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- /* 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 "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 (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;
- }
- PROTECTED int
- unw_step (unw_cursor_t *cursor)
- {
- struct cursor *c = (struct cursor *) cursor;
- int ret, i;
- #if CONSERVATIVE_CHECKS
- int val = c->validate;
- c->validate = 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
- c->validate = val;
- #endif
- if (ret < 0 && ret != -UNW_ENOINFO)
- {
- Debug (2, "returning %d\n", ret);
- return ret;
- }
- if (likely (ret >= 0))
- {
- /* x86_64 ABI specifies that end of call-chain is marked with a
- NULL RBP. */
- 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 prev_ip = c->dwarf.ip, prev_cfa = c->dwarf.cfa;
- struct dwarf_loc rbp_loc, rsp_loc, rip_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))
- {
- ret = unw_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 (DWARF_IS_NULL_LOC (c->dwarf.loc[RBP]))
- {
- 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;
- }
- if (!rbp)
- {
- /* 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
- {
- unw_word_t rbp1 = 0;
- rbp_loc = DWARF_LOC(rbp, 0);
- rsp_loc = DWARF_NULL_LOC;
- 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.ret_addr_column = RIP;
- 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;
- }
- 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;
- }
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