target/riscv/pmp.c

/*
 * QEMU RISC-V PMP (Physical Memory Protection)
 *
 * Author: Daire McNamara, daire.mcnamara@emdalo.com
 *         Ivan Griffin, ivan.griffin@emdalo.com
 *
 * This provides a RISC-V Physical Memory Protection implementation
 *
 * 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/>.
 */

/*
 * PMP (Physical Memory Protection) is as-of-yet unused and needs testing.
 */

#include "qemu/osdep.h"
#include "qemu/log.h"
#include "qapi/error.h"
#include "cpu.h"
#include "trace.h"
#include "exec/exec-all.h"

static void pmp_write_cfg(CPURISCVState *env, uint32_t addr_index,
    uint8_t val);
static uint8_t pmp_read_cfg(CPURISCVState *env, uint32_t addr_index);
static void pmp_update_rule(CPURISCVState *env, uint32_t pmp_index);

/*
 * Accessor method to extract address matching type 'a field' from cfg reg
 */
static inline uint8_t pmp_get_a_field(uint8_t cfg)
{
    uint8_t a = cfg >> 3;
    return a & 0x3;
}

/*
 * Check whether a PMP is locked or not.
 */
static inline int pmp_is_locked(CPURISCVState *env, uint32_t pmp_index)
{

    if (env->pmp_state.pmp[pmp_index].cfg_reg & PMP_LOCK) {
        return 1;
    }

    /* Top PMP has no 'next' to check */
    if ((pmp_index + 1u) >= MAX_RISCV_PMPS) {
        return 0;
    }

    /* In TOR mode, need to check the lock bit of the next pmp
     * (if there is a next)
     */
    const uint8_t a_field =
        pmp_get_a_field(env->pmp_state.pmp[pmp_index + 1].cfg_reg);
    if ((env->pmp_state.pmp[pmp_index + 1u].cfg_reg & PMP_LOCK) &&
         (PMP_AMATCH_TOR == a_field)) {
        return 1;
    }

    return 0;
}

/*
 * Count the number of active rules.
 */
uint32_t pmp_get_num_rules(CPURISCVState *env)
{
     return env->pmp_state.num_rules;
}

/*
 * Accessor to get the cfg reg for a specific PMP/HART
 */
static inline uint8_t pmp_read_cfg(CPURISCVState *env, uint32_t pmp_index)
{
    if (pmp_index < MAX_RISCV_PMPS) {
        return env->pmp_state.pmp[pmp_index].cfg_reg;
    }

    return 0;
}


/*
 * Accessor to set the cfg reg for a specific PMP/HART
 * Bounds checks and relevant lock bit.
 */
static void pmp_write_cfg(CPURISCVState *env, uint32_t pmp_index, uint8_t val)
{
    if (pmp_index < MAX_RISCV_PMPS) {
        if (!pmp_is_locked(env, pmp_index)) {
            env->pmp_state.pmp[pmp_index].cfg_reg = val;
            pmp_update_rule(env, pmp_index);
        } else {
            qemu_log_mask(LOG_GUEST_ERROR, "ignoring pmpcfg write - locked\n");
        }
    } else {
        qemu_log_mask(LOG_GUEST_ERROR,
                      "ignoring pmpcfg write - out of bounds\n");
    }
}

static void pmp_decode_napot(target_ulong a, target_ulong *sa, target_ulong *ea)
{
    /*
       aaaa...aaa0   8-byte NAPOT range
       aaaa...aa01   16-byte NAPOT range
       aaaa...a011   32-byte NAPOT range
       ...
       aa01...1111   2^XLEN-byte NAPOT range
       a011...1111   2^(XLEN+1)-byte NAPOT range
       0111...1111   2^(XLEN+2)-byte NAPOT range
       1111...1111   Reserved
    */
    if (a == -1) {
        *sa = 0u;
        *ea = -1;
        return;
    } else {
        target_ulong t1 = ctz64(~a);
        target_ulong base = (a & ~(((target_ulong)1 << t1) - 1)) << 2;
        target_ulong range = ((target_ulong)1 << (t1 + 3)) - 1;
        *sa = base;
        *ea = base + range;
    }
}

void pmp_update_rule_addr(CPURISCVState *env, uint32_t pmp_index)
{
    uint8_t this_cfg = env->pmp_state.pmp[pmp_index].cfg_reg;
    target_ulong this_addr = env->pmp_state.pmp[pmp_index].addr_reg;
    target_ulong prev_addr = 0u;
    target_ulong sa = 0u;
    target_ulong ea = 0u;

    if (pmp_index >= 1u) {
        prev_addr = env->pmp_state.pmp[pmp_index - 1].addr_reg;
    }

    switch (pmp_get_a_field(this_cfg)) {
    case PMP_AMATCH_OFF:
        sa = 0u;
        ea = -1;
        break;

    case PMP_AMATCH_TOR:
        sa = prev_addr << 2; /* shift up from [xx:0] to [xx+2:2] */
        ea = (this_addr << 2) - 1u;
        break;

    case PMP_AMATCH_NA4:
        sa = this_addr << 2; /* shift up from [xx:0] to [xx+2:2] */
        ea = (sa + 4u) - 1u;
        break;

    case PMP_AMATCH_NAPOT:
        pmp_decode_napot(this_addr, &sa, &ea);
        break;

    default:
        sa = 0u;
        ea = 0u;
        break;
    }

    env->pmp_state.addr[pmp_index].sa = sa;
    env->pmp_state.addr[pmp_index].ea = ea;
}

void pmp_update_rule_nums(CPURISCVState *env)
{
    int i;

    env->pmp_state.num_rules = 0;
    for (i = 0; i < MAX_RISCV_PMPS; i++) {
        const uint8_t a_field =
            pmp_get_a_field(env->pmp_state.pmp[i].cfg_reg);
        if (PMP_AMATCH_OFF != a_field) {
            env->pmp_state.num_rules++;
        }
    }
}

/* Convert cfg/addr reg values here into simple 'sa' --> start address and 'ea'
 *   end address values.
 *   This function is called relatively infrequently whereas the check that
 *   an address is within a pmp rule is called often, so optimise that one
 */
static void pmp_update_rule(CPURISCVState *env, uint32_t pmp_index)
{
    pmp_update_rule_addr(env, pmp_index);
    pmp_update_rule_nums(env);
}

static int pmp_is_in_range(CPURISCVState *env, int pmp_index, target_ulong addr)
{
    int result = 0;

    if ((addr >= env->pmp_state.addr[pmp_index].sa)
        && (addr <= env->pmp_state.addr[pmp_index].ea)) {
        result = 1;
    } else {
        result = 0;
    }

    return result;
}

/*
 * Check if the address has required RWX privs when no PMP entry is matched.
 */
static bool pmp_hart_has_privs_default(CPURISCVState *env, target_ulong addr,
    target_ulong size, pmp_priv_t privs, pmp_priv_t *allowed_privs,
    target_ulong mode)
{
    bool ret;

    if ((!riscv_feature(env, RISCV_FEATURE_PMP)) || (mode == PRV_M)) {
        /*
         * Privileged spec v1.10 states if HW doesn't implement any PMP entry
         * or no PMP entry matches an M-Mode access, the access succeeds.
         */
        ret = true;
        *allowed_privs = PMP_READ | PMP_WRITE | PMP_EXEC;
    } else {
        /*
         * Other modes are not allowed to succeed if they don't * match a rule,
         * but there are rules. We've checked for no rule earlier in this
         * function.
         */
        ret = false;
        *allowed_privs = 0;
    }

    return ret;
}


/*
 * Public Interface
 */

/*
 * Check if the address has required RWX privs to complete desired operation
 */
bool pmp_hart_has_privs(CPURISCVState *env, target_ulong addr,
    target_ulong size, pmp_priv_t privs, pmp_priv_t *allowed_privs,
    target_ulong mode)
{
    int i = 0;
    int ret = -1;
    int pmp_size = 0;
    target_ulong s = 0;
    target_ulong e = 0;

    /* Short cut if no rules */
    if (0 == pmp_get_num_rules(env)) {
        return pmp_hart_has_privs_default(env, addr, size, privs,
                                          allowed_privs, mode);
    }

    if (size == 0) {
        if (riscv_feature(env, RISCV_FEATURE_MMU)) {
            /*
             * If size is unknown (0), assume that all bytes
             * from addr to the end of the page will be accessed.
             */
            pmp_size = -(addr | TARGET_PAGE_MASK);
        } else {
            pmp_size = sizeof(target_ulong);
        }
    } else {
        pmp_size = size;
    }

    /* 1.10 draft priv spec states there is an implicit order
         from low to high */
    for (i = 0; i < MAX_RISCV_PMPS; i++) {
        s = pmp_is_in_range(env, i, addr);
        e = pmp_is_in_range(env, i, addr + pmp_size - 1);

        /* partially inside */
        if ((s + e) == 1) {
            qemu_log_mask(LOG_GUEST_ERROR,
                          "pmp violation - access is partially inside\n");
            ret = 0;
            break;
        }

        /* fully inside */
        const uint8_t a_field =
            pmp_get_a_field(env->pmp_state.pmp[i].cfg_reg);

        /*
         * If the PMP entry is not off and the address is in range, do the priv
         * check
         */
        if (((s + e) == 2) && (PMP_AMATCH_OFF != a_field)) {
            *allowed_privs = PMP_READ | PMP_WRITE | PMP_EXEC;
            if ((mode != PRV_M) || pmp_is_locked(env, i)) {
                *allowed_privs &= env->pmp_state.pmp[i].cfg_reg;
            }

            ret = ((privs & *allowed_privs) == privs);
            break;
        }
    }

    /* No rule matched */
    if (ret == -1) {
        return pmp_hart_has_privs_default(env, addr, size, privs,
                                          allowed_privs, mode);
    }

    return ret == 1 ? true : false;
}

/*
 * Handle a write to a pmpcfg CSP
 */
void pmpcfg_csr_write(CPURISCVState *env, uint32_t reg_index,
    target_ulong val)
{
    int i;
    uint8_t cfg_val;

    trace_pmpcfg_csr_write(env->mhartid, reg_index, val);

    if ((reg_index & 1) && (sizeof(target_ulong) == 8)) {
        qemu_log_mask(LOG_GUEST_ERROR,
                      "ignoring pmpcfg write - incorrect address\n");
        return;
    }

    for (i = 0; i < sizeof(target_ulong); i++) {
        cfg_val = (val >> 8 * i)  & 0xff;
        pmp_write_cfg(env, (reg_index * 4) + i, cfg_val);
    }

    /* If PMP permission of any addr has been changed, flush TLB pages. */
    tlb_flush(env_cpu(env));
}


/*
 * Handle a read from a pmpcfg CSP
 */
target_ulong pmpcfg_csr_read(CPURISCVState *env, uint32_t reg_index)
{
    int i;
    target_ulong cfg_val = 0;
    target_ulong val = 0;

    for (i = 0; i < sizeof(target_ulong); i++) {
        val = pmp_read_cfg(env, (reg_index * 4) + i);
        cfg_val |= (val << (i * 8));
    }
    trace_pmpcfg_csr_read(env->mhartid, reg_index, cfg_val);

    return cfg_val;
}


/*
 * Handle a write to a pmpaddr CSP
 */
void pmpaddr_csr_write(CPURISCVState *env, uint32_t addr_index,
    target_ulong val)
{
    trace_pmpaddr_csr_write(env->mhartid, addr_index, val);
    if (addr_index < MAX_RISCV_PMPS) {
        if (!pmp_is_locked(env, addr_index)) {
            env->pmp_state.pmp[addr_index].addr_reg = val;
            pmp_update_rule(env, addr_index);
        } else {
            qemu_log_mask(LOG_GUEST_ERROR,
                          "ignoring pmpaddr write - locked\n");
        }
    } else {
        qemu_log_mask(LOG_GUEST_ERROR,
                      "ignoring pmpaddr write - out of bounds\n");
    }
}


/*
 * Handle a read from a pmpaddr CSP
 */
target_ulong pmpaddr_csr_read(CPURISCVState *env, uint32_t addr_index)
{
    target_ulong val = 0;

    if (addr_index < MAX_RISCV_PMPS) {
        val = env->pmp_state.pmp[addr_index].addr_reg;
        trace_pmpaddr_csr_read(env->mhartid, addr_index, val);
    } else {
        qemu_log_mask(LOG_GUEST_ERROR,
                      "ignoring pmpaddr read - out of bounds\n");
    }

    return val;
}

/*
 * Calculate the TLB size if the start address or the end address of
 * PMP entry is presented in thie TLB page.
 */
static target_ulong pmp_get_tlb_size(CPURISCVState *env, int pmp_index,
                                     target_ulong tlb_sa, target_ulong tlb_ea)
{
    target_ulong pmp_sa = env->pmp_state.addr[pmp_index].sa;
    target_ulong pmp_ea = env->pmp_state.addr[pmp_index].ea;

    if (pmp_sa >= tlb_sa && pmp_ea <= tlb_ea) {
        return pmp_ea - pmp_sa + 1;
    }

    if (pmp_sa >= tlb_sa && pmp_sa <= tlb_ea && pmp_ea >= tlb_ea) {
        return tlb_ea - pmp_sa + 1;
    }

    if (pmp_ea <= tlb_ea && pmp_ea >= tlb_sa && pmp_sa <= tlb_sa) {
        return pmp_ea - tlb_sa + 1;
    }

    return 0;
}

/*
 * Check is there a PMP entry which range covers this page. If so,
 * try to find the minimum granularity for the TLB size.
 */
bool pmp_is_range_in_tlb(CPURISCVState *env, hwaddr tlb_sa,
                         target_ulong *tlb_size)
{
    int i;
    target_ulong val;
    target_ulong tlb_ea = (tlb_sa + TARGET_PAGE_SIZE - 1);

    for (i = 0; i < MAX_RISCV_PMPS; i++) {
        val = pmp_get_tlb_size(env, i, tlb_sa, tlb_ea);
        if (val) {
            if (*tlb_size == 0 || *tlb_size > val) {
                *tlb_size = val;
            }
        }
    }

    if (*tlb_size != 0) {
        return true;
    }

    return false;
}

/*
 * Convert PMP privilege to TLB page privilege.
 */
int pmp_priv_to_page_prot(pmp_priv_t pmp_priv)
{
    int prot = 0;

    if (pmp_priv & PMP_READ) {
        prot |= PAGE_READ;
    }
    if (pmp_priv & PMP_WRITE) {
        prot |= PAGE_WRITE;
    }
    if (pmp_priv & PMP_EXEC) {
        prot |= PAGE_EXEC;
    }

    return prot;
}