path: root/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, write to the
 * Free Software Foundation, Inc.,
 * 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include "armv4_5.h"		/* REVISIT to become arm.h */
#include "arm_dpm.h"
#include "jtag.h"
#include "register.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.
 */

/*
 * 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, 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);

	/* (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, 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);

	/* (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!!
 */
static int dpm_modeswitch(struct arm_dpm *dpm, enum armv4_5_mode mode)
{
	int retval;
	uint32_t cpsr;

	/* restore previous mode */
	if (mode == ARMV4_5_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 (dpm->instr_cpsr_sync)
		retval = dpm->instr_cpsr_sync(dpm);

	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 ARMV4_5_STATE_ARM:
			value -= 8;
			break;
		case ARMV4_5_STATE_THUMB:
		case ARM_STATE_THUMB_EE:
			value -= 4;
			break;
		case ARMV4_5_STATE_JAZELLE:
			/* core-specific ... ? */
			LOG_WARNING("Jazelle PC adjustment unknown");
			break;
		}
		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;
}

/* 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:  "MCR 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;
	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 (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;
}

/**
 * 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 first (it's used for scratch), then CPSR */
	r = arm->core_cache->reg_list + 0;
	if (!r->valid) {
		retval = dpm_read_reg(dpm, r, 0);
		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 = 1; 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). */

fail:
	/* (void) */ dpm->finish(dpm);
	return retval;
}

/**
 * Writes all modified core registers for all processor modes.  In normal
 * operation this is called on exit from halting debug state.
 */
int arm_dpm_write_dirty_registers(struct arm_dpm *dpm)
{
	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;

	/* 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 armv4_5_mode mode = ARMV4_5_MODE_ANY;

		did_write = false;

		/* check everything except our scratch register R0 */
		for (unsigned i = 1; 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 armv4_5_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 == ARMV4_5_MODE_FIQ
							&& ARMV4_5_MODE_ANY
								!= mode)
						tmode = ARMV4_5_MODE_USR;
					break;
				case 16:
					/* SPSR */
					regnum++;
					break;
				}

				/* REVISIT error checks */
				if (tmode != ARMV4_5_MODE_ANY)
					retval = dpm_modeswitch(dpm, tmode);
			}
			if (r->mode != mode)
				continue;

			retval = dpm_write_reg(dpm,
					&cache->reg_list[i],
					regnum);

		}

	} 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, ARMV4_5_MODE_ANY);
	arm->cpsr->dirty = false;

	retval = dpm_write_reg(dpm, &cache->reg_list[15], 15);
	cache->reg_list[15].dirty = false;

	/* flush R0 -- it's *very* dirty by now */
	retval = dpm_write_reg(dpm, &cache->reg_list[0], 0);
	cache->reg_list[0].dirty = false;

	/* (void) */ dpm->finish(dpm);
done:
	return retval;
}

/* Returns ARMV4_5_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 armv4_5_mode dpm_mapmode(struct arm *arm,
		unsigned num, enum armv4_5_mode mode)
{
	enum armv4_5_mode amode = arm->core_mode;

	/* don't switch if the mode is already correct */
	if (amode == ARMV4_5_MODE_SYS)
		 amode = ARMV4_5_MODE_USR;
	if (mode == amode)
		return ARMV4_5_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 == ARMV4_5_MODE_FIQ)
			return mode;
		break;
	/* r13/sp, and r14/lr are always shadowed */
	case 13:
	case 14:
		return mode;
	default:
		LOG_WARNING("invalid register #%u", num);
		break;
	}
	return ARMV4_5_MODE_ANY;
}

static int arm_dpm_read_core_reg(struct target *target, struct reg *r,
		int regnum, enum armv4_5_mode mode)
{
	struct arm_dpm *dpm = target_to_arm(target)->dpm;
	int retval;

	if (regnum < 0 || regnum > 16)
		return ERROR_INVALID_ARGUMENTS;

	if (regnum == 16) {
		if (mode != ARMV4_5_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 != ARMV4_5_MODE_ANY) {
		retval = dpm_modeswitch(dpm, mode);
		if (retval != ERROR_OK)
			goto fail;
	}

	retval = dpm_read_reg(dpm, r, regnum);
	/* always clean up, regardless of error */

	if (mode != ARMV4_5_MODE_ANY)
		/* (void) */ dpm_modeswitch(dpm, ARMV4_5_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 armv4_5_mode mode, uint32_t value)
{
	struct arm_dpm *dpm = target_to_arm(target)->dpm;
	int retval;


	if (regnum < 0 || regnum > 16)
		return ERROR_INVALID_ARGUMENTS;

	if (regnum == 16) {
		if (mode != ARMV4_5_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 != ARMV4_5_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 != ARMV4_5_MODE_ANY)
		/* (void) */ dpm_modeswitch(dpm, ARMV4_5_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 armv4_5_mode mode = ARMV4_5_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 R8..R12 when we've entered debug
				 * state in FIQ mode... patch mode.
				 */
				if (mode == ARMV4_5_MODE_ANY)
					mode = ARMV4_5_MODE_USR;

				/* REVISIT error checks */
				retval = dpm_modeswitch(dpm, mode);
			}
			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);

		}

	} while (did_read);

	retval = dpm_modeswitch(dpm, ARMV4_5_MODE_ANY);
	/* (void) */ dpm->finish(dpm);
done:
	return retval;
}

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

	arm->dpm = dpm;

	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;

	cache = armv4_5_build_reg_cache(target, arm);
	if (!cache)
		return ERROR_FAIL;

	*register_get_last_cache_p(&target->reg_cache) = cache;

	arm->mrc = dpm_mrc;
	arm->mcr = dpm_mcr;

	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)
{
	/* FIXME -- nothing yet */
	return ERROR_OK;
}