示例#1
0
文件: sym.c 项目: izh1979/systemtap
static const char *_stp_kallsyms_lookup(unsigned long addr,
                                        unsigned long *symbolsize,
                                        unsigned long *offset, 
                                        const char **modname, 
                                        /* char ** secname? */
					struct task_struct *task)
{
	struct _stp_module *m = NULL;
	struct _stp_section *sec = NULL;
	struct _stp_symbol *s = NULL;
	unsigned end, begin = 0;
	unsigned long rel_addr = 0;

	if (addr == 0)
	  return NULL;

	if (task)
	  {
	    unsigned long vm_start = 0;
	    unsigned long vm_end = 0;
#ifdef CONFIG_COMPAT
        /* Handle 32bit signed values in 64bit longs, chop off top bits.
           _stp_umod_lookup does the same, but we need it here for the
           binary search on addr below. */
        if (test_tsk_thread_flag(task, TIF_32BIT))
          addr &= ((compat_ulong_t) ~0);
#endif
	    m = _stp_umod_lookup(addr, task, modname, &vm_start, &vm_end);
	    if (m)
	      {
		sec = &m->sections[0];
		/* XXX .absolute sections really shouldn't be here... */
		if (strcmp(".dynamic", m->sections[0].name) == 0)
		  rel_addr = addr - vm_start;
		else
		  rel_addr = addr;
	      }
	    if (modname && *modname)
	      {
		/* In case no symbol is found, fill in based on module. */
		if (offset)
		  *offset = addr - vm_start;
		if (symbolsize)
		  *symbolsize = vm_end - vm_start;
	      }
	  }
	else
	  {
	    m = _stp_kmod_sec_lookup(addr, &sec);
	    if (m)
	      {
	        rel_addr = addr - sec->static_addr;
		if (modname)
		  *modname = m->name;
	      }
	  }

        if (unlikely (m == NULL || sec == NULL))
          return NULL;
        
        /* NB: relativize the address to the section. */
        addr = rel_addr;
	end = sec->num_symbols;

	/* binary search for symbols within the module */
	do {
		unsigned mid = (begin + end) / 2;
		if (addr < sec->symbols[mid].addr)
			end = mid;
		else
			begin = mid;
	} while (begin + 1 < end);
	/* result index in $begin */

	s = & sec->symbols[begin];
	if (likely(addr >= s->addr)) {
		if (offset)
			*offset = addr - s->addr;
                /* We could also pass sec->name here. */
		if (symbolsize) {
			if ((begin + 1) < sec->num_symbols)
				*symbolsize = sec->symbols[begin + 1].addr - s->addr;
			else
				*symbolsize = 0;
			// NB: This is only a heuristic.  Sometimes there are large
			// gaps between text areas of modules.
		}
		return s->symbol;
	}
	return NULL;
}
示例#2
0
unsigned long _stp_linenumber_lookup(unsigned long addr, struct task_struct *task, char ** filename, int need_filename)
{
  struct _stp_module *m;
  struct _stp_section *sec;
  const char *modname = NULL;
  uint8_t *linep, *enddatap;
  int compat_task = _stp_is_compat_task();
  int user = (task ? 1 : 0);

// the portion below is encased in this conditional because some of the functions
// and constants needed are encased in a similar condition
#ifdef STP_NEED_LINE_DATA
  if (addr == 0)
      return 0;

  if (task)
    {
	    unsigned long vm_start = 0;
	    unsigned long vm_end = 0;
#ifdef CONFIG_COMPAT
      /* Handle 32bit signed values in 64bit longs, chop off top bits. */
      if (test_tsk_thread_flag(task, TIF_32BIT))
        addr &= ((compat_ulong_t) ~0);
#endif
	    m = _stp_umod_lookup(addr, task, &modname, &vm_start, &vm_end);
    }
  else
    m = _stp_kmod_sec_lookup(addr, &sec);

  if (m == NULL || m->debug_line == NULL)
    return 0;

  // if addr is a kernel address, it will need to be adjusted
  if (!task)
    {
      int i;
      unsigned long offset = 0;
      // have to factor in the load_offset of (specifically) the .text section
      for (i=0; i<m->num_sections; i++)
        if (!strcmp(m->sections[i].name, ".text"))
          {
            offset = (m->sections[i].static_addr - m->sections[i].sec_load_offset);
            break;
          }

      if (addr < offset)
        return 0;
      addr = addr - offset;
    }


  linep = m->debug_line;
  enddatap = m->debug_line + m->debug_line_len;

  while (linep < enddatap)
    {
      // similar to print_debug_line_section() in elfutils
      unsigned int length = 4, curr_file_idx = 1, prev_file_idx = 1;
      unsigned int skip_to_seq_end = 0, op_index = 0;
      uint64_t unit_length, hdr_length, curr_addr = 0;
      uint8_t *endunitp, *endhdrp, *dirsecp, *stdopcode_lens_secp;
      uint16_t version;
      uint8_t opcode_base, line_range, min_instr_len = 0, max_ops = 1;
      unsigned long curr_linenum = 1;
      int8_t line_base;
      long cumm_line_adv = 0;

      unit_length = (uint64_t) read_pointer ((const uint8_t **) &linep, enddatap, DW_EH_PE_data4, user, compat_task);
      if (unit_length == 0xffffffff)
        {
          if (unlikely (linep + 8 > enddatap))
            return 0;
          unit_length = (uint64_t) read_pointer ((const uint8_t **) &linep, enddatap, DW_EH_PE_data8, user, compat_task);
          length = 8;
        }
      if (unit_length < (length + 2) || (linep + unit_length) > enddatap)
        return 0;

      endunitp = linep + unit_length;

      version = read_pointer ((const uint8_t **) &linep, endunitp, DW_EH_PE_data2, user, compat_task);

      if (length == 4)
        hdr_length = (uint64_t) read_pointer ((const uint8_t **) &linep, endunitp, DW_EH_PE_data4, user, compat_task);
      else
        hdr_length = (uint64_t) read_pointer ((const uint8_t **) &linep, endunitp, DW_EH_PE_data8, user, compat_task);

      if ((linep + hdr_length) > endunitp || hdr_length < (version >= 4 ? 6 : 5))
        return 0;

      endhdrp = linep + hdr_length;

      // minimum instruction length
      min_instr_len = *linep++;
      // max operations per instruction
      if (version >= 4)
        {
          max_ops = *linep++;
          if (max_ops == 0)
              return 0; // max operations per instruction is supposed to > 0;
        }
      // default value of the is_stmt register
      ++linep;
      // line base. this is a signed value.
      line_base = *linep++;
      // line range
      line_range = *linep++;
      if (line_range == 0)
        return 0;
      // opcode base
      opcode_base = *linep++;
      // opcodes
      stdopcode_lens_secp = linep - 1;
      // need this check if the header length check covers this region?
      if ((linep + opcode_base - 1) >= endhdrp)
        return 0;
      linep += opcode_base - 1;

      // at the directory table. don't need an other information from the header
      // in order to find the desired line number, so we will save a pointer to
      // this point and skip ahead to the end of the header. this portion of the
      // header will be visited again after a line number has been found if a
      // filename is needed.
      dirsecp = linep;
      linep = endhdrp;

      // iterating through the opcodes. will deal with three defined types of
      // opcode: special, extended and standard. there is also a portion at
      // the end of this loop that will deal with unknown (standard) opcodes.
      while (linep < endunitp)
        {
          uint8_t opcode = *linep++;
          long addr_adv = 0;

          if (opcode >= opcode_base) // special opcode
            {
              // line range was checked before this point. this variable is not altered after it is initialized.
              cumm_line_adv += (line_base + ((opcode - opcode_base) % line_range));
              addr_adv = ((opcode - opcode_base) / line_range);
            }

          else if (opcode == 0) // extended opcode
            {
              int len;
              uint8_t subopcode;

              if (linep + 1 > endunitp)
                return 0;

              len = *linep++;
              if (linep + len > endunitp || len < 1)
                return 0;

              subopcode = *linep++; // the sub opcode
              switch (subopcode)
                {
                  case DW_LNE_end_sequence:
                    // reset the line and address.
                    cumm_line_adv = 1 - curr_linenum;
                    addr_adv = 0 - curr_addr;
                    skip_to_seq_end = 0;
                    op_index = 0;
                    break;
                  case DW_LNE_set_address:
                    if ((len - 1) == 4) // account for the opcode (the -1)
                      curr_addr = (uint64_t) read_pointer ((const uint8_t **) &linep, endunitp, DW_EH_PE_data4, user, compat_task);
                    else if ((len - 1) == 8)
                      curr_addr = (uint64_t) read_pointer ((const uint8_t **) &linep, endunitp, DW_EH_PE_data8, user, compat_task);
                    else
                      return 0;

                    // if the set address is past the address we want, iterate
                    // to the end of the sequence without doing more address
                    // and linenumber calcs than necessary
                    if (curr_addr > addr)
                      skip_to_seq_end = 1;
                    op_index = 0;
                    break;
                  default: // advance the ptr by the specified amount
                    linep += len-1;
                    break;
                }
            }
          else if (opcode <= DW_LNS_set_isa) // known standard opcode
            {
              uint8_t *linep_before = linep;
              switch (opcode)
                {
                  case DW_LNS_advance_pc:
                    addr_adv = read_pointer ((const uint8_t **) &linep, endunitp, DW_EH_PE_leb128, user, compat_task);
                    break;
                  case DW_LNS_fixed_advance_pc:
                    addr_adv = read_pointer ((const uint8_t **) &linep, endunitp, DW_EH_PE_data2, user, compat_task);
                    if (linep_before == linep) // the read failed
                      return 0;
                    op_index = 0;
                    break;
                  case DW_LNS_advance_line:
                    cumm_line_adv += read_pointer ((const uint8_t **) &linep, endunitp, DW_EH_PE_leb128+DW_EH_PE_signed, user, compat_task);
                    break;
                  case DW_LNS_set_file:
                    curr_file_idx = read_pointer ((const uint8_t **) &linep, endunitp, DW_EH_PE_leb128, user, compat_task);
                    break;
                  case DW_LNS_set_column:
                    read_pointer ((const uint8_t **) &linep, endunitp, DW_EH_PE_leb128, user, compat_task);
                    break;
                  case DW_LNS_const_add_pc:
                    addr_adv = ((255 - opcode_base) / line_range);
                    break;
                  case DW_LNS_set_isa:
                    read_pointer ((const uint8_t **) &linep, endunitp, DW_EH_PE_leb128, user, compat_task);
                    break;
                }
                if (linep > endunitp) // reading in the leb128 failed
                  return 0;
            }
          else
            {
              int i;
              for (i=stdopcode_lens_secp[opcode]; i>0; --i)
                {
                  read_pointer ((const uint8_t **) &linep, endunitp, DW_EH_PE_leb128, user, compat_task);
                  if (linep > endunitp)
                    return 0;
                }
            }

          // don't worry about doing line/address advances since we are waiting
          // till we hit the end of the sequence or the end of the unit at which
          // point the address and linenumber will be reset
          if (skip_to_seq_end == 1)
            continue;

          // calculate actual address advance
          if (opcode != 0 && opcode != DW_LNS_fixed_advance_pc)
            {
              addr_adv = min_instr_len * (op_index + addr_adv) / max_ops;
              op_index =  (op_index + addr_adv) % max_ops;
            }

          // found an address that at least sort of matches the address we
          // were looking for
          if ((curr_addr <= addr && addr < (curr_addr + addr_adv))
              || (curr_addr == addr && addr_adv != 0))
            {

              if (need_filename)
                _stp_filename_lookup(m, filename, dirsecp, endhdrp,
                                     prev_file_idx, user, compat_task);
              return curr_linenum;
            }

          // update the linenumber and file index if the curr_addr is to be updated
          if (addr_adv != 0)
            {
              prev_file_idx = curr_file_idx;
            }
          if (prev_file_idx == curr_file_idx)
          {
              curr_linenum += cumm_line_adv;
              cumm_line_adv = 0;
            }

          curr_addr += addr_adv;
        }
    }
#endif /* STP_NEED_LINE_DATA */

  // no linenumber was found otherwise this function would have returned before this point
  return 0;
}