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