// SPDX-License-Identifier: GPL-2.0
/*
 *   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/log2.h>
#include <linux/kprobes.h>
#include <linux/kmemleak.h>
#include <linux/time.h>
#include <linux/module.h>
#include <linux/sched/signal.h>

#include <linux/export.h>
#include <asm/lowcore.h>
#include <asm/smp.h>
#include <asm/stp.h>
#include <asm/cputime.h>
#include <asm/nmi.h>
#include <asm/crw.h>
#include <asm/switch_to.h>
#include <asm/ctl_reg.h>
#include <asm/asm-offsets.h>
#include <linux/kvm_host.h>

struct mcck_struct {
        unsigned int kill_task : 1;
        unsigned int channel_report : 1;
        unsigned int warning : 1;
        unsigned int stp_queue : 1;
        unsigned long mcck_code;
};

static DEFINE_PER_CPU(struct mcck_struct, cpu_mcck);
static struct kmem_cache *mcesa_cache;
static unsigned long mcesa_origin_lc;

static inline int nmi_needs_mcesa(void)
{
        return MACHINE_HAS_VX || MACHINE_HAS_GS;
}

static inline unsigned long nmi_get_mcesa_size(void)
{
        if (MACHINE_HAS_GS)
                return MCESA_MAX_SIZE;
        return MCESA_MIN_SIZE;
}

/*
 * The initial machine check extended save area for the boot CPU.
 * It will be replaced by nmi_init() with an allocated structure.
 * The structure is required for machine check happening early in
 * the boot process.
 */
static struct mcesa boot_mcesa __initdata __aligned(MCESA_MAX_SIZE);

void __init nmi_alloc_boot_cpu(struct lowcore *lc)
{
        if (!nmi_needs_mcesa())
                return;
        lc->mcesad = (unsigned long) &boot_mcesa;
        if (MACHINE_HAS_GS)
                lc->mcesad |= ilog2(MCESA_MAX_SIZE);
}

static int __init nmi_init(void)
{
        unsigned long origin, cr0, size;

        if (!nmi_needs_mcesa())
                return 0;
        size = nmi_get_mcesa_size();
        if (size > MCESA_MIN_SIZE)
                mcesa_origin_lc = ilog2(size);
        /* create slab cache for the machine-check-extended-save-areas */
        mcesa_cache = kmem_cache_create("nmi_save_areas", size, size, 0, NULL);
        if (!mcesa_cache)
                panic("Couldn't create nmi save area cache");
        origin = (unsigned long) kmem_cache_alloc(mcesa_cache, GFP_KERNEL);
        if (!origin)
                panic("Couldn't allocate nmi save area");
        /* The pointer is stored with mcesa_bits ORed in */
        kmemleak_not_leak((void *) origin);
        __ctl_store(cr0, 0, 0);
        __ctl_clear_bit(0, 28); /* disable lowcore protection */
        /* Replace boot_mcesa on the boot CPU */
        S390_lowcore.mcesad = origin | mcesa_origin_lc;
        __ctl_load(cr0, 0, 0);
        return 0;
}
early_initcall(nmi_init);

int nmi_alloc_per_cpu(struct lowcore *lc)
{
        unsigned long origin;

        if (!nmi_needs_mcesa())
                return 0;
        origin = (unsigned long) kmem_cache_alloc(mcesa_cache, GFP_KERNEL);
        if (!origin)
                return -ENOMEM;
        /* The pointer is stored with mcesa_bits ORed in */
        kmemleak_not_leak((void *) origin);
        lc->mcesad = origin | mcesa_origin_lc;
        return 0;
}

void nmi_free_per_cpu(struct lowcore *lc)
{
        if (!nmi_needs_mcesa())
                return;
        kmem_cache_free(mcesa_cache, (void *)(lc->mcesad & MCESA_ORIGIN_MASK));
}

static notrace void s390_handle_damage(void)
{
        smp_emergency_stop();
        disabled_wait();
        while (1);
}
NOKPROBE_SYMBOL(s390_handle_damage);

/*
 * Main machine check handler function. Will be called with interrupts disabled
 * and machine checks enabled.
 */
void __s390_handle_mcck(void)
{
        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_mcck_disable();
        mcck = *this_cpu_ptr(&cpu_mcck);
        memset(this_cpu_ptr(&cpu_mcck), 0, sizeof(mcck));
        local_mcck_enable();

        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.stp_queue)
                stp_queue_work();
        if (mcck.kill_task) {
                local_irq_enable();
                printk(KERN_EMERG "mcck: Terminating task because of machine "
                       "malfunction (code 0x%016lx).\n", mcck.mcck_code);
                printk(KERN_EMERG "mcck: task: %s, pid: %d.\n",
                       current->comm, current->pid);
                do_exit(SIGSEGV);
        }
}

void noinstr s390_handle_mcck(void)
{
        trace_hardirqs_off();
        __s390_handle_mcck();
        trace_hardirqs_on();
}
/*
 * returns 0 if all required registers are available
 * returns 1 otherwise
 */
static int notrace s390_check_registers(union mci mci, int umode)
{
        union ctlreg2 cr2;
        int kill_task;

        kill_task = 0;

        if (!mci.gr) {
                /*
                 * General purpose registers couldn't be restored and have
                 * unknown contents. Stop system or terminate process.
                 */
                if (!umode)
                        s390_handle_damage();
                kill_task = 1;
        }
        /* Check control registers */
        if (!mci.cr) {
                /*
                 * Control registers have unknown contents.
                 * Can't recover and therefore stopping machine.
                 */
                s390_handle_damage();
        }
        if (!mci.fp) {
                /*
                 * Floating point registers can't be restored. If the
                 * kernel currently uses floating point registers the
                 * system is stopped. If the process has its floating
                 * pointer registers loaded it is terminated.
                 */
                if (S390_lowcore.fpu_flags & KERNEL_VXR_V0V7)
                        s390_handle_damage();
                if (!test_cpu_flag(CIF_FPU))
                        kill_task = 1;
        }
        if (!mci.fc) {
                /*
                 * Floating point control register can't be restored.
                 * If the kernel currently uses the floating pointer
                 * registers and needs the FPC register the system is
                 * stopped. If the process has its floating pointer
                 * registers loaded it is terminated.
                 */
                if (S390_lowcore.fpu_flags & KERNEL_FPC)
                        s390_handle_damage();
                if (!test_cpu_flag(CIF_FPU))
                        kill_task = 1;
        }

        if (MACHINE_HAS_VX) {
                if (!mci.vr) {
                        /*
                         * Vector registers can't be restored. If the kernel
                         * currently uses vector registers the system is
                         * stopped. If the process has its vector registers
                         * loaded it is terminated.
                         */
                        if (S390_lowcore.fpu_flags & KERNEL_VXR)
                                s390_handle_damage();
                        if (!test_cpu_flag(CIF_FPU))
                                kill_task = 1;
                }
        }
        /* Check if access registers are valid */
        if (!mci.ar) {
                /*
                 * Access registers have unknown contents.
                 * Terminating task.
                 */
                kill_task = 1;
        }
        /* Check guarded storage registers */
        cr2.val = S390_lowcore.cregs_save_area[2];
        if (cr2.gse) {
                if (!mci.gs) {
                        /*
                         * Guarded storage register can't be restored and
                         * the current processes uses guarded storage.
                         * It has to be terminated.
                         */
                        kill_task = 1;
                }
        }
        /* 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();
        }
        /* Check for invalid kernel instruction address */
        if (!mci.ia && !umode) {
                /*
                 * The instruction address got lost while running
                 * in the kernel -> stopping machine.
                 */
                s390_handle_damage();
        }

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

        return kill_task;
}
NOKPROBE_SYMBOL(s390_check_registers);

/*
 * Backup the guest's machine check info to its description block
 */
static void notrace s390_backup_mcck_info(struct pt_regs *regs)
{
        struct mcck_volatile_info *mcck_backup;
        struct sie_page *sie_page;

        /* r14 contains the sie block, which was set in sie64a */
        struct kvm_s390_sie_block *sie_block =
                        (struct kvm_s390_sie_block *) regs->gprs[14];

        if (sie_block == NULL)
                /* Something's seriously wrong, stop system. */
                s390_handle_damage();

        sie_page = container_of(sie_block, struct sie_page, sie_block);
        mcck_backup = &sie_page->mcck_info;
        mcck_backup->mcic = S390_lowcore.mcck_interruption_code &
                                ~(MCCK_CODE_CP | MCCK_CODE_EXT_DAMAGE);
        mcck_backup->ext_damage_code = S390_lowcore.external_damage_code;
        mcck_backup->failing_storage_address
                        = S390_lowcore.failing_storage_address;
}
NOKPROBE_SYMBOL(s390_backup_mcck_info);

#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 MCCK_CODE_NO_GUEST      (MCCK_CODE_CP | MCCK_CODE_EXT_DAMAGE)

/*
 * machine check handler.
 */
int 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;
        union mci mci;
        unsigned long mcck_dam_code;
        int mcck_pending = 0;

        nmi_enter();

        if (user_mode(regs))
                update_timer_mcck();
        inc_irq_stat(NMI_NMI);
        mci.val = S390_lowcore.mcck_interruption_code;
        mcck = this_cpu_ptr(&cpu_mcck);

        if (mci.sd) {
                /* System damage -> stopping machine */
                s390_handle_damage();
        }

        /*
         * Reinject the instruction processing damages' machine checks
         * including Delayed Access Exception into the guest
         * instead of damaging the host if they happen in the guest.
         */
        if (mci.pd && !test_cpu_flag(CIF_MCCK_GUEST)) {
                if (mci.b) {
                        /* Processing backup -> verify if we can survive this */
                        u64 z_mcic, o_mcic, t_mcic;
                        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);
                        t_mcic = mci.val;

                        if (((t_mcic & z_mcic) != 0) ||
                            ((t_mcic & o_mcic) != o_mcic)) {
                                s390_handle_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();
                        spin_unlock(&ipd_lock);
                } else {
                        /* Processing damage -> stopping machine */
                        s390_handle_damage();
                }
        }
        if (s390_check_registers(mci, user_mode(regs))) {
                /*
                 * Couldn't restore all register contents for the
                 * user space process -> mark task for termination.
                 */
                mcck->kill_task = 1;
                mcck->mcck_code = mci.val;
                mcck_pending = 1;
        }

        /*
         * Backup the machine check's info if it happens when the guest
         * is running.
         */
        if (test_cpu_flag(CIF_MCCK_GUEST))
                s390_backup_mcck_info(regs);

        if (mci.cd) {
                /* Timing facility damage */
                s390_handle_damage();
        }
        if (mci.ed && mci.ec) {
                /* External damage */
                if (S390_lowcore.external_damage_code & (1U << ED_STP_SYNC))
                        mcck->stp_queue |= stp_sync_check();
                if (S390_lowcore.external_damage_code & (1U << ED_STP_ISLAND))
                        mcck->stp_queue |= stp_island_check();
                mcck_pending = 1;
        }

        /*
         * Reinject storage related machine checks into the guest if they
         * happen when the guest is running.
         */
        if (!test_cpu_flag(CIF_MCCK_GUEST)) {
                if (mci.se)
                        /* Storage error uncorrected */
                        s390_handle_damage();
                if (mci.ke)
                        /* Storage key-error uncorrected */
                        s390_handle_damage();
                if (mci.ds && mci.fa)
                        /* Storage degradation */
                        s390_handle_damage();
        }
        if (mci.cp) {
                /* Channel report word pending */
                mcck->channel_report = 1;
                mcck_pending = 1;
        }
        if (mci.w) {
                /* Warning pending */
                mcck->warning = 1;
                mcck_pending = 1;
        }

        /*
         * If there are only Channel Report Pending and External Damage
         * machine checks, they will not be reinjected into the guest
         * because they refer to host conditions only.
         */
        mcck_dam_code = (mci.val & MCIC_SUBCLASS_MASK);
        if (test_cpu_flag(CIF_MCCK_GUEST) &&
        (mcck_dam_code & MCCK_CODE_NO_GUEST) != mcck_dam_code) {
                /* Set exit reason code for host's later handling */
                *((long *)(regs->gprs[15] + __SF_SIE_REASON)) = -EINTR;
        }
        clear_cpu_flag(CIF_MCCK_GUEST);

        if (user_mode(regs) && mcck_pending) {
                nmi_exit();
                return 1;
        }

        if (mcck_pending)
                schedule_mcck_handler();

        nmi_exit();
        return 0;
}
NOKPROBE_SYMBOL(s390_do_machine_check);

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;
}
early_initcall(machine_check_init);