i] = handler;
263                         rc = 0;
264                         break;
265                 }
266 
267         if (i == CRASH_HANDLER_MAX) {
268                 printk(KERN_ERR "Crash shutdown handles full, "
269                        "not registered.\n");
270                 rc = 1;
271         }
272 
273         spin_unlock(&crash_handlers_lock);
274         return rc;
275 }
276 EXPORT_SYMBOL(crash_shutdown_register);
277 
278 int crash_shutdown_unregister(crash_shutdown_t handler)
279 {
280         unsigned int i, rc;
281 
282         spin_lock(&crash_handlers_lock);
283         for (i = 0 ; i < CRASH_HANDLER_MAX; i++)
284                 if (crash_shutdown_handles[i] == handler)
285                         break;
286 
287         if (i == CRASH_HANDLER_MAX) {
288                 printk(KERN_ERR "Crash shutdown handle not found\n");
289                 rc = 1;
290         } else {
291                 /* Shift handles down */
292                 for (; crash_shutdown_handles[i]; i++)
293                         crash_shutdown_handles[i] =
294                                 crash_shutdown_handles[i+1];
295                 rc = 0;
296         }
297 
298         spin_unlock(&crash_handlers_lock);
299         return rc;
300 }
301 EXPORT_SYMBOL(crash_shutdown_unregister);
302 
303 void default_machine_crash_shutdown(struct pt_regs *regs)
304 {
305         unsigned int i;
306         int (*old_handler)(struct pt_regs *regs);
307 
308         /*
309          * This function is only called after the system
310          * has panicked or is otherwise in a critical state.
311          * The minimum amount of code to allow a kexec'd kernel
312          * to run successfully needs to happen here.
313          *
314          * In practice this means stopping other cpus in
315          * an SMP system.
316          * The kernel is broken so disable interrupts.
317          */
318         hard_irq_disable();
319 
320         /*
321          * Make a note of crashing cpu. Will be used in machine_kexec
322          * such that another IPI will not be sent.
323          */
324         crashing_cpu = smp_processor_id();
325 
326         /*
327          * If we came in via system reset, wait a while for the secondary
328          * CPUs to enter.
329          */
330         if (TRAP(regs) == 0x100)
331                 mdelay(PRIMARY_TIMEOUT);
332 
333         crash_kexec_prepare_cpus(crashing_cpu);
334 
335         crash_save_cpu(regs, crashing_cpu);
336 
337         time_to_dump = 1;
338 
339         crash_kexec_wait_realmode(crashing_cpu);
340 
341         machine_kexec_mask_interrupts();
342 
343         /*
344          * Call registered shutdown routines safely.  Swap out
345          * __debugger_fault_handler, and replace on exit.
346          */
347         old_handler = __debugger_fault_handler;
348         __debugger_fault_handler = handle_fault;
349         crash_shutdown_cpu = smp_processor_id();
350         for (i = 0; crash_shutdown_handles[i]; i++) {
351                 if (setjmp(crash_shutdown_buf) == 0) {
352                         /*
353                          * Insert syncs and delay to ensure
354                          * instructions in the dangerous region don't
355                          * leak away from this protected region.
356                          */
357                         asm volatile("sync; isync");
358                         /* dangerous region */
359                         crash_shutdown_handles[i]();
360                         asm volatile("sync; isync");
361                 }
362         }
363         crash_shutdown_cpu = -1;
364         __debugger_fault_handler = old_handler;
365 
366         if (ppc_md.kexec_cpu_down)
367                 ppc_md.kexec_cpu_down(1, 0);
368 }
369 

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