text: /* libunwind - a platform-independent unwind library
     Copyright (C) 2002-2004 Hewlett-Packard Co
          Contributed by David Mosberger-Tang <davidm@hpl.hp.com>
  
  This file is part of libunwind.
  
  Permission is hereby granted, free of charge, to any person obtaining
  a copy of this software and associated documentation files (the
  "Software"), to deal in the Software without restriction, including
  without limitation the rights to use, copy, modify, merge, publish,
  distribute, sublicense, and/or sell copies of the Software, and to
  permit persons to whom the Software is furnished to do so, subject to
  the following conditions:
  
  The above copyright notice and this permission notice shall be
  included in all copies or substantial portions of the Software.
  
  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.  */
  
  #include "unwind_i.h"
  #include "offsets.h"
  
  int
  unw_step (unw_cursor_t *cursor)
  {
    struct cursor *c = (struct cursor *) cursor;
    int ret, i;
  
    Debug (1, "(cursor=%p, ip=0x%08x)\n", c, (unsigned) c->dwarf.ip);
  
    /* Try DWARF-based unwinding... */
    ret = dwarf_step (&c->dwarf);
  
    if (ret < 0 && ret != -UNW_ENOINFO)
      {
        Debug (2, "returning %d\n", ret);
        return ret;
      }
  
    if (unlikely (ret < 0))
      {
        /* DWARF failed, let's see if we can follow the frame-chain
           or skip over the signal trampoline.  */
        struct dwarf_loc ebp_loc, eip_loc, esp_loc;
  
        /* We could get here because of missing/bad unwind information.
           Validate all addresses before dereferencing. */
        c->validate = 1;
  
        Debug (13, "dwarf_step() failed (ret=%d), trying frame-chain\n", ret);
  
        if (unw_is_signal_frame (cursor) > 0)
          {
            ret = x86_handle_signal_frame(cursor);
            if (ret < 0)
              {
                Debug (2, "returning 0\n");
                return 0;
              }
          }
        else
          {
            ret = dwarf_get (&c->dwarf, c->dwarf.loc[EBP], &c->dwarf.cfa);
            if (ret < 0)
              {
                Debug (2, "returning %d\n", ret);
                return ret;
              }
  
            Debug (13, "[EBP=0x%x] = 0x%x\n", DWARF_GET_LOC (c->dwarf.loc[EBP]),
                   c->dwarf.cfa);
  
            ebp_loc = DWARF_LOC (c->dwarf.cfa, 0);
            esp_loc = DWARF_VAL_LOC (c, c->dwarf.cfa + 8);
            eip_loc = DWARF_LOC (c->dwarf.cfa + 4, 0);
            c->dwarf.cfa += 8;
  
            /* Mark all registers unsaved, since we don't know where
               they are saved (if at all), except for the EBP and
               EIP.  */
            for (i = 0; i < DWARF_NUM_PRESERVED_REGS; ++i)
              c->dwarf.loc[i] = DWARF_NULL_LOC;
  
            c->dwarf.loc[EBP] = ebp_loc;
            c->dwarf.loc[ESP] = esp_loc;
            c->dwarf.loc[EIP] = eip_loc;
            c->dwarf.use_prev_instr = 1;
          }
  
        if (!DWARF_IS_NULL_LOC (c->dwarf.loc[EBP]))
          {
            ret = dwarf_get (&c->dwarf, c->dwarf.loc[EIP], &c->dwarf.ip);
            if (ret < 0)
              {
                Debug (13, "dwarf_get([EIP=0x%x]) failed\n", DWARF_GET_LOC (c->dwarf.loc[EIP]));
                Debug (2, "returning %d\n", ret);
                return ret;
              }
            else
              {
                Debug (13, "[EIP=0x%x] = 0x%x\n", DWARF_GET_LOC (c->dwarf.loc[EIP]),
                  c->dwarf.ip);
              }
          }
        else
          c->dwarf.ip = 0;
      }
    ret = (c->dwarf.ip == 0) ? 0 : 1;
    Debug (2, "returning %d\n", ret);
    return ret;
  }
  