/*
 *   Machine check handler
 *
 *    Copyright IBM Corp. 2000, 2009
 *    Author(s): Ingo Adlung <adlung@de.ibm.com>,
 *               Martin Schwidefsky <schwidefsky@de.ibm.com>,
 *               Cornelia Huck <cornelia.huck@de.ibm.com>,
 *               Heiko Carstens <heiko.carstens@de.ibm.com>,
 */

#include <linux/kernel_stat.h>
#include <linux/init.h>
#include <linux/errno.h>
#include <linux/hardirq.h>
#include <linux/time.h>
#include <linux/module.h>
#include <asm/lowcore.h>
#include <asm/smp.h>
#include <asm/etr.h>
#include <asm/cputime.h>
#include <asm/nmi.h>
#include <asm/crw.h>

struct mcck_struct {
        int kill_task;
        int channel_report;
        int warning;
        unsigned long long mcck_code;
};

static DEFINE_PER_CPU(struct mcck_struct, cpu_mcck);

static void s390_handle_damage(char *msg)
{
        smp_send_stop();
        disabled_wait((unsigned long) __builtin_return_address(0));
        while (1);
}

/*
 * Main machine check handler function. Will be called with interrupts enabled
 * or disabled and machine checks enabled or disabled.
 */
void s390_handle_mcck(void)
{
        unsigned long flags;
        struct mcck_struct mcck;

        /*
         * Disable machine checks and get the current state of accumulated
         * machine checks. Afterwards delete the old state and enable machine
         * checks again.
         */
        local_irq_save(flags);
        local_mcck_disable();
        mcck = __get_cpu_var(cpu_mcck);
        memset(&__get_cpu_var(cpu_mcck), 0, sizeof(struct mcck_struct));
        clear_thread_flag(TIF_MCCK_PENDING);
        local_mcck_enable();
        local_irq_restore(flags);

        if (mcck.channel_report)
                crw_handle_channel_report();
        /*
         * A warning may remain for a prolonged period on the bare iron.
         * (actually until the machine is powered off, or the problem is gone)
         * So we just stop listening for the WARNING MCH and avoid continuously
         * being interrupted.  One caveat is however, that we must do this per
         * processor and cannot use the smp version of ctl_clear_bit().
         * On VM we only get one interrupt per virtally presented machinecheck.
         * Though one suffices, we may get one interrupt per (virtual) cpu.
         */
        if (mcck.warning) {     /* WARNING pending ? */
                static int mchchk_wng_posted = 0;

                /* Use single cpu clear, as we cannot handle smp here. */
                __ctl_clear_bit(14, 24);        /* Disable WARNING MCH */
                if (xchg(&mchchk_wng_posted, 1) == 0)
                        kill_cad_pid(SIGPWR, 1);
        }
        if (mcck.kill_task) {
                local_irq_enable();
                printk(KERN_EMERG "mcck: Terminating task because of machine "
                       "malfunction (code 0x%016llx).\n", mcck.mcck_code);
                printk(KERN_EMERG "mcck: task: %s, pid: %d.\n",
                       current->comm, current->pid);
                do_exit(SIGSEGV);
        }
}
EXPORT_SYMBOL_GPL(s390_handle_mcck);

/*
 * returns 0 if all registers could be validated
 * returns 1 otherwise
 */
static int notrace s390_revalidate_registers(struct mci *mci)
{
        int kill_task;
        u64 zero;
        void *fpt_save_area, *fpt_creg_save_area;

        kill_task = 0;
        zero = 0;

        if (!mci->gr) {
                /*
                 * General purpose registers couldn't be restored and have
                 * unknown contents. Process needs to be terminated.
                 */
                kill_task = 1;
        }
        if (!mci->fp) {
                /*
                 * Floating point registers can't be restored and
                 * therefore the process needs to be terminated.
                 */
                kill_task = 1;
        }
#ifndef CONFIG_64BIT
        asm volatile(
                "       ld      0,0(%0)\n"
                "       ld      2,8(%0)\n"
                "       ld      4,16(%0)\n"
                "       ld      6,24(%0)"
                : : "a" (&S390_lowcore.floating_pt_save_area));
#endif

        if (MACHINE_HAS_IEEE) {
#ifdef CONFIG_64BIT
                fpt_save_area = &S390_lowcore.floating_pt_save_area;
                fpt_creg_save_area = &S390_lowcore.fpt_creg_save_area;
#else
                fpt_save_area = (void *) S390_lowcore.extended_save_area_addr;
                fpt_creg_save_area = fpt_save_area + 128;
#endif
                if (!mci->fc) {
                        /*
                         * Floating point control register can't be restored.
                         * Task will be terminated.
                         */
                        asm volatile("lfpc 0(%0)" : : "a" (&zero), "m" (zero));
                        kill_task = 1;

                } else
                        asm volatile("lfpc 0(%0)" : : "a" (fpt_creg_save_area));

                asm volatile(
                        "       ld      0,0(%0)\n"
                        "       ld      1,8(%0)\n"
                        "       ld      2,16(%0)\n"
                        "       ld      3,24(%0)\n"
                        "       ld      4,32(%0)\n"
                        "       ld      5,40(%0)\n"
                        "       ld      6,48(%0)\n"
                        "       ld      7,56(%0)\n"
                        "       ld      8,64(%0)\n"
                        "       ld      9,72(%0)\n"
                        "       ld      10,80(%0)\n"
                        "       ld      11,88(%0)\n"
                        "       ld      12,96(%0)\n"
                        "       ld      13,104(%0)\n"
                        "       ld      14,112(%0)\n"
                        "       ld      15,120(%0)\n"
                        : : "a" (fpt_save_area));
        }
        /* Revalidate access registers */
        asm volatile(
                "       lam     0,15,0(%0)"
                : : "a" (&S390_lowcore.access_regs_save_area));
        if (!mci->ar) {
                /*
                 * Access registers have unknown contents.
                 * Terminating task.
                 */
                kill_task = 1;
        }
        /* Revalidate control registers */
        if (!mci->cr) {
                /*
                 * Control registers have unknown contents.
                 * Can't recover and therefore stopping machine.
                 */
                s390_handle_damage("invalid control registers.");
        } else {
#ifdef CONFIG_64BIT
                asm volatile(
                        "       lctlg   0,15,0(%0)"
                        : : "a" (&S390_lowcore.cregs_save_area));
#else
                asm volatile(
                        "       lctl    0,15,0(%0)"
                        : : "a" (&S390_lowcore.cregs_save_area));
#endif
        }
        /*
         * We don't even try to revalidate the TOD register, since we simply
         * can't write something sensible into that register.
         */
#ifdef CONFIG_64BIT
        /*
         * See if we can revalidate the TOD programmable register with its
         * old contents (should be zero) otherwise set it to zero.
         */
        if (!mci->pr)
                asm volatile(
                        "       sr      0,0\n"
                        "       sckpf"
                        : : : "0", "cc");
        else
                asm volatile(
                        "       l       0,0(%0)\n"
                        "       sckpf"
                        : : "a" (&S390_lowcore.tod_progreg_save_area)
                        : "0", "cc");
#endif
        /* Revalidate clock comparator register */
        set_clock_comparator(S390_lowcore.clock_comparator);
        /* Check if old PSW is valid */
        if (!mci->wp)
                /*
                 * Can't tell if we come from user or kernel mode
                 * -> stopping machine.
                 */
                s390_handle_damage("old psw invalid.");

        if (!mci->ms || !mci->pm || !mci->ia)
                kill_task = 1;

        return kill_task;
}

#define MAX_IPD_COUNT   29
#define MAX_IPD_TIME    (5 * 60 * USEC_PER_SEC) /* 5 minutes */

#define ED_STP_ISLAND   6       /* External damage STP island check */
#define ED_STP_SYNC     7       /* External damage STP sync check */
#define ED_ETR_SYNC     12      /* External damage ETR sync check */
#define ED_ETR_SWITCH   13      /* External damage ETR switch to local */

/*
 * machine check handler.
 */
void notrace s390_do_machine_check(struct pt_regs *regs)
{
        static int ipd_count;
        static DEFINE_SPINLOCK(ipd_lock);
        static unsigned long long last_ipd;
        struct mcck_struct *mcck;
        unsigned long long tmp;
        struct mci *mci;
        int umode;

        nmi_enter();
        inc_irq_stat(NMI_NMI);
        mci = (struct mci *) &S390_lowcore.mcck_interruption_code;
        mcck = &__get_cpu_var(cpu_mcck);
        umode = user_mode(regs);

        if (mci->sd) {
                /* System damage -> stopping machine */
                s390_handle_damage("received system damage machine check.");
        }
        if (mci->pd) {
                if (mci->b) {
                        /* Processing backup -> verify if we can survive this */
                        u64 z_mcic, o_mcic, t_mcic;
#ifdef CONFIG_64BIT
                        z_mcic = (1ULL<<63 | 1ULL<<59 | 1ULL<<29);
                        o_mcic = (1ULL<<43 | 1ULL<<42 | 1ULL<<41 | 1ULL<<40 |
                                  1ULL<<36 | 1ULL<<35 | 1ULL<<34 | 1ULL<<32 |
                                  1ULL<<30 | 1ULL<<21 | 1ULL<<20 | 1ULL<<17 |
                                  1ULL<<16);
#else
                        z_mcic = (1ULL<<63 | 1ULL<<59 | 1ULL<<57 | 1ULL<<50 |
                                  1ULL<<29);
                        o_mcic = (1ULL<<43 | 1ULL<<42 | 1ULL<<41 | 1ULL<<40 |
                                  1ULL<<36 | 1ULL<<35 | 1ULL<<34 | 1ULL<<32 |
                                  1ULL<<30 | 1ULL<<20 | 1ULL<<17 | 1ULL<<16);
#endif
                        t_mcic = *(u64 *)mci;

                        if (((t_mcic & z_mcic) != 0) ||
                            ((t_mcic & o_mcic) != o_mcic)) {
                                s390_handle_damage("processing backup machine "
                                                   "check with damage.");
                        }

                        /*
                         * Nullifying exigent condition, therefore we might
                         * retry this instruction.
                         */
                        spin_lock(&ipd_lock);
                        tmp = get_tod_clock();
                        if (((tmp - last_ipd) >> 12) < MAX_IPD_TIME)
                                ipd_count++;
                        else
                                ipd_count = 1;
                        last_ipd = tmp;
                        if (ipd_count == MAX_IPD_COUNT)
                                s390_handle_damage("too many ipd retries.");
                        spin_unlock(&ipd_lock);
                } else {
                        /* Processing damage -> stopping machine */
                        s390_handle_damage("received instruction processing "
                                           "damage machine check.");
                }
        }
        if (s390_revalidate_registers(mci)) {
                if (umode) {
                        /*
                         * Couldn't restore all register contents while in
                         * user mode -> mark task for termination.
                         */
                        mcck->kill_task = 1;
                        mcck->mcck_code = *(unsigned long long *) mci;
                        set_thread_flag(TIF_MCCK_PENDING);
                } else {
                        /*
                         * Couldn't restore all register contents while in
                         * kernel mode -> stopping machine.
                         */
                        s390_handle_damage("unable to revalidate registers.");
                }
        }
        if (mci->cd) {
                /* Timing facility damage */
                s390_handle_damage("TOD clock damaged");
        }
        if (mci->ed && mci->ec) {
                /* External damage */
                if (S390_lowcore.external_damage_code & (1U << ED_ETR_SYNC))
                        etr_sync_check();
                if (S390_lowcore.external_damage_code & (1U << ED_ETR_SWITCH))
                        etr_switch_to_local();
                if (S390_lowcore.external_damage_code & (1U << ED_STP_SYNC))
                        stp_sync_check();
                if (S390_lowcore.external_damage_code & (1U << ED_STP_ISLAND))
                        stp_island_check();
        }
        if (mci->se)
                /* Storage error uncorrected */
                s390_handle_damage("received storage error uncorrected "
                                   "machine check.");
        if (mci->ke)
                /* Storage key-error uncorrected */
                s390_handle_damage("received storage key-error uncorrected "
                                   "machine check.");
        if (mci->ds && mci->fa)
                /* Storage degradation */
                s390_handle_damage("received storage degradation machine "
                                   "check.");
        if (mci->cp) {
                /* Channel report word pending */
                mcck->channel_report = 1;
                set_thread_flag(TIF_MCCK_PENDING);
        }
        if (mci->w) {
                /* Warning pending */
                mcck->warning = 1;
                set_thread_flag(TIF_MCCK_PENDING);
        }
        nmi_exit();
}

static int __init machine_check_init(void)
{
        ctl_set_bit(14, 25);    /* enable external damage MCH */
        ctl_set_bit(14, 27);    /* enable system recovery MCH */
        ctl_set_bit(14, 24);    /* enable warning MCH */
        return 0;
}
arch_initcall(machine_check_init);