unwind-arm.c

Android 一些工具

   Returns _URC_FAILURE if an error occurred, _URC_OK on success.  */

static _Unwind_Reason_Code
get_eit_entry (_Unwind_Control_Block *ucbp, _uw return_address, pid_t pid, 
               mapinfo *map, mapinfo **containing_map)
{
  const __EIT_entry *eitp;
  
  eitp = get_eitp(return_address, pid, map, containing_map);

  if (!eitp)
    {
      UCB_PR_ADDR (ucbp) = 0;
      return _URC_FAILURE;
    }
  ucbp->pr_cache.fnstart = selfrel_offset31 (&eitp->fnoffset, pid);

  _uw eitp_content = get_remote_word(pid, (void *)&eitp->content);

  /* Can this frame be unwound at all?  */
  if (eitp_content == EXIDX_CANTUNWIND)
    {
      UCB_PR_ADDR (ucbp) = 0;
      return _URC_END_OF_STACK;
    }

  /* Obtain the address of the "real" __EHT_Header word.  */

  if (eitp_content & uint32_highbit)
    {
      /* It is immediate data.  */
      ucbp->pr_cache.ehtp = (_Unwind_EHT_Header *)&eitp->content;
      ucbp->pr_cache.additional = 1;
    }
  else
    {
      /* The low 31 bits of the content field are a self-relative
	 offset to an _Unwind_EHT_Entry structure.  */
      ucbp->pr_cache.ehtp =
	(_Unwind_EHT_Header *) selfrel_offset31 (&eitp->content, pid);
      ucbp->pr_cache.additional = 0;
    }

  /* Discover the personality routine address.  */
  if (get_remote_word(pid, ucbp->pr_cache.ehtp) & (1u << 31))
    {
      /* One of the predefined standard routines.  */
      _uw idx = (get_remote_word(pid, ucbp->pr_cache.ehtp) >> 24) & 0xf;
      if (idx == 0)
	UCB_PR_ADDR (ucbp) = (_uw) &unwind_cpp_pr0_with_ptrace;
      else if (idx == 1)
	UCB_PR_ADDR (ucbp) = (_uw) &unwind_cpp_pr1_with_ptrace;
      else if (idx == 2)
	UCB_PR_ADDR (ucbp) = (_uw) &unwind_cpp_pr2_with_ptrace;
      else
	{ /* Failed */
	  UCB_PR_ADDR (ucbp) = 0;
	  return _URC_FAILURE;
	}
    } 
  else
    {
      /* Execute region offset to PR */
      UCB_PR_ADDR (ucbp) = selfrel_offset31 (ucbp->pr_cache.ehtp, pid);
      /* Since we are unwinding the stack from a different process, it is
       * impossible to execute the personality routine in debuggerd. Punt here.
       */
	  return _URC_FAILURE;
    }
  return _URC_OK;
}

/* Print out the current call level, pc, and module name in the crash log */
static _Unwind_Reason_Code log_function(_Unwind_Context *context, int tfd,
                                        int stack_level,
                                        mapinfo *map,
                                        unsigned int sp_list[],
                                        bool at_fault)
{
    _uw pc;
    phase2_vrs *vrs = (phase2_vrs*) context;
    const mapinfo *mi;
    bool only_in_tombstone = !at_fault;

    if (stack_level < STACK_CONTENT_DEPTH) {
        sp_list[stack_level] = vrs->core.r[R_SP];
    }
    pc = vrs->core.r[R_PC];

    // Top level frame
    if (stack_level == 0) {
        pc &= ~1;
    }
    // For deeper framers, rollback pc by one instruction
    else {
        pc = vrs->core.r[R_PC];
        // Thumb mode
        if (pc & 1) {
            pc = (pc & ~1) - 2;
        }
        else { 
            pc -= 4;
        }
    }

    mi = pc_to_mapinfo(map, pc);

    _LOG(tfd, only_in_tombstone, 
         "         #%02d  pc %08x  %s\n", stack_level, pc, 
         mi ? mi->name : "");

    return _URC_NO_REASON;
}

/* Derived from __gnu_Unwind_Backtrace to use ptrace */
/* Perform stack backtrace through unwind data. Return the level of stack it
 * unwinds.
 */
int unwind_backtrace_with_ptrace(int tfd, pid_t pid, mapinfo *map, 
                                 unsigned int sp_list[], int *frame0_pc_sane,
                                 bool at_fault)
{
    phase1_vrs saved_vrs;
    _Unwind_Reason_Code code = _URC_OK;
    struct pt_regs r;
    int i;
    int stack_level = 0;

    _Unwind_Control_Block ucb;
    _Unwind_Control_Block *ucbp = &ucb;

    if(ptrace(PTRACE_GETREGS, pid, 0, &r)) return 0;

    for (i = 0; i < 16; i++) {
        saved_vrs.core.r[i] = r.uregs[i];
        /*
        _LOG(tfd, "r[%d] = 0x%x\n", i, saved_vrs.core.r[i]);
        */
    }

    /* Set demand-save flags.  */
    saved_vrs.demand_save_flags = ~(_uw) 0;

    /* 
     * If the app crashes because of calling the weeds, we cannot pass the PC 
     * to the usual unwinding code as the EXIDX mapping will fail. 
     * Instead, we simply print out the 0 as the top frame, and resume the 
     * unwinding process with the value stored in LR.
     */
    if (get_eitp(saved_vrs.core.r[R_PC], pid, map, NULL) == NULL) { 
        *frame0_pc_sane = 0;
        log_function ((_Unwind_Context *) &saved_vrs, tfd, stack_level, 
                      map, sp_list, at_fault);
        saved_vrs.core.r[R_PC] = saved_vrs.core.r[R_LR];
        stack_level++;
    }

    do {
        mapinfo *this_map = NULL;
        /* Find the entry for this routine.  */
        if (get_eit_entry(ucbp, saved_vrs.core.r[R_PC], pid, map, &this_map)
            != _URC_OK) {
            /* Uncomment the code below to study why the unwinder failed */
#if 0
            /* Shed more debugging info for stack unwinder improvement */
            if (this_map) {
                _LOG(tfd, 1, 
                     "Relative PC=%#x from %s not contained in EXIDX\n", 
                     saved_vrs.core.r[R_PC] - this_map->start, this_map->name);
            }
            _LOG(tfd, 1, "PC=%#x SP=%#x\n", 
                 saved_vrs.core.r[R_PC], saved_vrs.core.r[R_SP]);
#endif
            code = _URC_FAILURE;
            break;
        }

        /* The dwarf unwinder assumes the context structure holds things
        like the function and LSDA pointers.  The ARM implementation
        caches these in the exception header (UCB).  To avoid
        rewriting everything we make the virtual IP register point at
        the UCB.  */
        _Unwind_SetGR((_Unwind_Context *)&saved_vrs, 12, (_Unwind_Ptr) ucbp);

        /* Call log function.  */
        if (log_function ((_Unwind_Context *) &saved_vrs, tfd, stack_level, 
                          map, sp_list, at_fault) != _URC_NO_REASON) {
            code = _URC_FAILURE;
            break;
        }
        stack_level++;

        /* Call the pr to decide what to do.  */
        code = ((personality_routine_with_ptrace) UCB_PR_ADDR (ucbp))(
                _US_VIRTUAL_UNWIND_FRAME | _US_FORCE_UNWIND, ucbp, 
                (void *) &saved_vrs, pid);
    /* 
     * In theory the unwinding process will stop when the end of stack is
     * reached or there is no unwinding information for the code address.
     * To add another level of guarantee that the unwinding process
     * will terminate we will stop it when the STACK_CONTENT_DEPTH is reached.
     */
    } while (code != _URC_END_OF_STACK && code != _URC_FAILURE && 
             stack_level < STACK_CONTENT_DEPTH);
    return stack_level;
}


/* Derived version to use ptrace */
/* Common implementation for ARM ABI defined personality routines.
   ID is the index of the personality routine, other arguments are as defined
   by __aeabi_unwind_cpp_pr{0,1,2}.  */

static _Unwind_Reason_Code
unwind_pr_common_with_ptrace (_Unwind_State state,
			_Unwind_Control_Block *ucbp,
			_Unwind_Context *context,
			int id,
            pid_t pid)
{
  __gnu_unwind_state uws;
  _uw *data;
  int phase2_call_unexpected_after_unwind = 0;

  state &= _US_ACTION_MASK;

  data = (_uw *) ucbp->pr_cache.ehtp;
  uws.data = get_remote_word(pid, data);
  data++;
  uws.next = data;
  if (id == 0)
    {
      uws.data <<= 8;
      uws.words_left = 0;
      uws.bytes_left = 3;
    }
  else
    {
      uws.words_left = (uws.data >> 16) & 0xff;
      uws.data <<= 16;
      uws.bytes_left = 2;
      data += uws.words_left;
    }

  /* Restore the saved pointer.  */
  if (state == _US_UNWIND_FRAME_RESUME)
    data = (_uw *) ucbp->cleanup_cache.bitpattern[0];

  if ((ucbp->pr_cache.additional & 1) == 0)
    {
      /* Process descriptors.  */
      while (get_remote_word(pid, data)) {
      /**********************************************************************
       * The original code here seems to deal with exceptions that are not
       * applicable in our toolchain, thus there is no way to test it for now.
       * Instead of leaving it here and causing potential instability in
       * debuggerd, we'd better punt here and leave the stack unwound.
       * In the future when we discover cases where the stack should be unwound
       * further but is not, we can revisit the code here.
       **********************************************************************/
        return _URC_FAILURE;
	  }
	  /* Finished processing this descriptor.  */
    }

  if (unwind_execute_with_ptrace (context, &uws, pid) != _URC_OK)
    return _URC_FAILURE;

  if (phase2_call_unexpected_after_unwind)
    {
      /* Enter __cxa_unexpected as if called from the call site.  */
      _Unwind_SetGR (context, R_LR, _Unwind_GetGR (context, R_PC));
      _Unwind_SetGR (context, R_PC, (_uw) &__cxa_call_unexpected);
      return _URC_INSTALL_CONTEXT;
    }

  return _URC_CONTINUE_UNWIND;
}


/* ABI defined personality routine entry points.  */

static _Unwind_Reason_Code
unwind_cpp_pr0_with_ptrace (_Unwind_State state,
			_Unwind_Control_Block *ucbp,
			_Unwind_Context *context,
            pid_t pid)
{
  return unwind_pr_common_with_ptrace (state, ucbp, context, 0, pid);
}

static _Unwind_Reason_Code
unwind_cpp_pr1_with_ptrace (_Unwind_State state,
			_Unwind_Control_Block *ucbp,
			_Unwind_Context *context,
            pid_t pid)
{
  return unwind_pr_common_with_ptrace (state, ucbp, context, 1, pid);
}

static _Unwind_Reason_Code
unwind_cpp_pr2_with_ptrace (_Unwind_State state,
			_Unwind_Control_Block *ucbp,
			_Unwind_Context *context,
            pid_t pid)
{
  return unwind_pr_common_with_ptrace (state, ucbp, context, 2, pid);
}