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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.
     14 //     * Neither the name of Google Inc. nor the names of its
     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
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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 
     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 
     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 
     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 
    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 
    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