Release 4.14 arch/powerpc/kernel/crash.c

/*
 * Architecture specific (PPC64) functions for kexec based crash dumps.
 *
 * Copyright (C) 2005, IBM Corp.
 *
 * Created by: Haren Myneni
 *
 * This source code is licensed under the GNU General Public License,
 * Version 2.  See the file COPYING for more details.
 *
 */

#include <linux/kernel.h>
#include <linux/smp.h>
#include <linux/reboot.h>
#include <linux/kexec.h>
#include <linux/export.h>
#include <linux/crash_dump.h>
#include <linux/delay.h>
#include <linux/irq.h>
#include <linux/types.h>

#include <asm/processor.h>
#include <asm/machdep.h>
#include <asm/kexec.h>
#include <asm/kdump.h>
#include <asm/prom.h>
#include <asm/smp.h>
#include <asm/setjmp.h>
#include <asm/debug.h>

/*
 * The primary CPU waits a while for all secondary CPUs to enter. This is to
 * avoid sending an IPI if the secondary CPUs are entering
 * crash_kexec_secondary on their own (eg via a system reset).
 *
 * The secondary timeout has to be longer than the primary. Both timeouts are
 * in milliseconds.
 */

#define PRIMARY_TIMEOUT		500

#define SECONDARY_TIMEOUT	1000


#define IPI_TIMEOUT		10000

#define REAL_MODE_TIMEOUT	10000


static int time_to_dump;


#define CRASH_HANDLER_MAX 3
/* List of shutdown handles */

static crash_shutdown_t crash_shutdown_handles[CRASH_HANDLER_MAX];
static DEFINE_SPINLOCK(crash_handlers_lock);


static unsigned long crash_shutdown_buf[JMP_BUF_LEN];

static int crash_shutdown_cpu = -1;



static int handle_fault(struct pt_regs *regs)
{
	if (crash_shutdown_cpu == smp_processor_id())
		longjmp(crash_shutdown_buf, 1);
	return 0;
}

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#ifdef CONFIG_SMP


static atomic_t cpus_in_crash;


static void crash_ipi_callback(struct pt_regs *regs)
{
	static cpumask_t cpus_state_saved = CPU_MASK_NONE;

	int cpu = smp_processor_id();

	if (!cpu_online(cpu))
		return;

	hard_irq_disable();
	if (!cpumask_test_cpu(cpu, &cpus_state_saved)) {
		crash_save_cpu(regs, cpu);
		cpumask_set_cpu(cpu, &cpus_state_saved);
	}

	atomic_inc(&cpus_in_crash);
	smp_mb__after_atomic();

	/*
         * Starting the kdump boot.
         * This barrier is needed to make sure that all CPUs are stopped.
         */
	while (!time_to_dump)
		cpu_relax();

	if (ppc_md.kexec_cpu_down)
		ppc_md.kexec_cpu_down(1, 1);

#ifdef CONFIG_PPC64
	kexec_smp_wait();
#else
	for (;;);	/* FIXME */
#endif

	/* NOTREACHED */
}

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static void crash_kexec_prepare_cpus(int cpu)
{
	unsigned int msecs;
	unsigned int ncpus = num_online_cpus() - 1;/* Excluding the panic cpu */
	int tries = 0;
	int (*old_handler)(struct pt_regs *regs);

	printk(KERN_EMERG "Sending IPI to other CPUs\n");

	crash_send_ipi(crash_ipi_callback);
	smp_wmb();

again:
	/*
         * FIXME: Until we will have the way to stop other CPUs reliably,
         * the crash CPU will send an IPI and wait for other CPUs to
         * respond.
         */
	msecs = IPI_TIMEOUT;
	while ((atomic_read(&cpus_in_crash) < ncpus) && (--msecs > 0))
		mdelay(1);

	/* Would it be better to replace the trap vector here? */

	if (atomic_read(&cpus_in_crash) >= ncpus) {
		printk(KERN_EMERG "IPI complete\n");
		return;
	}

	printk(KERN_EMERG "ERROR: %d cpu(s) not responding\n",
		ncpus - atomic_read(&cpus_in_crash));

	/*
         * If we have a panic timeout set then we can't wait indefinitely
         * for someone to activate system reset. We also give up on the
         * second time through if system reset fail to work.
         */
	if ((panic_timeout > 0) || (tries > 0))
		return;

	/*
         * A system reset will cause all CPUs to take an 0x100 exception.
         * The primary CPU returns here via setjmp, and the secondary
         * CPUs reexecute the crash_kexec_secondary path.
         */
	old_handler = __debugger;
	__debugger = handle_fault;
	crash_shutdown_cpu = smp_processor_id();

	if (setjmp(crash_shutdown_buf) == 0) {
		printk(KERN_EMERG "Activate system reset (dumprestart) "
				  "to stop other cpu(s)\n");

		/*
                 * A system reset will force all CPUs to execute the
                 * crash code again. We need to reset cpus_in_crash so we
                 * wait for everyone to do this.
                 */
		atomic_set(&cpus_in_crash, 0);
		smp_mb();

		while (atomic_read(&cpus_in_crash) < ncpus)
			cpu_relax();
	}

	crash_shutdown_cpu = -1;
	__debugger = old_handler;

	tries++;
	goto again;
}

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/*
 * This function will be called by secondary cpus.
 */


void crash_kexec_secondary(struct pt_regs *regs)
{
	unsigned long flags;
	int msecs = SECONDARY_TIMEOUT;

	local_irq_save(flags);

	/* Wait for the primary crash CPU to signal its progress */
	while (crashing_cpu < 0) {
		if (--msecs < 0) {
			/* No response, kdump image may not have been loaded */
			local_irq_restore(flags);
			return;
		}

		mdelay(1);
	}

	crash_ipi_callback(regs);
}

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#else	/* ! CONFIG_SMP */



static void crash_kexec_prepare_cpus(int cpu)
{
	/*
         * move the secondaries to us so that we can copy
         * the new kernel 0-0x100 safely
         *
         * do this if kexec in setup.c ?
         */
#ifdef CONFIG_PPC64
	smp_release_cpus();
#else
	/* FIXME */
#endif
}

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void crash_kexec_secondary(struct pt_regs *regs)
{
}
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#endif	/* CONFIG_SMP */

/* wait for all the CPUs to hit real mode but timeout if they don't come in */
#if defined(CONFIG_SMP) && defined(CONFIG_PPC64)


static void __maybe_unused crash_kexec_wait_realmode(int cpu)
{
	unsigned int msecs;
	int i;

	msecs = REAL_MODE_TIMEOUT;
	for (i=0; i < nr_cpu_ids && msecs > 0; i++) {
		if (i == cpu)
			continue;

		while (paca[i].kexec_state < KEXEC_STATE_REAL_MODE) {
			barrier();
			if (!cpu_possible(i) || !cpu_online(i) || (msecs <= 0))
				break;
			msecs--;
			mdelay(1);
		}
	}
	mb();
}
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#else


static inline void crash_kexec_wait_realmode(int cpu) {}
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#endif	/* CONFIG_SMP && CONFIG_PPC64 */

/*
 * Register a function to be called on shutdown.  Only use this if you
 * can't reset your device in the second kernel.
 */


int crash_shutdown_register(crash_shutdown_t handler)
{
	unsigned int i, rc;

	spin_lock(&crash_handlers_lock);
	for (i = 0 ; i < CRASH_HANDLER_MAX; i++)
		if (!crash_shutdown_handles[i]) {
			/* Insert handle at first empty entry */
			crash_shutdown_handles[i] = handler;
			rc = 0;
			break;
		}

	if (i == CRASH_HANDLER_MAX) {
		printk(KERN_ERR "Crash shutdown handles full, "
		       "not registered.\n");
		rc = 1;
	}

	spin_unlock(&crash_handlers_lock);
	return rc;
}
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EXPORT_SYMBOL(crash_shutdown_register);



int crash_shutdown_unregister(crash_shutdown_t handler)
{
	unsigned int i, rc;

	spin_lock(&crash_handlers_lock);
	for (i = 0 ; i < CRASH_HANDLER_MAX; i++)
		if (crash_shutdown_handles[i] == handler)
			break;

	if (i == CRASH_HANDLER_MAX) {
		printk(KERN_ERR "Crash shutdown handle not found\n");
		rc = 1;
	} else {
		/* Shift handles down */
		for (; i < (CRASH_HANDLER_MAX - 1); i++)
			crash_shutdown_handles[i] =
				crash_shutdown_handles[i+1];
		/*
                 * Reset last entry to NULL now that it has been shifted down,
                 * this will allow new handles to be added here.
                 */
		crash_shutdown_handles[i] = NULL;
		rc = 0;
	}

	spin_unlock(&crash_handlers_lock);
	return rc;
}
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EXPORT_SYMBOL(crash_shutdown_unregister);



void default_machine_crash_shutdown(struct pt_regs *regs)
{
	unsigned int i;
	int (*old_handler)(struct pt_regs *regs);

	/*
         * This function is only called after the system
         * has panicked or is otherwise in a critical state.
         * The minimum amount of code to allow a kexec'd kernel
         * to run successfully needs to happen here.
         *
         * In practice this means stopping other cpus in
         * an SMP system.
         * The kernel is broken so disable interrupts.
         */
	hard_irq_disable();

	/*
         * Make a note of crashing cpu. Will be used in machine_kexec
         * such that another IPI will not be sent.
         */
	crashing_cpu = smp_processor_id();

	/*
         * If we came in via system reset, wait a while for the secondary
         * CPUs to enter.
         */
	if (TRAP(regs) == 0x100)
		mdelay(PRIMARY_TIMEOUT);

	crash_kexec_prepare_cpus(crashing_cpu);

	crash_save_cpu(regs, crashing_cpu);

	time_to_dump = 1;

	crash_kexec_wait_realmode(crashing_cpu);

	machine_kexec_mask_interrupts();

	/*
         * Call registered shutdown routines safely.  Swap out
         * __debugger_fault_handler, and replace on exit.
         */
	old_handler = __debugger_fault_handler;
	__debugger_fault_handler = handle_fault;
	crash_shutdown_cpu = smp_processor_id();
	for (i = 0; i < CRASH_HANDLER_MAX && crash_shutdown_handles[i]; i++) {
		if (setjmp(crash_shutdown_buf) == 0) {
			/*
                         * Insert syncs and delay to ensure
                         * instructions in the dangerous region don't
                         * leak away from this protected region.
                         */
			asm volatile("sync; isync");
			/* dangerous region */
			crash_shutdown_handles[i]();
			asm volatile("sync; isync");
		}
	}
	crash_shutdown_cpu = -1;
	__debugger_fault_handler = old_handler;

	if (ppc_md.kexec_cpu_down)
		ppc_md.kexec_cpu_down(1, 0);
}
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Directory: arch/powerpc/kernel

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