1 /* libunwind - a platform-independent unwind library 2 Copyright (C) 2002-2004 Hewlett-Packard Co 3 Contributed by David Mosberger-Tang <davidm (at) hpl.hp.com> 4 5 Modified for x86_64 by Max Asbock <masbock (at) 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 "unwind_i.h" 29 #include <signal.h> 30 31 /* Recognise PLT entries such as: 32 3bdf0: ff 25 e2 49 13 00 jmpq *0x1349e2(%rip) 33 3bdf6: 68 ae 03 00 00 pushq $0x3ae 34 3bdfb: e9 00 c5 ff ff jmpq 38300 <_init+0x18> */ 35 static int 36 is_plt_entry (struct dwarf_cursor *c) 37 { 38 unw_word_t w0, w1; 39 unw_accessors_t *a; 40 int ret; 41 42 a = unw_get_accessors (c->as); 43 if ((ret = (*a->access_mem) (c->as, c->ip, &w0, 0, c->as_arg)) < 0 44 || (ret = (*a->access_mem) (c->as, c->ip + 8, &w1, 0, c->as_arg)) < 0) 45 return 0; 46 47 ret = (((w0 & 0xffff) == 0x25ff) 48 && (((w0 >> 48) & 0xff) == 0x68) 49 && (((w1 >> 24) & 0xff) == 0xe9)); 50 51 Debug (14, "ip=0x%lx => 0x%016lx 0x%016lx, ret = %d\n", c->ip, w0, w1, ret); 52 return ret; 53 } 54 55 PROTECTED int 56 unw_step (unw_cursor_t *cursor) 57 { 58 struct cursor *c = (struct cursor *) cursor; 59 int ret, i; 60 61 #if CONSERVATIVE_CHECKS 62 int val = c->validate; 63 c->validate = 1; 64 #endif 65 66 Debug (1, "(cursor=%p, ip=0x%016lx, cfa=0x%016lx)\n", 67 c, c->dwarf.ip, c->dwarf.cfa); 68 69 unw_word_t old_ip = c->dwarf.ip; 70 unw_word_t old_cfa = c->dwarf.cfa; 71 72 /* Try DWARF-based unwinding... */ 73 c->sigcontext_format = X86_64_SCF_NONE; 74 ret = dwarf_step (&c->dwarf); 75 76 #if CONSERVATIVE_CHECKS 77 c->validate = val; 78 #endif 79 80 if (ret < 0 && ret != -UNW_ENOINFO) 81 { 82 Debug (2, "returning %d\n", ret); 83 return ret; 84 } 85 86 if (likely (ret >= 0)) 87 { 88 /* x86_64 ABI specifies that end of call-chain is marked with a 89 NULL RBP. */ 90 if (DWARF_IS_NULL_LOC (c->dwarf.loc[RBP])) 91 { 92 c->dwarf.ip = 0; 93 ret = 0; 94 } 95 } 96 else 97 { 98 /* DWARF failed. There isn't much of a usable frame-chain on x86-64, 99 but we do need to handle two special-cases: 100 101 (i) signal trampoline: Old kernels and older libcs don't 102 export the vDSO needed to get proper unwind info for the 103 trampoline. Recognize that case by looking at the code 104 and filling in things by hand. 105 106 (ii) PLT (shared-library) call-stubs: PLT stubs are invoked 107 via CALLQ. Try this for all non-signal trampoline 108 code. */ 109 110 unw_word_t prev_ip = c->dwarf.ip, prev_cfa = c->dwarf.cfa; 111 struct dwarf_loc rbp_loc, rsp_loc, rip_loc; 112 113 /* We could get here because of missing/bad unwind information. 114 Validate all addresses before dereferencing. */ 115 c->validate = 1; 116 117 Debug (13, "dwarf_step() failed (ret=%d), trying frame-chain\n", ret); 118 119 if (unw_is_signal_frame (cursor)) 120 { 121 ret = unw_handle_signal_frame(cursor); 122 if (ret < 0) 123 { 124 Debug (2, "returning 0\n"); 125 return 0; 126 } 127 } 128 else if (is_plt_entry (&c->dwarf)) 129 { 130 /* Like regular frame, CFA = RSP+8, RA = [CFA-8], no regs saved. */ 131 Debug (2, "found plt entry\n"); 132 c->frame_info.cfa_reg_offset = 8; 133 c->frame_info.cfa_reg_rsp = -1; 134 c->frame_info.frame_type = UNW_X86_64_FRAME_STANDARD; 135 c->dwarf.loc[RIP] = DWARF_LOC (c->dwarf.cfa, 0); 136 c->dwarf.cfa += 8; 137 } 138 else if (DWARF_IS_NULL_LOC (c->dwarf.loc[RBP])) 139 { 140 for (i = 0; i < DWARF_NUM_PRESERVED_REGS; ++i) 141 c->dwarf.loc[i] = DWARF_NULL_LOC; 142 } 143 else 144 { 145 unw_word_t rbp; 146 147 ret = dwarf_get (&c->dwarf, c->dwarf.loc[RBP], &rbp); 148 if (ret < 0) 149 { 150 Debug (2, "returning %d [RBP=0x%lx]\n", ret, 151 DWARF_GET_LOC (c->dwarf.loc[RBP])); 152 return ret; 153 } 154 155 if (!rbp) 156 { 157 /* Looks like we may have reached the end of the call-chain. */ 158 rbp_loc = DWARF_NULL_LOC; 159 rsp_loc = DWARF_NULL_LOC; 160 rip_loc = DWARF_NULL_LOC; 161 } 162 else 163 { 164 unw_word_t rbp1 = 0; 165 rbp_loc = DWARF_LOC(rbp, 0); 166 rsp_loc = DWARF_NULL_LOC; 167 rip_loc = DWARF_LOC (rbp + 8, 0); 168 ret = dwarf_get (&c->dwarf, rbp_loc, &rbp1); 169 Debug (1, "[RBP=0x%lx] = 0x%lx (cfa = 0x%lx) -> 0x%lx\n", 170 (unsigned long) DWARF_GET_LOC (c->dwarf.loc[RBP]), 171 rbp, c->dwarf.cfa, rbp1); 172 173 /* Heuristic to determine incorrect guess. For RBP to be a 174 valid frame it needs to be above current CFA, but don't 175 let it go more than a little. Note that we can't deduce 176 anything about new RBP (rbp1) since it may not be a frame 177 pointer in the frame above. Just check we get the value. */ 178 if (ret < 0 179 || rbp <= c->dwarf.cfa 180 || (rbp - c->dwarf.cfa) > 0x4000) 181 { 182 rip_loc = DWARF_NULL_LOC; 183 rbp_loc = DWARF_NULL_LOC; 184 } 185 186 c->frame_info.frame_type = UNW_X86_64_FRAME_GUESSED; 187 c->frame_info.cfa_reg_rsp = 0; 188 c->frame_info.cfa_reg_offset = 16; 189 c->frame_info.rbp_cfa_offset = -16; 190 c->dwarf.cfa += 16; 191 } 192 193 /* Mark all registers unsaved */ 194 for (i = 0; i < DWARF_NUM_PRESERVED_REGS; ++i) 195 c->dwarf.loc[i] = DWARF_NULL_LOC; 196 197 c->dwarf.loc[RBP] = rbp_loc; 198 c->dwarf.loc[RSP] = rsp_loc; 199 c->dwarf.loc[RIP] = rip_loc; 200 } 201 202 c->dwarf.ret_addr_column = RIP; 203 204 if (DWARF_IS_NULL_LOC (c->dwarf.loc[RBP])) 205 { 206 ret = 0; 207 Debug (2, "NULL %%rbp loc, returning %d\n", ret); 208 return ret; 209 } 210 if (!DWARF_IS_NULL_LOC (c->dwarf.loc[RIP])) 211 { 212 ret = dwarf_get (&c->dwarf, c->dwarf.loc[RIP], &c->dwarf.ip); 213 Debug (1, "Frame Chain [RIP=0x%Lx] = 0x%Lx\n", 214 (unsigned long long) DWARF_GET_LOC (c->dwarf.loc[RIP]), 215 (unsigned long long) c->dwarf.ip); 216 if (ret < 0) 217 { 218 Debug (2, "returning %d\n", ret); 219 return ret; 220 } 221 ret = 1; 222 } 223 else 224 c->dwarf.ip = 0; 225 226 if (c->dwarf.ip == prev_ip && c->dwarf.cfa == prev_cfa) 227 return -UNW_EBADFRAME; 228 } 229 /* ANDROID support update. */ 230 /* Adjust the pc to the instruction before. */ 231 if (c->dwarf.ip) 232 c->dwarf.ip--; 233 /* If the decode yields the exact same ip/cfa as before, then indicate 234 the unwind is complete. */ 235 if (c->dwarf.ip == old_ip && c->dwarf.cfa == old_cfa) 236 { 237 Dprintf ("%s: ip and cfa unchanged; stopping here (ip=0x%lx)\n", 238 __FUNCTION__, (long) c->dwarf.ip); 239 return -UNW_EBADFRAME; 240 } 241 /* End of ANDROID update. */ 242 Debug (2, "returning %d\n", ret); 243 return ret; 244 } 245
