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. */
 48int crashing_cpu = -1;
 49static int time_to_dump;
 50
 51#define CRASH_HANDLER_MAX 3
 52/* NULL terminated list of shutdown handles */
 53static crash_shutdown_t crash_shutdown_handles[CRASH_HANDLER_MAX+1];
 54static DEFINE_SPINLOCK(crash_handlers_lock);
 55
 56static unsigned long crash_shutdown_buf[JMP_BUF_LEN];
 57static int crash_shutdown_cpu = -1;
 58
 59static 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
 68static atomic_t cpus_in_crash;
 69void 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
106static 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
118again:
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 */
181void 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
204static 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
219void 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)
226static 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
247static 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 */
254int 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}
276EXPORT_SYMBOL(crash_shutdown_register);
277
278int 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}
301EXPORT_SYMBOL(crash_shutdown_unregister);
302
303void 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}