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 This file is part of libunwind. 6 7 Permission is hereby granted, free of charge, to any person obtaining 8 a copy of this software and associated documentation files (the 9 "Software"), to deal in the Software without restriction, including 10 without limitation the rights to use, copy, modify, merge, publish, 11 distribute, sublicense, and/or sell copies of the Software, and to 12 permit persons to whom the Software is furnished to do so, subject to 13 the following conditions: 14 15 The above copyright notice and this permission notice shall be 16 included in all copies or substantial portions of the Software. 17 18 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 19 EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF 20 MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 21 NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE 22 LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION 23 OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION 24 WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. */ 25 26 #include "unwind_i.h" 27 #include "offsets.h" 28 29 PROTECTED int 30 unw_step (unw_cursor_t *cursor) 31 { 32 struct cursor *c = (struct cursor *) cursor; 33 int ret, i; 34 35 Debug (1, "(cursor=%p, ip=0x%08x)\n", c, (unsigned) c->dwarf.ip); 36 37 /* ANDROID support update. */ 38 /* Save the current ip/cfa to prevent looping if the decode yields 39 the same ip/cfa as before. */ 40 unw_word_t old_ip = c->dwarf.ip; 41 unw_word_t old_cfa = c->dwarf.cfa; 42 /* End of ANDROID update. */ 43 44 /* Try DWARF-based unwinding... */ 45 ret = dwarf_step (&c->dwarf); 46 47 #if !defined(UNW_LOCAL_ONLY) 48 /* Do not use this method on a local unwind. There is a very high 49 * probability this method will try to access unmapped memory, which 50 * will crash the process. Since this almost never actually works, 51 * it should be okay to skip. 52 */ 53 if (ret < 0) 54 { 55 /* DWARF failed, let's see if we can follow the frame-chain 56 or skip over the signal trampoline. */ 57 struct dwarf_loc ebp_loc, eip_loc; 58 59 /* We could get here because of missing/bad unwind information. 60 Validate all addresses before dereferencing. */ 61 c->validate = 1; 62 63 Debug (13, "dwarf_step() failed (ret=%d), trying frame-chain\n", ret); 64 65 if (unw_is_signal_frame (cursor)) 66 { 67 ret = unw_handle_signal_frame(cursor); 68 if (ret < 0) 69 { 70 Debug (2, "returning 0\n"); 71 return 0; 72 } 73 } 74 else 75 { 76 ret = dwarf_get (&c->dwarf, c->dwarf.loc[EBP], &c->dwarf.cfa); 77 if (ret < 0) 78 { 79 Debug (2, "returning %d\n", ret); 80 return ret; 81 } 82 83 Debug (13, "[EBP=0x%x] = 0x%x\n", DWARF_GET_LOC (c->dwarf.loc[EBP]), 84 c->dwarf.cfa); 85 86 ebp_loc = DWARF_LOC (c->dwarf.cfa, 0); 87 eip_loc = DWARF_LOC (c->dwarf.cfa + 4, 0); 88 c->dwarf.cfa += 8; 89 90 /* Mark all registers unsaved, since we don't know where 91 they are saved (if at all), except for the EBP and 92 EIP. */ 93 for (i = 0; i < DWARF_NUM_PRESERVED_REGS; ++i) 94 c->dwarf.loc[i] = DWARF_NULL_LOC; 95 96 c->dwarf.loc[EBP] = ebp_loc; 97 c->dwarf.loc[EIP] = eip_loc; 98 } 99 c->dwarf.ret_addr_column = EIP; 100 101 if (!DWARF_IS_NULL_LOC (c->dwarf.loc[EBP])) 102 { 103 ret = dwarf_get (&c->dwarf, c->dwarf.loc[EIP], &c->dwarf.ip); 104 if (ret < 0) 105 { 106 Debug (13, "dwarf_get([EIP=0x%x]) failed\n", DWARF_GET_LOC (c->dwarf.loc[EIP])); 107 Debug (2, "returning %d\n", ret); 108 return ret; 109 } 110 else 111 { 112 Debug (13, "[EIP=0x%x] = 0x%x\n", DWARF_GET_LOC (c->dwarf.loc[EIP]), 113 c->dwarf.ip); 114 } 115 } 116 else 117 c->dwarf.ip = 0; 118 } 119 #endif 120 121 /* ANDROID support update. */ 122 if (ret >= 0) 123 { 124 if (c->dwarf.ip) 125 { 126 /* Adjust the pc to the instruction before. */ 127 c->dwarf.ip--; 128 } 129 /* If the decode yields the exact same ip/cfa as before, then indicate 130 the unwind is complete. */ 131 if (old_ip == c->dwarf.ip && old_cfa == c->dwarf.cfa) 132 { 133 Dprintf ("%s: ip and cfa unchanged; stopping here (ip=0x%lx)\n", 134 __FUNCTION__, (long) c->dwarf.ip); 135 return -UNW_EBADFRAME; 136 } 137 c->dwarf.frame++; 138 } 139 /* End of ANDROID update. */ 140 if (unlikely (ret <= 0)) 141 return 0; 142 143 return (c->dwarf.ip == 0) ? 0 : 1; 144 } 145
