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 // Copyright (c) 2010 Google Inc.

 // All rights reserved.

 //

 // Redistribution and use in source and binary forms, with or without

 // modification, are permitted provided that the following conditions are

 // met:

 //

 //     * Redistributions of source code must retain the above copyright

 // notice, this list of conditions and the following disclaimer.

 //     * Redistributions in binary form must reproduce the above

 // copyright notice, this list of conditions and the following disclaimer

 // in the documentation and/or other materials provided with the

 // distribution.

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

 // contributors may be used to endorse or promote products derived from

 // this software without specific prior written permission.

 //

 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR

 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT

 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,

 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT

 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,

 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY

 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE

 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 // stackwalker_arm.cc: arm-specific stackwalker.

 //

 // See stackwalker_arm.h for documentation.

 //

 // Author: Mark Mentovai, Ted Mielczarek, Jim Blandy

 #include <vector>

 #include "common/scoped_ptr.h"

 #include "google_breakpad/processor/call_stack.h"

 #include "google_breakpad/processor/memory_region.h"

 #include "google_breakpad/processor/source_line_resolver_interface.h"

 #include "google_breakpad/processor/stack_frame_cpu.h"

 #include "processor/cfi_frame_info.h"

 #include "common/logging.h"

 #include "processor/stackwalker_arm.h"

 namespace google_breakpad {

 StackwalkerARM::StackwalkerARM(const SystemInfo* system_info,

                                const MDRawContextARM* context,

                                int fp_register,

                                MemoryRegion* memory,

                                const CodeModules* modules,

                                StackFrameSymbolizer* resolver_helper)

     : Stackwalker(system_info, memory, modules, resolver_helper),

       context_(context), fp_register_(fp_register),

       context_frame_validity_(StackFrameARM::CONTEXT_VALID_ALL) { }

 StackFrame* StackwalkerARM::GetContextFrame() {

   if (!context_) {

     BPLOG(ERROR) << "Can't get context frame without context";

     return NULL;

   }

   StackFrameARM* frame = new StackFrameARM();

   // The instruction pointer is stored directly in a register (r15), so pull it

   // straight out of the CPU context structure.

   frame->context = *context_;

   frame->context_validity = context_frame_validity_;

   frame->trust = StackFrame::FRAME_TRUST_CONTEXT;

   frame->instruction = frame->context.iregs[MD_CONTEXT_ARM_REG_PC];

   return frame;

 }

 StackFrameARM* StackwalkerARM::GetCallerByCFIFrameInfo(

     const vector<StackFrame*> &frames,

     CFIFrameInfo* cfi_frame_info) {

   StackFrameARM* last_frame = static_cast<StackFrameARM*>(frames.back());

   static const UniqueString *register_names[] = {

     ToUniqueString("r0"),  ToUniqueString("r1"),

     ToUniqueString("r2"),  ToUniqueString("r3"),

     ToUniqueString("r4"),  ToUniqueString("r5"),

     ToUniqueString("r6"),  ToUniqueString("r7"),

     ToUniqueString("r8"),  ToUniqueString("r9"),

     ToUniqueString("r10"), ToUniqueString("r11"),

     ToUniqueString("r12"), ToUniqueString("sp"),

     ToUniqueString("lr"),  ToUniqueString("pc"),

     ToUniqueString("f0"),  ToUniqueString("f1"),

     ToUniqueString("f2"),  ToUniqueString("f3"),

     ToUniqueString("f4"),  ToUniqueString("f5"),

     ToUniqueString("f6"),  ToUniqueString("f7"),

     ToUniqueString("fps"), ToUniqueString("cpsr"),

     NULL

   };

   // Populate a dictionary with the valid register values in last_frame.

   CFIFrameInfo::RegisterValueMap<uint32_t> callee_registers;

   for (int i = 0; register_names[i]; i++)

     if (last_frame->context_validity & StackFrameARM::RegisterValidFlag(i))

       callee_registers.set(register_names[i], last_frame->context.iregs[i]);

   // Use the STACK CFI data to recover the caller's register values.

   CFIFrameInfo::RegisterValueMap<uint32_t> caller_registers;

   if (!cfi_frame_info->FindCallerRegs(callee_registers, *memory_,

                                       &caller_registers))

     return NULL;

   // Construct a new stack frame given the values the CFI recovered.

   scoped_ptr<StackFrameARM> frame(new StackFrameARM());

   for (int i = 0; register_names[i]; i++) {

     bool found = false;

     uint32_t v = caller_registers.get(&found, register_names[i]);

     if (found) {

       // We recovered the value of this register; fill the context with the

       // value from caller_registers.

       frame->context_validity |= StackFrameARM::RegisterValidFlag(i);

       frame->context.iregs[i] = v;

     } else if (4 <= i && i <= 11 && (last_frame->context_validity &

                                      StackFrameARM::RegisterValidFlag(i))) {

       // If the STACK CFI data doesn't mention some callee-saves register, and

       // it is valid in the callee, assume the callee has not yet changed it.

       // Registers r4 through r11 are callee-saves, according to the Procedure

       // Call Standard for the ARM Architecture, which the Linux ABI follows.

       frame->context_validity |= StackFrameARM::RegisterValidFlag(i);

       frame->context.iregs[i] = last_frame->context.iregs[i];

     }

   }

   // If the CFI doesn't recover the PC explicitly, then use .ra.

   if (!(frame->context_validity & StackFrameARM::CONTEXT_VALID_PC)) {

     bool found = false;

     uint32_t v = caller_registers.get(&found, ustr__ZDra());

     if (found) {

       if (fp_register_ == -1) {

         frame->context_validity |= StackFrameARM::CONTEXT_VALID_PC;

         frame->context.iregs[MD_CONTEXT_ARM_REG_PC] = v;

       } else {

         // The CFI updated the link register and not the program counter.

         // Handle getting the program counter from the link register.

         frame->context_validity |= StackFrameARM::CONTEXT_VALID_PC;

         frame->context_validity |= StackFrameARM::CONTEXT_VALID_LR;

         frame->context.iregs[MD_CONTEXT_ARM_REG_LR] = v;

         frame->context.iregs[MD_CONTEXT_ARM_REG_PC] =

             last_frame->context.iregs[MD_CONTEXT_ARM_REG_LR];

       }

     }

   }

   // If the CFI doesn't recover the SP explicitly, then use .cfa.

   if (!(frame->context_validity & StackFrameARM::CONTEXT_VALID_SP)) {

     bool found = false;

     uint32_t v = caller_registers.get(&found, ustr__ZDcfa());

     if (found) {

       frame->context_validity |= StackFrameARM::CONTEXT_VALID_SP;

       frame->context.iregs[MD_CONTEXT_ARM_REG_SP] = v;

     }

   }

   // If we didn't recover the PC and the SP, then the frame isn't very useful.

   static const int essentials = (StackFrameARM::CONTEXT_VALID_SP

                                  | StackFrameARM::CONTEXT_VALID_PC);

   if ((frame->context_validity & essentials) != essentials)

     return NULL;

   frame->trust = StackFrame::FRAME_TRUST_CFI;

   return frame.release();

 }

 StackFrameARM* StackwalkerARM::GetCallerByStackScan(

     const vector<StackFrame*> &frames) {

   StackFrameARM* last_frame = static_cast<StackFrameARM*>(frames.back());

   uint32_t last_sp = last_frame->context.iregs[MD_CONTEXT_ARM_REG_SP];

   uint32_t caller_sp, caller_pc;

   // When searching for the caller of the context frame,

   // allow the scanner to look farther down the stack.

   const int kRASearchWords = frames.size() == 1 ?

     Stackwalker::kRASearchWords * 4 :

     Stackwalker::kRASearchWords;

   if (!ScanForReturnAddress(last_sp, &caller_sp, &caller_pc,

                             kRASearchWords)) {

     // No plausible return address was found.

     return NULL;

   }

   // ScanForReturnAddress found a reasonable return address. Advance

   // %sp to the location above the one where the return address was

   // found.

   caller_sp += 4;

   // Create a new stack frame (ownership will be transferred to the caller)

   // and fill it in.

   StackFrameARM* frame = new StackFrameARM();

   frame->trust = StackFrame::FRAME_TRUST_SCAN;

   frame->context = last_frame->context;

   frame->context.iregs[MD_CONTEXT_ARM_REG_PC] = caller_pc;

   frame->context.iregs[MD_CONTEXT_ARM_REG_SP] = caller_sp;

   frame->context_validity = StackFrameARM::CONTEXT_VALID_PC |

                             StackFrameARM::CONTEXT_VALID_SP;

   return frame;

 }

 StackFrameARM* StackwalkerARM::GetCallerByFramePointer(

     const vector<StackFrame*> &frames) {

   StackFrameARM* last_frame = static_cast<StackFrameARM*>(frames.back());

   if (!(last_frame->context_validity &

         StackFrameARM::RegisterValidFlag(fp_register_))) {

     return NULL;

   }

   uint32_t last_fp = last_frame->context.iregs[fp_register_];

   uint32_t caller_fp = 0;

   if (last_fp && !memory_->GetMemoryAtAddress(last_fp, &caller_fp)) {

     BPLOG(ERROR) << "Unable to read caller_fp from last_fp: 0x"

                  << std::hex << last_fp;

     return NULL;

   }

   uint32_t caller_lr = 0;

   if (last_fp && !memory_->GetMemoryAtAddress(last_fp + 4, &caller_lr)) {

     BPLOG(ERROR) << "Unable to read caller_lr from last_fp + 4: 0x"

                  << std::hex << (last_fp + 4);

     return NULL;

   }

   uint32_t caller_sp = last_fp ? last_fp + 8 :

       last_frame->context.iregs[MD_CONTEXT_ARM_REG_SP];

   // Create a new stack frame (ownership will be transferred to the caller)

   // and fill it in.

   StackFrameARM* frame = new StackFrameARM();

   frame->trust = StackFrame::FRAME_TRUST_FP;

   frame->context = last_frame->context;

   frame->context.iregs[fp_register_] = caller_fp;

   frame->context.iregs[MD_CONTEXT_ARM_REG_SP] = caller_sp;

   frame->context.iregs[MD_CONTEXT_ARM_REG_PC] =

       last_frame->context.iregs[MD_CONTEXT_ARM_REG_LR];

   frame->context.iregs[MD_CONTEXT_ARM_REG_LR] = caller_lr;

   frame->context_validity = StackFrameARM::CONTEXT_VALID_PC |

                             StackFrameARM::CONTEXT_VALID_LR |

                             StackFrameARM::RegisterValidFlag(fp_register_) |

                             StackFrameARM::CONTEXT_VALID_SP;

   return frame;

 }

 StackFrame* StackwalkerARM::GetCallerFrame(const CallStack* stack,

                                            bool stack_scan_allowed) {

   if (!memory_ || !stack) {

     BPLOG(ERROR) << "Can't get caller frame without memory or stack";

     return NULL;

   }

   const vector<StackFrame*> &frames = *stack->frames();

   StackFrameARM* last_frame = static_cast<StackFrameARM*>(frames.back());

   scoped_ptr<StackFrameARM> frame;

   // See if there is DWARF call frame information covering this address.

   scoped_ptr<CFIFrameInfo> cfi_frame_info(

       frame_symbolizer_->FindCFIFrameInfo(last_frame));

   if (cfi_frame_info.get())

     frame.reset(GetCallerByCFIFrameInfo(frames, cfi_frame_info.get()));

   // If CFI failed, or there wasn't CFI available, fall back

   // to frame pointer, if this is configured.

   if (fp_register_ >= 0 && !frame.get())

     frame.reset(GetCallerByFramePointer(frames));

   // If everuthing failed, fall back to stack scanning.

   if (stack_scan_allowed && !frame.get())

     frame.reset(GetCallerByStackScan(frames));

   // If nothing worked, tell the caller.

   if (!frame.get())

     return NULL;

   // An instruction address of zero marks the end of the stack.

   if (frame->context.iregs[MD_CONTEXT_ARM_REG_PC] == 0)

     return NULL;

   // If the new stack pointer is at a lower address than the old, then

   // that's clearly incorrect. Treat this as end-of-stack to enforce

   // progress and avoid infinite loops.

   if (frame->context.iregs[MD_CONTEXT_ARM_REG_SP]

       < last_frame->context.iregs[MD_CONTEXT_ARM_REG_SP])

     return NULL;

   // The new frame's context's PC is the return address, which is one

   // instruction past the instruction that caused us to arrive at the

   // callee. Set new_frame->instruction to one less than the PC. This won't

   // reference the beginning of the call instruction, but it's at least

   // within it, which is sufficient to get the source line information to

   // match up with the line that contains the function call. Callers that

   // require the exact return address value may access

   // frame->context.iregs[MD_CONTEXT_ARM_REG_PC].

   frame->instruction = frame->context.iregs[MD_CONTEXT_ARM_REG_PC] - 2;

   return frame.release();

 }

 }  // namespace google_breakpad