/src/libunwind/src/x86_64/Gstep.c

Source
/* libunwind - a platform-independent unwind library
   Copyright (C) 2002-2004 Hewlett-Packard Co
        Contributed by David Mosberger-Tang <davidm@hpl.hp.com>

   Modified for x86_64 by Max Asbock <masbock@us.ibm.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 "libunwind_i.h"
#include "unwind_i.h"
#include <signal.h>

/* Recognise PLT entries such as:
     3bdf0: ff 25 e2 49 13 00 jmpq   *0x1349e2(%rip)
     3bdf6: 68 ae 03 00 00    pushq  $0x3ae
     3bdfb: e9 00 c5 ff ff    jmpq   38300 <_init+0x18> */
static int
_is_plt_entry (struct dwarf_cursor *c)
{
  unw_word_t w0, w1;
  unw_accessors_t *a;
  int ret;

  a = unw_get_accessors_int (c->as);
  if ((ret = (*a->access_mem) (c->as, c->ip, &w0, 0, c->as_arg)) < 0
      || (ret = (*a->access_mem) (c->as, c->ip + 8, &w1, 0, c->as_arg)) < 0)
    return 0;

  ret = (((w0 & 0xffff) == 0x25ff)
         && (((w0 >> 48) & 0xff) == 0x68)
         && (((w1 >> 24) & 0xff) == 0xe9));

  Debug (14, "ip=0x%lx => 0x%016lx 0x%016lx, ret = %d\n", c->ip, w0, w1, ret);
  return ret;
}

int
unw_is_plt_entry (unw_cursor_t *uc)
{
  return _is_plt_entry (&((struct cursor *)uc)->dwarf);
}

int
unw_step (unw_cursor_t *cursor)
{
  struct cursor *c = (struct cursor *) cursor;
  int ret, i;

#if CONSERVATIVE_CHECKS
  int val = 0;
  if (c->dwarf.as == unw_local_addr_space) {
    val = dwarf_get_validate(&c->dwarf);
    dwarf_set_validate(&c->dwarf, 1);
  }
#endif

  Debug (1, "(cursor=%p, ip=0x%016lx, cfa=0x%016lx)\n",
         c, c->dwarf.ip, c->dwarf.cfa);

  /* Try DWARF-based unwinding... */
  c->sigcontext_format = X86_64_SCF_NONE;
  ret = dwarf_step (&c->dwarf);

#if CONSERVATIVE_CHECKS
  if (c->dwarf.as == unw_local_addr_space) {
    dwarf_set_validate(&c->dwarf, val);
  }
#endif

  if (ret < 0 && ret != -UNW_ENOINFO)
    {
      Debug (2, "returning %d\n", ret);
      return ret;
    }

  c->frames++;

  if (likely (ret >= 0))
    {
      /* x86_64 ABI specifies that end of call-chain is marked with a
         NULL RBP or undefined return address  */
      if (DWARF_IS_NULL_LOC (c->dwarf.loc[RBP]))
          {
            c->dwarf.ip = 0;
            ret = 0;
          }
    }
  else
    {
      /* DWARF failed.  There isn't much of a usable frame-chain on x86-64,
         but we do need to handle two special-cases:

          (i) signal trampoline: Old kernels and older libcs don't
              export the vDSO needed to get proper unwind info for the
              trampoline.  Recognize that case by looking at the code
              and filling in things by hand.

          (ii) PLT (shared-library) call-stubs: PLT stubs are invoked
              via CALLQ.  Try this for all non-signal trampoline
              code.  */

      unw_word_t invalid_prev_rip = 0;
      unw_word_t prev_ip = c->dwarf.ip;
      unw_word_t prev_cfa = c->dwarf.cfa;
      struct dwarf_loc rbp_loc = DWARF_NULL_LOC, rsp_loc = DWARF_NULL_LOC, rip_loc = DWARF_NULL_LOC;

      /* We could get here because of missing/bad unwind information.
         Validate all addresses before dereferencing. */
      if (c->dwarf.as == unw_local_addr_space) {
          dwarf_set_validate(&c->dwarf, 1);
      }

      Debug (13, "dwarf_step() failed (ret=%d), trying frame-chain\n", ret);

      if ((ret = x86_64_os_step (c)) != 0)
        {
          if (ret < 0)
            {
              Debug (2, "returning 0\n");
              return 0;
            }
        }
      else if (unw_is_signal_frame (cursor) > 0)
        {
          ret = x86_64_handle_signal_frame(cursor);
          if (ret < 0)
            {
              Debug (2, "returning 0\n");
              return 0;
            }
        }
      else if (_is_plt_entry (&c->dwarf))
        {
          /* Like regular frame, CFA = RSP+8, RA = [CFA-8], no regs saved. */
          Debug (2, "found plt entry\n");
          c->frame_info.cfa_reg_offset = 8;
          c->frame_info.cfa_reg_rsp = -1;
          c->frame_info.frame_type = UNW_X86_64_FRAME_STANDARD;
          c->dwarf.loc[RIP] = DWARF_LOC (c->dwarf.cfa, 0);
          c->dwarf.cfa += 8;
        }
      else if (prev_ip == 0 || (DWARF_IS_NULL_LOC (c->dwarf.loc[RBP])))
        {
          Debug (2, "End of call chain detected\n");
          for (i = 0; i < DWARF_NUM_PRESERVED_REGS; ++i)
            c->dwarf.loc[i] = DWARF_NULL_LOC;
        }
      else
        {
          unw_word_t rbp;

          ret = dwarf_get (&c->dwarf, c->dwarf.loc[RBP], &rbp);
          if (ret < 0)
            {
              Debug (2, "returning %d [RBP=0x%lx]\n", ret,
                     DWARF_GET_LOC (c->dwarf.loc[RBP]));
              return ret;
            }

          unw_word_t not_used;
          invalid_prev_rip = dwarf_get (&c->dwarf,  DWARF_MEM_LOC (c->dwarf, prev_ip), &not_used);

          if (!rbp && invalid_prev_rip == 0)
            {
              /* Looks like we may have reached the end of the call-chain.  */
              rbp_loc = DWARF_NULL_LOC;
              rsp_loc = DWARF_NULL_LOC;
              rip_loc = DWARF_NULL_LOC;
            }
          else
            {
              /*
               * Check if previous RIP was invalid
               * This could happen if a bad function pointer was
               * followed and so the stack wasn't updated by the
               * preamble
               */
              int rip_fixup_success = 0;
              if (invalid_prev_rip != 0)
                {
                    Debug (2, "Previous RIP %#010lx was invalid, attempting fixup\n", prev_ip);
                    unw_word_t rsp;
                    ret = dwarf_get (&c->dwarf, c->dwarf.loc[RSP], &rsp);
                    Debug (2, "get rsp %#010lx returned %d\n", rsp, ret);

                    /*Test to see if what we think is the previous RIP is valid*/
                    unw_word_t new_ip = 0;
                    if (dwarf_get(&c->dwarf, DWARF_MEM_LOC(c->dwarf, rsp), &new_ip) == 0)
                      {
                        Debug (2, "RSP %#010lx (%#010lx) looks valid\n", rsp, new_ip);
                        if (new_ip == 0x00000000)
                          {
                            Debug (2, "End of call chain detected\n");
                            rip_fixup_success = 1;
                            rbp_loc = DWARF_NULL_LOC;
                            rsp_loc = DWARF_NULL_LOC;
                            rip_loc = DWARF_NULL_LOC;
                          }
                        else
                          {
                            if ((ret = dwarf_get(&c->dwarf, DWARF_MEM_LOC(c->dwarf, new_ip), &not_used)) == 0)
                              {
                                Debug (2, "new_ip %#010lx looks valid\n", new_ip);
                                rip_fixup_success = 1;
                                c->frame_info.cfa_reg_offset = 8;
                                c->frame_info.cfa_reg_rsp = -1;
                                c->frame_info.rbp_cfa_offset = -1;
                                c->frame_info.rsp_cfa_offset = -1;
                                c->frame_info.frame_type = UNW_X86_64_FRAME_OTHER;
                                /*
                                 * The call should have pushed RIP to the stack
                                 * and since there was no preamble RSP hasn't been
                                 * touched so RIP should be at RSP.
                                 */
                                c->dwarf.cfa += 8;
                                /* Optimised x64 binaries don't use RBP it seems? */
                                rbp_loc = c->dwarf.loc[RBP];
                                rsp_loc = DWARF_VAL_LOC (c, rsp + 8);
                                rip_loc = DWARF_LOC (rsp, 0);
                              }
                            else
                              {
                                Debug (2, "new_ip %#010lx dwarf_get(&c->dwarf, DWARF_MEM_LOC(c->dwarf, new_ip_addr), &new_ip) != 0\n", new_ip);
                              }
                          }
                      }
                    else
                      {
                        Debug (2, "rsp %#010lx dwarf_get(&c->dwarf, DWARF_MEM_LOC(c->dwarf, rsp), &new_ip_addr) != 0\n", rsp);
                      }
                  }
              /*
               * If the previous rip we found on the stack didn't look valid fall back
               * to the previous method for finding a valid stack frame
               */
              if (!rip_fixup_success)
                {
                  Debug (2, "RIP fixup didn't work, falling back\n");
                  unw_word_t rbp1 = 0;
                  rbp_loc = DWARF_LOC(rbp, 0);
                  rsp_loc = DWARF_VAL_LOC(c, rbp + 16);
                  rip_loc = DWARF_LOC (rbp + 8, 0);
                  ret = dwarf_get (&c->dwarf, rbp_loc, &rbp1);
                  Debug (1, "[RBP=0x%lx] = 0x%lx (cfa = 0x%lx) -> 0x%lx\n",
                         (unsigned long) DWARF_GET_LOC (c->dwarf.loc[RBP]),
                         rbp, c->dwarf.cfa, rbp1);

                  /* Heuristic to determine incorrect guess.  For RBP to be a
                     valid frame it needs to be above current CFA, but don't
                     let it go more than a little.  Note that we can't deduce
                     anything about new RBP (rbp1) since it may not be a frame
                     pointer in the frame above.  Just check we get the value. */
                  if (ret < 0
                      || rbp < c->dwarf.cfa
                      || (rbp - c->dwarf.cfa) > 0x4000)
                    {
                      rip_loc = DWARF_NULL_LOC;
                      rbp_loc = DWARF_NULL_LOC;
                    }

                  c->frame_info.frame_type = UNW_X86_64_FRAME_GUESSED;
                  c->frame_info.cfa_reg_rsp = 0;
                  c->frame_info.cfa_reg_offset = 16;
                  c->frame_info.rbp_cfa_offset = -16;
                  c->dwarf.cfa += 16;
                }
            }
          /* Mark all registers unsaved */
          for (i = 0; i < DWARF_NUM_PRESERVED_REGS; ++i)
            c->dwarf.loc[i] = DWARF_NULL_LOC;

          c->dwarf.loc[RBP] = rbp_loc;
          c->dwarf.loc[RSP] = rsp_loc;
          c->dwarf.loc[RIP] = rip_loc;
          c->dwarf.use_prev_instr = 1;
        }

      if (DWARF_IS_NULL_LOC (c->dwarf.loc[RBP]) && invalid_prev_rip == 0)
        {
          ret = 0;
          Debug (2, "NULL %%rbp loc, returning %d\n", ret);
          return ret;
        }
      if (!DWARF_IS_NULL_LOC (c->dwarf.loc[RIP]))
        {
          ret = dwarf_get (&c->dwarf, c->dwarf.loc[RIP], &c->dwarf.ip);
          Debug (1, "Frame Chain [RIP=0x%Lx] = 0x%Lx\n",
                     (unsigned long long) DWARF_GET_LOC (c->dwarf.loc[RIP]),
                     (unsigned long long) c->dwarf.ip);
          if (ret < 0)
            {
              Debug (2, "returning %d\n", ret);
              return ret;
            }
#if __sun
          if (c->dwarf.ip == 0)
            {
              Debug (2, "returning 0\n");
              return ret;
            }
#endif
          ret = 1;
        }
      else
        c->dwarf.ip = 0;

      if (c->dwarf.ip == prev_ip && c->dwarf.cfa == prev_cfa)
        return -UNW_EBADFRAME;
    }
  Debug (2, "returning %d\n", ret);
  return ret;
}

Coverage Report

Created: 2026-02-26 06:31

Line	Count	Source
1		/* libunwind - a platform-independent unwind library
2		Copyright (C) 2002-2004 Hewlett-Packard Co
3		Contributed by David Mosberger-Tang <davidm@hpl.hp.com>
4
5		Modified for x86_64 by Max Asbock <masbock@us.ibm.com>
6
7		This file is part of libunwind.
8
9		Permission is hereby granted, free of charge, to any person obtaining
10		a copy of this software and associated documentation files (the
11		"Software"), to deal in the Software without restriction, including
12		without limitation the rights to use, copy, modify, merge, publish,
13		distribute, sublicense, and/or sell copies of the Software, and to
14		permit persons to whom the Software is furnished to do so, subject to
15		the following conditions:
16
17		The above copyright notice and this permission notice shall be
18		included in all copies or substantial portions of the Software.
19
20		THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
21		EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
22		MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
23		NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
24		LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
25		OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
26		WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. */
27
28		#include "libunwind_i.h"
29		#include "unwind_i.h"
30		#include <signal.h>
31
32		/* Recognise PLT entries such as:
33		3bdf0: ff 25 e2 49 13 00 jmpq *0x1349e2(%rip)
34		3bdf6: 68 ae 03 00 00 pushq $0x3ae
35		3bdfb: e9 00 c5 ff ff jmpq 38300 <_init+0x18> */
36		static int
37		_is_plt_entry (struct dwarf_cursor *c)
38	0	{
39	0	unw_word_t w0, w1;
40	0	unw_accessors_t *a;
41	0	int ret;
42
43	0	a = unw_get_accessors_int (c->as);
44	0	if ((ret = (*a->access_mem) (c->as, c->ip, &w0, 0, c->as_arg)) < 0
45	0	\|\| (ret = (*a->access_mem) (c->as, c->ip + 8, &w1, 0, c->as_arg)) < 0)
46	0	return 0;
47
48	0	ret = (((w0 & 0xffff) == 0x25ff)
49	0	&& (((w0 >> 48) & 0xff) == 0x68)
50	0	&& (((w1 >> 24) & 0xff) == 0xe9));
51
52	0	Debug (14, "ip=0x%lx => 0x%016lx 0x%016lx, ret = %d\n", c->ip, w0, w1, ret);
53	0	return ret;
54	0	}
55
56		int
57		unw_is_plt_entry (unw_cursor_t *uc)
58	0	{
59	0	return _is_plt_entry (&((struct cursor *)uc)->dwarf);
60	0	}
61
62		int
63		unw_step (unw_cursor_t *cursor)
64	57.6k	{
65	57.6k	struct cursor c = (struct cursor ) cursor;
66	57.6k	int ret, i;
67
68	57.6k	#if CONSERVATIVE_CHECKS
69	57.6k	int val = 0;
70	57.6k	if (c->dwarf.as == unw_local_addr_space) {
71	57.6k	val = dwarf_get_validate(&c->dwarf);
72	57.6k	dwarf_set_validate(&c->dwarf, 1);
73	57.6k	}
74	57.6k	#endif
75
76	57.6k	Debug (1, "(cursor=%p, ip=0x%016lx, cfa=0x%016lx)\n",
77	57.6k	c, c->dwarf.ip, c->dwarf.cfa);
78
79		/* Try DWARF-based unwinding... */
80	57.6k	c->sigcontext_format = X86_64_SCF_NONE;
81	57.6k	ret = dwarf_step (&c->dwarf);
82
83	57.6k	#if CONSERVATIVE_CHECKS
84	57.6k	if (c->dwarf.as == unw_local_addr_space) {
85	57.6k	dwarf_set_validate(&c->dwarf, val);
86	57.6k	}
87	57.6k	#endif
88
89	57.6k	if (ret < 0 && ret != -UNW_ENOINFO)
90	0	{
91	0	Debug (2, "returning %d\n", ret);
92	0	return ret;
93	0	}
94
95	57.6k	c->frames++;
96
97	57.6k	if (likely (ret >= 0))
98	57.6k	{
99		/* x86_64 ABI specifies that end of call-chain is marked with a
100		NULL RBP or undefined return address */
101	57.6k	if (DWARF_IS_NULL_LOC (c->dwarf.loc[RBP]))
102	0	{
103	0	c->dwarf.ip = 0;
104	0	ret = 0;
105	0	}
106	57.6k	}
107	0	else
108	0	{
109		/* DWARF failed. There isn't much of a usable frame-chain on x86-64,
110		but we do need to handle two special-cases:
111
112		(i) signal trampoline: Old kernels and older libcs don't
113		export the vDSO needed to get proper unwind info for the
114		trampoline. Recognize that case by looking at the code
115		and filling in things by hand.
116
117		(ii) PLT (shared-library) call-stubs: PLT stubs are invoked
118		via CALLQ. Try this for all non-signal trampoline
119		code. */
120
121	0	unw_word_t invalid_prev_rip = 0;
122	0	unw_word_t prev_ip = c->dwarf.ip;
123	0	unw_word_t prev_cfa = c->dwarf.cfa;
124	0	struct dwarf_loc rbp_loc = DWARF_NULL_LOC, rsp_loc = DWARF_NULL_LOC, rip_loc = DWARF_NULL_LOC;
125
126		/* We could get here because of missing/bad unwind information.
127		Validate all addresses before dereferencing. */
128	0	if (c->dwarf.as == unw_local_addr_space) {
129	0	dwarf_set_validate(&c->dwarf, 1);
130	0	}
131
132	0	Debug (13, "dwarf_step() failed (ret=%d), trying frame-chain\n", ret);
133
134	0	if ((ret = x86_64_os_step (c)) != 0)
135	0	{
136	0	if (ret < 0)
137	0	{
138	0	Debug (2, "returning 0\n");
139	0	return 0;
140	0	}
141	0	}
142	0	else if (unw_is_signal_frame (cursor) > 0)
143	0	{
144	0	ret = x86_64_handle_signal_frame(cursor);
145	0	if (ret < 0)
146	0	{
147	0	Debug (2, "returning 0\n");
148	0	return 0;
149	0	}
150	0	}
151	0	else if (_is_plt_entry (&c->dwarf))
152	0	{
153		/* Like regular frame, CFA = RSP+8, RA = [CFA-8], no regs saved. */
154	0	Debug (2, "found plt entry\n");
155	0	c->frame_info.cfa_reg_offset = 8;
156	0	c->frame_info.cfa_reg_rsp = -1;
157	0	c->frame_info.frame_type = UNW_X86_64_FRAME_STANDARD;
158	0	c->dwarf.loc[RIP] = DWARF_LOC (c->dwarf.cfa, 0);
159	0	c->dwarf.cfa += 8;
160	0	}
161	0	else if (prev_ip == 0 \|\| (DWARF_IS_NULL_LOC (c->dwarf.loc[RBP])))
162	0	{
163	0	Debug (2, "End of call chain detected\n");
164	0	for (i = 0; i < DWARF_NUM_PRESERVED_REGS; ++i)
165	0	c->dwarf.loc[i] = DWARF_NULL_LOC;
166	0	}
167	0	else
168	0	{
169	0	unw_word_t rbp;
170
171	0	ret = dwarf_get (&c->dwarf, c->dwarf.loc[RBP], &rbp);
172	0	if (ret < 0)
173	0	{
174	0	Debug (2, "returning %d [RBP=0x%lx]\n", ret,
175	0	DWARF_GET_LOC (c->dwarf.loc[RBP]));
176	0	return ret;
177	0	}
178
179	0	unw_word_t not_used;
180	0	invalid_prev_rip = dwarf_get (&c->dwarf, DWARF_MEM_LOC (c->dwarf, prev_ip), &not_used);
181
182	0	if (!rbp && invalid_prev_rip == 0)
183	0	{
184		/* Looks like we may have reached the end of the call-chain. */
185	0	rbp_loc = DWARF_NULL_LOC;
186	0	rsp_loc = DWARF_NULL_LOC;
187	0	rip_loc = DWARF_NULL_LOC;
188	0	}
189	0	else
190	0	{
191		/*
192		* Check if previous RIP was invalid
193		* This could happen if a bad function pointer was
194		* followed and so the stack wasn't updated by the
195		* preamble
196		*/
197	0	int rip_fixup_success = 0;
198	0	if (invalid_prev_rip != 0)
199	0	{
200	0	Debug (2, "Previous RIP %#010lx was invalid, attempting fixup\n", prev_ip);
201	0	unw_word_t rsp;
202	0	ret = dwarf_get (&c->dwarf, c->dwarf.loc[RSP], &rsp);
203	0	Debug (2, "get rsp %#010lx returned %d\n", rsp, ret);
204
205		/Test to see if what we think is the previous RIP is valid/
206	0	unw_word_t new_ip = 0;
207	0	if (dwarf_get(&c->dwarf, DWARF_MEM_LOC(c->dwarf, rsp), &new_ip) == 0)
208	0	{
209	0	Debug (2, "RSP %#010lx (%#010lx) looks valid\n", rsp, new_ip);
210	0	if (new_ip == 0x00000000)
211	0	{
212	0	Debug (2, "End of call chain detected\n");
213	0	rip_fixup_success = 1;
214	0	rbp_loc = DWARF_NULL_LOC;
215	0	rsp_loc = DWARF_NULL_LOC;
216	0	rip_loc = DWARF_NULL_LOC;
217	0	}
218	0	else
219	0	{
220	0	if ((ret = dwarf_get(&c->dwarf, DWARF_MEM_LOC(c->dwarf, new_ip), &not_used)) == 0)
221	0	{
222	0	Debug (2, "new_ip %#010lx looks valid\n", new_ip);
223	0	rip_fixup_success = 1;
224	0	c->frame_info.cfa_reg_offset = 8;
225	0	c->frame_info.cfa_reg_rsp = -1;
226	0	c->frame_info.rbp_cfa_offset = -1;
227	0	c->frame_info.rsp_cfa_offset = -1;
228	0	c->frame_info.frame_type = UNW_X86_64_FRAME_OTHER;
229		/*
230		* The call should have pushed RIP to the stack
231		* and since there was no preamble RSP hasn't been
232		* touched so RIP should be at RSP.
233		*/
234	0	c->dwarf.cfa += 8;
235		/* Optimised x64 binaries don't use RBP it seems? */
236	0	rbp_loc = c->dwarf.loc[RBP];
237	0	rsp_loc = DWARF_VAL_LOC (c, rsp + 8);
238	0	rip_loc = DWARF_LOC (rsp, 0);
239	0	}
240	0	else
241	0	{
242	0	Debug (2, "new_ip %#010lx dwarf_get(&c->dwarf, DWARF_MEM_LOC(c->dwarf, new_ip_addr), &new_ip) != 0\n", new_ip);
243	0	}
244	0	}
245	0	}
246	0	else
247	0	{
248	0	Debug (2, "rsp %#010lx dwarf_get(&c->dwarf, DWARF_MEM_LOC(c->dwarf, rsp), &new_ip_addr) != 0\n", rsp);
249	0	}
250	0	}
251		/*
252		* If the previous rip we found on the stack didn't look valid fall back
253		* to the previous method for finding a valid stack frame
254		*/
255	0	if (!rip_fixup_success)
256	0	{
257	0	Debug (2, "RIP fixup didn't work, falling back\n");
258	0	unw_word_t rbp1 = 0;
259	0	rbp_loc = DWARF_LOC(rbp, 0);
260	0	rsp_loc = DWARF_VAL_LOC(c, rbp + 16);
261	0	rip_loc = DWARF_LOC (rbp + 8, 0);
262	0	ret = dwarf_get (&c->dwarf, rbp_loc, &rbp1);
263	0	Debug (1, "[RBP=0x%lx] = 0x%lx (cfa = 0x%lx) -> 0x%lx\n",
264	0	(unsigned long) DWARF_GET_LOC (c->dwarf.loc[RBP]),
265	0	rbp, c->dwarf.cfa, rbp1);
266
267		/* Heuristic to determine incorrect guess. For RBP to be a
268		valid frame it needs to be above current CFA, but don't
269		let it go more than a little. Note that we can't deduce
270		anything about new RBP (rbp1) since it may not be a frame
271		pointer in the frame above. Just check we get the value. */
272	0	if (ret < 0
273	0	\|\| rbp < c->dwarf.cfa
274	0	\|\| (rbp - c->dwarf.cfa) > 0x4000)
275	0	{
276	0	rip_loc = DWARF_NULL_LOC;
277	0	rbp_loc = DWARF_NULL_LOC;
278	0	}
279
280	0	c->frame_info.frame_type = UNW_X86_64_FRAME_GUESSED;
281	0	c->frame_info.cfa_reg_rsp = 0;
282	0	c->frame_info.cfa_reg_offset = 16;
283	0	c->frame_info.rbp_cfa_offset = -16;
284	0	c->dwarf.cfa += 16;
285	0	}
286	0	}
287		/* Mark all registers unsaved */
288	0	for (i = 0; i < DWARF_NUM_PRESERVED_REGS; ++i)
289	0	c->dwarf.loc[i] = DWARF_NULL_LOC;
290
291	0	c->dwarf.loc[RBP] = rbp_loc;
292	0	c->dwarf.loc[RSP] = rsp_loc;
293	0	c->dwarf.loc[RIP] = rip_loc;
294	0	c->dwarf.use_prev_instr = 1;
295	0	}
296
297	0	if (DWARF_IS_NULL_LOC (c->dwarf.loc[RBP]) && invalid_prev_rip == 0)
298	0	{
299	0	ret = 0;
300	0	Debug (2, "NULL %%rbp loc, returning %d\n", ret);
301	0	return ret;
302	0	}
303	0	if (!DWARF_IS_NULL_LOC (c->dwarf.loc[RIP]))
304	0	{
305	0	ret = dwarf_get (&c->dwarf, c->dwarf.loc[RIP], &c->dwarf.ip);
306	0	Debug (1, "Frame Chain [RIP=0x%Lx] = 0x%Lx\n",
307	0	(unsigned long long) DWARF_GET_LOC (c->dwarf.loc[RIP]),
308	0	(unsigned long long) c->dwarf.ip);
309	0	if (ret < 0)
310	0	{
311	0	Debug (2, "returning %d\n", ret);
312	0	return ret;
313	0	}
314		#if __sun
315		if (c->dwarf.ip == 0)
316		{
317		Debug (2, "returning 0\n");
318		return ret;
319		}
320		#endif
321	0	ret = 1;
322	0	}
323	0	else
324	0	c->dwarf.ip = 0;
325
326	0	if (c->dwarf.ip == prev_ip && c->dwarf.cfa == prev_cfa)
327	0	return -UNW_EBADFRAME;
328	0	}
329	57.6k	Debug (2, "returning %d\n", ret);
330	57.6k	return ret;
331	57.6k	}