target/riscv/op_helper.c

/*
 * RISC-V Emulation Helpers for QEMU.
 *
 * Copyright (c) 2016-2017 Sagar Karandikar, sagark@eecs.berkeley.edu
 * Copyright (c) 2017-2018 SiFive, Inc.
 * Copyright (c) 2022      VRULL GmbH
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2 or later, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include "qemu/osdep.h"
#include "cpu.h"
#include "internals.h"
#include "exec/exec-all.h"
#include "exec/cpu_ldst.h"
#include "exec/helper-proto.h"
#include "trace.h"

/* Exceptions processing helpers */
G_NORETURN void riscv_raise_exception(CPURISCVState *env,
                                      RISCVException exception,
                                      uintptr_t pc)
{
    CPUState *cs = env_cpu(env);

    trace_riscv_exception(exception,
                          riscv_cpu_get_trap_name(exception, false),
                          env->pc);

    cs->exception_index = exception;
    cpu_loop_exit_restore(cs, pc);
}

void helper_raise_exception(CPURISCVState *env, uint32_t exception)
{
    riscv_raise_exception(env, exception, 0);
}

target_ulong helper_csrr(CPURISCVState *env, int csr)
{
    /*
     * The seed CSR must be accessed with a read-write instruction. A
     * read-only instruction such as CSRRS/CSRRC with rs1=x0 or CSRRSI/
     * CSRRCI with uimm=0 will raise an illegal instruction exception.
     */
    if (csr == CSR_SEED) {
        riscv_raise_exception(env, RISCV_EXCP_ILLEGAL_INST, GETPC());
    }

    target_ulong val = 0;
    RISCVException ret = riscv_csrr(env, csr, &val);

    if (ret != RISCV_EXCP_NONE) {
        riscv_raise_exception(env, ret, GETPC());
    }
    return val;
}

void helper_csrw(CPURISCVState *env, int csr, target_ulong src)
{
    target_ulong mask = env->xl == MXL_RV32 ? UINT32_MAX : (target_ulong)-1;
    RISCVException ret = riscv_csrrw(env, csr, NULL, src, mask);

    if (ret != RISCV_EXCP_NONE) {
        riscv_raise_exception(env, ret, GETPC());
    }
}

target_ulong helper_csrrw(CPURISCVState *env, int csr,
                          target_ulong src, target_ulong write_mask)
{
    target_ulong val = 0;
    RISCVException ret = riscv_csrrw(env, csr, &val, src, write_mask);

    if (ret != RISCV_EXCP_NONE) {
        riscv_raise_exception(env, ret, GETPC());
    }
    return val;
}

target_ulong helper_csrr_i128(CPURISCVState *env, int csr)
{
    Int128 rv = int128_zero();
    RISCVException ret = riscv_csrr_i128(env, csr, &rv);

    if (ret != RISCV_EXCP_NONE) {
        riscv_raise_exception(env, ret, GETPC());
    }

    env->retxh = int128_gethi(rv);
    return int128_getlo(rv);
}

void helper_csrw_i128(CPURISCVState *env, int csr,
                      target_ulong srcl, target_ulong srch)
{
    RISCVException ret = riscv_csrrw_i128(env, csr, NULL,
                                          int128_make128(srcl, srch),
                                          UINT128_MAX);

    if (ret != RISCV_EXCP_NONE) {
        riscv_raise_exception(env, ret, GETPC());
    }
}

target_ulong helper_csrrw_i128(CPURISCVState *env, int csr,
                       target_ulong srcl, target_ulong srch,
                       target_ulong maskl, target_ulong maskh)
{
    Int128 rv = int128_zero();
    RISCVException ret = riscv_csrrw_i128(env, csr, &rv,
                                          int128_make128(srcl, srch),
                                          int128_make128(maskl, maskh));

    if (ret != RISCV_EXCP_NONE) {
        riscv_raise_exception(env, ret, GETPC());
    }

    env->retxh = int128_gethi(rv);
    return int128_getlo(rv);
}


/*
 * check_zicbo_envcfg
 *
 * Raise virtual exceptions and illegal instruction exceptions for
 * Zicbo[mz] instructions based on the settings of [mhs]envcfg as
 * specified in section 2.5.1 of the CMO specification.
 */
static void check_zicbo_envcfg(CPURISCVState *env, target_ulong envbits,
                                uintptr_t ra)
{
#ifndef CONFIG_USER_ONLY
    if ((env->priv < PRV_M) && !get_field(env->menvcfg, envbits)) {
        riscv_raise_exception(env, RISCV_EXCP_ILLEGAL_INST, ra);
    }

    if (env->virt_enabled &&
        (((env->priv <= PRV_S) && !get_field(env->henvcfg, envbits)) ||
         ((env->priv < PRV_S) && !get_field(env->senvcfg, envbits)))) {
        riscv_raise_exception(env, RISCV_EXCP_VIRT_INSTRUCTION_FAULT, ra);
    }

    if ((env->priv < PRV_S) && !get_field(env->senvcfg, envbits)) {
        riscv_raise_exception(env, RISCV_EXCP_ILLEGAL_INST, ra);
    }
#endif
}

void helper_cbo_zero(CPURISCVState *env, target_ulong address)
{
    RISCVCPU *cpu = env_archcpu(env);
    uint16_t cbozlen = cpu->cfg.cboz_blocksize;
    int mmu_idx = riscv_env_mmu_index(env, false);
    uintptr_t ra = GETPC();
    void *mem;

    check_zicbo_envcfg(env, MENVCFG_CBZE, ra);

    /* Mask off low-bits to align-down to the cache-block. */
    address &= ~(cbozlen - 1);

    /*
     * cbo.zero requires MMU_DATA_STORE access. Do a probe_write()
     * to raise any exceptions, including PMP.
     */
    mem = probe_write(env, address, cbozlen, mmu_idx, ra);

    if (likely(mem)) {
        memset(mem, 0, cbozlen);
    } else {
        /*
         * This means that we're dealing with an I/O page. Section 4.2
         * of cmobase v1.0.1 says:
         *
         * "Cache-block zero instructions store zeros independently
         * of whether data from the underlying memory locations are
         * cacheable."
         *
         * Write zeros in address + cbozlen regardless of not being
         * a RAM page.
         */
        for (int i = 0; i < cbozlen; i++) {
            cpu_stb_mmuidx_ra(env, address + i, 0, mmu_idx, ra);
        }
    }
}

/*
 * check_zicbom_access
 *
 * Check access permissions (LOAD, STORE or FETCH as specified in
 * section 2.5.2 of the CMO specification) for Zicbom, raising
 * either store page-fault (non-virtualized) or store guest-page
 * fault (virtualized).
 */
static void check_zicbom_access(CPURISCVState *env,
                                target_ulong address,
                                uintptr_t ra)
{
    RISCVCPU *cpu = env_archcpu(env);
    int mmu_idx = riscv_env_mmu_index(env, false);
    uint16_t cbomlen = cpu->cfg.cbom_blocksize;
    void *phost;
    int ret;

    /* Mask off low-bits to align-down to the cache-block. */
    address &= ~(cbomlen - 1);

    /*
     * Section 2.5.2 of cmobase v1.0.1:
     *
     * "A cache-block management instruction is permitted to
     * access the specified cache block whenever a load instruction
     * or store instruction is permitted to access the corresponding
     * physical addresses. If neither a load instruction nor store
     * instruction is permitted to access the physical addresses,
     * but an instruction fetch is permitted to access the physical
     * addresses, whether a cache-block management instruction is
     * permitted to access the cache block is UNSPECIFIED."
     */
    ret = probe_access_flags(env, address, cbomlen, MMU_DATA_LOAD,
                             mmu_idx, true, &phost, ra);
    if (ret != TLB_INVALID_MASK) {
        /* Success: readable */
        return;
    }

    /*
     * Since not readable, must be writable. On failure, store
     * fault/store guest amo fault will be raised by
     * riscv_cpu_tlb_fill(). PMP exceptions will be caught
     * there as well.
     */
    probe_write(env, address, cbomlen, mmu_idx, ra);
}

void helper_cbo_clean_flush(CPURISCVState *env, target_ulong address)
{
    uintptr_t ra = GETPC();
    check_zicbo_envcfg(env, MENVCFG_CBCFE, ra);
    check_zicbom_access(env, address, ra);

    /* We don't emulate the cache-hierarchy, so we're done. */
}

void helper_cbo_inval(CPURISCVState *env, target_ulong address)
{
    uintptr_t ra = GETPC();
    check_zicbo_envcfg(env, MENVCFG_CBIE, ra);
    check_zicbom_access(env, address, ra);

    /* We don't emulate the cache-hierarchy, so we're done. */
}

#ifndef CONFIG_USER_ONLY

target_ulong helper_sret(CPURISCVState *env)
{
    uint64_t mstatus;
    target_ulong prev_priv, prev_virt = env->virt_enabled;

    if (!(env->priv >= PRV_S)) {
        riscv_raise_exception(env, RISCV_EXCP_ILLEGAL_INST, GETPC());
    }

    target_ulong retpc = env->sepc;
    if (!riscv_has_ext(env, RVC) && (retpc & 0x3)) {
        riscv_raise_exception(env, RISCV_EXCP_INST_ADDR_MIS, GETPC());
    }

    if (get_field(env->mstatus, MSTATUS_TSR) && !(env->priv >= PRV_M)) {
        riscv_raise_exception(env, RISCV_EXCP_ILLEGAL_INST, GETPC());
    }

    if (env->virt_enabled && get_field(env->hstatus, HSTATUS_VTSR)) {
        riscv_raise_exception(env, RISCV_EXCP_VIRT_INSTRUCTION_FAULT, GETPC());
    }

    mstatus = env->mstatus;
    prev_priv = get_field(mstatus, MSTATUS_SPP);
    mstatus = set_field(mstatus, MSTATUS_SIE,
                        get_field(mstatus, MSTATUS_SPIE));
    mstatus = set_field(mstatus, MSTATUS_SPIE, 1);
    mstatus = set_field(mstatus, MSTATUS_SPP, PRV_U);
    if (env->priv_ver >= PRIV_VERSION_1_12_0) {
        mstatus = set_field(mstatus, MSTATUS_MPRV, 0);
    }
    env->mstatus = mstatus;

    if (riscv_has_ext(env, RVH) && !env->virt_enabled) {
        /* We support Hypervisor extensions and virtulisation is disabled */
        target_ulong hstatus = env->hstatus;

        prev_virt = get_field(hstatus, HSTATUS_SPV);

        hstatus = set_field(hstatus, HSTATUS_SPV, 0);

        env->hstatus = hstatus;

        if (prev_virt) {
            riscv_cpu_swap_hypervisor_regs(env);
        }
    }

    riscv_cpu_set_mode(env, prev_priv, prev_virt);

    /*
     * If forward cfi enabled for new priv, restore elp status
     * and clear spelp in mstatus
     */
    if (cpu_get_fcfien(env)) {
        env->elp = get_field(env->mstatus, MSTATUS_SPELP);
    }
    env->mstatus = set_field(env->mstatus, MSTATUS_SPELP, 0);

    return retpc;
}

static void check_ret_from_m_mode(CPURISCVState *env, target_ulong retpc,
                                  target_ulong prev_priv)
{
    if (!(env->priv >= PRV_M)) {
        riscv_raise_exception(env, RISCV_EXCP_ILLEGAL_INST, GETPC());
    }

    if (!riscv_has_ext(env, RVC) && (retpc & 0x3)) {
        riscv_raise_exception(env, RISCV_EXCP_INST_ADDR_MIS, GETPC());
    }

    if (riscv_cpu_cfg(env)->pmp &&
        !pmp_get_num_rules(env) && (prev_priv != PRV_M)) {
        riscv_raise_exception(env, RISCV_EXCP_INST_ACCESS_FAULT, GETPC());
    }
}

target_ulong helper_mret(CPURISCVState *env)
{
    target_ulong retpc = env->mepc;
    uint64_t mstatus = env->mstatus;
    target_ulong prev_priv = get_field(mstatus, MSTATUS_MPP);

    check_ret_from_m_mode(env, retpc, prev_priv);

    target_ulong prev_virt = get_field(env->mstatus, MSTATUS_MPV) &&
                             (prev_priv != PRV_M);
    mstatus = set_field(mstatus, MSTATUS_MIE,
                        get_field(mstatus, MSTATUS_MPIE));
    mstatus = set_field(mstatus, MSTATUS_MPIE, 1);
    mstatus = set_field(mstatus, MSTATUS_MPP,
                        riscv_has_ext(env, RVU) ? PRV_U : PRV_M);
    mstatus = set_field(mstatus, MSTATUS_MPV, 0);
    if ((env->priv_ver >= PRIV_VERSION_1_12_0) && (prev_priv != PRV_M)) {
        mstatus = set_field(mstatus, MSTATUS_MPRV, 0);
    }
    env->mstatus = mstatus;

    if (riscv_has_ext(env, RVH) && prev_virt) {
        riscv_cpu_swap_hypervisor_regs(env);
    }

    riscv_cpu_set_mode(env, prev_priv, prev_virt);
    /*
     * If forward cfi enabled for new priv, restore elp status
     * and clear mpelp in mstatus
     */
    if (cpu_get_fcfien(env)) {
        env->elp = get_field(env->mstatus, MSTATUS_MPELP);
    }
    env->mstatus = set_field(env->mstatus, MSTATUS_MPELP, 0);

    return retpc;
}

target_ulong helper_mnret(CPURISCVState *env)
{
    target_ulong retpc = env->mnepc;
    target_ulong prev_priv = get_field(env->mnstatus, MNSTATUS_MNPP);
    target_ulong prev_virt;

    check_ret_from_m_mode(env, retpc, prev_priv);

    prev_virt = get_field(env->mnstatus, MNSTATUS_MNPV) &&
                (prev_priv != PRV_M);
    env->mnstatus = set_field(env->mnstatus, MNSTATUS_NMIE, true);

    /*
     * If MNRET changes the privilege mode to a mode
     * less privileged than M, it also sets mstatus.MPRV to 0.
     */
    if (prev_priv < PRV_M) {
        env->mstatus = set_field(env->mstatus, MSTATUS_MPRV, false);
    }

    if (riscv_has_ext(env, RVH) && prev_virt) {
        riscv_cpu_swap_hypervisor_regs(env);
    }

    riscv_cpu_set_mode(env, prev_priv, prev_virt);

    /*
     * If forward cfi enabled for new priv, restore elp status
     * and clear mnpelp in mnstatus
     */
    if (cpu_get_fcfien(env)) {
        env->elp = get_field(env->mnstatus, MNSTATUS_MNPELP);
    }
    env->mnstatus = set_field(env->mnstatus, MNSTATUS_MNPELP, 0);

    return retpc;
}

void helper_wfi(CPURISCVState *env)
{
    CPUState *cs = env_cpu(env);
    bool rvs = riscv_has_ext(env, RVS);
    bool prv_u = env->priv == PRV_U;
    bool prv_s = env->priv == PRV_S;

    if (((prv_s || (!rvs && prv_u)) && get_field(env->mstatus, MSTATUS_TW)) ||
        (rvs && prv_u && !env->virt_enabled)) {
        riscv_raise_exception(env, RISCV_EXCP_ILLEGAL_INST, GETPC());
    } else if (env->virt_enabled &&
               (prv_u || (prv_s && get_field(env->hstatus, HSTATUS_VTW)))) {
        riscv_raise_exception(env, RISCV_EXCP_VIRT_INSTRUCTION_FAULT, GETPC());
    } else {
        cs->halted = 1;
        cs->exception_index = EXCP_HLT;
        cpu_loop_exit(cs);
    }
}

void helper_wrs_nto(CPURISCVState *env)
{
    if (env->virt_enabled && (env->priv == PRV_S || env->priv == PRV_U) &&
        get_field(env->hstatus, HSTATUS_VTW) &&
        !get_field(env->mstatus, MSTATUS_TW)) {
        riscv_raise_exception(env, RISCV_EXCP_VIRT_INSTRUCTION_FAULT, GETPC());
    } else if (env->priv != PRV_M && get_field(env->mstatus, MSTATUS_TW)) {
        riscv_raise_exception(env, RISCV_EXCP_ILLEGAL_INST, GETPC());
    }
}

void helper_tlb_flush(CPURISCVState *env)
{
    CPUState *cs = env_cpu(env);
    if (!env->virt_enabled &&
        (env->priv == PRV_U ||
         (env->priv == PRV_S && get_field(env->mstatus, MSTATUS_TVM)))) {
        riscv_raise_exception(env, RISCV_EXCP_ILLEGAL_INST, GETPC());
    } else if (env->virt_enabled &&
               (env->priv == PRV_U || get_field(env->hstatus, HSTATUS_VTVM))) {
        riscv_raise_exception(env, RISCV_EXCP_VIRT_INSTRUCTION_FAULT, GETPC());
    } else {
        tlb_flush(cs);
    }
}

void helper_tlb_flush_all(CPURISCVState *env)
{
    CPUState *cs = env_cpu(env);
    tlb_flush_all_cpus_synced(cs);
}

void helper_hyp_tlb_flush(CPURISCVState *env)
{
    CPUState *cs = env_cpu(env);

    if (env->virt_enabled) {
        riscv_raise_exception(env, RISCV_EXCP_VIRT_INSTRUCTION_FAULT, GETPC());
    }

    if (env->priv == PRV_M ||
        (env->priv == PRV_S && !env->virt_enabled)) {
        tlb_flush(cs);
        return;
    }

    riscv_raise_exception(env, RISCV_EXCP_ILLEGAL_INST, GETPC());
}

void helper_hyp_gvma_tlb_flush(CPURISCVState *env)
{
    if (env->priv == PRV_S && !env->virt_enabled &&
        get_field(env->mstatus, MSTATUS_TVM)) {
        riscv_raise_exception(env, RISCV_EXCP_ILLEGAL_INST, GETPC());
    }

    helper_hyp_tlb_flush(env);
}

static int check_access_hlsv(CPURISCVState *env, bool x, uintptr_t ra)
{
    if (env->priv == PRV_M) {
        /* always allowed */
    } else if (env->virt_enabled) {
        riscv_raise_exception(env, RISCV_EXCP_VIRT_INSTRUCTION_FAULT, ra);
    } else if (env->priv == PRV_U && !get_field(env->hstatus, HSTATUS_HU)) {
        riscv_raise_exception(env, RISCV_EXCP_ILLEGAL_INST, ra);
    }

    int mode = get_field(env->hstatus, HSTATUS_SPVP);
    if (!x && mode == PRV_S && get_field(env->vsstatus, MSTATUS_SUM)) {
        mode = MMUIdx_S_SUM;
    }
    return mode | MMU_2STAGE_BIT;
}

target_ulong helper_hyp_hlv_bu(CPURISCVState *env, target_ulong addr)
{
    uintptr_t ra = GETPC();
    int mmu_idx = check_access_hlsv(env, false, ra);
    MemOpIdx oi = make_memop_idx(MO_UB, mmu_idx);

    return cpu_ldb_mmu(env, adjust_addr_virt(env, addr), oi, ra);
}

target_ulong helper_hyp_hlv_hu(CPURISCVState *env, target_ulong addr)
{
    uintptr_t ra = GETPC();
    int mmu_idx = check_access_hlsv(env, false, ra);
    MemOpIdx oi = make_memop_idx(MO_TEUW, mmu_idx);

    return cpu_ldw_mmu(env, adjust_addr_virt(env, addr), oi, ra);
}

target_ulong helper_hyp_hlv_wu(CPURISCVState *env, target_ulong addr)
{
    uintptr_t ra = GETPC();
    int mmu_idx = check_access_hlsv(env, false, ra);
    MemOpIdx oi = make_memop_idx(MO_TEUL, mmu_idx);

    return cpu_ldl_mmu(env, adjust_addr_virt(env, addr), oi, ra);
}

target_ulong helper_hyp_hlv_d(CPURISCVState *env, target_ulong addr)
{
    uintptr_t ra = GETPC();
    int mmu_idx = check_access_hlsv(env, false, ra);
    MemOpIdx oi = make_memop_idx(MO_TEUQ, mmu_idx);

    return cpu_ldq_mmu(env, adjust_addr_virt(env, addr), oi, ra);
}

void helper_hyp_hsv_b(CPURISCVState *env, target_ulong addr, target_ulong val)
{
    uintptr_t ra = GETPC();
    int mmu_idx = check_access_hlsv(env, false, ra);
    MemOpIdx oi = make_memop_idx(MO_UB, mmu_idx);

    cpu_stb_mmu(env, adjust_addr_virt(env, addr), val, oi, ra);
}

void helper_hyp_hsv_h(CPURISCVState *env, target_ulong addr, target_ulong val)
{
    uintptr_t ra = GETPC();
    int mmu_idx = check_access_hlsv(env, false, ra);
    MemOpIdx oi = make_memop_idx(MO_TEUW, mmu_idx);

    cpu_stw_mmu(env, adjust_addr_virt(env, addr), val, oi, ra);
}

void helper_hyp_hsv_w(CPURISCVState *env, target_ulong addr, target_ulong val)
{
    uintptr_t ra = GETPC();
    int mmu_idx = check_access_hlsv(env, false, ra);
    MemOpIdx oi = make_memop_idx(MO_TEUL, mmu_idx);

    cpu_stl_mmu(env, adjust_addr_virt(env, addr), val, oi, ra);
}

void helper_hyp_hsv_d(CPURISCVState *env, target_ulong addr, target_ulong val)
{
    uintptr_t ra = GETPC();
    int mmu_idx = check_access_hlsv(env, false, ra);
    MemOpIdx oi = make_memop_idx(MO_TEUQ, mmu_idx);

    cpu_stq_mmu(env, adjust_addr_virt(env, addr), val, oi, ra);
}

/*
 * TODO: These implementations are not quite correct.  They perform the
 * access using execute permission just fine, but the final PMP check
 * is supposed to have read permission as well.  Without replicating
 * a fair fraction of cputlb.c, fixing this requires adding new mmu_idx
 * which would imply that exact check in tlb_fill.
 */
target_ulong helper_hyp_hlvx_hu(CPURISCVState *env, target_ulong addr)
{
    uintptr_t ra = GETPC();
    int mmu_idx = check_access_hlsv(env, true, ra);
    MemOpIdx oi = make_memop_idx(MO_TEUW, mmu_idx);

    return cpu_ldw_code_mmu(env, addr, oi, GETPC());
}

target_ulong helper_hyp_hlvx_wu(CPURISCVState *env, target_ulong addr)
{
    uintptr_t ra = GETPC();
    int mmu_idx = check_access_hlsv(env, true, ra);
    MemOpIdx oi = make_memop_idx(MO_TEUL, mmu_idx);

    return cpu_ldl_code_mmu(env, addr, oi, ra);
}

#endif /* !CONFIG_USER_ONLY */