crash.c

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/*
 * 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/init.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

/* This keeps a track of which one is the crashing cpu. */
int crashing_cpu = -1;
static int time_to_dump;

#define CRASH_HANDLER_MAX 3
/* NULL terminated list of shutdown handles */
static crash_shutdown_t crash_shutdown_handles[CRASH_HANDLER_MAX+1];
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;
}

#ifdef CONFIG_SMP

static atomic_t cpus_in_crash;
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_inc();

    /*
     * 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 */
}

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;
}

/*
 * 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);
}

#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
}

void crash_kexec_secondary(struct pt_regs *regs)
{
}
#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_PPC_STD_MMU_64)
static void 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();
}
#else
static inline void crash_kexec_wait_realmode(int cpu) {}
#endif  /* CONFIG_SMP && CONFIG_PPC_STD_MMU_64 */

/*
 * 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;
}
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 (; crash_shutdown_handles[i]; i++)
            crash_shutdown_handles[i] =
                crash_shutdown_handles[i+1];
        rc = 0;
    }

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