// SPDX-License-Identifier: GPL-2.0

#ifndef pr_fmt
#define pr_fmt(fmt)     "alt: " fmt
#endif

#include <linux/hex.h>
#include <linux/uaccess.h>
#include <linux/printk.h>
#include <asm/nospec-branch.h>
#include <asm/abs_lowcore.h>
#include <asm/alternative.h>
#include <asm/facility.h>
#include <asm/sections.h>
#include <asm/machine.h>

#ifndef a_debug
#define a_debug         pr_debug
#endif

#ifndef __kernel_va
#define __kernel_va(x)  (void *)(x)
#endif

unsigned long __bootdata_preserved(machine_features[1]);

struct alt_debug {
        unsigned long facilities[MAX_FACILITY_BIT / BITS_PER_LONG];
        unsigned long mfeatures[MAX_MFEATURE_BIT / BITS_PER_LONG];
        int spec;
};

static struct alt_debug __bootdata_preserved(alt_debug);

static void alternative_dump(u8 *old, u8 *new, unsigned int len, unsigned int type, unsigned int data)
{
        char oinsn[33], ninsn[33];
        unsigned long kptr;
        unsigned int pos;

        for (pos = 0; pos < len && 2 * pos < sizeof(oinsn) - 3; pos++)
                hex_byte_pack(&oinsn[2 * pos], old[pos]);
        oinsn[2 * pos] = 0;
        for (pos = 0; pos < len && 2 * pos < sizeof(ninsn) - 3; pos++)
                hex_byte_pack(&ninsn[2 * pos], new[pos]);
        ninsn[2 * pos] = 0;
        kptr = (unsigned long)__kernel_va(old);
        a_debug("[%d/%3d] %016lx: %s -> %s\n", type, data, kptr, oinsn, ninsn);
}

void __apply_alternatives(struct alt_instr *start, struct alt_instr *end, unsigned int ctx)
{
        struct alt_debug *d;
        struct alt_instr *a;
        bool debug, replace;
        u8 *old, *new;

        /*
         * The scan order should be from start to end. A later scanned
         * alternative code can overwrite previously scanned alternative code.
         */
        d = &alt_debug;
        for (a = start; a < end; a++) {
                if (!(a->ctx & ctx))
                        continue;
                switch (a->type) {
                case ALT_TYPE_FACILITY:
                        replace = test_facility(a->data);
                        debug = __test_facility(a->data, d->facilities);
                        break;
                case ALT_TYPE_FEATURE:
                        replace = test_machine_feature(a->data);
                        debug = __test_machine_feature(a->data, d->mfeatures);
                        break;
                case ALT_TYPE_SPEC:
                        replace = nobp_enabled();
                        debug = d->spec;
                        break;
                default:
                        replace = false;
                        debug = false;
                }
                if (!replace)
                        continue;
                old = (u8 *)&a->instr_offset + a->instr_offset;
                new = (u8 *)&a->repl_offset + a->repl_offset;
                if (debug)
                        alternative_dump(old, new, a->instrlen, a->type, a->data);
                s390_kernel_write(old, new, a->instrlen);
        }
}