arm_semihosting: fix two dead assignments

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

/***************************************************************************
 *   Copyright (C) 2009 by Marvell Technology Group Ltd.                   *
 *   Written by Nicolas Pitre <nico@marvell.com>                           *
 *                                                                         *
 *   Copyright (C) 2010 by Spencer Oliver                                  *
 *   spen@spen-soft.co.uk                                                  *
 *                                                                         *
 *   Copyright (C) 2016 by Square, Inc.                                    *
 *   Steven Stallion <stallion@squareup.com>                               *
 *                                                                         *
 *   Copyright (C) 2018 by Liviu Ionescu                                   *
 *   <ilg@livius.net>                                                      *
 *                                                                         *
 *   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/>. *
 ***************************************************************************/

/**
 * @file
 * Hold ARM semihosting support.
 *
 * Semihosting enables code running on an ARM target to use the I/O
 * facilities on the host computer. The target application must be linked
 * against a library that forwards operation requests by using the SVC
 * instruction trapped at the Supervisor Call vector by the debugger.
 * Details can be found in chapter 8 of DUI0203I_rvct_developer_guide.pdf
 * from ARM Ltd.
 */

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

#include "arm.h"
#include "armv4_5.h"
#include "arm7_9_common.h"
#include "armv7m.h"
#include "armv7a.h"
#include "armv8.h"
#include "cortex_m.h"
#include "register.h"
#include "arm_opcodes.h"
#include "target_type.h"
#include "arm_semihosting.h"
#include <helper/binarybuffer.h>
#include <helper/log.h>
#include <sys/stat.h>

static int arm_semihosting_resume(struct target *target, int *retval)
{
        if (is_armv8(target_to_armv8(target))) {
                struct armv8_common *armv8 = target_to_armv8(target);
                if (armv8->last_run_control_op == ARMV8_RUNCONTROL_RESUME) {
                        *retval = target_resume(target, 1, 0, 0, 0);
                        if (*retval != ERROR_OK) {
                                LOG_ERROR("Failed to resume target");
                                return 0;
                        }
                } else if (armv8->last_run_control_op == ARMV8_RUNCONTROL_STEP)
                        target->debug_reason = DBG_REASON_SINGLESTEP;
        } else {
                *retval = target_resume(target, 1, 0, 0, 0);
                if (*retval != ERROR_OK) {
                        LOG_ERROR("Failed to resume target");
                        return 0;
                }
        }
        return 1;
}

static int post_result(struct target *target)
{
        struct arm *arm = target_to_arm(target);

        if (!target->semihosting)
                return ERROR_FAIL;

        /* REVISIT this looks wrong ... ARM11 and Cortex-A8
         * should work this way at least sometimes.
         */
        if (is_arm7_9(target_to_arm7_9(target)) ||
            is_armv7a(target_to_armv7a(target))) {
                uint32_t spsr;

                /* return value in R0 */
                buf_set_u32(arm->core_cache->reg_list[0].value, 0, 32, target->semihosting->result);
                arm->core_cache->reg_list[0].dirty = true;

                /* LR --> PC */
                buf_set_u32(arm->core_cache->reg_list[15].value, 0, 32,
                        buf_get_u32(arm_reg_current(arm, 14)->value, 0, 32));
                arm->core_cache->reg_list[15].dirty = true;

                /* saved PSR --> current PSR */
                spsr = buf_get_u32(arm->spsr->value, 0, 32);

                /* REVISIT should this be arm_set_cpsr(arm, spsr)
                 * instead of a partially unrolled version?
                 */

                buf_set_u32(arm->cpsr->value, 0, 32, spsr);
                arm->cpsr->dirty = true;
                arm->core_mode = spsr & 0x1f;
                if (spsr & 0x20)
                        arm->core_state = ARM_STATE_THUMB;

        } else if (is_armv8(target_to_armv8(target))) {
                if (arm->core_state == ARM_STATE_AARCH64) {
                        /* return value in R0 */
                        buf_set_u64(arm->core_cache->reg_list[0].value, 0, 64, target->semihosting->result);
                        arm->core_cache->reg_list[0].dirty = true;

                        uint64_t pc = buf_get_u64(arm->core_cache->reg_list[32].value, 0, 64);
                        buf_set_u64(arm->pc->value, 0, 64, pc + 4);
                        arm->pc->dirty = true;
                }  else if (arm->core_state == ARM_STATE_ARM) {
                        /* return value in R0 */
                        buf_set_u32(arm->core_cache->reg_list[0].value, 0, 32, target->semihosting->result);
                        arm->core_cache->reg_list[0].dirty = true;

                        uint32_t pc = buf_get_u32(arm->core_cache->reg_list[32].value, 0, 32);
                        buf_set_u32(arm->pc->value, 0, 32, pc + 4);
                        arm->pc->dirty = true;
                } else if (arm->core_state == ARM_STATE_THUMB) {
                        /* return value in R0 */
                        buf_set_u32(arm->core_cache->reg_list[0].value, 0, 32, target->semihosting->result);
                        arm->core_cache->reg_list[0].dirty = true;

                        uint32_t pc = buf_get_u32(arm->core_cache->reg_list[32].value, 0, 32);
                        buf_set_u32(arm->pc->value, 0, 32, pc + 2);
                        arm->pc->dirty = true;
                }
        } else {
                /* resume execution, this will be pc+2 to skip over the
                 * bkpt instruction */

                /* return result in R0 */
                buf_set_u32(arm->core_cache->reg_list[0].value, 0, 32, target->semihosting->result);
                arm->core_cache->reg_list[0].dirty = true;
        }

        return ERROR_OK;
}

/**
 * Initialize ARM semihosting support.
 *
 * @param target Pointer to the ARM target to initialize.
 * @return An error status if there is a problem during initialization.
 */
int arm_semihosting_init(struct target *target)
{
        struct arm *arm = target_to_arm(target);
        assert(arm->setup_semihosting);
        semihosting_common_init(target, arm->setup_semihosting, post_result);

        return ERROR_OK;
}

/**
 * Checks for and processes an ARM semihosting request.  This is meant
 * to be called when the target is stopped due to a debug mode entry.
 * If the value 0 is returned then there was nothing to process. A non-zero
 * return value signifies that a request was processed and the target resumed,
 * or an error was encountered, in which case the caller must return
 * immediately.
 *
 * @param target Pointer to the ARM target to process.  This target must
 *      not represent an ARMv6-M or ARMv7-M processor.
 * @param retval Pointer to a location where the return code will be stored
 * @return non-zero value if a request was processed or an error encountered
 */
int arm_semihosting(struct target *target, int *retval)
{
        struct arm *arm = target_to_arm(target);
        struct armv7a_common *armv7a = target_to_armv7a(target);
        uint32_t pc, lr, spsr;
        struct reg *r;

        struct semihosting *semihosting = target->semihosting;
        if (!semihosting)
                return 0;

        if (!semihosting->is_active)
                return 0;

        if (is_arm7_9(target_to_arm7_9(target)) ||
            is_armv7a(armv7a)) {
                uint32_t vbar = 0x00000000;

                if (arm->core_mode != ARM_MODE_SVC)
                        return 0;

                if (is_armv7a(armv7a)) {
                        struct arm_dpm *dpm = armv7a->arm.dpm;

                        *retval = dpm->prepare(dpm);
                        if (*retval == ERROR_OK) {
                                *retval = dpm->instr_read_data_r0(dpm,
                                                                 ARMV4_5_MRC(15, 0, 0, 12, 0, 0),
                                                                 &vbar);

                                dpm->finish(dpm);

                                if (*retval != ERROR_OK)
                                        return 1;
                        } else {
                                return 1;
                        }
                }

                /* Check for PC == 0x00000008 or 0xffff0008: Supervisor Call vector. */
                r = arm->pc;
                pc = buf_get_u32(r->value, 0, 32);
                if (pc != (vbar + 0x00000008) && pc != 0xffff0008)
                        return 0;

                r = arm_reg_current(arm, 14);
                lr = buf_get_u32(r->value, 0, 32);

                /* Core-specific code should make sure SPSR is retrieved
                 * when the above checks pass...
                 */
                if (!arm->spsr->valid) {
                        LOG_ERROR("SPSR not valid!");
                        *retval = ERROR_FAIL;
                        return 1;
                }

                spsr = buf_get_u32(arm->spsr->value, 0, 32);

                /* check instruction that triggered this trap */
                if (spsr & (1 << 5)) {
                        /* was in Thumb (or ThumbEE) mode */
                        uint8_t insn_buf[2];
                        uint16_t insn;

                        *retval = target_read_memory(target, lr-2, 2, 1, insn_buf);
                        if (*retval != ERROR_OK)
                                return 1;
                        insn = target_buffer_get_u16(target, insn_buf);

                        /* SVC 0xab */
                        if (insn != 0xDFAB)
                                return 0;
                } else if (spsr & (1 << 24)) {
                        /* was in Jazelle mode */
                        return 0;
                } else {
                        /* was in ARM mode */
                        uint8_t insn_buf[4];
                        uint32_t insn;

                        *retval = target_read_memory(target, lr-4, 4, 1, insn_buf);
                        if (*retval != ERROR_OK)
                                return 1;
                        insn = target_buffer_get_u32(target, insn_buf);

                        /* SVC 0x123456 */
                        if (insn != 0xEF123456)
                                return 0;
                }
        } else if (is_armv7m(target_to_armv7m(target))) {
                uint16_t insn;

                if (target->debug_reason != DBG_REASON_BREAKPOINT)
                        return 0;

                r = arm->pc;
                pc = buf_get_u32(r->value, 0, 32);

                pc &= ~1;
                *retval = target_read_u16(target, pc, &insn);
                if (*retval != ERROR_OK)
                        return 1;

                /* bkpt 0xAB */
                if (insn != 0xBEAB)
                        return 0;
        } else if (is_armv8(target_to_armv8(target))) {
                if (target->debug_reason != DBG_REASON_BREAKPOINT)
                        return 0;

                /* According to ARM Semihosting for AArch32 and AArch64:
                 * The HLT encodings are new in version 2.0 of the semihosting specification.
                 * Where possible, have semihosting callers continue to use the previously
                 * existing trap instructions to ensure compatibility with legacy semihosting
                 * implementations.
                 * These trap instructions are HLT for A64, SVC on A+R profile A32 or T32,
                 * and BKPT on M profile.
                 * However, it is necessary to change from SVC to HLT instructions to support
                 * AArch32 semihosting properly in a mixed AArch32/AArch64 system. */

                if (arm->core_state == ARM_STATE_AARCH64) {
                        uint32_t insn = 0;
                        r = arm->pc;
                        uint64_t pc64 = buf_get_u64(r->value, 0, 64);
                        *retval = target_read_u32(target, pc64, &insn);

                        if (*retval != ERROR_OK)
                                return 1;

                        /* HLT 0xF000 */
                        if (insn != 0xD45E0000)
                                return 0;
                } else if (arm->core_state == ARM_STATE_ARM) {
                        r = arm->pc;
                        pc = buf_get_u32(r->value, 0, 32);

                        /* A32 instruction => check for HLT 0xF000 (0xE10F0070) */
                        uint32_t insn = 0;

                        *retval = target_read_u32(target, pc, &insn);

                        if (*retval != ERROR_OK)
                                return 1;

                        /* HLT 0xF000*/
                        if (insn != 0xE10F0070)
                                return 0;
                } else if (arm->core_state == ARM_STATE_THUMB) {
                        r = arm->pc;
                        pc = buf_get_u32(r->value, 0, 32);

                        /* T32 instruction => check for HLT 0x3C (0xBABC) */
                        uint16_t insn = 0;
                        *retval = target_read_u16(target, pc, &insn);

                        if (*retval != ERROR_OK)
                                return 1;

                        /* HLT 0x3C*/
                        if (insn != 0xBABC)
                                return 0;
                } else
                        return 1;
        } else {
                LOG_ERROR("Unsupported semi-hosting Target");
                return 0;
        }

        /* Perform semihosting if we are not waiting on a fileio
         * operation to complete.
         */
        if (!semihosting->hit_fileio) {
                if (is_armv8(target_to_armv8(target)) &&
                                arm->core_state == ARM_STATE_AARCH64) {
                        /* Read op and param from register x0 and x1 respectively. */
                        semihosting->op = buf_get_u64(arm->core_cache->reg_list[0].value, 0, 64);
                        semihosting->param = buf_get_u64(arm->core_cache->reg_list[1].value, 0, 64);
                        semihosting->word_size_bytes = 8;
                } else {
                        /* Read op and param from register r0 and r1 respectively. */
                        semihosting->op = buf_get_u32(arm->core_cache->reg_list[0].value, 0, 32);
                        semihosting->param = buf_get_u32(arm->core_cache->reg_list[1].value, 0, 32);
                        semihosting->word_size_bytes = 4;
                }

                /* Check for ARM operation numbers. */
                if (semihosting->op >= 0 && semihosting->op <= 0x31) {
                        *retval = semihosting_common(target);
                        if (*retval != ERROR_OK) {
                                LOG_ERROR("Failed semihosting operation (0x%02X)", semihosting->op);
                                return 0;
                        }
                } else {
                        /* Unknown operation number, not a semihosting call. */
                        return 0;
                }
        }

        /* Resume if target it is resumable and we are not waiting on a fileio
         * operation to complete:
         */
        if (semihosting->is_resumable && !semihosting->hit_fileio)
                return arm_semihosting_resume(target, retval);

        return 0;
}