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4509adb853
When JITs generate code without unwind information, it may be possible to continue unwinding via RBP chaining. However, we currently disallow RBP==RSP condition even though we can make forward progress. Relax the check a bit in the code where we switch from one type of unwinding to another to handle this situation. JIT authors are encouraged to use the dynamic unwind info registration API when the underlying platform supports it. Signed-off-by: Kevin Modzelewski <kmod@dropbox.com>
229 lines
6.7 KiB
C
229 lines
6.7 KiB
C
/* libunwind - a platform-independent unwind library
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Copyright (C) 2002-2004 Hewlett-Packard Co
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Contributed by David Mosberger-Tang <davidm@hpl.hp.com>
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Modified for x86_64 by Max Asbock <masbock@us.ibm.com>
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This file is part of libunwind.
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Permission is hereby granted, free of charge, to any person obtaining
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a copy of this software and associated documentation files (the
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"Software"), to deal in the Software without restriction, including
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without limitation the rights to use, copy, modify, merge, publish,
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distribute, sublicense, and/or sell copies of the Software, and to
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permit persons to whom the Software is furnished to do so, subject to
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the following conditions:
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The above copyright notice and this permission notice shall be
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included in all copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
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LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
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OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
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WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. */
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#include "unwind_i.h"
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#include <signal.h>
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/* Recognise PLT entries such as:
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3bdf0: ff 25 e2 49 13 00 jmpq *0x1349e2(%rip)
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3bdf6: 68 ae 03 00 00 pushq $0x3ae
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3bdfb: e9 00 c5 ff ff jmpq 38300 <_init+0x18> */
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static int
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is_plt_entry (struct dwarf_cursor *c)
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{
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unw_word_t w0, w1;
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unw_accessors_t *a;
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int ret;
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a = unw_get_accessors (c->as);
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if ((ret = (*a->access_mem) (c->as, c->ip, &w0, 0, c->as_arg)) < 0
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|| (ret = (*a->access_mem) (c->as, c->ip + 8, &w1, 0, c->as_arg)) < 0)
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return 0;
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ret = (((w0 & 0xffff) == 0x25ff)
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&& (((w0 >> 48) & 0xff) == 0x68)
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&& (((w1 >> 24) & 0xff) == 0xe9));
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Debug (14, "ip=0x%lx => 0x%016lx 0x%016lx, ret = %d\n", c->ip, w0, w1, ret);
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return ret;
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}
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PROTECTED int
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unw_step (unw_cursor_t *cursor)
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{
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struct cursor *c = (struct cursor *) cursor;
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int ret, i;
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#if CONSERVATIVE_CHECKS
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int val = c->validate;
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c->validate = 1;
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#endif
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Debug (1, "(cursor=%p, ip=0x%016lx, cfa=0x%016lx)\n",
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c, c->dwarf.ip, c->dwarf.cfa);
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/* Try DWARF-based unwinding... */
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c->sigcontext_format = X86_64_SCF_NONE;
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ret = dwarf_step (&c->dwarf);
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#if CONSERVATIVE_CHECKS
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c->validate = val;
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#endif
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if (ret < 0 && ret != -UNW_ENOINFO)
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{
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Debug (2, "returning %d\n", ret);
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return ret;
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}
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if (likely (ret >= 0))
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{
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/* x86_64 ABI specifies that end of call-chain is marked with a
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NULL RBP. */
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if (DWARF_IS_NULL_LOC (c->dwarf.loc[RBP]))
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{
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c->dwarf.ip = 0;
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ret = 0;
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}
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}
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else
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{
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/* DWARF failed. There isn't much of a usable frame-chain on x86-64,
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but we do need to handle two special-cases:
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(i) signal trampoline: Old kernels and older libcs don't
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export the vDSO needed to get proper unwind info for the
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trampoline. Recognize that case by looking at the code
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and filling in things by hand.
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(ii) PLT (shared-library) call-stubs: PLT stubs are invoked
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via CALLQ. Try this for all non-signal trampoline
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code. */
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unw_word_t prev_ip = c->dwarf.ip, prev_cfa = c->dwarf.cfa;
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struct dwarf_loc rbp_loc, rsp_loc, rip_loc;
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/* We could get here because of missing/bad unwind information.
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Validate all addresses before dereferencing. */
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c->validate = 1;
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Debug (13, "dwarf_step() failed (ret=%d), trying frame-chain\n", ret);
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if (unw_is_signal_frame (cursor))
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{
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ret = unw_handle_signal_frame(cursor);
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if (ret < 0)
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{
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Debug (2, "returning 0\n");
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return 0;
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}
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}
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else if (is_plt_entry (&c->dwarf))
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{
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/* Like regular frame, CFA = RSP+8, RA = [CFA-8], no regs saved. */
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Debug (2, "found plt entry\n");
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c->frame_info.cfa_reg_offset = 8;
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c->frame_info.cfa_reg_rsp = -1;
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c->frame_info.frame_type = UNW_X86_64_FRAME_STANDARD;
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c->dwarf.loc[RIP] = DWARF_LOC (c->dwarf.cfa, 0);
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c->dwarf.cfa += 8;
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}
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else if (DWARF_IS_NULL_LOC (c->dwarf.loc[RBP]))
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{
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for (i = 0; i < DWARF_NUM_PRESERVED_REGS; ++i)
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c->dwarf.loc[i] = DWARF_NULL_LOC;
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}
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else
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{
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unw_word_t rbp;
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ret = dwarf_get (&c->dwarf, c->dwarf.loc[RBP], &rbp);
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if (ret < 0)
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{
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Debug (2, "returning %d [RBP=0x%lx]\n", ret,
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DWARF_GET_LOC (c->dwarf.loc[RBP]));
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return ret;
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}
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if (!rbp)
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{
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/* Looks like we may have reached the end of the call-chain. */
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rbp_loc = DWARF_NULL_LOC;
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rsp_loc = DWARF_NULL_LOC;
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rip_loc = DWARF_NULL_LOC;
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}
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else
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{
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unw_word_t rbp1 = 0;
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rbp_loc = DWARF_LOC(rbp, 0);
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rsp_loc = DWARF_NULL_LOC;
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rip_loc = DWARF_LOC (rbp + 8, 0);
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ret = dwarf_get (&c->dwarf, rbp_loc, &rbp1);
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Debug (1, "[RBP=0x%lx] = 0x%lx (cfa = 0x%lx) -> 0x%lx\n",
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(unsigned long) DWARF_GET_LOC (c->dwarf.loc[RBP]),
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rbp, c->dwarf.cfa, rbp1);
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/* Heuristic to determine incorrect guess. For RBP to be a
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valid frame it needs to be above current CFA, but don't
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let it go more than a little. Note that we can't deduce
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anything about new RBP (rbp1) since it may not be a frame
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pointer in the frame above. Just check we get the value. */
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if (ret < 0
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|| rbp < c->dwarf.cfa
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|| (rbp - c->dwarf.cfa) > 0x4000)
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{
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rip_loc = DWARF_NULL_LOC;
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rbp_loc = DWARF_NULL_LOC;
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}
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c->frame_info.frame_type = UNW_X86_64_FRAME_GUESSED;
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c->frame_info.cfa_reg_rsp = 0;
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c->frame_info.cfa_reg_offset = 16;
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c->frame_info.rbp_cfa_offset = -16;
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c->dwarf.cfa += 16;
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}
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/* Mark all registers unsaved */
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for (i = 0; i < DWARF_NUM_PRESERVED_REGS; ++i)
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c->dwarf.loc[i] = DWARF_NULL_LOC;
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c->dwarf.loc[RBP] = rbp_loc;
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c->dwarf.loc[RSP] = rsp_loc;
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c->dwarf.loc[RIP] = rip_loc;
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}
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c->dwarf.ret_addr_column = RIP;
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if (DWARF_IS_NULL_LOC (c->dwarf.loc[RBP]))
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{
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ret = 0;
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Debug (2, "NULL %%rbp loc, returning %d\n", ret);
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return ret;
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}
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if (!DWARF_IS_NULL_LOC (c->dwarf.loc[RIP]))
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{
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ret = dwarf_get (&c->dwarf, c->dwarf.loc[RIP], &c->dwarf.ip);
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Debug (1, "Frame Chain [RIP=0x%Lx] = 0x%Lx\n",
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(unsigned long long) DWARF_GET_LOC (c->dwarf.loc[RIP]),
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(unsigned long long) c->dwarf.ip);
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if (ret < 0)
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{
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Debug (2, "returning %d\n", ret);
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return ret;
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}
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ret = 1;
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}
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else
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c->dwarf.ip = 0;
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if (c->dwarf.ip == prev_ip && c->dwarf.cfa == prev_cfa)
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return -UNW_EBADFRAME;
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}
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Debug (2, "returning %d\n", ret);
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return ret;
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}
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