riscv-013_reg.c

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// SPDX-License-Identifier: GPL-2.0-or-later
 
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
 
#include "riscv-013_reg.h"
#include "field_helpers.h"
 
#include "riscv_reg.h"
#include "riscv_reg_impl.h"
#include "riscv-013.h"
#include "debug_defines.h"
#include <helper/time_support.h>
 
static int riscv013_reg_get(struct reg *reg)
{
    struct target *target = riscv_reg_impl_get_target(reg);
 
    /* TODO: Hack to deal with gdb that thinks these registers still exist. */
    if (reg->number > GDB_REGNO_XPR15 && reg->number <= GDB_REGNO_XPR31 &&
            riscv_supports_extension(target, 'E')) {
        buf_set_u64(reg->value, 0, reg->size, 0);
        return ERROR_OK;
    }
 
    if (reg->number >= GDB_REGNO_V0 && reg->number <= GDB_REGNO_V31) {
        if (riscv013_get_register_buf(target, reg->value, reg->number) != ERROR_OK)
            return ERROR_FAIL;
 
        reg->valid = riscv_reg_impl_gdb_regno_cacheable(reg->number, /* is write? */ false);
    } else {
        uint64_t value;
        int result = riscv_reg_get(target, &value, reg->number);
        if (result != ERROR_OK)
            return result;
        buf_set_u64(reg->value, 0, reg->size, value);
    }
    char *str = buf_to_hex_str(reg->value, reg->size);
    LOG_TARGET_DEBUG(target, "Read 0x%s from %s (valid=%d).", str, reg->name,
            reg->valid);
    free(str);
    return ERROR_OK;
}
 
static int riscv013_reg_set(struct reg *reg, uint8_t *buf)
{
    struct target *target = riscv_reg_impl_get_target(reg);
 
    char *str = buf_to_hex_str(buf, reg->size);
    LOG_TARGET_DEBUG(target, "Write 0x%s to %s (valid=%d).", str, reg->name,
            reg->valid);
    free(str);
 
    /* TODO: Hack to deal with gdb that thinks these registers still exist. */
    if (reg->number > GDB_REGNO_XPR15 && reg->number <= GDB_REGNO_XPR31 &&
            riscv_supports_extension(target, 'E') &&
            buf_get_u64(buf, 0, reg->size) == 0)
        return ERROR_OK;
 
    if (reg->number >= GDB_REGNO_V0 && reg->number <= GDB_REGNO_V31) {
        if (riscv013_set_register_buf(target, reg->number, buf) != ERROR_OK)
            return ERROR_FAIL;
 
        memcpy(reg->value, buf, DIV_ROUND_UP(reg->size, 8));
        reg->valid = riscv_reg_impl_gdb_regno_cacheable(reg->number, /* is write? */ true);
    } else {
        const riscv_reg_t value = buf_get_u64(buf, 0, reg->size);
        if (riscv_reg_set(target, reg->number, value) != ERROR_OK)
            return ERROR_FAIL;
    }
 
    return ERROR_OK;
}
 
static const struct reg_arch_type *riscv013_gdb_regno_reg_type(uint32_t regno)
{
    static const struct reg_arch_type riscv013_reg_type = {
        .get = riscv013_reg_get,
        .set = riscv013_reg_set
    };
    return &riscv013_reg_type;
}
 
static int init_cache_entry(struct target *target, uint32_t regno)
{
    struct reg * const reg = riscv_reg_impl_cache_entry(target, regno);
    if (riscv_reg_impl_is_initialized(reg))
        return ERROR_OK;
    return riscv_reg_impl_init_cache_entry(target, regno,
            riscv_reg_impl_gdb_regno_exist(target, regno),
            riscv013_gdb_regno_reg_type(regno));
}
 
static int assume_reg_exist(struct target *target, uint32_t regno)
{
    return riscv_reg_impl_init_cache_entry(target, regno,
            /* exist */ true, riscv013_gdb_regno_reg_type(regno));
}
 
static int examine_xlen(struct target *target)
{
    RISCV_INFO(r);
    unsigned int cmderr;
 
    const uint32_t command = riscv013_access_register_command(target,
            GDB_REGNO_S0, /* size */ 64, AC_ACCESS_REGISTER_TRANSFER);
    int res = riscv013_execute_abstract_command(target, command, &cmderr);
    if (res == ERROR_OK) {
        r->xlen = 64;
        return ERROR_OK;
    }
    if (res == ERROR_TIMEOUT_REACHED)
        return ERROR_FAIL;
    r->xlen = 32;
 
    return ERROR_OK;
}
 
static int examine_vlenb(struct target *target)
{
    RISCV_INFO(r);
 
    /* Reading "vlenb" requires "mstatus.vs" to be set, so "mstatus" should
     * be accessible.*/
    int res = init_cache_entry(target, GDB_REGNO_MSTATUS);
    if (res != ERROR_OK)
        return res;
 
    res = assume_reg_exist(target, GDB_REGNO_VLENB);
    if (res != ERROR_OK)
        return res;
 
    riscv_reg_t vlenb_val;
    if (riscv_reg_get(target, &vlenb_val, GDB_REGNO_VLENB) != ERROR_OK) {
        if (riscv_supports_extension(target, 'V'))
            LOG_TARGET_WARNING(target, "Couldn't read vlenb; vector register access won't work.");
        r->vlenb = 0;
        return riscv_reg_impl_set_exist(target, GDB_REGNO_VLENB, false);
    }
    /* As defined by RISC-V V extension specification:
     * https://github.com/riscv/riscv-v-spec/blob/2f68ef7256d6ec53e4d2bd7cb12862f406d64e34/v-spec.adoc?plain=1#L67-L72 */
    const unsigned int vlen_max = 65536;
    const unsigned int vlenb_max = vlen_max / 8;
    if (vlenb_val > vlenb_max) {
        LOG_TARGET_WARNING(target, "'vlenb == %" PRIu64
                "' is greater than maximum allowed by specification (%u); vector register access won't work.",
                vlenb_val, vlenb_max);
        r->vlenb = 0;
        return ERROR_OK;
    }
    assert(vlenb_max <= UINT_MAX);
    r->vlenb = (unsigned int)vlenb_val;
 
    LOG_TARGET_INFO(target, "Vector support with vlenb=%u", r->vlenb);
    return ERROR_OK;
}
 
enum misa_mxl {
    MISA_MXL_INVALID = 0,
    MISA_MXL_32 = 1,
    MISA_MXL_64 = 2,
    MISA_MXL_128 = 3
};
 
unsigned int mxl_to_xlen(enum misa_mxl mxl)
{
    switch (mxl) {
    case MISA_MXL_32:
        return 32;
    case MISA_MXL_64:
        return 64;
    case MISA_MXL_128:
        return 128;
    case MISA_MXL_INVALID:
        assert(0);
    }
    return 0;
}
 
static int check_misa_mxl(const struct target *target)
{
    RISCV_INFO(r);
 
    if (r->misa == 0) {
        LOG_TARGET_WARNING(target, "'misa' register is read as zero."
                "OpenOCD will not be able to determine some hart's capabilities.");
        return ERROR_OK;
    }
    const unsigned int dxlen = riscv_xlen(target);
    assert(dxlen <= sizeof(riscv_reg_t) * CHAR_BIT);
    assert(dxlen >= 2);
    const riscv_reg_t misa_mxl_mask = (riscv_reg_t)0x3 << (dxlen - 2);
    const unsigned int mxl = get_field(r->misa, misa_mxl_mask);
    if (mxl == MISA_MXL_INVALID) {
        /* This is not an error!
         * Imagine the platform that:
         * - Has no abstract access to CSRs, so that CSRs are read
         *   through Program Buffer via "csrr" instruction.
         * - Complies to v1.10 of the Priveleged Spec, so that misa.mxl
         *   is WARL and MXLEN may be chainged.
         *   https://github.com/riscv/riscv-isa-manual/commit/9a7dd2fe29011587954560b5dcf1875477b27ad8
         * - DXLEN == MXLEN on reset == 64.
         * In a following scenario:
         * - misa.mxl was written, so that MXLEN is 32.
         * - Debugger connects to the target.
         * - Debugger observes DXLEN == 64.
         * - Debugger reads misa:
         *   - Abstract access fails with "cmderr == not supported".
         *   - Access via Program Buffer involves reading "misa" to an
         *     "xreg" via "csrr", so that the "xreg" is filled with
         *     zero-extended value of "misa" (since "misa" is
         *     MXLEN-wide).
         * - Debugger derives "misa.mxl" assumig "misa" is DXLEN-bit
         *   wide (64) while MXLEN is 32 and therefore erroneously
         *   assumes "misa.mxl" to be zero (invalid).
         */
        LOG_TARGET_WARNING(target, "Detected DXLEN (%u) does not match "
                "MXLEN: misa.mxl == 0, misa == 0x%" PRIx64 ".",
                dxlen, r->misa);
        return ERROR_OK;
    }
    const unsigned int mxlen = mxl_to_xlen(mxl);
    if (dxlen < mxlen) {
        LOG_TARGET_ERROR(target,
                "MXLEN (%u) reported in misa.mxl field exceeds "
                "the detected DXLEN (%u)",
                mxlen, dxlen);
        return ERROR_FAIL;
    }
    /* NOTE:
     * The value of "misa.mxl" may stil not coincide with "xlen".
     * "misa[26:XLEN-3]" bits are marked as WIRI in at least version 1.10
     * of RISC-V Priveleged Spec. Therefore, if "xlen" is erroneously
     * assumed to be 32 when it actually is 64, "mxl" will be read from
     * this WIRI field and may be equal to "MISA_MXL_32" by coincidence.
     * This is not an issue though from the version 1.11 onward, since
     * "misa[26:XLEN-3]" became WARL and equal to 0.
     */
 
    /* Display this as early as possible to help people who are using
     * really slow simulators. */
    LOG_TARGET_DEBUG(target, " XLEN=%d, misa=0x%" PRIx64, riscv_xlen(target), r->misa);
    return ERROR_OK;
}
 
static int examine_misa(struct target *target)
{
    RISCV_INFO(r);
 
    int res = init_cache_entry(target, GDB_REGNO_MISA);
    if (res != ERROR_OK)
        return res;
 
    res = riscv_reg_get(target, &r->misa, GDB_REGNO_MISA);
    if (res != ERROR_OK)
        return res;
    return check_misa_mxl(target);
}
 
static int examine_mtopi(struct target *target)
{
    /* Assume the registers exist */
    int res = assume_reg_exist(target, GDB_REGNO_MTOPI);
    if (res != ERROR_OK)
        return res;
    res = assume_reg_exist(target, GDB_REGNO_MTOPEI);
    if (res != ERROR_OK)
        return res;
 
    riscv_reg_t value;
    if (riscv_reg_get(target, &value, GDB_REGNO_MTOPI) != ERROR_OK) {
        res = riscv_reg_impl_set_exist(target, GDB_REGNO_MTOPI, false);
        if (res != ERROR_OK)
            return res;
        return riscv_reg_impl_set_exist(target, GDB_REGNO_MTOPEI, false);
    }
    if (riscv_reg_get(target, &value, GDB_REGNO_MTOPEI) != ERROR_OK) {
        LOG_TARGET_INFO(target, "S?aia detected without IMSIC");
        return riscv_reg_impl_set_exist(target, GDB_REGNO_MTOPEI, false);
    }
    LOG_TARGET_INFO(target, "S?aia detected with IMSIC");
    return ERROR_OK;
}
 
int riscv013_reg_examine_all(struct target *target)
{
    int res = riscv_reg_impl_init_cache(target);
    if (res != ERROR_OK)
        return res;
 
    init_shared_reg_info(target);
 
    assert(target->state == TARGET_HALTED);
 
    res = examine_xlen(target);
    if (res != ERROR_OK)
        return res;
 
    /* Reading CSRs may clobber "s0", "s1", so it should be possible to
     * save them in cache. */
    res = init_cache_entry(target, GDB_REGNO_S0);
    if (res != ERROR_OK)
        return res;
    res = init_cache_entry(target, GDB_REGNO_S1);
    if (res != ERROR_OK)
        return res;
 
    res = examine_misa(target);
    if (res != ERROR_OK)
        return res;
 
    res = examine_vlenb(target);
    if (res != ERROR_OK)
        return res;
 
    riscv_reg_impl_init_vector_reg_type(target);
 
    res = examine_mtopi(target);
    if (res != ERROR_OK)
        return res;
 
    for (uint32_t regno = 0; regno < target->reg_cache->num_regs; ++regno) {
        res = init_cache_entry(target, regno);
        if (res != ERROR_OK)
            return res;
    }
 
    res = riscv_reg_impl_expose_csrs(target);
    if (res != ERROR_OK)
        return res;
 
    riscv_reg_impl_hide_csrs(target);
 
    return ERROR_OK;
}
 
int riscv013_reg_save(struct target *target, enum gdb_regno regid)
{
    if (target->state != TARGET_HALTED) {
        LOG_TARGET_ERROR(target, "Can't save register %s on a hart that is not halted.",
                 riscv_reg_gdb_regno_name(target, regid));
        return ERROR_FAIL;
    }
    assert(riscv_reg_impl_gdb_regno_cacheable(regid, /* is write? */ false) &&
            "Only cacheable registers can be saved.");
 
    RISCV_INFO(r);
    riscv_reg_t value;
    if (!target->reg_cache) {
        assert(!target_was_examined(target));
        /* To create register cache it is needed to examine the target first,
         * therefore during examine, any changed register needs to be saved
         * and restored manually.
         */
        return ERROR_OK;
    }
 
    struct reg *reg = riscv_reg_impl_cache_entry(target, regid);
 
    LOG_TARGET_DEBUG(target, "Saving %s", reg->name);
    if (riscv_reg_get(target, &value, regid) != ERROR_OK)
        return ERROR_FAIL;
 
    assert(reg->valid &&
            "The register is cacheable, so the cache entry must be valid now.");
    /* Mark the register dirty. We assume that this function is called
     * because the caller is about to mess with the underlying value of the
     * register. */
    reg->dirty = true;
 
    r->last_activity = timeval_ms();
 
    return ERROR_OK;
}