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   1 /***************************************************************************
   2  *   Copyright (C) 2009 by Marvell Technology Group Ltd.                   *
   3  *   Written by Nicolas Pitre <nico@marvell.com>                           *
   4  *                                                                         *
   5  *   Copyright (C) 2010 by Spencer Oliver                                  *
   6  *   spen@spen-soft.co.uk                                                  *
   7  *                                                                         *
   8  *   Copyright (C) 2016 by Square, Inc.                                    *
   9  *   Steven Stallion <stallion@squareup.com>                               *
  10  *                                                                         *
  11  *   Copyright (C) 2018 by Liviu Ionescu                                   *
  12  *   <ilg@livius.net>                                                      *
  13  *                                                                         *
  14  *   This program is free software; you can redistribute it and/or modify  *
  15  *   it under the terms of the GNU General Public License as published by  *
  16  *   the Free Software Foundation; either version 2 of the License, or     *
  17  *   (at your option) any later version.                                   *
  18  *                                                                         *
  19  *   This program is distributed in the hope that it will be useful,       *
  20  *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
  21  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
  22  *   GNU General Public License for more details.                          *
  23  *                                                                         *
  24  *   You should have received a copy of the GNU General Public License     *
  25  *   along with this program.  If not, see <http://www.gnu.org/licenses/>. *
  26  ***************************************************************************/
  27
  28 /**
  29  * @file
  30  * Hold ARM semihosting support.
  31  *
  32  * Semihosting enables code running on an ARM target to use the I/O
  33  * facilities on the host computer. The target application must be linked
  34  * against a library that forwards operation requests by using the SVC
  35  * instruction trapped at the Supervisor Call vector by the debugger.
  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 "arm.h"
  45 #include "armv4_5.h"
  46 #include "arm7_9_common.h"
  47 #include "armv7m.h"
  48 #include "armv7a.h"
  49 #include "cortex_m.h"
  50 #include "register.h"
  51 #include "arm_opcodes.h"
  52 #include "target_type.h"
  53 #include "arm_semihosting.h"
  54 #include <helper/binarybuffer.h>
  55 #include <helper/log.h>
  56 #include <sys/stat.h>
  57
  58 static int post_result(struct target *target)
  59 {
  60         struct arm *arm = target_to_arm(target);
  61
  62         /* REVISIT this looks wrong ... ARM11 and Cortex-A8
  63          * should work this way at least sometimes.
  64          */
  65         if (is_arm7_9(target_to_arm7_9(target)) ||
  66             is_armv7a(target_to_armv7a(target))) {
  67                 uint32_t spsr;
  68
  69                 /* return value in R0 */
  70                 buf_set_u32(arm->core_cache->reg_list[0].value, 0, 32, target->semihosting->result);
  71                 arm->core_cache->reg_list[0].dirty = 1;
  72
  73                 /* LR --> PC */
  74                 buf_set_u32(arm->core_cache->reg_list[15].value, 0, 32,
  75                         buf_get_u32(arm_reg_current(arm, 14)->value, 0, 32));
  76                 arm->core_cache->reg_list[15].dirty = 1;
  77
  78                 /* saved PSR --> current PSR */
  79                 spsr = buf_get_u32(arm->spsr->value, 0, 32);
  80
  81                 /* REVISIT should this be arm_set_cpsr(arm, spsr)
  82                  * instead of a partially unrolled version?
  83                  */
  84
  85                 buf_set_u32(arm->cpsr->value, 0, 32, spsr);
  86                 arm->cpsr->dirty = 1;
  87                 arm->core_mode = spsr & 0x1f;
  88                 if (spsr & 0x20)
  89                         arm->core_state = ARM_STATE_THUMB;
  90
  91         } else {
  92                 /* resume execution, this will be pc+2 to skip over the
  93                  * bkpt instruction */
  94
  95                 /* return result in R0 */
  96                 buf_set_u32(arm->core_cache->reg_list[0].value, 0, 32, target->semihosting->result);
  97                 arm->core_cache->reg_list[0].dirty = 1;
  98         }
  99
 100         return ERROR_OK;
 101 }
 102
 103 /**
 104  * Initialize ARM semihosting support.
 105  *
 106  * @param target Pointer to the ARM target to initialize.
 107  * @return An error status if there is a problem during initialization.
 108  */
 109 int arm_semihosting_init(struct target *target)
 110 {
 111         struct arm *arm = target_to_arm(target);
 112         assert(arm->setup_semihosting);
 113         semihosting_common_init(target, arm->setup_semihosting, post_result);
 114
 115         return ERROR_OK;
 116 }
 117
 118 /**
 119  * Checks for and processes an ARM semihosting request.  This is meant
 120  * to be called when the target is stopped due to a debug mode entry.
 121  * If the value 0 is returned then there was nothing to process. A non-zero
 122  * return value signifies that a request was processed and the target resumed,
 123  * or an error was encountered, in which case the caller must return
 124  * immediately.
 125  *
 126  * @param target Pointer to the ARM target to process.  This target must
 127  *      not represent an ARMv6-M or ARMv7-M processor.
 128  * @param retval Pointer to a location where the return code will be stored
 129  * @return non-zero value if a request was processed or an error encountered
 130  */
 131 int arm_semihosting(struct target *target, int *retval)
 132 {
 133         struct arm *arm = target_to_arm(target);
 134         struct armv7a_common *armv7a = target_to_armv7a(target);
 135         uint32_t pc, lr, spsr;
 136         struct reg *r;
 137
 138         struct semihosting *semihosting = target->semihosting;
 139         if (!semihosting)
 140                 return 0;
 141
 142         if (!semihosting->is_active)
 143                 return 0;
 144
 145         if (is_arm7_9(target_to_arm7_9(target)) ||
 146             is_armv7a(armv7a)) {
 147                 uint32_t vbar = 0x00000000;
 148
 149                 if (arm->core_mode != ARM_MODE_SVC)
 150                         return 0;
 151
 152                 if (is_armv7a(armv7a)) {
 153                         struct arm_dpm *dpm = armv7a->arm.dpm;
 154
 155                         *retval = dpm->prepare(dpm);
 156                         if (*retval == ERROR_OK) {
 157                                 *retval = dpm->instr_read_data_r0(dpm,
 158                                                                  ARMV4_5_MRC(15, 0, 0, 12, 0, 0),
 159                                                                  &vbar);
 160
 161                                 dpm->finish(dpm);
 162
 163                                 if (*retval != ERROR_OK)
 164                                         return 1;
 165                         } else {
 166                                 return 1;
 167                         }
 168                 }
 169
 170                 /* Check for PC == 0x00000008 or 0xffff0008: Supervisor Call vector. */
 171                 r = arm->pc;
 172                 pc = buf_get_u32(r->value, 0, 32);
 173                 if (pc != (vbar + 0x00000008) && pc != 0xffff0008)
 174                         return 0;
 175
 176                 r = arm_reg_current(arm, 14);
 177                 lr = buf_get_u32(r->value, 0, 32);
 178
 179                 /* Core-specific code should make sure SPSR is retrieved
 180                  * when the above checks pass...
 181                  */
 182                 if (!arm->spsr->valid) {
 183                         LOG_ERROR("SPSR not valid!");
 184                         *retval = ERROR_FAIL;
 185                         return 1;
 186                 }
 187
 188                 spsr = buf_get_u32(arm->spsr->value, 0, 32);
 189
 190                 /* check instruction that triggered this trap */
 191                 if (spsr & (1 << 5)) {
 192                         /* was in Thumb (or ThumbEE) mode */
 193                         uint8_t insn_buf[2];
 194                         uint16_t insn;
 195
 196                         *retval = target_read_memory(target, lr-2, 2, 1, insn_buf);
 197                         if (*retval != ERROR_OK)
 198                                 return 1;
 199                         insn = target_buffer_get_u16(target, insn_buf);
 200
 201                         /* SVC 0xab */
 202                         if (insn != 0xDFAB)
 203                                 return 0;
 204                 } else if (spsr & (1 << 24)) {
 205                         /* was in Jazelle mode */
 206                         return 0;
 207                 } else {
 208                         /* was in ARM mode */
 209                         uint8_t insn_buf[4];
 210                         uint32_t insn;
 211
 212                         *retval = target_read_memory(target, lr-4, 4, 1, insn_buf);
 213                         if (*retval != ERROR_OK)
 214                                 return 1;
 215                         insn = target_buffer_get_u32(target, insn_buf);
 216
 217                         /* SVC 0x123456 */
 218                         if (insn != 0xEF123456)
 219                                 return 0;
 220                 }
 221         } else if (is_armv7m(target_to_armv7m(target))) {
 222                 uint16_t insn;
 223
 224                 if (target->debug_reason != DBG_REASON_BREAKPOINT)
 225                         return 0;
 226
 227                 r = arm->pc;
 228                 pc = buf_get_u32(r->value, 0, 32);
 229
 230                 pc &= ~1;
 231                 *retval = target_read_u16(target, pc, &insn);
 232                 if (*retval != ERROR_OK)
 233                         return 1;
 234
 235                 /* bkpt 0xAB */
 236                 if (insn != 0xBEAB)
 237                         return 0;
 238         } else {
 239                 LOG_ERROR("Unsupported semi-hosting Target");
 240                 return 0;
 241         }
 242
 243         /* Perform semihosting if we are not waiting on a fileio
 244          * operation to complete.
 245          */
 246         if (!semihosting->hit_fileio) {
 247                 /* TODO: update for 64-bits */
 248                 uint32_t r0 = buf_get_u32(arm->core_cache->reg_list[0].value, 0, 32);
 249                 uint32_t r1 = buf_get_u32(arm->core_cache->reg_list[1].value, 0, 32);
 250
 251                 semihosting->op = r0;
 252                 semihosting->param = r1;
 253                 semihosting->word_size_bytes = 4;
 254
 255                 /* Check for ARM operation numbers. */
 256                 if (0 <= semihosting->op && semihosting->op <= 0x31) {
 257                         *retval = semihosting_common(target);
 258                         if (*retval != ERROR_OK) {
 259                                 LOG_ERROR("Failed semihosting operation");
 260                                 return 0;
 261                         }
 262                 } else {
 263                         /* Unknown operation number, not a semihosting call. */
 264                         return 0;
 265                 }
 266         }
 267
 268         /* Post result to target if we are not waiting on a fileio
 269          * operation to complete:
 270          */
 271         if (semihosting->is_resumable && !semihosting->hit_fileio) {
 272                 /* Resume right after the BRK instruction. */
 273                 *retval = target_resume(target, 1, 0, 0, 0);
 274                 if (*retval != ERROR_OK) {
 275                         LOG_ERROR("Failed to resume target");
 276                         return 0;
 277                 }
 278
 279                 return 1;
 280         }
 281
 282         return 0;
 283 }