// SPDX-License-Identifier: GPL-2.0
/*
 * Early cpufeature override framework
 *
 * Copyright (C) 2020 Google LLC
 * Author: Marc Zyngier <maz@kernel.org>
 */

#include <linux/ctype.h>
#include <linux/kernel.h>
#include <linux/libfdt.h>

#include <asm/cacheflush.h>
#include <asm/cpufeature.h>
#include <asm/setup.h>

#include "pi.h"

#define FTR_DESC_NAME_LEN       20
#define FTR_DESC_FIELD_LEN      10
#define FTR_ALIAS_NAME_LEN      30
#define FTR_ALIAS_OPTION_LEN    116

static u64 __boot_status __initdata;

typedef bool filter_t(u64 val);

struct ftr_set_desc {
        char                            name[FTR_DESC_NAME_LEN];
        PREL64(struct arm64_ftr_override, override);
        struct {
                char                    name[FTR_DESC_FIELD_LEN];
                u8                      shift;
                u8                      width;
                PREL64(filter_t,        filter);
        }                               fields[];
};

#define FIELD(n, s, f)  { .name = n, .shift = s, .width = 4, .filter = f }

static const struct ftr_set_desc mmfr0 __prel64_initconst = {
        .name           = "id_aa64mmfr0",
        .override       = &id_aa64mmfr0_override,
        .fields         = {
                FIELD("ecv", ID_AA64MMFR0_EL1_ECV_SHIFT, NULL),
                {}
        },
};

static bool __init mmfr1_vh_filter(u64 val)
{
        /*
         * If we ever reach this point while running VHE, we're
         * guaranteed to be on one of these funky, VHE-stuck CPUs. If
         * the user was trying to force nVHE on us, proceed with
         * attitude adjustment.
         */
        return !(__boot_status == (BOOT_CPU_FLAG_E2H | BOOT_CPU_MODE_EL2) &&
                 val == 0);
}

static const struct ftr_set_desc mmfr1 __prel64_initconst = {
        .name           = "id_aa64mmfr1",
        .override       = &id_aa64mmfr1_override,
        .fields         = {
                FIELD("vh", ID_AA64MMFR1_EL1_VH_SHIFT, mmfr1_vh_filter),
                {}
        },
};


static bool __init mmfr2_varange_filter(u64 val)
{
        int __maybe_unused feat;

        if (val)
                return false;

#ifdef CONFIG_ARM64_LPA2
        feat = cpuid_feature_extract_signed_field(read_sysreg(id_aa64mmfr0_el1),
                                                  ID_AA64MMFR0_EL1_TGRAN_SHIFT);
        if (feat >= ID_AA64MMFR0_EL1_TGRAN_LPA2) {
                id_aa64mmfr0_override.val |=
                        (ID_AA64MMFR0_EL1_TGRAN_LPA2 - 1) << ID_AA64MMFR0_EL1_TGRAN_SHIFT;
                id_aa64mmfr0_override.mask |= 0xfU << ID_AA64MMFR0_EL1_TGRAN_SHIFT;

                /*
                 * Override PARange to 48 bits - the override will just be
                 * ignored if the actual PARange is smaller, but this is
                 * unlikely to be the case for LPA2 capable silicon.
                 */
                id_aa64mmfr0_override.val |=
                        ID_AA64MMFR0_EL1_PARANGE_48 << ID_AA64MMFR0_EL1_PARANGE_SHIFT;
                id_aa64mmfr0_override.mask |= 0xfU << ID_AA64MMFR0_EL1_PARANGE_SHIFT;
        }
#endif
        return true;
}

static const struct ftr_set_desc mmfr2 __prel64_initconst = {
        .name           = "id_aa64mmfr2",
        .override       = &id_aa64mmfr2_override,
        .fields         = {
                FIELD("varange", ID_AA64MMFR2_EL1_VARange_SHIFT, mmfr2_varange_filter),
                {}
        },
};

static bool __init pfr0_sve_filter(u64 val)
{
        /*
         * Disabling SVE also means disabling all the features that
         * are associated with it. The easiest way to do it is just to
         * override id_aa64zfr0_el1 to be 0.
         */
        if (!val) {
                id_aa64zfr0_override.val = 0;
                id_aa64zfr0_override.mask = GENMASK(63, 0);
        }

        return true;
}

static const struct ftr_set_desc pfr0 __prel64_initconst = {
        .name           = "id_aa64pfr0",
        .override       = &id_aa64pfr0_override,
        .fields         = {
                FIELD("sve", ID_AA64PFR0_EL1_SVE_SHIFT, pfr0_sve_filter),
                FIELD("el0", ID_AA64PFR0_EL1_EL0_SHIFT, NULL),
                FIELD("mpam", ID_AA64PFR0_EL1_MPAM_SHIFT, NULL),
                {}
        },
};

static bool __init pfr1_sme_filter(u64 val)
{
        /*
         * Similarly to SVE, disabling SME also means disabling all
         * the features that are associated with it. Just set
         * id_aa64smfr0_el1 to 0 and don't look back.
         */
        if (!val) {
                id_aa64smfr0_override.val = 0;
                id_aa64smfr0_override.mask = GENMASK(63, 0);
        }

        return true;
}

static const struct ftr_set_desc pfr1 __prel64_initconst = {
        .name           = "id_aa64pfr1",
        .override       = &id_aa64pfr1_override,
        .fields         = {
                FIELD("bt", ID_AA64PFR1_EL1_BT_SHIFT, NULL ),
                FIELD("gcs", ID_AA64PFR1_EL1_GCS_SHIFT, NULL),
                FIELD("mte", ID_AA64PFR1_EL1_MTE_SHIFT, NULL),
                FIELD("sme", ID_AA64PFR1_EL1_SME_SHIFT, pfr1_sme_filter),
                FIELD("mpam_frac", ID_AA64PFR1_EL1_MPAM_frac_SHIFT, NULL),
                {}
        },
};

static const struct ftr_set_desc isar1 __prel64_initconst = {
        .name           = "id_aa64isar1",
        .override       = &id_aa64isar1_override,
        .fields         = {
                FIELD("gpi", ID_AA64ISAR1_EL1_GPI_SHIFT, NULL),
                FIELD("gpa", ID_AA64ISAR1_EL1_GPA_SHIFT, NULL),
                FIELD("api", ID_AA64ISAR1_EL1_API_SHIFT, NULL),
                FIELD("apa", ID_AA64ISAR1_EL1_APA_SHIFT, NULL),
                {}
        },
};

static const struct ftr_set_desc isar2 __prel64_initconst = {
        .name           = "id_aa64isar2",
        .override       = &id_aa64isar2_override,
        .fields         = {
                FIELD("gpa3", ID_AA64ISAR2_EL1_GPA3_SHIFT, NULL),
                FIELD("apa3", ID_AA64ISAR2_EL1_APA3_SHIFT, NULL),
                FIELD("mops", ID_AA64ISAR2_EL1_MOPS_SHIFT, NULL),
                {}
        },
};

static const struct ftr_set_desc smfr0 __prel64_initconst = {
        .name           = "id_aa64smfr0",
        .override       = &id_aa64smfr0_override,
        .fields         = {
                FIELD("smever", ID_AA64SMFR0_EL1_SMEver_SHIFT, NULL),
                /* FA64 is a one bit field... :-/ */
                { "fa64", ID_AA64SMFR0_EL1_FA64_SHIFT, 1, },
                {}
        },
};

static bool __init hvhe_filter(u64 val)
{
        u64 mmfr1 = read_sysreg(id_aa64mmfr1_el1);

        return (val == 1 &&
                lower_32_bits(__boot_status) == BOOT_CPU_MODE_EL2 &&
                cpuid_feature_extract_unsigned_field(mmfr1,
                                                     ID_AA64MMFR1_EL1_VH_SHIFT));
}

static const struct ftr_set_desc sw_features __prel64_initconst = {
        .name           = "arm64_sw",
        .override       = &arm64_sw_feature_override,
        .fields         = {
                FIELD("nokaslr", ARM64_SW_FEATURE_OVERRIDE_NOKASLR, NULL),
                FIELD("hvhe", ARM64_SW_FEATURE_OVERRIDE_HVHE, hvhe_filter),
                FIELD("rodataoff", ARM64_SW_FEATURE_OVERRIDE_RODATA_OFF, NULL),
                {}
        },
};

static const
PREL64(const struct ftr_set_desc, reg) regs[] __prel64_initconst = {
        { &mmfr0        },
        { &mmfr1        },
        { &mmfr2        },
        { &pfr0         },
        { &pfr1         },
        { &isar1        },
        { &isar2        },
        { &smfr0        },
        { &sw_features  },
};

static const struct {
        char    alias[FTR_ALIAS_NAME_LEN];
        char    feature[FTR_ALIAS_OPTION_LEN];
} aliases[] __initconst = {
        { "kvm_arm.mode=nvhe",          "arm64_sw.hvhe=0 id_aa64mmfr1.vh=0" },
        { "kvm_arm.mode=protected",     "arm64_sw.hvhe=1" },
        { "arm64.nosve",                "id_aa64pfr0.sve=0" },
        { "arm64.nosme",                "id_aa64pfr1.sme=0" },
        { "arm64.nobti",                "id_aa64pfr1.bt=0" },
        { "arm64.nogcs",                "id_aa64pfr1.gcs=0" },
        { "arm64.nopauth",
          "id_aa64isar1.gpi=0 id_aa64isar1.gpa=0 "
          "id_aa64isar1.api=0 id_aa64isar1.apa=0 "
          "id_aa64isar2.gpa3=0 id_aa64isar2.apa3=0"        },
        { "arm64.nomops",               "id_aa64isar2.mops=0" },
        { "arm64.nomte",                "id_aa64pfr1.mte=0" },
        { "nokaslr",                    "arm64_sw.nokaslr=1" },
        { "rodata=off",                 "arm64_sw.rodataoff=1" },
        { "arm64.nolva",                "id_aa64mmfr2.varange=0" },
        { "arm64.no32bit_el0",          "id_aa64pfr0.el0=1" },
        { "arm64.nompam",               "id_aa64pfr0.mpam=0 id_aa64pfr1.mpam_frac=0" },
};

static int __init parse_hexdigit(const char *p, u64 *v)
{
        // skip "0x" if it comes next
        if (p[0] == '0' && tolower(p[1]) == 'x')
                p += 2;

        // check whether the RHS is a single hex digit
        if (!isxdigit(p[0]) || (p[1] && !isspace(p[1])))
                return -EINVAL;

        *v = tolower(*p) - (isdigit(*p) ? '0' : 'a' - 10);
        return 0;
}

static int __init find_field(const char *cmdline, char *opt, int len,
                             const struct ftr_set_desc *reg, int f, u64 *v)
{
        int flen = strlen(reg->fields[f].name);

        // append '<fieldname>=' to obtain '<name>.<fieldname>='
        memcpy(opt + len, reg->fields[f].name, flen);
        len += flen;
        opt[len++] = '=';

        if (memcmp(cmdline, opt, len))
                return -1;

        return parse_hexdigit(cmdline + len, v);
}

static void __init match_options(const char *cmdline)
{
        char opt[FTR_DESC_NAME_LEN + FTR_DESC_FIELD_LEN + 2];
        int i;

        for (i = 0; i < ARRAY_SIZE(regs); i++) {
                const struct ftr_set_desc *reg = prel64_pointer(regs[i].reg);
                struct arm64_ftr_override *override;
                int len = strlen(reg->name);
                int f;

                override = prel64_pointer(reg->override);

                // set opt[] to '<name>.'
                memcpy(opt, reg->name, len);
                opt[len++] = '.';

                for (f = 0; reg->fields[f].name[0] != '\0'; f++) {
                        u64 shift = reg->fields[f].shift;
                        u64 width = reg->fields[f].width ?: 4;
                        u64 mask = GENMASK_ULL(shift + width - 1, shift);
                        bool (*filter)(u64 val);
                        u64 v;

                        if (find_field(cmdline, opt, len, reg, f, &v))
                                continue;

                        /*
                         * If an override gets filtered out, advertise
                         * it by setting the value to the all-ones while
                         * clearing the mask... Yes, this is fragile.
                         */
                        filter = prel64_pointer(reg->fields[f].filter);
                        if (filter && !filter(v)) {
                                override->val  |= mask;
                                override->mask &= ~mask;
                                continue;
                        }

                        override->val  &= ~mask;
                        override->val  |= (v << shift) & mask;
                        override->mask |= mask;

                        return;
                }
        }
}

static __init void __parse_cmdline(const char *cmdline, bool parse_aliases)
{
        do {
                char buf[256];
                size_t len;
                int i;

                cmdline = skip_spaces(cmdline);

                /* terminate on "--" appearing on the command line by itself */
                if (cmdline[0] == '-' && cmdline[1] == '-' && isspace(cmdline[2]))
                        return;

                for (len = 0; cmdline[len] && !isspace(cmdline[len]); len++) {
                        if (len >= sizeof(buf) - 1)
                                break;
                        if (cmdline[len] == '-')
                                buf[len] = '_';
                        else
                                buf[len] = cmdline[len];
                }
                if (!len)
                        return;

                buf[len] = 0;

                cmdline += len;

                match_options(buf);

                for (i = 0; parse_aliases && i < ARRAY_SIZE(aliases); i++)
                        if (!memcmp(buf, aliases[i].alias, len + 1))
                                __parse_cmdline(aliases[i].feature, false);
        } while (1);
}

static __init const u8 *get_bootargs_cmdline(const void *fdt, int node)
{
        static char const bootargs[] __initconst = "bootargs";
        const u8 *prop;

        if (node < 0)
                return NULL;

        prop = fdt_getprop(fdt, node, bootargs, NULL);
        if (!prop)
                return NULL;

        return strlen(prop) ? prop : NULL;
}

static __init void parse_cmdline(const void *fdt, int chosen)
{
        static char const cmdline[] __initconst = CONFIG_CMDLINE;
        const u8 *prop = get_bootargs_cmdline(fdt, chosen);

        if (IS_ENABLED(CONFIG_CMDLINE_FORCE) || !prop)
                __parse_cmdline(cmdline, true);

        if (!IS_ENABLED(CONFIG_CMDLINE_FORCE) && prop)
                __parse_cmdline(prop, true);
}

void __init init_feature_override(u64 boot_status, const void *fdt,
                                  int chosen)
{
        struct arm64_ftr_override *override;
        const struct ftr_set_desc *reg;
        int i;

        for (i = 0; i < ARRAY_SIZE(regs); i++) {
                reg = prel64_pointer(regs[i].reg);
                override = prel64_pointer(reg->override);

                override->val  = 0;
                override->mask = 0;
        }

        __boot_status = boot_status;

        parse_cmdline(fdt, chosen);

        for (i = 0; i < ARRAY_SIZE(regs); i++) {
                reg = prel64_pointer(regs[i].reg);
                override = prel64_pointer(reg->override);
                dcache_clean_inval_poc((unsigned long)override,
                                       (unsigned long)(override + 1));
        }
}

char * __init skip_spaces(const char *str)
{
        while (isspace(*str))
                ++str;
        return (char *)str;
}