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29 | |
30 | // stackwalker_arm.cc: arm-specific stackwalker. |
31 | // |
32 | // See stackwalker_arm.h for documentation. |
33 | // |
34 | // Author: Mark Mentovai, Ted Mielczarek, Jim Blandy |
35 | |
36 | #include <vector> |
37 | |
38 | #include "common/scoped_ptr.h" |
39 | #include "google_breakpad/processor/call_stack.h" |
40 | #include "google_breakpad/processor/memory_region.h" |
41 | #include "google_breakpad/processor/source_line_resolver_interface.h" |
42 | #include "google_breakpad/processor/stack_frame_cpu.h" |
43 | #include "google_breakpad/processor/system_info.h" |
44 | #include "processor/cfi_frame_info.h" |
45 | #include "processor/logging.h" |
46 | #include "processor/stackwalker_arm.h" |
47 | |
48 | namespace google_breakpad { |
49 | |
50 | |
51 | StackwalkerARM::StackwalkerARM(const SystemInfo* system_info, |
52 | const MDRawContextARM* context, |
53 | int fp_register, |
54 | MemoryRegion* memory, |
55 | const CodeModules* modules, |
56 | StackFrameSymbolizer* resolver_helper) |
57 | : Stackwalker(system_info, memory, modules, resolver_helper), |
58 | context_(context), fp_register_(fp_register), |
59 | context_frame_validity_(StackFrameARM::CONTEXT_VALID_ALL) { } |
60 | |
61 | |
62 | StackFrame* StackwalkerARM::GetContextFrame() { |
63 | if (!context_) { |
64 | BPLOG(ERROR) << "Can't get context frame without context" ; |
65 | return NULL; |
66 | } |
67 | |
68 | StackFrameARM* frame = new StackFrameARM(); |
69 | |
70 | // The instruction pointer is stored directly in a register (r15), so pull it |
71 | // straight out of the CPU context structure. |
72 | frame->context = *context_; |
73 | frame->context_validity = context_frame_validity_; |
74 | frame->trust = StackFrame::FRAME_TRUST_CONTEXT; |
75 | frame->instruction = frame->context.iregs[MD_CONTEXT_ARM_REG_PC]; |
76 | |
77 | return frame; |
78 | } |
79 | |
80 | StackFrameARM* StackwalkerARM::GetCallerByCFIFrameInfo( |
81 | const vector<StackFrame*>& frames, |
82 | CFIFrameInfo* cfi_frame_info) { |
83 | StackFrameARM* last_frame = static_cast<StackFrameARM*>(frames.back()); |
84 | |
85 | static const char* register_names[] = { |
86 | "r0" , "r1" , "r2" , "r3" , "r4" , "r5" , "r6" , "r7" , |
87 | "r8" , "r9" , "r10" , "r11" , "r12" , "sp" , "lr" , "pc" , |
88 | "f0" , "f1" , "f2" , "f3" , "f4" , "f5" , "f6" , "f7" , |
89 | "fps" , "cpsr" , |
90 | NULL |
91 | }; |
92 | |
93 | // Populate a dictionary with the valid register values in last_frame. |
94 | CFIFrameInfo::RegisterValueMap<uint32_t> callee_registers; |
95 | for (int i = 0; register_names[i]; i++) |
96 | if (last_frame->context_validity & StackFrameARM::RegisterValidFlag(i)) |
97 | callee_registers[register_names[i]] = last_frame->context.iregs[i]; |
98 | |
99 | // Use the STACK CFI data to recover the caller's register values. |
100 | CFIFrameInfo::RegisterValueMap<uint32_t> caller_registers; |
101 | if (!cfi_frame_info->FindCallerRegs(callee_registers, *memory_, |
102 | &caller_registers)) |
103 | return NULL; |
104 | |
105 | // Construct a new stack frame given the values the CFI recovered. |
106 | scoped_ptr<StackFrameARM> frame(new StackFrameARM()); |
107 | for (int i = 0; register_names[i]; i++) { |
108 | CFIFrameInfo::RegisterValueMap<uint32_t>::iterator entry = |
109 | caller_registers.find(register_names[i]); |
110 | if (entry != caller_registers.end()) { |
111 | // We recovered the value of this register; fill the context with the |
112 | // value from caller_registers. |
113 | frame->context_validity |= StackFrameARM::RegisterValidFlag(i); |
114 | frame->context.iregs[i] = entry->second; |
115 | } else if (4 <= i && i <= 11 && (last_frame->context_validity & |
116 | StackFrameARM::RegisterValidFlag(i))) { |
117 | // If the STACK CFI data doesn't mention some callee-saves register, and |
118 | // it is valid in the callee, assume the callee has not yet changed it. |
119 | // Registers r4 through r11 are callee-saves, according to the Procedure |
120 | // Call Standard for the ARM Architecture, which the Linux ABI follows. |
121 | frame->context_validity |= StackFrameARM::RegisterValidFlag(i); |
122 | frame->context.iregs[i] = last_frame->context.iregs[i]; |
123 | } |
124 | } |
125 | // If the CFI doesn't recover the PC explicitly, then use .ra. |
126 | if (!(frame->context_validity & StackFrameARM::CONTEXT_VALID_PC)) { |
127 | CFIFrameInfo::RegisterValueMap<uint32_t>::iterator entry = |
128 | caller_registers.find(".ra" ); |
129 | if (entry != caller_registers.end()) { |
130 | if (fp_register_ == -1) { |
131 | frame->context_validity |= StackFrameARM::CONTEXT_VALID_PC; |
132 | frame->context.iregs[MD_CONTEXT_ARM_REG_PC] = entry->second; |
133 | } else { |
134 | // The CFI updated the link register and not the program counter. |
135 | // Handle getting the program counter from the link register. |
136 | frame->context_validity |= StackFrameARM::CONTEXT_VALID_PC; |
137 | frame->context_validity |= StackFrameARM::CONTEXT_VALID_LR; |
138 | frame->context.iregs[MD_CONTEXT_ARM_REG_LR] = entry->second; |
139 | frame->context.iregs[MD_CONTEXT_ARM_REG_PC] = |
140 | last_frame->context.iregs[MD_CONTEXT_ARM_REG_LR]; |
141 | } |
142 | } |
143 | } |
144 | // If the CFI doesn't recover the SP explicitly, then use .cfa. |
145 | if (!(frame->context_validity & StackFrameARM::CONTEXT_VALID_SP)) { |
146 | CFIFrameInfo::RegisterValueMap<uint32_t>::iterator entry = |
147 | caller_registers.find(".cfa" ); |
148 | if (entry != caller_registers.end()) { |
149 | frame->context_validity |= StackFrameARM::CONTEXT_VALID_SP; |
150 | frame->context.iregs[MD_CONTEXT_ARM_REG_SP] = entry->second; |
151 | } |
152 | } |
153 | |
154 | // If we didn't recover the PC and the SP, then the frame isn't very useful. |
155 | static const int essentials = (StackFrameARM::CONTEXT_VALID_SP |
156 | | StackFrameARM::CONTEXT_VALID_PC); |
157 | if ((frame->context_validity & essentials) != essentials) |
158 | return NULL; |
159 | |
160 | frame->trust = StackFrame::FRAME_TRUST_CFI; |
161 | return frame.release(); |
162 | } |
163 | |
164 | StackFrameARM* StackwalkerARM::GetCallerByStackScan( |
165 | const vector<StackFrame*>& frames) { |
166 | StackFrameARM* last_frame = static_cast<StackFrameARM*>(frames.back()); |
167 | uint32_t last_sp = last_frame->context.iregs[MD_CONTEXT_ARM_REG_SP]; |
168 | uint32_t caller_sp, caller_pc; |
169 | |
170 | if (!ScanForReturnAddress(last_sp, &caller_sp, &caller_pc, |
171 | frames.size() == 1 /* is_context_frame */)) { |
172 | // No plausible return address was found. |
173 | return NULL; |
174 | } |
175 | |
176 | // ScanForReturnAddress found a reasonable return address. Advance |
177 | // %sp to the location above the one where the return address was |
178 | // found. |
179 | caller_sp += 4; |
180 | |
181 | // Create a new stack frame (ownership will be transferred to the caller) |
182 | // and fill it in. |
183 | StackFrameARM* frame = new StackFrameARM(); |
184 | |
185 | frame->trust = StackFrame::FRAME_TRUST_SCAN; |
186 | frame->context = last_frame->context; |
187 | frame->context.iregs[MD_CONTEXT_ARM_REG_PC] = caller_pc; |
188 | frame->context.iregs[MD_CONTEXT_ARM_REG_SP] = caller_sp; |
189 | frame->context_validity = StackFrameARM::CONTEXT_VALID_PC | |
190 | StackFrameARM::CONTEXT_VALID_SP; |
191 | |
192 | return frame; |
193 | } |
194 | |
195 | StackFrameARM* StackwalkerARM::GetCallerByFramePointer( |
196 | const vector<StackFrame*>& frames) { |
197 | StackFrameARM* last_frame = static_cast<StackFrameARM*>(frames.back()); |
198 | |
199 | if (!(last_frame->context_validity & |
200 | StackFrameARM::RegisterValidFlag(fp_register_))) { |
201 | return NULL; |
202 | } |
203 | |
204 | uint32_t last_fp = last_frame->context.iregs[fp_register_]; |
205 | |
206 | uint32_t caller_fp = 0; |
207 | if (last_fp && !memory_->GetMemoryAtAddress(last_fp, &caller_fp)) { |
208 | BPLOG(ERROR) << "Unable to read caller_fp from last_fp: 0x" |
209 | << std::hex << last_fp; |
210 | return NULL; |
211 | } |
212 | |
213 | uint32_t caller_lr = 0; |
214 | if (last_fp && !memory_->GetMemoryAtAddress(last_fp + 4, &caller_lr)) { |
215 | BPLOG(ERROR) << "Unable to read caller_lr from last_fp + 4: 0x" |
216 | << std::hex << (last_fp + 4); |
217 | return NULL; |
218 | } |
219 | |
220 | uint32_t caller_sp = last_fp ? last_fp + 8 : |
221 | last_frame->context.iregs[MD_CONTEXT_ARM_REG_SP]; |
222 | |
223 | // Create a new stack frame (ownership will be transferred to the caller) |
224 | // and fill it in. |
225 | StackFrameARM* frame = new StackFrameARM(); |
226 | |
227 | frame->trust = StackFrame::FRAME_TRUST_FP; |
228 | frame->context = last_frame->context; |
229 | frame->context.iregs[fp_register_] = caller_fp; |
230 | frame->context.iregs[MD_CONTEXT_ARM_REG_SP] = caller_sp; |
231 | frame->context.iregs[MD_CONTEXT_ARM_REG_PC] = |
232 | last_frame->context.iregs[MD_CONTEXT_ARM_REG_LR]; |
233 | frame->context.iregs[MD_CONTEXT_ARM_REG_LR] = caller_lr; |
234 | frame->context_validity = StackFrameARM::CONTEXT_VALID_PC | |
235 | StackFrameARM::CONTEXT_VALID_LR | |
236 | StackFrameARM::RegisterValidFlag(fp_register_) | |
237 | StackFrameARM::CONTEXT_VALID_SP; |
238 | return frame; |
239 | } |
240 | |
241 | StackFrame* StackwalkerARM::GetCallerFrame(const CallStack* stack, |
242 | bool stack_scan_allowed) { |
243 | if (!memory_ || !stack) { |
244 | BPLOG(ERROR) << "Can't get caller frame without memory or stack" ; |
245 | return NULL; |
246 | } |
247 | |
248 | const vector<StackFrame*>& frames = *stack->frames(); |
249 | StackFrameARM* last_frame = static_cast<StackFrameARM*>(frames.back()); |
250 | scoped_ptr<StackFrameARM> frame; |
251 | |
252 | // See if there is DWARF call frame information covering this address. |
253 | // TODO(jperaza): Ignore iOS CFI info until it is properly collected. |
254 | // https://bugs.chromium.org/p/google-breakpad/issues/detail?id=764 |
255 | if (!system_info_ || system_info_->os != "iOS" ) { |
256 | scoped_ptr<CFIFrameInfo> cfi_frame_info( |
257 | frame_symbolizer_->FindCFIFrameInfo(last_frame)); |
258 | if (cfi_frame_info.get()) |
259 | frame.reset(GetCallerByCFIFrameInfo(frames, cfi_frame_info.get())); |
260 | } |
261 | |
262 | // If CFI failed, or there wasn't CFI available, fall back |
263 | // to frame pointer, if this is configured. |
264 | if (fp_register_ >= 0 && !frame.get()) |
265 | frame.reset(GetCallerByFramePointer(frames)); |
266 | |
267 | // If everuthing failed, fall back to stack scanning. |
268 | if (stack_scan_allowed && !frame.get()) |
269 | frame.reset(GetCallerByStackScan(frames)); |
270 | |
271 | // If nothing worked, tell the caller. |
272 | if (!frame.get()) |
273 | return NULL; |
274 | |
275 | // Should we terminate the stack walk? (end-of-stack or broken invariant) |
276 | if (TerminateWalk(frame->context.iregs[MD_CONTEXT_ARM_REG_PC], |
277 | frame->context.iregs[MD_CONTEXT_ARM_REG_SP], |
278 | last_frame->context.iregs[MD_CONTEXT_ARM_REG_SP], |
279 | frames.size() == 1)) { |
280 | return NULL; |
281 | } |
282 | |
283 | // The new frame's context's PC is the return address, which is one |
284 | // instruction past the instruction that caused us to arrive at the |
285 | // callee. Set new_frame->instruction to one less than the PC. This won't |
286 | // reference the beginning of the call instruction, but it's at least |
287 | // within it, which is sufficient to get the source line information to |
288 | // match up with the line that contains the function call. Callers that |
289 | // require the exact return address value may access |
290 | // frame->context.iregs[MD_CONTEXT_ARM_REG_PC]. |
291 | frame->instruction = frame->context.iregs[MD_CONTEXT_ARM_REG_PC] - 2; |
292 | |
293 | return frame.release(); |
294 | } |
295 | |
296 | |
297 | } // namespace google_breakpad |
298 | |