src/target/riscv/riscv_semihosting.c

   1 /* SPDX-License-Identifier: GPL-2.0-or-later */
   2
   3 /***************************************************************************
   4  *   Copyright (C) 2018 by Liviu Ionescu                                   *
   5  *   ilg@livius.net                                                        *
   6  *                                                                         *
   7  *   Copyright (C) 2009 by Marvell Technology Group Ltd.                   *
   8  *   Written by Nicolas Pitre <nico@marvell.com>                           *
   9  *                                                                         *
  10  *   Copyright (C) 2010 by Spencer Oliver                                  *
  11  *   spen@spen-soft.co.uk                                                  *
  12  *                                                                         *
  13  *   Copyright (C) 2016 by Square, Inc.                                    *
  14  *   Steven Stallion <stallion@squareup.com>                               *
  15  *                                                                         *
  16  *   This program is free software; you can redistribute it and/or modify  *
  17  *   it under the terms of the GNU General Public License as published by  *
  18  *   the Free Software Foundation; either version 2 of the License, or     *
  19  *   (at your option) any later version.                                   *
  20  *                                                                         *
  21  *   This program is distributed in the hope that it will be useful,       *
  22  *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
  23  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
  24  *   GNU General Public License for more details.                          *
  25  *                                                                         *
  26  *   You should have received a copy of the GNU General Public License     *
  27  *   along with this program.  If not, see <http://www.gnu.org/licenses/>. *
  28  ***************************************************************************/
  29
  30 /**
  31  * @file
  32  * Hold RISC-V semihosting support.
  33  *
  34  * The RISC-V code is inspired from ARM semihosting.
  35  *
  36  * Details can be found in chapter 8 of DUI0203I_rvct_developer_guide.pdf
  37  * from ARM Ltd.
  38  */
  39
  40 #ifdef HAVE_CONFIG_H
  41 #include "config.h"
  42 #endif
  43
  44 #include <helper/log.h>
  45
  46 #include "target/target.h"
  47 #include "target/semihosting_common.h"
  48 #include "riscv.h"
  49
  50 static int riscv_semihosting_setup(struct target *target, int enable);
  51 static int riscv_semihosting_post_result(struct target *target);
  52
  53 /**
  54  * Initialize RISC-V semihosting. Use common ARM code.
  55  */
  56 void riscv_semihosting_init(struct target *target)
  57 {
  58         semihosting_common_init(target, riscv_semihosting_setup,
  59                 riscv_semihosting_post_result);
  60 }
  61
  62 /**
  63  * Check for and process a semihosting request using the ARM protocol). This
  64  * is meant to be called when the target is stopped due to a debug mode entry.
  65  *
  66  * @param target Pointer to the target to process.
  67  * @param retval Pointer to a location where the return code will be stored
  68  * @return non-zero value if a request was processed or an error encountered
  69  */
  70 semihosting_result_t riscv_semihosting(struct target *target, int *retval)
  71 {
  72         struct semihosting *semihosting = target->semihosting;
  73         if (!semihosting) {
  74                 LOG_DEBUG("   -> NONE (!semihosting)");
  75                 return SEMI_NONE;
  76         }
  77
  78         if (!semihosting->is_active) {
  79                 LOG_DEBUG("   -> NONE (!semihosting->is_active)");
  80                 return SEMI_NONE;
  81         }
  82
  83         riscv_reg_t pc;
  84         int result = riscv_get_register(target, &pc, GDB_REGNO_PC);
  85         if (result != ERROR_OK)
  86                 return SEMI_ERROR;
  87
  88         uint8_t tmp_buf[12];
  89
  90         /* Read three uncompressed instructions: The previous, the current one (pointed to by PC) and the next one */
  91         for (int i = 0; i < 3; i++) {
  92                 /* Instruction memories may not support arbitrary read size. Use any size that will work. */
  93                 *retval = riscv_read_by_any_size(target, (pc - 4) + 4 * i, 4, tmp_buf + 4 * i);
  94                 if (*retval != ERROR_OK)
  95                         return SEMI_ERROR;
  96         }
  97
  98         /*
  99          * The instructions that trigger a semihosting call,
 100          * always uncompressed, should look like:
 101          *
 102          * 01f01013              slli    zero,zero,0x1f
 103          * 00100073              ebreak
 104          * 40705013              srai    zero,zero,0x7
 105          */
 106         uint32_t pre = target_buffer_get_u32(target, tmp_buf);
 107         uint32_t ebreak = target_buffer_get_u32(target, tmp_buf + 4);
 108         uint32_t post = target_buffer_get_u32(target, tmp_buf + 8);
 109         LOG_DEBUG("check %08x %08x %08x from 0x%" PRIx64 "-4", pre, ebreak, post, pc);
 110
 111         if (pre != 0x01f01013 || ebreak != 0x00100073 || post != 0x40705013) {
 112                 /* Not the magic sequence defining semihosting. */
 113                 LOG_DEBUG("   -> NONE (no magic)");
 114                 return SEMI_NONE;
 115         }
 116
 117         /*
 118          * Perform semihosting call if we are not waiting on a fileio
 119          * operation to complete.
 120          */
 121         if (!semihosting->hit_fileio) {
 122                 /* RISC-V uses A0 and A1 to pass function arguments */
 123                 riscv_reg_t r0;
 124                 riscv_reg_t r1;
 125
 126                 result = riscv_get_register(target, &r0, GDB_REGNO_A0);
 127                 if (result != ERROR_OK) {
 128                         LOG_DEBUG("   -> ERROR (couldn't read a0)");
 129                         return SEMI_ERROR;
 130                 }
 131
 132                 result = riscv_get_register(target, &r1, GDB_REGNO_A1);
 133                 if (result != ERROR_OK) {
 134                         LOG_DEBUG("   -> ERROR (couldn't read a1)");
 135                         return SEMI_ERROR;
 136                 }
 137
 138                 semihosting->op = r0;
 139                 semihosting->param = r1;
 140                 semihosting->word_size_bytes = riscv_xlen(target) / 8;
 141
 142                 /* Check for ARM operation numbers. */
 143                 if (semihosting->op >= 0 && semihosting->op <= 0x31) {
 144                         *retval = semihosting_common(target);
 145                         if (*retval != ERROR_OK) {
 146                                 LOG_ERROR("Failed semihosting operation (0x%02X)", semihosting->op);
 147                                 return SEMI_ERROR;
 148                         }
 149                 } else {
 150                         /* Unknown operation number, not a semihosting call. */
 151                         LOG_DEBUG("   -> NONE (unknown operation number)");
 152                         return SEMI_NONE;
 153                 }
 154         }
 155
 156         /*
 157          * Resume target if we are not waiting on a fileio
 158          * operation to complete.
 159          */
 160         if (semihosting->is_resumable && !semihosting->hit_fileio) {
 161                 /* Resume right after the EBREAK 4 bytes instruction. */
 162                 *retval = riscv_set_register(target, GDB_REGNO_PC, pc + 4);
 163                 if (*retval != ERROR_OK)
 164                         return SEMI_ERROR;
 165
 166                 LOG_DEBUG("   -> HANDLED");
 167                 return SEMI_HANDLED;
 168         }
 169
 170         LOG_DEBUG("   -> WAITING");
 171         return SEMI_WAITING;
 172 }
 173
 174 /* -------------------------------------------------------------------------
 175  * Local functions. */
 176
 177 /**
 178  * Called via semihosting->setup() later, after the target is known,
 179  * usually on the first semihosting command.
 180  */
 181 static int riscv_semihosting_setup(struct target *target, int enable)
 182 {
 183         LOG_DEBUG("[%s] enable=%d", target_name(target), enable);
 184
 185         struct semihosting *semihosting = target->semihosting;
 186         if (semihosting)
 187                 semihosting->setup_time = clock();
 188
 189         return ERROR_OK;
 190 }
 191
 192 static int riscv_semihosting_post_result(struct target *target)
 193 {
 194         struct semihosting *semihosting = target->semihosting;
 195         if (!semihosting) {
 196                 /* If not enabled, silently ignored. */
 197                 return 0;
 198         }
 199
 200         LOG_DEBUG("0x%" PRIx64, semihosting->result);
 201         riscv_set_register(target, GDB_REGNO_A0, semihosting->result);
 202         return 0;
 203 }