arm_dpm.c

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// SPDX-License-Identifier: GPL-2.0-or-later
 
/*
 * Copyright (C) 2009 by David Brownell
 */
 
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
 
#include "arm.h"
#include "arm_dpm.h"
#include "armv8_dpm.h"
#include <jtag/jtag.h>
#include "register.h"
#include "breakpoints.h"
#include "target_type.h"
#include "arm_opcodes.h"
 
 
/*----------------------------------------------------------------------*/
 
/*
 * Coprocessor support
 */
 
/* Read coprocessor */
static int dpm_mrc(struct target *target, int cpnum,
    uint32_t op1, uint32_t op2, uint32_t crn, uint32_t crm,
    uint32_t *value)
{
    struct arm *arm = target_to_arm(target);
    struct arm_dpm *dpm = arm->dpm;
    int retval;
 
    retval = dpm->prepare(dpm);
    if (retval != ERROR_OK)
        return retval;
 
    LOG_TARGET_DEBUG(target, "MRC p%d, %" PRId32 ", r0, c%" PRId32 ", c%" PRId32 ", %" PRId32,
        cpnum, op1, crn, crm, op2);
 
    /* read coprocessor register into R0; return via DCC */
    retval = dpm->instr_read_data_r0(dpm,
            ARMV4_5_MRC(cpnum, op1, 0, crn, crm, op2),
            value);
 
    dpm->finish(dpm);
    return retval;
}
 
static int dpm_mrrc(struct target *target, int cpnum,
    uint32_t op, uint32_t crm, uint64_t *value)
{
    struct arm *arm = target_to_arm(target);
    struct arm_dpm *dpm = arm->dpm;
    int retval;
 
    retval = dpm->prepare(dpm);
    if (retval != ERROR_OK)
        return retval;
 
    LOG_TARGET_DEBUG(target, "MRRC p%d, %" PRId32 ", r0, r1, c%" PRId32,
        cpnum, op, crm);
 
    /* read coprocessor register into R0, R1; return via DCC */
    retval = dpm->instr_read_data_r0_r1(dpm,
            ARMV5_T_MRRC(cpnum, op, 0, 1, crm),
            value);
 
    dpm->finish(dpm);
    return retval;
}
 
static int dpm_mcr(struct target *target, int cpnum,
    uint32_t op1, uint32_t op2, uint32_t crn, uint32_t crm,
    uint32_t value)
{
    struct arm *arm = target_to_arm(target);
    struct arm_dpm *dpm = arm->dpm;
    int retval;
 
    retval = dpm->prepare(dpm);
    if (retval != ERROR_OK)
        return retval;
 
    LOG_TARGET_DEBUG(target, "MCR p%d, %" PRId32 ", r0, c%" PRId32 ", c%" PRId32 ", %" PRId32,
        cpnum, op1, crn, crm, op2);
 
    /* read DCC into r0; then write coprocessor register from R0 */
    retval = dpm->instr_write_data_r0(dpm,
            ARMV4_5_MCR(cpnum, op1, 0, crn, crm, op2),
            value);
 
    dpm->finish(dpm);
    return retval;
}
 
static int dpm_mcrr(struct target *target, int cpnum,
    uint32_t op, uint32_t crm, uint64_t value)
{
    struct arm *arm = target_to_arm(target);
    struct arm_dpm *dpm = arm->dpm;
    int retval;
 
    retval = dpm->prepare(dpm);
    if (retval != ERROR_OK)
        return retval;
 
    LOG_TARGET_DEBUG(target, "MCRR p%d, %" PRId32 ", r0, r1, c%" PRId32,
        cpnum, op, crm);
 
    /* read DCC into r0, r1; then write coprocessor register from R0, R1 */
    retval = dpm->instr_write_data_r0_r1(dpm,
            ARMV5_T_MCRR(cpnum, op, 0, 1, crm), value);
 
    dpm->finish(dpm);
 
    return retval;
}
 
/*----------------------------------------------------------------------*/
 
/*
 * Register access utilities
 */
 
/* Toggles between recorded core mode (USR, SVC, etc) and a temporary one.
 * Routines *must* restore the original mode before returning!!
 */
int arm_dpm_modeswitch(struct arm_dpm *dpm, enum arm_mode mode)
{
    int retval;
    uint32_t cpsr;
 
    /* restore previous mode */
    if (mode == ARM_MODE_ANY)
        cpsr = buf_get_u32(dpm->arm->cpsr->value, 0, 32);
 
    /* else force to the specified mode */
    else
        cpsr = mode;
 
    retval = dpm->instr_write_data_r0(dpm, ARMV4_5_MSR_GP(0, 0xf, 0), cpsr);
    if (retval != ERROR_OK)
        return retval;
 
    if (dpm->instr_cpsr_sync)
        retval = dpm->instr_cpsr_sync(dpm);
 
    return retval;
}
 
/* Read 64bit VFP registers */
static int dpm_read_reg_u64(struct arm_dpm *dpm, struct reg *r, unsigned int regnum)
{
    int retval = ERROR_FAIL;
    uint32_t value_r0, value_r1;
 
    switch (regnum) {
        case ARM_VFP_V3_D0 ... ARM_VFP_V3_D31:
            /* move from double word register to r0:r1: "vmov r0, r1, vm"
             * then read r0 via dcc
             */
            retval = dpm->instr_read_data_r0(dpm,
                ARMV4_5_VMOV(1, 1, 0, ((regnum - ARM_VFP_V3_D0) >> 4),
                ((regnum - ARM_VFP_V3_D0) & 0xf)), &value_r0);
            if (retval != ERROR_OK)
                break;
 
            /* read r1 via dcc */
            retval = dpm->instr_read_data_dcc(dpm,
                ARMV4_5_MCR(14, 0, 1, 0, 5, 0),
                &value_r1);
            break;
        default:
 
            break;
    }
 
    if (retval == ERROR_OK) {
        buf_set_u32(r->value, 0, 32, value_r0);
        buf_set_u32(r->value + 4, 0, 32, value_r1);
        r->valid = true;
        r->dirty = false;
        LOG_TARGET_DEBUG(dpm->arm->target, "READ: %s, %8.8" PRIx32 ", %8.8" PRIx32,
            r->name, value_r0, value_r1);
    }
 
    return retval;
}
 
/* just read the register -- rely on the core mode being right */
int arm_dpm_read_reg(struct arm_dpm *dpm, struct reg *r, unsigned int regnum)
{
    uint32_t value;
    int retval;
 
    switch (regnum) {
        case 0 ... 14:
            /* return via DCC:  "MCR p14, 0, Rnum, c0, c5, 0" */
            retval = dpm->instr_read_data_dcc(dpm,
                ARMV4_5_MCR(14, 0, regnum, 0, 5, 0),
                &value);
            break;
        case 15:/* PC
             * "MOV r0, pc"; then return via DCC */
            retval = dpm->instr_read_data_r0(dpm, 0xe1a0000f, &value);
 
            /* NOTE: this seems like a slightly awkward place to update
             * this value ... but if the PC gets written (the only way
             * to change what we compute), the arch spec says subsequent
             * reads return values which are "unpredictable".  So this
             * is always right except in those broken-by-intent cases.
             */
            switch (dpm->arm->core_state) {
                case ARM_STATE_ARM:
                    value -= 8;
                    break;
                case ARM_STATE_THUMB:
                case ARM_STATE_THUMB_EE:
                    value -= 4;
                    break;
                case ARM_STATE_JAZELLE:
                    /* core-specific ... ? */
                    LOG_TARGET_WARNING(dpm->arm->target, "Jazelle PC adjustment unknown");
                    break;
                default:
                    LOG_TARGET_WARNING(dpm->arm->target, "unknown core state");
                    break;
            }
            break;
        case ARM_VFP_V3_D0 ... ARM_VFP_V3_D31:
            return dpm_read_reg_u64(dpm, r, regnum);
        case ARM_VFP_V3_FPSCR:
            /* "VMRS r0, FPSCR"; then return via DCC */
            retval = dpm->instr_read_data_r0(dpm,
                ARMV4_5_VMRS(0), &value);
            break;
        default:
            /* 16: "MRS r0, CPSR"; then return via DCC
             * 17: "MRS r0, SPSR"; then return via DCC
             */
            retval = dpm->instr_read_data_r0(dpm,
                ARMV4_5_MRS(0, regnum & 1),
                &value);
            break;
    }
 
    if (retval == ERROR_OK) {
        buf_set_u32(r->value, 0, 32, value);
        r->valid = true;
        r->dirty = false;
        LOG_TARGET_DEBUG(dpm->arm->target, "READ: %s, %8.8" PRIx32, r->name,
            value);
    }
 
    return retval;
}
 
/* Write 64bit VFP registers */
static int dpm_write_reg_u64(struct arm_dpm *dpm, struct reg *r, unsigned int regnum)
{
    int retval = ERROR_FAIL;
    uint32_t value_r0 = buf_get_u32(r->value, 0, 32);
    uint32_t value_r1 = buf_get_u32(r->value + 4, 0, 32);
 
    switch (regnum) {
        case ARM_VFP_V3_D0 ... ARM_VFP_V3_D31:
            /* write value_r1 to r1 via dcc */
            retval = dpm->instr_write_data_dcc(dpm,
                ARMV4_5_MRC(14, 0, 1, 0, 5, 0),
                value_r1);
            if (retval != ERROR_OK)
                break;
 
            /* write value_r0 to r0 via dcc then,
             * move to double word register from r0:r1: "vmov vm, r0, r1"
             */
            retval = dpm->instr_write_data_r0(dpm,
                ARMV4_5_VMOV(0, 1, 0, ((regnum - ARM_VFP_V3_D0) >> 4),
                ((regnum - ARM_VFP_V3_D0) & 0xf)), value_r0);
            break;
        default:
 
            break;
    }
 
    if (retval == ERROR_OK) {
        r->dirty = false;
        LOG_TARGET_DEBUG(dpm->arm->target, "WRITE: %s, %8.8" PRIx32 ", %8.8" PRIx32,
            r->name, value_r0, value_r1);
    }
 
    return retval;
}
 
/* just write the register -- rely on the core mode being right */
static int dpm_write_reg(struct arm_dpm *dpm, struct reg *r, unsigned int regnum)
{
    int retval;
    uint32_t value = buf_get_u32(r->value, 0, 32);
 
    switch (regnum) {
        case 0 ... 14:
            /* load register from DCC:  "MRC p14, 0, Rnum, c0, c5, 0" */
            retval = dpm->instr_write_data_dcc(dpm,
                ARMV4_5_MRC(14, 0, regnum, 0, 5, 0),
                value);
            break;
        case 15:/* PC
             * read r0 from DCC; then "MOV pc, r0" */
            retval = dpm->instr_write_data_r0(dpm, 0xe1a0f000, value);
            break;
        case ARM_VFP_V3_D0 ... ARM_VFP_V3_D31:
            return dpm_write_reg_u64(dpm, r, regnum);
        case ARM_VFP_V3_FPSCR:
            /* move to r0 from DCC, then "VMSR FPSCR, r0" */
            retval = dpm->instr_write_data_r0(dpm,
                ARMV4_5_VMSR(0), value);
            break;
        default:
            /* 16: read r0 from DCC, then "MSR r0, CPSR_cxsf"
             * 17: read r0 from DCC, then "MSR r0, SPSR_cxsf"
             */
            retval = dpm->instr_write_data_r0(dpm,
                ARMV4_5_MSR_GP(0, 0xf, regnum & 1),
                value);
            if (retval != ERROR_OK)
                return retval;
 
            if (regnum == 16 && dpm->instr_cpsr_sync)
                retval = dpm->instr_cpsr_sync(dpm);
 
            break;
    }
 
    if (retval == ERROR_OK) {
        r->dirty = false;
        LOG_TARGET_DEBUG(dpm->arm->target, "WRITE: %s, %8.8" PRIx32, r->name,
            value);
    }
 
    return retval;
}
 
static int dpm_write_pc_core_state(struct arm_dpm *dpm, struct reg *r)
{
    uint32_t value = buf_get_u32(r->value, 0, 32);
 
    /* read r0 from DCC; then "BX r0" */
    return dpm->instr_write_data_r0(dpm, ARMV4_5_BX(0), value);
}
 
int arm_dpm_read_current_registers(struct arm_dpm *dpm)
{
    struct arm *arm = dpm->arm;
    uint32_t cpsr;
    int retval;
    struct reg *r;
 
    retval = dpm->prepare(dpm);
    if (retval != ERROR_OK)
        return retval;
 
    /* read R0 and R1 first (it's used for scratch), then CPSR */
    for (unsigned int i = 0; i < 2; i++) {
        r = arm->core_cache->reg_list + i;
        if (!r->valid) {
            retval = arm_dpm_read_reg(dpm, r, i);
            if (retval != ERROR_OK)
                goto fail;
        }
        r->dirty = true;
    }
 
    retval = dpm->instr_read_data_r0(dpm, ARMV4_5_MRS(0, 0), &cpsr);
    if (retval != ERROR_OK)
        goto fail;
 
    /* update core mode and state, plus shadow mapping for R8..R14 */
    arm_set_cpsr(arm, cpsr);
 
    /* REVISIT we can probably avoid reading R1..R14, saving time... */
    for (unsigned int i = 2; i < 16; i++) {
        r = arm_reg_current(arm, i);
        if (r->valid)
            continue;
 
        retval = arm_dpm_read_reg(dpm, r, i);
        if (retval != ERROR_OK)
            goto fail;
    }
 
    /* NOTE: SPSR ignored (if it's even relevant). */
 
    /* REVISIT the debugger can trigger various exceptions.  See the
     * ARMv7A architecture spec, section C5.7, for more info about
     * what defenses are needed; v6 debug has the most issues.
     */
 
fail:
    dpm->finish(dpm);
    return retval;
}
 
/* Avoid needless I/O ... leave breakpoints and watchpoints alone
 * unless they're removed, or need updating because of single-stepping
 * or running debugger code.
 */
static int dpm_maybe_update_bpwp(struct arm_dpm *dpm, bool bpwp,
    struct dpm_bpwp *xp, bool *set_p)
{
    int retval = ERROR_OK;
    bool disable;
 
    if (!set_p) {
        if (!xp->dirty)
            goto done;
        xp->dirty = false;
        /* removed or startup; we must disable it */
        disable = true;
    } else if (bpwp) {
        if (!xp->dirty)
            goto done;
        /* disabled, but we must set it */
        xp->dirty = disable = false;
        *set_p = true;
    } else {
        if (!*set_p)
            goto done;
        /* set, but we must temporarily disable it */
        xp->dirty = disable = true;
        *set_p = false;
    }
 
    if (disable)
        retval = dpm->bpwp_disable(dpm, xp->number);
    else
        retval = dpm->bpwp_enable(dpm, xp->number,
                xp->address, xp->control);
 
    if (retval != ERROR_OK)
        LOG_TARGET_ERROR(dpm->arm->target, "can't %s HW %spoint %d",
            disable ? "disable" : "enable",
            (xp->number < 16) ? "break" : "watch",
            xp->number & 0xf);
done:
    return retval;
}
 
static int dpm_add_breakpoint(struct target *target, struct breakpoint *bp);
 
int arm_dpm_write_dirty_registers(struct arm_dpm *dpm, bool bpwp)
{
    struct arm *arm = dpm->arm;
    struct reg_cache *cache = arm->core_cache;
    int retval;
    bool did_write;
 
    retval = dpm->prepare(dpm);
    if (retval != ERROR_OK)
        goto done;
 
    /* If we're managing hardware breakpoints for this core, enable
     * or disable them as requested.
     *
     * REVISIT We don't yet manage them for ANY cores.  Eventually
     * we should be able to assume we handle them; but until then,
     * cope with the hand-crafted breakpoint code.
     */
    if (arm->target->type->add_breakpoint == dpm_add_breakpoint) {
        for (unsigned int i = 0; i < dpm->nbp; i++) {
            struct dpm_bp *dbp = dpm->dbp + i;
            struct breakpoint *bp = dbp->bp;
 
            retval = dpm_maybe_update_bpwp(dpm, bpwp, &dbp->bpwp,
                    bp ? &bp->is_set : NULL);
            if (retval != ERROR_OK)
                goto done;
        }
    }
 
    /* enable/disable watchpoints */
    for (unsigned int i = 0; i < dpm->nwp; i++) {
        struct dpm_wp *dwp = dpm->dwp + i;
        struct watchpoint *wp = dwp->wp;
 
        retval = dpm_maybe_update_bpwp(dpm, bpwp, &dwp->bpwp,
                wp ? &wp->is_set : NULL);
        if (retval != ERROR_OK)
            goto done;
    }
 
    /* NOTE:  writes to breakpoint and watchpoint registers might
     * be queued, and need (efficient/batched) flushing later.
     */
 
    /* Scan the registers until we find one that's both dirty and
     * eligible for flushing.  Flush that and everything else that
     * shares the same core mode setting.  Typically this won't
     * actually find anything to do...
     */
    do {
        enum arm_mode mode = ARM_MODE_ANY;
 
        did_write = false;
 
        /* check everything except our scratch registers R0 and R1 */
        for (unsigned int i = 2; i < cache->num_regs; i++) {
            struct arm_reg *r;
            unsigned int regnum;
 
            /* also skip PC, CPSR, and non-dirty */
            if (i == 15)
                continue;
            if (arm->cpsr == cache->reg_list + i)
                continue;
            if (!cache->reg_list[i].exist || !cache->reg_list[i].dirty)
                continue;
 
            r = cache->reg_list[i].arch_info;
            regnum = r->num;
 
            /* may need to pick and set a mode */
            if (!did_write) {
                enum arm_mode tmode;
 
                did_write = true;
                mode = tmode = r->mode;
 
                /* cope with special cases */
                switch (regnum) {
                case 8 ... 12:
                    /* r8..r12 "anything but FIQ" case;
                     * we "know" core mode is accurate
                     * since we haven't changed it yet
                     */
                    if (arm->core_mode == ARM_MODE_FIQ
                        && ARM_MODE_ANY
                        != mode)
                        tmode = ARM_MODE_USR;
                    break;
                case 16:
                    /* SPSR */
                    regnum++;
                    break;
                }
 
                /* REVISIT error checks */
                if (tmode != ARM_MODE_ANY) {
                    retval = arm_dpm_modeswitch(dpm, tmode);
                    if (retval != ERROR_OK)
                        goto done;
                }
            }
            if (r->mode != mode)
                continue;
 
            retval = dpm_write_reg(dpm,
                           &cache->reg_list[i],
                           regnum);
            if (retval != ERROR_OK)
                goto done;
        }
 
    } while (did_write);
 
    /* Restore original CPSR ... assuming either that we changed it,
     * or it's dirty.  Must write PC to ensure the return address is
     * defined, and must not write it before CPSR.
     */
    retval = arm_dpm_modeswitch(dpm, ARM_MODE_ANY);
    if (retval != ERROR_OK)
        goto done;
    arm->cpsr->dirty = false;
 
    /* restore the PC, make sure to also switch the core state
     * to whatever it was set to with "arm core_state" command.
     * target code will have set PC to an appropriate resume address.
     */
    retval = dpm_write_pc_core_state(dpm, arm->pc);
    if (retval != ERROR_OK)
        goto done;
    /* on Cortex-A5 (as found on NXP VF610 SoC), BX instruction
     * executed in debug state doesn't appear to set the PC,
     * explicitly set it with a "MOV pc, r0". This doesn't influence
     * CPSR on Cortex-A9 so it should be OK. Maybe due to different
     * debug version?
     */
    retval = dpm_write_reg(dpm, arm->pc, 15);
    if (retval != ERROR_OK)
        goto done;
    arm->pc->dirty = false;
 
    /* flush R0 and R1 (our scratch registers) */
    for (unsigned int i = 0; i < 2; i++) {
        retval = dpm_write_reg(dpm, &cache->reg_list[i], i);
        if (retval != ERROR_OK)
            goto done;
        cache->reg_list[i].dirty = false;
    }
 
    dpm->finish(dpm);
done:
    return retval;
}
 
/* Returns ARM_MODE_ANY or temporary mode to use while reading the
 * specified register ... works around flakiness from ARM core calls.
 * Caller already filtered out SPSR access; mode is never MODE_SYS
 * or MODE_ANY.
 */
static enum arm_mode dpm_mapmode(struct arm *arm,
    unsigned int num, enum arm_mode mode)
{
    enum arm_mode amode = arm->core_mode;
 
    /* don't switch if the mode is already correct */
    if (amode == ARM_MODE_SYS)
        amode = ARM_MODE_USR;
    if (mode == amode)
        return ARM_MODE_ANY;
 
    switch (num) {
        /* don't switch for non-shadowed registers (r0..r7, r15/pc, cpsr) */
        case 0 ... 7:
        case 15:
        case 16:
            break;
        /* r8..r12 aren't shadowed for anything except FIQ */
        case 8 ... 12:
            if (mode == ARM_MODE_FIQ)
                return mode;
            break;
        /* r13/sp, and r14/lr are always shadowed */
        case 13:
        case 14:
        case ARM_VFP_V3_D0 ... ARM_VFP_V3_FPSCR:
            return mode;
        default:
            LOG_TARGET_WARNING(arm->target, "invalid register #%u", num);
            break;
    }
    return ARM_MODE_ANY;
}
 
 
/*
 * Standard ARM register accessors ... there are three methods
 * in "struct arm", to support individual read/write and bulk read
 * of registers.
 */
 
static int arm_dpm_read_core_reg(struct target *target, struct reg *r,
    int regnum, enum arm_mode mode)
{
    struct arm_dpm *dpm = target_to_arm(target)->dpm;
    int retval;
 
    if (regnum < 0 || (regnum > 16 && regnum < ARM_VFP_V3_D0) ||
        (regnum > ARM_VFP_V3_FPSCR))
        return ERROR_COMMAND_SYNTAX_ERROR;
 
    if (regnum == 16) {
        if (mode != ARM_MODE_ANY)
            regnum = 17;
    } else
        mode = dpm_mapmode(dpm->arm, regnum, mode);
 
    /* REVISIT what happens if we try to read SPSR in a core mode
     * which has no such register?
     */
 
    retval = dpm->prepare(dpm);
    if (retval != ERROR_OK)
        return retval;
 
    if (mode != ARM_MODE_ANY) {
        retval = arm_dpm_modeswitch(dpm, mode);
        if (retval != ERROR_OK)
            goto fail;
    }
 
    retval = arm_dpm_read_reg(dpm, r, regnum);
    if (retval != ERROR_OK)
        goto fail;
    /* always clean up, regardless of error */
 
    if (mode != ARM_MODE_ANY)
        arm_dpm_modeswitch(dpm, ARM_MODE_ANY);
 
fail:
    dpm->finish(dpm);
    return retval;
}
 
static int arm_dpm_write_core_reg(struct target *target, struct reg *r,
    int regnum, enum arm_mode mode, uint8_t *value)
{
    struct arm_dpm *dpm = target_to_arm(target)->dpm;
    int retval;
 
 
    if (regnum < 0 || (regnum > 16 && regnum < ARM_VFP_V3_D0) ||
            (regnum > ARM_VFP_V3_FPSCR))
        return ERROR_COMMAND_SYNTAX_ERROR;
 
    if (regnum == 16) {
        if (mode != ARM_MODE_ANY)
            regnum = 17;
    } else
        mode = dpm_mapmode(dpm->arm, regnum, mode);
 
    /* REVISIT what happens if we try to write SPSR in a core mode
     * which has no such register?
     */
 
    retval = dpm->prepare(dpm);
    if (retval != ERROR_OK)
        return retval;
 
    if (mode != ARM_MODE_ANY) {
        retval = arm_dpm_modeswitch(dpm, mode);
        if (retval != ERROR_OK)
            goto fail;
    }
 
    retval = dpm_write_reg(dpm, r, regnum);
    /* always clean up, regardless of error */
 
    if (mode != ARM_MODE_ANY)
        arm_dpm_modeswitch(dpm, ARM_MODE_ANY);
 
fail:
    dpm->finish(dpm);
    return retval;
}
 
static int arm_dpm_full_context(struct target *target)
{
    struct arm *arm = target_to_arm(target);
    struct arm_dpm *dpm = arm->dpm;
    struct reg_cache *cache = arm->core_cache;
    int retval;
    bool did_read;
 
    retval = dpm->prepare(dpm);
    if (retval != ERROR_OK)
        goto done;
 
    do {
        enum arm_mode mode = ARM_MODE_ANY;
 
        did_read = false;
 
        /* We "know" arm_dpm_read_current_registers() was called so
         * the unmapped registers (R0..R7, PC, AND CPSR) and some
         * view of R8..R14 are current.  We also "know" oddities of
         * register mapping: special cases for R8..R12 and SPSR.
         *
         * Pick some mode with unread registers and read them all.
         * Repeat until done.
         */
        for (unsigned int i = 0; i < cache->num_regs; i++) {
            struct arm_reg *r;
 
            if (!cache->reg_list[i].exist || cache->reg_list[i].valid)
                continue;
            r = cache->reg_list[i].arch_info;
 
            /* may need to pick a mode and set CPSR */
            if (!did_read) {
                did_read = true;
                mode = r->mode;
 
                /* For regular (ARM_MODE_ANY) R8..R12
                 * in case we've entered debug state
                 * in FIQ mode we need to patch mode.
                 */
                if (mode != ARM_MODE_ANY)
                    retval = arm_dpm_modeswitch(dpm, mode);
                else
                    retval = arm_dpm_modeswitch(dpm, ARM_MODE_USR);
 
                if (retval != ERROR_OK)
                    goto done;
            }
            if (r->mode != mode)
                continue;
 
            /* CPSR was read, so "R16" must mean SPSR */
            retval = arm_dpm_read_reg(dpm,
                    &cache->reg_list[i],
                    (r->num == 16) ? 17 : r->num);
            if (retval != ERROR_OK)
                goto done;
        }
 
    } while (did_read);
 
    retval = arm_dpm_modeswitch(dpm, ARM_MODE_ANY);
    dpm->finish(dpm);
done:
    return retval;
}
 
 
/*----------------------------------------------------------------------*/
 
/*
 * Breakpoint and Watchpoint support.
 *
 * Hardware {break,watch}points are usually left active, to minimize
 * debug entry/exit costs.  When they are set or cleared, it's done in
 * batches.  Also, DPM-conformant hardware can update debug registers
 * regardless of whether the CPU is running or halted ... though that
 * fact isn't currently leveraged.
 */
 
static int dpm_bpwp_setup(struct arm_dpm *dpm, struct dpm_bpwp *xp,
    uint32_t addr, uint32_t length)
{
    uint32_t control;
 
    control = (1 << 0)  /* enable */
        | (3 << 1); /* both user and privileged access */
 
    /* Match 1, 2, or all 4 byte addresses in this word.
     *
     * FIXME:  v7 hardware allows lengths up to 2 GB for BP and WP.
     * Support larger length, when addr is suitably aligned.  In
     * particular, allow watchpoints on 8 byte "double" values.
     *
     * REVISIT allow watchpoints on unaligned 2-bit values; and on
     * v7 hardware, unaligned 4-byte ones too.
     */
    switch (length) {
        case 1:
            control |= (1 << (addr & 3)) << 5;
            break;
        case 2:
            /* require 2-byte alignment */
            if (!(addr & 1)) {
                control |= (3 << (addr & 2)) << 5;
                break;
            }
        /* FALL THROUGH */
        case 4:
            /* require 4-byte alignment */
            if (!(addr & 3)) {
                control |= 0xf << 5;
                break;
            }
        /* FALL THROUGH */
        default:
            LOG_TARGET_ERROR(dpm->arm->target, "unsupported {break,watch}point length/alignment");
            return ERROR_COMMAND_SYNTAX_ERROR;
    }
 
    /* other shared control bits:
     * bits 15:14 == 0 ... both secure and nonsecure states (v6.1+ only)
     * bit 20 == 0 ... not linked to a context ID
     * bit 28:24 == 0 ... not ignoring N LSBs (v7 only)
     */
 
    xp->address = addr & ~3;
    xp->control = control;
    xp->dirty = true;
 
    LOG_TARGET_DEBUG(dpm->arm->target, "BPWP: addr %8.8" PRIx32 ", control %" PRIx32 ", number %d",
        xp->address, control, xp->number);
 
    /* hardware is updated in write_dirty_registers() */
    return ERROR_OK;
}
 
static int dpm_add_breakpoint(struct target *target, struct breakpoint *bp)
{
    struct arm *arm = target_to_arm(target);
    struct arm_dpm *dpm = arm->dpm;
    int retval = ERROR_TARGET_RESOURCE_NOT_AVAILABLE;
 
    if (bp->length < 2)
        return ERROR_COMMAND_SYNTAX_ERROR;
    if (!dpm->bpwp_enable)
        return retval;
 
    /* FIXME we need a generic solution for software breakpoints. */
    if (bp->type == BKPT_SOFT)
        LOG_TARGET_DEBUG(dpm->arm->target, "using HW breakpoint instead of SW");
 
    for (unsigned int i = 0; i < dpm->nbp; i++) {
        if (!dpm->dbp[i].bp) {
            retval = dpm_bpwp_setup(dpm, &dpm->dbp[i].bpwp,
                    bp->address, bp->length);
            if (retval == ERROR_OK)
                dpm->dbp[i].bp = bp;
            break;
        }
    }
 
    return retval;
}
 
static int dpm_remove_breakpoint(struct target *target, struct breakpoint *bp)
{
    struct arm *arm = target_to_arm(target);
    struct arm_dpm *dpm = arm->dpm;
    int retval = ERROR_COMMAND_SYNTAX_ERROR;
 
    for (unsigned int i = 0; i < dpm->nbp; i++) {
        if (dpm->dbp[i].bp == bp) {
            dpm->dbp[i].bp = NULL;
            dpm->dbp[i].bpwp.dirty = true;
 
            /* hardware is updated in write_dirty_registers() */
            retval = ERROR_OK;
            break;
        }
    }
 
    return retval;
}
 
static int dpm_watchpoint_setup(struct arm_dpm *dpm, unsigned int index_t,
    struct watchpoint *wp)
{
    int retval;
    struct dpm_wp *dwp = dpm->dwp + index_t;
    uint32_t control;
 
    /* this hardware doesn't support data value matching or masking */
    if (wp->mask != WATCHPOINT_IGNORE_DATA_VALUE_MASK) {
        LOG_TARGET_ERROR(dpm->arm->target, "watchpoint values and masking not supported");
        return ERROR_TARGET_RESOURCE_NOT_AVAILABLE;
    }
 
    retval = dpm_bpwp_setup(dpm, &dwp->bpwp, wp->address, wp->length);
    if (retval != ERROR_OK)
        return retval;
 
    control = dwp->bpwp.control;
    switch (wp->rw) {
        case WPT_READ:
            control |= 1 << 3;
            break;
        case WPT_WRITE:
            control |= 2 << 3;
            break;
        case WPT_ACCESS:
            control |= 3 << 3;
            break;
    }
    dwp->bpwp.control = control;
 
    dpm->dwp[index_t].wp = wp;
 
    return retval;
}
 
static int dpm_add_watchpoint(struct target *target, struct watchpoint *wp)
{
    struct arm *arm = target_to_arm(target);
    struct arm_dpm *dpm = arm->dpm;
    int retval = ERROR_TARGET_RESOURCE_NOT_AVAILABLE;
 
    if (dpm->bpwp_enable) {
        for (unsigned int i = 0; i < dpm->nwp; i++) {
            if (!dpm->dwp[i].wp) {
                retval = dpm_watchpoint_setup(dpm, i, wp);
                break;
            }
        }
    }
 
    return retval;
}
 
static int dpm_remove_watchpoint(struct target *target, struct watchpoint *wp)
{
    struct arm *arm = target_to_arm(target);
    struct arm_dpm *dpm = arm->dpm;
    int retval = ERROR_COMMAND_SYNTAX_ERROR;
 
    for (unsigned int i = 0; i < dpm->nwp; i++) {
        if (dpm->dwp[i].wp == wp) {
            dpm->dwp[i].wp = NULL;
            dpm->dwp[i].bpwp.dirty = true;
 
            /* hardware is updated in write_dirty_registers() */
            retval = ERROR_OK;
            break;
        }
    }
 
    return retval;
}
 
void arm_dpm_report_wfar(struct arm_dpm *dpm, uint32_t addr)
{
    switch (dpm->arm->core_state) {
        case ARM_STATE_ARM:
            addr -= 8;
            break;
        case ARM_STATE_THUMB:
        case ARM_STATE_THUMB_EE:
            addr -= 4;
            break;
        case ARM_STATE_JAZELLE:
        case ARM_STATE_AARCH64:
            /* ?? */
            break;
    }
    dpm->wp_addr = addr;
}
 
/*----------------------------------------------------------------------*/
 
/*
 * Other debug and support utilities
 */
 
void arm_dpm_report_dscr(struct arm_dpm *dpm, uint32_t dscr)
{
    struct target *target = dpm->arm->target;
 
    dpm->dscr = dscr;
 
    /* Examine debug reason */
    switch (DSCR_ENTRY(dscr)) {
        case DSCR_ENTRY_HALT_REQ:   /* HALT request from debugger */
        case DSCR_ENTRY_EXT_DBG_REQ:    /* EDBGRQ */
            target->debug_reason = DBG_REASON_DBGRQ;
            break;
        case DSCR_ENTRY_BREAKPOINT: /* HW breakpoint */
        case DSCR_ENTRY_BKPT_INSTR: /* vector catch */
            target->debug_reason = DBG_REASON_BREAKPOINT;
            break;
        case DSCR_ENTRY_IMPRECISE_WATCHPT:  /* asynch watchpoint */
        case DSCR_ENTRY_PRECISE_WATCHPT:/* precise watchpoint */
            target->debug_reason = DBG_REASON_WATCHPOINT;
            break;
        default:
            target->debug_reason = DBG_REASON_UNDEFINED;
            break;
    }
}
 
/*----------------------------------------------------------------------*/
 
/*
 * Setup and management support.
 */
 
int arm_dpm_setup(struct arm_dpm *dpm)
{
    struct arm *arm = dpm->arm;
    struct target *target = arm->target;
    struct reg_cache *cache = NULL;
 
    arm->dpm = dpm;
 
    /* register access setup */
    arm->full_context = arm_dpm_full_context;
    arm->read_core_reg = arm_dpm_read_core_reg;
    arm->write_core_reg = arm_dpm_write_core_reg;
 
    if (!arm->core_cache) {
        cache = arm_build_reg_cache(target, arm);
        if (!cache)
            return ERROR_FAIL;
 
        *register_get_last_cache_p(&target->reg_cache) = cache;
    }
 
    /* coprocessor access setup */
    arm->mrc = dpm_mrc;
    arm->mcr = dpm_mcr;
    arm->mrrc = dpm_mrrc;
    arm->mcrr = dpm_mcrr;
 
    /* breakpoint setup -- optional until it works everywhere */
    if (!target->type->add_breakpoint) {
        target->type->add_breakpoint = dpm_add_breakpoint;
        target->type->remove_breakpoint = dpm_remove_breakpoint;
    }
 
    /* watchpoint setup -- optional until it works everywhere */
    if (!target->type->add_watchpoint) {
        target->type->add_watchpoint = dpm_add_watchpoint;
        target->type->remove_watchpoint = dpm_remove_watchpoint;
    }
 
    /* FIXME add vector catch support */
 
    dpm->nbp = 1 + ((dpm->didr >> 24) & 0xf);
    dpm->nwp = 1 + ((dpm->didr >> 28) & 0xf);
    dpm->dbp = calloc(dpm->nbp, sizeof(*dpm->dbp));
    dpm->dwp = calloc(dpm->nwp, sizeof(*dpm->dwp));
 
    if (!dpm->dbp || !dpm->dwp) {
        arm_free_reg_cache(arm);
        free(dpm->dbp);
        free(dpm->dwp);
        return ERROR_FAIL;
    }
 
    LOG_TARGET_INFO(target, "hardware has %d breakpoints, %d watchpoints",
        dpm->nbp, dpm->nwp);
 
    /* REVISIT ... and some of those breakpoints could match
     * execution context IDs...
     */
 
    return ERROR_OK;
}
 
int arm_dpm_initialize(struct arm_dpm *dpm)
{
    /* Disable all breakpoints and watchpoints at startup. */
    if (dpm->bpwp_disable) {
        unsigned int i;
 
        for (i = 0; i < dpm->nbp; i++) {
            dpm->dbp[i].bpwp.number = i;
            (void) dpm->bpwp_disable(dpm, i);
        }
        for (i = 0; i < dpm->nwp; i++) {
            dpm->dwp[i].bpwp.number = 16 + i;
            (void) dpm->bpwp_disable(dpm, 16 + i);
        }
    } else
        LOG_TARGET_WARNING(dpm->arm->target, "can't disable breakpoints and watchpoints");
 
    return ERROR_OK;
}