Support for Arm VFP v3 registers read/write

[openocd.git] / src / target / arm_dpm.c

/*
 * Copyright (C) 2009 by David Brownell
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that 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/>.
 */

#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"


/**
 * @file
 * Implements various ARM DPM operations using architectural debug registers.
 * These routines layer over core-specific communication methods to cope with
 * implementation differences between cores like ARM1136 and Cortex-A8.
 *
 * The "Debug Programmers' Model" (DPM) for ARMv6 and ARMv7 is defined by
 * Part C (Debug Architecture) of the ARM Architecture Reference Manual,
 * ARMv7-A and ARMv7-R edition (ARM DDI 0406B).  In OpenOCD, DPM operations
 * are abstracted through internal programming interfaces to share code and
 * to minimize needless differences in debug behavior between cores.
 */

/*----------------------------------------------------------------------*/

/*
 * 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_DEBUG("MRC p%d, %d, r0, c%d, c%d, %d", cpnum,
                (int) op1, (int) CRn,
                (int) CRm, (int) 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);

        /* (void) */ 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_DEBUG("MCR p%d, %d, r0, c%d, c%d, %d", cpnum,
                (int) op1, (int) CRn,
                (int) CRm, (int) 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);

        /* (void) */ 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 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 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);
                        /* 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_DEBUG("READ: %s, %8.8x, %8.8x", r->name,
                                (unsigned) value_r0, (unsigned) value_r1);
        }

        return retval;
}

/* just read the register -- rely on the core mode being right */
static int dpm_read_reg(struct arm_dpm *dpm, struct reg *r, unsigned 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_WARNING("Jazelle PC adjustment unknown");
                                        break;
                                default:
                                        LOG_WARNING("unknow core state");
                                        break;
                        }
                        break;
                case ARM_VFP_V3_D0 ... ARM_VFP_V3_D31:
                        return dpm_read_reg_u64(dpm, r, regnum);
                        break;
                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_DEBUG("READ: %s, %8.8x", r->name, (unsigned) value);
        }

        return retval;
}

/* Write 64bit VFP registers */
static int dpm_write_reg_u64(struct arm_dpm *dpm, struct reg *r, unsigned 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);
                        /* 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_DEBUG("WRITE: %s, %8.8x, %8.8x", r->name,
                                (unsigned) value_r0, (unsigned) 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 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);
                        break;
                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_DEBUG("WRITE: %s, %8.8x", r->name, (unsigned) value);
        }

        return retval;
}

/**
 * Write to program counter and switch the core state (arm/thumb) according to
 * the address.
 */
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);
}

/**
 * Read basic registers of the the current context:  R0 to R15, and CPSR;
 * sets the core mode (such as USR or IRQ) and state (such as ARM or Thumb).
 * In normal operation this is called on entry to halting debug state,
 * possibly after some other operations supporting restore of debug state
 * or making sure the CPU is fully idle (drain write buffer, etc).
 */
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 i = 0; i < 2; i++) {
                r = arm->core_cache->reg_list + i;
                if (!r->valid) {
                        retval = 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 i = 2; i < 16; i++) {
                r = arm_reg_current(arm, i);
                if (r->valid)
                        continue;

                retval = 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:
        /* (void) */ 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, int *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_ERROR("%s: can't %s HW %spoint %d",
                        disable ? "disable" : "enable",
                        target_name(dpm->arm->target),
                        (xp->number < 16) ? "break" : "watch",
                        xp->number & 0xf);
done:
        return retval;
}

static int dpm_add_breakpoint(struct target *target, struct breakpoint *bp);

/**
 * Writes all modified core registers for all processor modes.  In normal
 * operation this is called on exit from halting debug state.
 *
 * @param dpm: represents the processor
 * @param bpwp: true ensures breakpoints and watchpoints are set,
 *      false ensures they are cleared
 */
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 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->set : NULL);
                        if (retval != ERROR_OK)
                                goto done;
                }
        }

        /* enable/disable watchpoints */
        for (unsigned 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->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 i = 2; i < cache->num_regs; i++) {
                        struct arm_reg *r;
                        unsigned 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].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 = 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 = 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 -- it's *very* dirty by now */
        retval = dpm_write_reg(dpm, &cache->reg_list[0], 0);
        if (retval != ERROR_OK)
                goto done;
        cache->reg_list[0].dirty = false;

        /* (void) */ 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 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_WARNING("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 = dpm_modeswitch(dpm, mode);
                if (retval != ERROR_OK)
                        goto fail;
        }

        retval = dpm_read_reg(dpm, r, regnum);
        if (retval != ERROR_OK)
                goto fail;
        /* always clean up, regardless of error */

        if (mode != ARM_MODE_ANY)
                /* (void) */ dpm_modeswitch(dpm, ARM_MODE_ANY);

fail:
        /* (void) */ 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 = 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)
                /* (void) */ dpm_modeswitch(dpm, ARM_MODE_ANY);

fail:
        /* (void) */ 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 i = 0; i < cache->num_regs; i++) {
                        struct arm_reg *r;

                        if (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 = dpm_modeswitch(dpm, mode);
                                else
                                        retval = 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 = dpm_read_reg(dpm,
                                        &cache->reg_list[i],
                                        (r->num == 16) ? 17 : r->num);
                        if (retval != ERROR_OK)
                                goto done;
                }

        } while (did_read);

        retval = dpm_modeswitch(dpm, ARM_MODE_ANY);
        /* (void) */ 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_ERROR("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_DEBUG("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_DEBUG("using HW bkpt, not SW...");

        for (unsigned 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 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 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->value || wp->mask != ~(uint32_t)0) {
                LOG_DEBUG("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 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 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_pc = 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.
 */

/**
 * Hooks up this DPM to its associated target; call only once.
 * Initially this only covers the register cache.
 *
 * Oh, and watchpoints.  Yeah.
 */
int arm_dpm_setup(struct arm_dpm *dpm)
{
        struct arm *arm = dpm->arm;
        struct target *target = arm->target;
        struct reg_cache *cache = 0;

        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 == NULL) {
                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;

        /* 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 */
        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) {
                free(dpm->dbp);
                free(dpm->dwp);
                return ERROR_FAIL;
        }

        LOG_INFO("%s: hardware has %d breakpoints, %d watchpoints",
                target_name(target), dpm->nbp, dpm->nwp);

        /* REVISIT ... and some of those breakpoints could match
         * execution context IDs...
         */

        return ERROR_OK;
}

/**
 * Reinitializes DPM state at the beginning of a new debug session
 * or after a reset which may have affected the debug module.
 */
int arm_dpm_initialize(struct arm_dpm *dpm)
{
        /* Disable all breakpoints and watchpoints at startup. */
        if (dpm->bpwp_disable) {
                unsigned 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_WARNING("%s: can't disable breakpoints and watchpoints",
                        target_name(dpm->arm->target));

        return ERROR_OK;
}