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1 // Copyright (c) 2013 Google Inc.
2 // All rights reserved.
3 //
4 // Redistribution and use in source and binary forms, with or without
5 // modification, are permitted provided that the following conditions are
6 // met:
7 //
8 //     * Redistributions of source code must retain the above copyright
9 // notice, this list of conditions and the following disclaimer.
10 //     * Redistributions in binary form must reproduce the above
11 // copyright notice, this list of conditions and the following disclaimer
12 // in the documentation and/or other materials provided with the
13 // distribution.
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15 // contributors may be used to endorse or promote products derived from
16 // this software without specific prior written permission.
17 //
18 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
19 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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21 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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27 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
28 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29 
30 // stackwalker_mips.cc: MIPS-specific stackwalker.
31 //
32 // See stackwalker_mips.h for documentation.
33 //
34 // Author: Tata Elxsi
35 
36 #include "common/scoped_ptr.h"
37 #include "google_breakpad/processor/call_stack.h"
38 #include "google_breakpad/processor/code_modules.h"
39 #include "google_breakpad/processor/memory_region.h"
40 #include "google_breakpad/processor/source_line_resolver_interface.h"
41 #include "google_breakpad/processor/stack_frame_cpu.h"
42 #include "processor/cfi_frame_info.h"
43 #include "processor/logging.h"
44 #include "processor/postfix_evaluator-inl.h"
45 #include "processor/stackwalker_mips.h"
46 #include "processor/windows_frame_info.h"
47 #include "google_breakpad/common/minidump_cpu_mips.h"
48 
49 namespace google_breakpad {
50 
StackwalkerMIPS(const SystemInfo * system_info,const MDRawContextMIPS * context,MemoryRegion * memory,const CodeModules * modules,StackFrameSymbolizer * resolver_helper)51 StackwalkerMIPS::StackwalkerMIPS(const SystemInfo* system_info,
52                                  const MDRawContextMIPS* context,
53                                  MemoryRegion* memory,
54                                  const CodeModules* modules,
55                                  StackFrameSymbolizer* resolver_helper)
56     : Stackwalker(system_info, memory, modules, resolver_helper),
57       context_(context) {
58   if (memory_ && memory_->GetBase() + memory_->GetSize() - 1 > 0xffffffff) {
59     BPLOG(ERROR) << "Memory out of range for stackwalking: "
60                  << HexString(memory_->GetBase())
61                  << "+"
62                  << HexString(memory_->GetSize());
63     memory_ = NULL;
64   }
65 }
66 
GetContextFrame()67 StackFrame* StackwalkerMIPS::GetContextFrame() {
68   if (!context_) {
69     BPLOG(ERROR) << "Can't get context frame without context.";
70     return NULL;
71   }
72 
73   StackFrameMIPS* frame = new StackFrameMIPS();
74 
75   // The instruction pointer is stored directly in a register, so pull it
76   // straight out of the CPU context structure.
77   frame->context = *context_;
78   frame->context_validity = StackFrameMIPS::CONTEXT_VALID_ALL;
79   frame->trust = StackFrame::FRAME_TRUST_CONTEXT;
80   frame->instruction = frame->context.epc;
81 
82   return frame;
83 }
84 
85 // Register names for mips.
86 static const char* const kRegisterNames[] = {
87    "$zero", "$at", "$v0", "$v1", "$a0", "$a1", "$a2", "$a3", "$to", "$t1",
88    "$t2",   "$t3", "$t4", "$t5", "$t6", "$t7", "$s0", "$s1", "$s2", "$s3",
89    "$s4",   "$s5", "$s6", "$s7", "$t8", "$t9", "$k0", "$k1", "$gp", "$sp",
90    "$fp",   "$ra", NULL
91   // TODO(gordanac): add float point save registers
92 };
93 
GetCallerByCFIFrameInfo(const vector<StackFrame * > & frames,CFIFrameInfo * cfi_frame_info)94 StackFrameMIPS* StackwalkerMIPS::GetCallerByCFIFrameInfo(
95     const vector<StackFrame*>& frames,
96     CFIFrameInfo* cfi_frame_info) {
97   StackFrameMIPS* last_frame = static_cast<StackFrameMIPS*>(frames.back());
98 
99   uint32_t sp = 0, pc = 0;
100 
101   // Populate a dictionary with the valid register values in last_frame.
102   CFIFrameInfo::RegisterValueMap<uint32_t> callee_registers;
103   // Use the STACK CFI data to recover the caller's register values.
104   CFIFrameInfo::RegisterValueMap<uint32_t> caller_registers;
105 
106   for (int i = 0; kRegisterNames[i]; ++i) {
107     caller_registers[kRegisterNames[i]] = last_frame->context.iregs[i];
108     callee_registers[kRegisterNames[i]] = last_frame->context.iregs[i];
109   }
110 
111   if (!cfi_frame_info->FindCallerRegs(callee_registers, *memory_,
112                                       &caller_registers))  {
113     return NULL;
114   }
115 
116   CFIFrameInfo::RegisterValueMap<uint32_t>::const_iterator entry =
117       caller_registers.find(".cfa");
118 
119   if (entry != caller_registers.end()) {
120     sp = entry->second;
121     caller_registers["$sp"] = entry->second;
122   }
123 
124   entry = caller_registers.find(".ra");
125   if (entry != caller_registers.end()) {
126     caller_registers["$ra"] = entry->second;
127     pc = entry->second - 2 * sizeof(pc);
128   }
129   caller_registers["$pc"] = pc;
130   // Construct a new stack frame given the values the CFI recovered.
131   scoped_ptr<StackFrameMIPS> frame(new StackFrameMIPS());
132 
133   for (int i = 0; kRegisterNames[i]; ++i) {
134     CFIFrameInfo::RegisterValueMap<uint32_t>::const_iterator caller_entry =
135         caller_registers.find(kRegisterNames[i]);
136 
137     if (caller_entry != caller_registers.end()) {
138       // The value of this register is recovered; fill the context with the
139       // value from caller_registers.
140       frame->context.iregs[i] = caller_entry->second;
141       frame->context_validity |= StackFrameMIPS::RegisterValidFlag(i);
142     } else if (((i >= INDEX_MIPS_REG_S0 && i <= INDEX_MIPS_REG_S7) ||
143                 (i > INDEX_MIPS_REG_GP && i < INDEX_MIPS_REG_RA)) &&
144                (last_frame->context_validity &
145                 StackFrameMIPS::RegisterValidFlag(i))) {
146       // If the STACK CFI data doesn't mention some callee-save register, and
147       // it is valid in the callee, assume the callee has not yet changed it.
148       // Calee-save registers according to the MIPS o32 ABI specification are:
149       // $s0 to $s7
150       // $sp, $s8
151       frame->context.iregs[i] = last_frame->context.iregs[i];
152       frame->context_validity |= StackFrameMIPS::RegisterValidFlag(i);
153     }
154   }
155 
156   frame->context.epc = caller_registers["$pc"];
157   frame->instruction = caller_registers["$pc"];
158   frame->context_validity |= StackFrameMIPS::CONTEXT_VALID_PC;
159 
160   frame->context.iregs[MD_CONTEXT_MIPS_REG_RA] = caller_registers["$ra"];
161   frame->context_validity |= StackFrameMIPS::CONTEXT_VALID_RA;
162 
163   frame->trust = StackFrame::FRAME_TRUST_CFI;
164 
165   return frame.release();
166 }
167 
GetCallerFrame(const CallStack * stack,bool stack_scan_allowed)168 StackFrame* StackwalkerMIPS::GetCallerFrame(const CallStack* stack,
169                                             bool stack_scan_allowed) {
170   if (!memory_ || !stack) {
171     BPLOG(ERROR) << "Can't get caller frame without memory or stack";
172     return NULL;
173   }
174 
175   const vector<StackFrame*>& frames = *stack->frames();
176   StackFrameMIPS* last_frame = static_cast<StackFrameMIPS*>(frames.back());
177   scoped_ptr<StackFrameMIPS> new_frame;
178 
179   // See if there is DWARF call frame information covering this address.
180   scoped_ptr<CFIFrameInfo> cfi_frame_info(
181     frame_symbolizer_->FindCFIFrameInfo(last_frame));
182   if (cfi_frame_info.get())
183     new_frame.reset(GetCallerByCFIFrameInfo(frames, cfi_frame_info.get()));
184 
185   // If caller frame is not found in CFI try analyzing the stack.
186   if (stack_scan_allowed && !new_frame.get()) {
187     new_frame.reset(GetCallerByStackScan(frames));
188   }
189 
190   // If nothing worked, tell the caller.
191   if (!new_frame.get()) {
192     return NULL;
193   }
194 
195   // Treat an instruction address of 0 as end-of-stack.
196   if (new_frame->context.epc == 0) {
197     return NULL;
198   }
199 
200   // If the new stack pointer is at a lower address than the old, then
201   // that's clearly incorrect. Treat this as end-of-stack to enforce
202   // progress and avoid infinite loops.
203   if (new_frame->context.iregs[MD_CONTEXT_MIPS_REG_SP] <=
204       last_frame->context.iregs[MD_CONTEXT_MIPS_REG_SP]) {
205     return NULL;
206   }
207 
208   return new_frame.release();
209 }
210 
GetCallerByStackScan(const vector<StackFrame * > & frames)211 StackFrameMIPS* StackwalkerMIPS::GetCallerByStackScan(
212     const vector<StackFrame*>& frames) {
213   const uint32_t kMaxFrameStackSize = 1024;
214   const uint32_t kMinArgsOnStack = 4;
215 
216   StackFrameMIPS* last_frame = static_cast<StackFrameMIPS*>(frames.back());
217 
218   uint32_t last_sp = last_frame->context.iregs[MD_CONTEXT_MIPS_REG_SP];
219   uint32_t caller_pc, caller_sp, caller_fp;
220 
221   // Return address cannot be obtained directly.
222   // Force stackwalking.
223 
224   // We cannot use frame pointer to get the return address.
225   // We'll scan the stack for a
226   // return address. This can happen if last_frame is executing code
227   // for a module for which we don't have symbols.
228   int count = kMaxFrameStackSize / sizeof(caller_pc);
229 
230   if (frames.size() > 1) {
231       // In case of mips32 ABI stack frame of a nonleaf function
232       // must have minimum stack frame assigned for 4 arguments (4 words).
233       // Move stack pointer for 4 words to avoid reporting non-existing frames
234       // for all frames except the topmost one.
235       // There is no way of knowing if topmost frame belongs to a leaf or
236       // a nonleaf function.
237       last_sp +=  kMinArgsOnStack * sizeof(caller_pc);
238       // Adjust 'count' so that return address is scanned only in limits
239       // of one stack frame.
240       count -= kMinArgsOnStack;
241   }
242 
243   do {
244     // Scanning for return address from stack pointer of the last frame.
245     if (!ScanForReturnAddress(last_sp, &caller_sp, &caller_pc, count)) {
246       // If we can't find an instruction pointer even with stack scanning,
247       // give up.
248       BPLOG(ERROR) << " ScanForReturnAddress failed ";
249       return NULL;
250     }
251     // Get $fp stored in the stack frame.
252     if (!memory_->GetMemoryAtAddress(caller_sp - sizeof(caller_pc),
253                                      &caller_fp)) {
254       BPLOG(INFO) << " GetMemoryAtAddress for fp failed " ;
255       return NULL;
256     }
257 
258     count = count - (caller_sp - last_sp) / sizeof(caller_pc);
259     // Now scan the next address in the stack.
260     last_sp = caller_sp + sizeof(caller_pc);
261   } while ((caller_fp - caller_sp >= kMaxFrameStackSize) && count > 0);
262 
263   if (!count) {
264     BPLOG(INFO) << " No frame found " ;
265     return NULL;
266   }
267 
268   // ScanForReturnAddress found a reasonable return address. Advance
269   // $sp to the location above the one where the return address was
270   // found.
271   caller_sp += sizeof(caller_pc);
272   // caller_pc is actually containing $ra value;
273   // $pc is two instructions before $ra,
274   // so the caller_pc needs to be decremented accordingly.
275   caller_pc -= 2 * sizeof(caller_pc);
276 
277 
278   // Create a new stack frame (ownership will be transferred to the caller)
279   // and fill it in.
280   StackFrameMIPS* frame = new StackFrameMIPS();
281   frame->trust = StackFrame::FRAME_TRUST_SCAN;
282   frame->context = last_frame->context;
283   frame->context.epc = caller_pc;
284   frame->context_validity |= StackFrameMIPS::CONTEXT_VALID_PC;
285   frame->instruction = caller_pc;
286 
287   frame->context.iregs[MD_CONTEXT_MIPS_REG_SP] = caller_sp;
288   frame->context_validity |= StackFrameMIPS::CONTEXT_VALID_SP;
289   frame->context.iregs[MD_CONTEXT_MIPS_REG_FP] = caller_fp;
290   frame->context_validity |= StackFrameMIPS::CONTEXT_VALID_FP;
291 
292   frame->context.iregs[MD_CONTEXT_MIPS_REG_RA] =
293       caller_pc + 2 * sizeof(caller_pc);
294   frame->context_validity |= StackFrameMIPS::CONTEXT_VALID_RA;
295 
296   return frame;
297 }
298 
299 }  // namespace google_breakpad
300 
301