// SPDX-License-Identifier: GPL-2.0
/*
 * kvm guest debug support
 *
 * Copyright IBM Corp. 2014
 *
 *    Author(s): David Hildenbrand <dahi@linux.vnet.ibm.com>
 */
#include <linux/kvm_host.h>
#include <linux/errno.h>
#include "kvm-s390.h"
#include "gaccess.h"

/*
 * Extends the address range given by *start and *stop to include the address
 * range starting with estart and the length len. Takes care of overflowing
 * intervals and tries to minimize the overall interval size.
 */
static void extend_address_range(u64 *start, u64 *stop, u64 estart, int len)
{
        u64 estop;

        if (len > 0)
                len--;
        else
                len = 0;

        estop = estart + len;

        /* 0-0 range represents "not set" */
        if ((*start == 0) && (*stop == 0)) {
                *start = estart;
                *stop = estop;
        } else if (*start <= *stop) {
                /* increase the existing range */
                if (estart < *start)
                        *start = estart;
                if (estop > *stop)
                        *stop = estop;
        } else {
                /* "overflowing" interval, whereby *stop > *start */
                if (estart <= *stop) {
                        if (estop > *stop)
                                *stop = estop;
                } else if (estop > *start) {
                        if (estart < *start)
                                *start = estart;
                }
                /* minimize the range */
                else if ((estop - *stop) < (*start - estart))
                        *stop = estop;
                else
                        *start = estart;
        }
}

#define MAX_INST_SIZE 6

static void enable_all_hw_bp(struct kvm_vcpu *vcpu)
{
        unsigned long start, len;
        u64 *cr9 = &vcpu->arch.sie_block->gcr[9];
        u64 *cr10 = &vcpu->arch.sie_block->gcr[10];
        u64 *cr11 = &vcpu->arch.sie_block->gcr[11];
        int i;

        if (vcpu->arch.guestdbg.nr_hw_bp <= 0 ||
            vcpu->arch.guestdbg.hw_bp_info == NULL)
                return;

        /*
         * If the guest is not interested in branching events, we can safely
         * limit them to the PER address range.
         */
        if (!(*cr9 & PER_EVENT_BRANCH))
                *cr9 |= PER_CONTROL_BRANCH_ADDRESS;
        *cr9 |= PER_EVENT_IFETCH | PER_EVENT_BRANCH;

        for (i = 0; i < vcpu->arch.guestdbg.nr_hw_bp; i++) {
                start = vcpu->arch.guestdbg.hw_bp_info[i].addr;
                len = vcpu->arch.guestdbg.hw_bp_info[i].len;

                /*
                 * The instruction in front of the desired bp has to
                 * report instruction-fetching events
                 */
                if (start < MAX_INST_SIZE) {
                        len += start;
                        start = 0;
                } else {
                        start -= MAX_INST_SIZE;
                        len += MAX_INST_SIZE;
                }

                extend_address_range(cr10, cr11, start, len);
        }
}

static void enable_all_hw_wp(struct kvm_vcpu *vcpu)
{
        unsigned long start, len;
        u64 *cr9 = &vcpu->arch.sie_block->gcr[9];
        u64 *cr10 = &vcpu->arch.sie_block->gcr[10];
        u64 *cr11 = &vcpu->arch.sie_block->gcr[11];
        int i;

        if (vcpu->arch.guestdbg.nr_hw_wp <= 0 ||
            vcpu->arch.guestdbg.hw_wp_info == NULL)
                return;

        /* if host uses storage alternation for special address
         * spaces, enable all events and give all to the guest */
        if (*cr9 & PER_EVENT_STORE && *cr9 & PER_CONTROL_ALTERATION) {
                *cr9 &= ~PER_CONTROL_ALTERATION;
                *cr10 = 0;
                *cr11 = -1UL;
        } else {
                *cr9 &= ~PER_CONTROL_ALTERATION;
                *cr9 |= PER_EVENT_STORE;

                for (i = 0; i < vcpu->arch.guestdbg.nr_hw_wp; i++) {
                        start = vcpu->arch.guestdbg.hw_wp_info[i].addr;
                        len = vcpu->arch.guestdbg.hw_wp_info[i].len;

                        extend_address_range(cr10, cr11, start, len);
                }
        }
}

void kvm_s390_backup_guest_per_regs(struct kvm_vcpu *vcpu)
{
        vcpu->arch.guestdbg.cr0 = vcpu->arch.sie_block->gcr[0];
        vcpu->arch.guestdbg.cr9 = vcpu->arch.sie_block->gcr[9];
        vcpu->arch.guestdbg.cr10 = vcpu->arch.sie_block->gcr[10];
        vcpu->arch.guestdbg.cr11 = vcpu->arch.sie_block->gcr[11];
}

void kvm_s390_restore_guest_per_regs(struct kvm_vcpu *vcpu)
{
        vcpu->arch.sie_block->gcr[0] = vcpu->arch.guestdbg.cr0;
        vcpu->arch.sie_block->gcr[9] = vcpu->arch.guestdbg.cr9;
        vcpu->arch.sie_block->gcr[10] = vcpu->arch.guestdbg.cr10;
        vcpu->arch.sie_block->gcr[11] = vcpu->arch.guestdbg.cr11;
}

void kvm_s390_patch_guest_per_regs(struct kvm_vcpu *vcpu)
{
        /*
         * TODO: if guest psw has per enabled, otherwise 0s!
         * This reduces the amount of reported events.
         * Need to intercept all psw changes!
         */

        if (guestdbg_sstep_enabled(vcpu)) {
                /* disable timer (clock-comparator) interrupts */
                vcpu->arch.sie_block->gcr[0] &= ~CR0_CLOCK_COMPARATOR_SUBMASK;
                vcpu->arch.sie_block->gcr[9] |= PER_EVENT_IFETCH;
                vcpu->arch.sie_block->gcr[10] = 0;
                vcpu->arch.sie_block->gcr[11] = -1UL;
        }

        if (guestdbg_hw_bp_enabled(vcpu)) {
                enable_all_hw_bp(vcpu);
                enable_all_hw_wp(vcpu);
        }

        /* TODO: Instruction-fetching-nullification not allowed for now */
        if (vcpu->arch.sie_block->gcr[9] & PER_EVENT_NULLIFICATION)
                vcpu->arch.sie_block->gcr[9] &= ~PER_EVENT_NULLIFICATION;
}

#define MAX_WP_SIZE 100

static int __import_wp_info(struct kvm_vcpu *vcpu,
                            struct kvm_hw_breakpoint *bp_data,
                            struct kvm_hw_wp_info_arch *wp_info)
{
        int ret = 0;
        wp_info->len = bp_data->len;
        wp_info->addr = bp_data->addr;
        wp_info->phys_addr = bp_data->phys_addr;
        wp_info->old_data = NULL;

        if (wp_info->len < 0 || wp_info->len > MAX_WP_SIZE)
                return -EINVAL;

        wp_info->old_data = kmalloc(bp_data->len, GFP_KERNEL_ACCOUNT);
        if (!wp_info->old_data)
                return -ENOMEM;
        /* try to backup the original value */
        ret = read_guest_abs(vcpu, wp_info->phys_addr, wp_info->old_data,
                             wp_info->len);
        if (ret) {
                kfree(wp_info->old_data);
                wp_info->old_data = NULL;
        }

        return ret;
}

#define MAX_BP_COUNT 50

int kvm_s390_import_bp_data(struct kvm_vcpu *vcpu,
                            struct kvm_guest_debug *dbg)
{
        int ret = 0, nr_wp = 0, nr_bp = 0, i;
        struct kvm_hw_breakpoint *bp_data = NULL;
        struct kvm_hw_wp_info_arch *wp_info = NULL;
        struct kvm_hw_bp_info_arch *bp_info = NULL;

        if (dbg->arch.nr_hw_bp <= 0 || !dbg->arch.hw_bp)
                return 0;
        else if (dbg->arch.nr_hw_bp > MAX_BP_COUNT)
                return -EINVAL;

        bp_data = memdup_user(dbg->arch.hw_bp,
                              sizeof(*bp_data) * dbg->arch.nr_hw_bp);
        if (IS_ERR(bp_data))
                return PTR_ERR(bp_data);

        for (i = 0; i < dbg->arch.nr_hw_bp; i++) {
                switch (bp_data[i].type) {
                case KVM_HW_WP_WRITE:
                        nr_wp++;
                        break;
                case KVM_HW_BP:
                        nr_bp++;
                        break;
                default:
                        break;
                }
        }

        if (nr_wp > 0) {
                wp_info = kmalloc_array(nr_wp,
                                        sizeof(*wp_info),
                                        GFP_KERNEL_ACCOUNT);
                if (!wp_info) {
                        ret = -ENOMEM;
                        goto error;
                }
        }
        if (nr_bp > 0) {
                bp_info = kmalloc_array(nr_bp,
                                        sizeof(*bp_info),
                                        GFP_KERNEL_ACCOUNT);
                if (!bp_info) {
                        ret = -ENOMEM;
                        goto error;
                }
        }

        for (nr_wp = 0, nr_bp = 0, i = 0; i < dbg->arch.nr_hw_bp; i++) {
                switch (bp_data[i].type) {
                case KVM_HW_WP_WRITE:
                        ret = __import_wp_info(vcpu, &bp_data[i],
                                               &wp_info[nr_wp]);
                        if (ret)
                                goto error;
                        nr_wp++;
                        break;
                case KVM_HW_BP:
                        bp_info[nr_bp].len = bp_data[i].len;
                        bp_info[nr_bp].addr = bp_data[i].addr;
                        nr_bp++;
                        break;
                }
        }

        vcpu->arch.guestdbg.nr_hw_bp = nr_bp;
        vcpu->arch.guestdbg.hw_bp_info = bp_info;
        vcpu->arch.guestdbg.nr_hw_wp = nr_wp;
        vcpu->arch.guestdbg.hw_wp_info = wp_info;
        return 0;
error:
        kfree(bp_data);
        kfree(wp_info);
        kfree(bp_info);
        return ret;
}

void kvm_s390_clear_bp_data(struct kvm_vcpu *vcpu)
{
        int i;
        struct kvm_hw_wp_info_arch *hw_wp_info = NULL;

        for (i = 0; i < vcpu->arch.guestdbg.nr_hw_wp; i++) {
                hw_wp_info = &vcpu->arch.guestdbg.hw_wp_info[i];
                kfree(hw_wp_info->old_data);
                hw_wp_info->old_data = NULL;
        }
        kfree(vcpu->arch.guestdbg.hw_wp_info);
        vcpu->arch.guestdbg.hw_wp_info = NULL;

        kfree(vcpu->arch.guestdbg.hw_bp_info);
        vcpu->arch.guestdbg.hw_bp_info = NULL;

        vcpu->arch.guestdbg.nr_hw_wp = 0;
        vcpu->arch.guestdbg.nr_hw_bp = 0;
}

static inline int in_addr_range(u64 addr, u64 a, u64 b)
{
        if (a <= b)
                return (addr >= a) && (addr <= b);
        else
                /* "overflowing" interval */
                return (addr >= a) || (addr <= b);
}

#define end_of_range(bp_info) (bp_info->addr + bp_info->len - 1)

static struct kvm_hw_bp_info_arch *find_hw_bp(struct kvm_vcpu *vcpu,
                                              unsigned long addr)
{
        struct kvm_hw_bp_info_arch *bp_info = vcpu->arch.guestdbg.hw_bp_info;
        int i;

        if (vcpu->arch.guestdbg.nr_hw_bp == 0)
                return NULL;

        for (i = 0; i < vcpu->arch.guestdbg.nr_hw_bp; i++) {
                /* addr is directly the start or in the range of a bp */
                if (addr == bp_info->addr)
                        goto found;
                if (bp_info->len > 0 &&
                    in_addr_range(addr, bp_info->addr, end_of_range(bp_info)))
                        goto found;

                bp_info++;
        }

        return NULL;
found:
        return bp_info;
}

static struct kvm_hw_wp_info_arch *any_wp_changed(struct kvm_vcpu *vcpu)
{
        int i;
        struct kvm_hw_wp_info_arch *wp_info = NULL;
        void *temp = NULL;

        if (vcpu->arch.guestdbg.nr_hw_wp == 0)
                return NULL;

        for (i = 0; i < vcpu->arch.guestdbg.nr_hw_wp; i++) {
                wp_info = &vcpu->arch.guestdbg.hw_wp_info[i];
                if (!wp_info || !wp_info->old_data || wp_info->len <= 0)
                        continue;

                temp = kmalloc(wp_info->len, GFP_KERNEL_ACCOUNT);
                if (!temp)
                        continue;

                /* refetch the wp data and compare it to the old value */
                if (!read_guest_abs(vcpu, wp_info->phys_addr, temp,
                                    wp_info->len)) {
                        if (memcmp(temp, wp_info->old_data, wp_info->len)) {
                                kfree(temp);
                                return wp_info;
                        }
                }
                kfree(temp);
                temp = NULL;
        }

        return NULL;
}

void kvm_s390_prepare_debug_exit(struct kvm_vcpu *vcpu)
{
        vcpu->run->exit_reason = KVM_EXIT_DEBUG;
        vcpu->guest_debug &= ~KVM_GUESTDBG_EXIT_PENDING;
}

#define PER_CODE_MASK           (PER_EVENT_MASK >> 24)
#define PER_CODE_BRANCH         (PER_EVENT_BRANCH >> 24)
#define PER_CODE_IFETCH         (PER_EVENT_IFETCH >> 24)
#define PER_CODE_STORE          (PER_EVENT_STORE >> 24)
#define PER_CODE_STORE_REAL     (PER_EVENT_STORE_REAL >> 24)

#define per_bp_event(code) \
                        (code & (PER_CODE_IFETCH | PER_CODE_BRANCH))
#define per_write_wp_event(code) \
                        (code & (PER_CODE_STORE | PER_CODE_STORE_REAL))

static int debug_exit_required(struct kvm_vcpu *vcpu, u8 perc,
                               unsigned long peraddr)
{
        struct kvm_debug_exit_arch *debug_exit = &vcpu->run->debug.arch;
        struct kvm_hw_wp_info_arch *wp_info = NULL;
        struct kvm_hw_bp_info_arch *bp_info = NULL;
        unsigned long addr = vcpu->arch.sie_block->gpsw.addr;

        if (guestdbg_hw_bp_enabled(vcpu)) {
                if (per_write_wp_event(perc) &&
                    vcpu->arch.guestdbg.nr_hw_wp > 0) {
                        wp_info = any_wp_changed(vcpu);
                        if (wp_info) {
                                debug_exit->addr = wp_info->addr;
                                debug_exit->type = KVM_HW_WP_WRITE;
                                goto exit_required;
                        }
                }
                if (per_bp_event(perc) &&
                         vcpu->arch.guestdbg.nr_hw_bp > 0) {
                        bp_info = find_hw_bp(vcpu, addr);
                        /* remove duplicate events if PC==PER address */
                        if (bp_info && (addr != peraddr)) {
                                debug_exit->addr = addr;
                                debug_exit->type = KVM_HW_BP;
                                vcpu->arch.guestdbg.last_bp = addr;
                                goto exit_required;
                        }
                        /* breakpoint missed */
                        bp_info = find_hw_bp(vcpu, peraddr);
                        if (bp_info && vcpu->arch.guestdbg.last_bp != peraddr) {
                                debug_exit->addr = peraddr;
                                debug_exit->type = KVM_HW_BP;
                                goto exit_required;
                        }
                }
        }
        if (guestdbg_sstep_enabled(vcpu) && per_bp_event(perc)) {
                debug_exit->addr = addr;
                debug_exit->type = KVM_SINGLESTEP;
                goto exit_required;
        }

        return 0;
exit_required:
        return 1;
}

static int per_fetched_addr(struct kvm_vcpu *vcpu, unsigned long *addr)
{
        u8 exec_ilen = 0;
        u16 opcode[3];
        int rc;

        if (vcpu->arch.sie_block->icptcode == ICPT_PROGI) {
                /* PER address references the fetched or the execute instr */
                *addr = vcpu->arch.sie_block->peraddr;
                /*
                 * Manually detect if we have an EXECUTE instruction. As
                 * instructions are always 2 byte aligned we can read the
                 * first two bytes unconditionally
                 */
                rc = read_guest_instr(vcpu, *addr, &opcode, 2);
                if (rc)
                        return rc;
                if (opcode[0] >> 8 == 0x44)
                        exec_ilen = 4;
                if ((opcode[0] & 0xff0f) == 0xc600)
                        exec_ilen = 6;
        } else {
                /* instr was suppressed, calculate the responsible instr */
                *addr = __rewind_psw(vcpu->arch.sie_block->gpsw,
                                     kvm_s390_get_ilen(vcpu));
                if (vcpu->arch.sie_block->icptstatus & 0x01) {
                        exec_ilen = (vcpu->arch.sie_block->icptstatus & 0x60) >> 4;
                        if (!exec_ilen)
                                exec_ilen = 4;
                }
        }

        if (exec_ilen) {
                /* read the complete EXECUTE instr to detect the fetched addr */
                rc = read_guest_instr(vcpu, *addr, &opcode, exec_ilen);
                if (rc)
                        return rc;
                if (exec_ilen == 6) {
                        /* EXECUTE RELATIVE LONG - RIL-b format */
                        s32 rl = *((s32 *) (opcode + 1));

                        /* rl is a _signed_ 32 bit value specifying halfwords */
                        *addr += (u64)(s64) rl * 2;
                } else {
                        /* EXECUTE - RX-a format */
                        u32 base = (opcode[1] & 0xf000) >> 12;
                        u32 disp = opcode[1] & 0x0fff;
                        u32 index = opcode[0] & 0x000f;

                        *addr = base ? vcpu->run->s.regs.gprs[base] : 0;
                        *addr += index ? vcpu->run->s.regs.gprs[index] : 0;
                        *addr += disp;
                }
                *addr = kvm_s390_logical_to_effective(vcpu, *addr);
        }
        return 0;
}

#define guest_per_enabled(vcpu) \
                             (vcpu->arch.sie_block->gpsw.mask & PSW_MASK_PER)

int kvm_s390_handle_per_ifetch_icpt(struct kvm_vcpu *vcpu)
{
        const u64 cr10 = vcpu->arch.sie_block->gcr[10];
        const u64 cr11 = vcpu->arch.sie_block->gcr[11];
        const u8 ilen = kvm_s390_get_ilen(vcpu);
        struct kvm_s390_pgm_info pgm_info = {
                .code = PGM_PER,
                .per_code = PER_CODE_IFETCH,
                .per_address = __rewind_psw(vcpu->arch.sie_block->gpsw, ilen),
        };
        unsigned long fetched_addr;
        int rc;

        /*
         * The PSW points to the next instruction, therefore the intercepted
         * instruction generated a PER i-fetch event. PER address therefore
         * points at the previous PSW address (could be an EXECUTE function).
         */
        if (!guestdbg_enabled(vcpu))
                return kvm_s390_inject_prog_irq(vcpu, &pgm_info);

        if (debug_exit_required(vcpu, pgm_info.per_code, pgm_info.per_address))
                vcpu->guest_debug |= KVM_GUESTDBG_EXIT_PENDING;

        if (!guest_per_enabled(vcpu) ||
            !(vcpu->arch.sie_block->gcr[9] & PER_EVENT_IFETCH))
                return 0;

        rc = per_fetched_addr(vcpu, &fetched_addr);
        if (rc < 0)
                return rc;
        if (rc)
                /* instruction-fetching exceptions */
                return kvm_s390_inject_program_int(vcpu, PGM_ADDRESSING);

        if (in_addr_range(fetched_addr, cr10, cr11))
                return kvm_s390_inject_prog_irq(vcpu, &pgm_info);
        return 0;
}

static int filter_guest_per_event(struct kvm_vcpu *vcpu)
{
        const u8 perc = vcpu->arch.sie_block->perc;
        u64 addr = vcpu->arch.sie_block->gpsw.addr;
        u64 cr9 = vcpu->arch.sie_block->gcr[9];
        u64 cr10 = vcpu->arch.sie_block->gcr[10];
        u64 cr11 = vcpu->arch.sie_block->gcr[11];
        /* filter all events, demanded by the guest */
        u8 guest_perc = perc & (cr9 >> 24) & PER_CODE_MASK;
        unsigned long fetched_addr;
        int rc;

        if (!guest_per_enabled(vcpu))
                guest_perc = 0;

        /* filter "successful-branching" events */
        if (guest_perc & PER_CODE_BRANCH &&
            cr9 & PER_CONTROL_BRANCH_ADDRESS &&
            !in_addr_range(addr, cr10, cr11))
                guest_perc &= ~PER_CODE_BRANCH;

        /* filter "instruction-fetching" events */
        if (guest_perc & PER_CODE_IFETCH) {
                rc = per_fetched_addr(vcpu, &fetched_addr);
                if (rc < 0)
                        return rc;
                /*
                 * Don't inject an irq on exceptions. This would make handling
                 * on icpt code 8 very complex (as PSW was already rewound).
                 */
                if (rc || !in_addr_range(fetched_addr, cr10, cr11))
                        guest_perc &= ~PER_CODE_IFETCH;
        }

        /* All other PER events will be given to the guest */
        /* TODO: Check altered address/address space */

        vcpu->arch.sie_block->perc = guest_perc;

        if (!guest_perc)
                vcpu->arch.sie_block->iprcc &= ~PGM_PER;
        return 0;
}

#define pssec(vcpu) (vcpu->arch.sie_block->gcr[1] & _ASCE_SPACE_SWITCH)
#define hssec(vcpu) (vcpu->arch.sie_block->gcr[13] & _ASCE_SPACE_SWITCH)
#define old_ssec(vcpu) ((vcpu->arch.sie_block->tecmc >> 31) & 0x1)
#define old_as_is_home(vcpu) !(vcpu->arch.sie_block->tecmc & 0xffff)

int kvm_s390_handle_per_event(struct kvm_vcpu *vcpu)
{
        int rc, new_as;

        if (debug_exit_required(vcpu, vcpu->arch.sie_block->perc,
                                vcpu->arch.sie_block->peraddr))
                vcpu->guest_debug |= KVM_GUESTDBG_EXIT_PENDING;

        rc = filter_guest_per_event(vcpu);
        if (rc)
                return rc;

        /*
         * Only RP, SAC, SACF, PT, PTI, PR, PC instructions can trigger
         * a space-switch event. PER events enforce space-switch events
         * for these instructions. So if no PER event for the guest is left,
         * we might have to filter the space-switch element out, too.
         */
        if (vcpu->arch.sie_block->iprcc == PGM_SPACE_SWITCH) {
                vcpu->arch.sie_block->iprcc = 0;
                new_as = psw_bits(vcpu->arch.sie_block->gpsw).as;

                /*
                 * If the AS changed from / to home, we had RP, SAC or SACF
                 * instruction. Check primary and home space-switch-event
                 * controls. (theoretically home -> home produced no event)
                 */
                if (((new_as == PSW_BITS_AS_HOME) ^ old_as_is_home(vcpu)) &&
                    (pssec(vcpu) || hssec(vcpu)))
                        vcpu->arch.sie_block->iprcc = PGM_SPACE_SWITCH;

                /*
                 * PT, PTI, PR, PC instruction operate on primary AS only. Check
                 * if the primary-space-switch-event control was or got set.
                 */
                if (new_as == PSW_BITS_AS_PRIMARY && !old_as_is_home(vcpu) &&
                    (pssec(vcpu) || old_ssec(vcpu)))
                        vcpu->arch.sie_block->iprcc = PGM_SPACE_SWITCH;
        }
        return 0;
}