rtems/cpukit/libdebugger/rtems-debugger-target.c

/*
 * Copyright (c) 2016-2019 Chris Johns <chrisj@rtems.org>.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#define TARGET_DEBUG 0

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

#include <errno.h>
#include <inttypes.h>
#include <stdlib.h>

#include <rtems.h>
#include <rtems/score/threadimpl.h>

#include "rtems-debugger-target.h"
#include "rtems-debugger-threads.h"

/**
 * Exception local stack frame data to synchronise with the debugger
 * server's events loop processor.
 */
typedef struct {
  rtems_chain_node node;
  rtems_id id;
  CPU_Exception_frame* frame;
  rtems_rx_cond cond;
} rtems_debugger_exception;

#if TARGET_DEBUG
#include <rtems/bspIo.h>
static void target_printk(const char* format, ...) RTEMS_PRINTFLIKE(1, 2);
static void target_printk(const char* format, ...) {
  rtems_interrupt_lock_context lock_context;
  va_list ap;
  va_start(ap, format);
  rtems_debugger_printk_lock(&lock_context);
  vprintk(format, ap);
  rtems_debugger_printk_unlock(&lock_context);
  va_end(ap);
}
#else
#define target_printk(_fmt, ...)
#endif

int rtems_debugger_target_create(void) {
  if (rtems_debugger->target == NULL) {
    rtems_debugger_target* target;
    int r;

    target = calloc(1, sizeof(rtems_debugger_target));
    if (target == NULL) {
      errno = ENOMEM;
      return -1;
    }

    r = rtems_debugger_target_configure(target);
    if (r < 0) {
      free(target);
      return -1;
    }

    if (target->breakpoint_size > RTEMS_DEBUGGER_TARGET_SWBREAK_MAX_SIZE) {
      free(target);
      rtems_debugger_printf(
          "error: rtems-db: target: breakpoint size too big\n");
      return -1;
    }

    r = rtems_debugger_block_create(&target->swbreaks,
                                    RTEMS_DEBUGGER_TARGET_SWBREAK_NUM,
                                    sizeof(rtems_debugger_target_swbreak));
    if (r < 0) {
      free(target);
      return -1;
    }

    rtems_debugger->target = target;
  }

  return 0;
}

int rtems_debugger_target_destroy(void) {
  if (rtems_debugger->target != NULL) {
    rtems_debugger_target* target = rtems_debugger->target;
    rtems_debugger_target_swbreak_remove();
    rtems_debugger_target_disable();
    rtems_debugger_block_destroy(&target->swbreaks);
    free(target);
    rtems_debugger->target = NULL;
  }
  return 0;
}

uint32_t rtems_debugger_target_capabilities(void) {
  if (rtems_debugger->target != NULL) {

    return rtems_debugger->target->capabilities;
  }
  return 0;
}

size_t rtems_debugger_target_reg_num(void) {
  rtems_debugger_target* target = rtems_debugger->target;
  if (target != NULL) {
    return target->reg_num;
  }
  return 0;
}

size_t rtems_debugger_target_reg_size(size_t reg) {
  rtems_debugger_target* target = rtems_debugger->target;
  if (target != NULL && reg < target->reg_num) {
    return target->reg_offset[reg + 1] - target->reg_offset[reg];
  }
  return 0;
}

size_t rtems_debugger_target_reg_offset(size_t reg) {
  rtems_debugger_target* target = rtems_debugger->target;
  if (target != NULL && reg < target->reg_num) {
    return target->reg_offset[reg];
  }
  return 0;
}

size_t rtems_debugger_target_reg_table_size(void) {
  rtems_debugger_target* target = rtems_debugger->target;
  if (target != NULL) {
    return target->reg_offset[target->reg_num];
  }
  return 0;
}

bool rtems_debugger_target_swbreak_is_configured(uintptr_t addr) {
  size_t i;
  rtems_debugger_target_swbreak* swbreaks;
  rtems_debugger_target* target = rtems_debugger->target;

  if (target == NULL) {
    return false;
  }

  swbreaks = target->swbreaks.block;

  if (swbreaks == NULL) {
    return false;
  }

  for (i = 0; i < target->swbreaks.level; ++i) {
    if ((uintptr_t)swbreaks[i].address == addr) {
      return true;
    }
  }

  return false;
}

int rtems_debugger_target_swbreak_control(bool insert, uintptr_t addr,
                                          DB_UINT kind) {
  rtems_debugger_target* target = rtems_debugger->target;
  rtems_debugger_target_swbreak* swbreaks;
  size_t swbreak_size;
  uint8_t* loc = (void*)addr;
  size_t i;
  int r;

  if (target == NULL || target->swbreaks.block == NULL ||
      kind != target->breakpoint_size) {
    errno = EIO;
    return -1;
  }

  swbreaks = target->swbreaks.block;
  swbreak_size =
      sizeof(rtems_debugger_target_swbreak) + target->breakpoint_size;

  for (i = 0; i < target->swbreaks.level; ++i) {
    if (loc == swbreaks[i].address) {
      size_t remaining;
      if (!insert) {
        if (target->code_writer != NULL) {
          r = target->code_writer(loc, &swbreaks[i].contents[0],
                                  target->breakpoint_size);
          if (r < 0) {
            return r;
          }
        } else {
          if (target->breakpoint_size > 4) {
            memcpy(loc, &swbreaks[i].contents[0], target->breakpoint_size);
          } else {
            switch (target->breakpoint_size) {
            case 4:
              loc[3] = swbreaks[i].contents[3];
              RTEMS_FALL_THROUGH();
            case 3:
              loc[2] = swbreaks[i].contents[2];
              RTEMS_FALL_THROUGH();
            case 2:
              loc[1] = swbreaks[i].contents[1];
              RTEMS_FALL_THROUGH();
            case 1:
              loc[0] = swbreaks[i].contents[0];
              break;
            }
          }
          rtems_debugger_target_cache_sync(&swbreaks[i]);
        }
        --target->swbreaks.level;
        remaining = (target->swbreaks.level - i) * swbreak_size;
        memmove(&swbreaks[i], &swbreaks[i + 1], remaining);
      }
      return 0;
    }
  }

  if (!insert) {
    return 0;
  }

  r = rtems_debugger_block_resize(&target->swbreaks);
  if (r < 0) {
    return -1;
  }

  swbreaks = target->swbreaks.block;

  swbreaks[target->swbreaks.level].address = loc;
  if (target->breakpoint_size > 4) {
    memcpy(&swbreaks[target->swbreaks.level].contents[0], loc,
           target->breakpoint_size);
  } else {
    uint8_t* contents = &swbreaks[target->swbreaks.level].contents[0];
    switch (target->breakpoint_size) {
    case 4:
      contents[3] = loc[3];
      RTEMS_FALL_THROUGH();
    case 3:
      contents[2] = loc[2];
      RTEMS_FALL_THROUGH();
    case 2:
      contents[1] = loc[1];
      RTEMS_FALL_THROUGH();
    case 1:
      contents[0] = loc[0];
      break;
    }
  }
  ++target->swbreaks.level;

  return 0;
}

int rtems_debugger_target_swbreak_insert(void) {
  rtems_debugger_target* target = rtems_debugger->target;
  int r = -1;
  if (target != NULL && target->swbreaks.block != NULL) {
    rtems_debugger_target_swbreak* swbreaks = target->swbreaks.block;
    size_t i;
    r = 0;
    for (i = 0; i < target->swbreaks.level; ++i) {
      uint8_t* loc = swbreaks[i].address;
      if (rtems_debugger_verbose()) {
        rtems_debugger_printf("rtems-db:  bp:  in: %p\n", swbreaks[i].address);
      }
      if (target->code_writer != NULL) {
        r = target->code_writer(loc, &target->breakpoint[0],
                                target->breakpoint_size);
        if (r < 0) {
          return r;
        }
      } else {
        if (target->breakpoint_size > 4) {
          memcpy(loc, &target->breakpoint[0], target->breakpoint_size);
        } else {
          if (rtems_debugger_verbose()) {
            rtems_debugger_printf("rtems-db:  bp:  in: %p %p %d %d %d\n", loc,
                                  &target->breakpoint[0],
                                  (int)target->breakpoint_size, (int)i,
                                  (int)target->swbreaks.level);
          }
          switch (target->breakpoint_size) {
          case 4:
            loc[3] = target->breakpoint[3];
            RTEMS_FALL_THROUGH();
          case 3:
            loc[2] = target->breakpoint[2];
            RTEMS_FALL_THROUGH();
          case 2:
            loc[1] = target->breakpoint[1];
            RTEMS_FALL_THROUGH();
          case 1:
            loc[0] = target->breakpoint[0];
            break;
          }
        }
        r = rtems_debugger_target_cache_sync(&swbreaks[i]);
      }
    }
  }
  return r;
}

int rtems_debugger_target_swbreak_remove(void) {
  rtems_debugger_target* target = rtems_debugger->target;
  int r = -1;
  if (target != NULL && target->swbreaks.block != NULL) {
    rtems_debugger_target* target = rtems_debugger->target;
    rtems_debugger_target_swbreak* swbreaks = target->swbreaks.block;
    size_t i;
    r = 0;
    for (i = 0; i < target->swbreaks.level; ++i) {
      uint8_t* loc = swbreaks[i].address;
      uint8_t* contents = &swbreaks[i].contents[0];
      if (rtems_debugger_verbose()) {
        rtems_debugger_printf("rtems-db:  bp: out: %p\n", swbreaks[i].address);
      }
      if (target->code_writer != NULL) {
        r = target->code_writer(loc, contents, target->breakpoint_size);
        if (r < 0) {
          return r;
        }
      } else {
        if (target->breakpoint_size > 4) {
          memcpy(loc, contents, target->breakpoint_size);
        } else {
          switch (target->breakpoint_size) {
          case 4:
            loc[3] = contents[3];
            RTEMS_FALL_THROUGH();
          case 3:
            loc[2] = contents[2];
            RTEMS_FALL_THROUGH();
          case 2:
            loc[1] = contents[1];
            RTEMS_FALL_THROUGH();
          case 1:
            loc[0] = contents[0];
            break;
          }
        }
        r = rtems_debugger_target_cache_sync(&swbreaks[i]);
      }
    }
  }
  return r;
}

static rtems_debugger_target_exc_action
rtems_debugger_soft_step_and_continue(CPU_Exception_frame* frame) {
  uintptr_t break_address;
  rtems_debugger_target* target = rtems_debugger->target;
  Thread_Control* thread = _Thread_Get_executing();
  const rtems_id tid = thread->Object.id;
  rtems_debugger_thread fake_debugger_thread;

  /*
   * If this was a hwbreak, cascade. If this is a swbreak replace the contents
   * of the instruction, step then return the swbreak's contents.
   */
  if ((target->capabilities & RTEMS_DEBUGGER_TARGET_CAP_SWBREAK) == 0) {
    target_printk("rtems-db: exception in an interrupt, cascading\n");
    rtems_debugger_unlock();
    return rtems_debugger_target_exc_cascade;
  }

  break_address = rtems_debugger_target_frame_pc(frame);
  if (rtems_debugger_target_swbreak_is_configured(break_address) == false) {
    target_printk("rtems-db: exception in an interrupt, cascading\n");
    rtems_debugger_unlock();
    return rtems_debugger_target_exc_cascade;
  }

  /*
   * Remove the current breakpoint
   */
  rtems_debugger_target_swbreak_control(false, break_address,
                                        target->breakpoint_size);

  /*
   * Save the thread ID and break address to recover after stepping
   */
  target->step_tid = tid;
  target->step_bp_address = break_address;

  /*
   * Populate the fake rtems_debugger_thread
   */
  fake_debugger_thread.flags |= RTEMS_DEBUGGER_THREAD_FLAG_STEP;
  fake_debugger_thread.frame = frame;
  target_printk("rtems-db: stepping to the next instruction\n");
  rtems_debugger_target_thread_stepping(&fake_debugger_thread);

  /*
   * rtems_debugger_unlock() not called until the step is resolved
   */
  return rtems_debugger_target_exc_step;
}

rtems_debugger_target_exc_action
rtems_debugger_target_exception(CPU_Exception_frame* frame) {
  rtems_debugger_target* target = rtems_debugger->target;
  Thread_Control* thread = _Thread_Get_executing();
  const rtems_id tid = thread->Object.id;

  /*
   * Resolve outstanding step+continue
   */
  if (target->step_bp_address != 0 && target->step_tid == tid) {
    rtems_debugger_target_swbreak_control(
        true, target->step_bp_address, rtems_debugger->target->breakpoint_size);
    target->step_bp_address = 0;
    target->step_tid = 0;

    /*
     * Release the debugger lock now that the step+continue is complete
     */
    target_printk("rtems-db: resuming after step\n");
    rtems_debugger_unlock();
    return rtems_debugger_target_exc_consumed;
  }

  rtems_debugger_lock();

  if (!rtems_interrupt_is_in_progress()) {
    rtems_debugger_threads* threads = rtems_debugger->threads;
    rtems_id* excludes;
    uintptr_t pc;
    const rtems_debugger_thread_stepper* stepper;
    rtems_debugger_exception target_exception;
    size_t i;

    target_printk("[} tid:%08" PRIx32 ": thread:%08" PRIxPTR
                  " frame:%08" PRIxPTR "\n",
                  tid, (intptr_t)thread, (intptr_t)frame);

    /*
     * If the thread is in the debugger recover. If the access is from gdb
     * continue else shutdown and let the user know.
     */
    if (tid == rtems_debugger->server_task ||
        tid == rtems_debugger->events_task) {
      bool memory_access = rtems_debugger_target_is_memory_access();
      rtems_debugger_unlock();
      /*
       * Has GDB has asked us to write to an address?
       */
      if (memory_access) {
        target_printk("[} server fault: memory access\n");
        longjmp(rtems_debugger->target->access_return, -1);
      }
      rtems_debugger_printf("rtems-db: server exception (report)\n");
      rtems_debugger_target_exception_print(frame);
      rtems_debugger_server_crash();
      return rtems_debugger_target_exc_cascade;
    }

    /*
     * See if the thread is excluded.
     */
    excludes = rtems_debugger_thread_excludes(threads);
    for (i = 0; i < threads->excludes.level; ++i) {
      if (tid == excludes[i]) {
        /*
         * We do nothing with this condition and cascade the exception.
         *
         * @todo: if this is a hwbreak carry on, if this is a swbreak replace
         *        the contents of the instruction, step then return the
         *        swbreak's contents.
         */
        target_printk("[} tid:%08" PRIx32 ": excluded\n", tid);
        rtems_debugger_unlock();
        return rtems_debugger_target_exc_cascade;
      }
    }

    /*
     * See if the thread is inside the stepping a range.
     */
    pc = rtems_debugger_target_frame_pc(frame);
    stepper = rtems_debugger_thread_is_stepping(tid, pc);
    if (stepper != NULL) {
      stepper->thread->frame = frame;
      rtems_debugger_target_thread_stepping(stepper->thread);
      target_printk("[} tid:%08" PRIx32 ": stepping\n", tid);
      rtems_debugger_unlock();
      return rtems_debugger_target_exc_step;
    }

    target_printk("[} tid:%08" PRIx32 ": suspending\n", tid);

    /*
     * Initialise the target exception data and queue ready for the debugger
     * server's event processor to handle.
     */
    rtems_chain_initialize_node(&target_exception.node);
    target_exception.frame = frame;
    target_exception.id = tid;
    _Condition_Initialize(&target_exception.cond);

    rtems_chain_append_unprotected(&rtems_debugger->exception_threads,
                                   &target_exception.node);

    /*
     * Signal the debug server's thread.
     */
    rtems_debugger_server_events_signal();

    /*
     * Block on the exception thread's condition variable unlocking the
     * debugger's mutex and letting the server's thread run.
     */
    _Condition_Wait_recursive(&target_exception.cond, &rtems_debugger->lock);

    /*
     * Unlock the debugger's lock now the exception is resuming.
     */
    rtems_debugger_unlock();

    target_printk("[} tid:%08" PRIx32 ": resuming\n", tid);

    return rtems_debugger_target_exc_consumed;
  }

  target_printk("[} tid:%08" PRIx32 ": exception in interrupt context\n", tid);

  /*
   * Soft_step_and_continue releases the debugger lock
   */
  return rtems_debugger_soft_step_and_continue(frame);
}

void rtems_debugger_target_exception_thread(rtems_debugger_thread* thread) {
  rtems_chain_node* node;
  thread->frame = NULL;
  thread->flags &= ~RTEMS_DEBUGGER_THREAD_FLAG_EXCEPTION;
  for (node = rtems_chain_first(&rtems_debugger->exception_threads);
       !rtems_chain_is_tail(&rtems_debugger->exception_threads, node);
       node = rtems_chain_next(node)) {
    rtems_debugger_exception* target_exception =
        (rtems_debugger_exception*)node;
    if (target_exception->id == thread->id) {
      thread->frame = target_exception->frame;
      thread->flags |= RTEMS_DEBUGGER_THREAD_FLAG_EXCEPTION;
    }
  }
}

void rtems_debugger_target_exception_thread_resume(
    rtems_debugger_thread* thread) {
  rtems_chain_node* node;
  for (node = rtems_chain_first(&rtems_debugger->exception_threads);
       !rtems_chain_is_tail(&rtems_debugger->exception_threads, node);
       node = rtems_chain_next(node)) {
    rtems_debugger_exception* target_exception =
        (rtems_debugger_exception*)node;
    if (target_exception->id == thread->id) {
      rtems_chain_extract(node);
      thread->frame = NULL;
      thread->flags &= ~RTEMS_DEBUGGER_THREAD_FLAG_EXCEPTION;
      _Condition_Signal(&target_exception->cond);
      break;
    }
  }
}

void rtems_debugger_target_end_memory_access(void) {
  rtems_debugger->target->memory_access = false;
}

bool rtems_debugger_target_is_memory_access(void) {
  return rtems_debugger->target->memory_access;
}