breakpad/src/processor/stackwalker_arm64.cc

// Copyright (c) 2013 Google Inc.
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// stackwalker_arm64.cc: arm64-specific stackwalker.
//
// See stackwalker_arm64.h for documentation.
//
// Author: Mark Mentovai, Ted Mielczarek, Jim Blandy, Colin Blundell

#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 "processor/logging.h"
#include "processor/stackwalker_arm64.h"

namespace google_breakpad {


StackwalkerARM64::StackwalkerARM64(const SystemInfo* system_info,
                                   const MDRawContextARM64* context,
                                   MemoryRegion* memory,
                                   const CodeModules* modules,
                                   StackFrameSymbolizer* resolver_helper)
    : Stackwalker(system_info, memory, modules, resolver_helper),
      context_(context),
      context_frame_validity_(StackFrameARM64::CONTEXT_VALID_ALL) { }


StackFrame* StackwalkerARM64::GetContextFrame() {
  if (!context_) {
    BPLOG(ERROR) << "Can't get context frame without context";
    return NULL;
  }

  StackFrameARM64* frame = new StackFrameARM64();

  // The instruction pointer is stored directly in a register (x32), 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_ARM64_REG_PC];

  return frame;
}

StackFrameARM64* StackwalkerARM64::GetCallerByCFIFrameInfo(
    const vector<StackFrame*> &frames,
    CFIFrameInfo* cfi_frame_info) {
  // Obtaining the stack frame from CFI info is not yet supported for ARM64.
  return NULL;
}

StackFrameARM64* StackwalkerARM64::GetCallerByStackScan(
    const vector<StackFrame*> &frames) {
  StackFrameARM64* last_frame = static_cast<StackFrameARM64*>(frames.back());
  uint64_t last_sp = last_frame->context.iregs[MD_CONTEXT_ARM64_REG_SP];
  uint64_t caller_sp, caller_pc;

  if (!ScanForReturnAddress(last_sp, &caller_sp, &caller_pc,
                            frames.size() == 1 /* is_context_frame */)) {
    // 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 += 8;

  // Create a new stack frame (ownership will be transferred to the caller)
  // and fill it in.
  StackFrameARM64* frame = new StackFrameARM64();

  frame->trust = StackFrame::FRAME_TRUST_SCAN;
  frame->context = last_frame->context;
  frame->context.iregs[MD_CONTEXT_ARM64_REG_PC] = caller_pc;
  frame->context.iregs[MD_CONTEXT_ARM64_REG_SP] = caller_sp;
  frame->context_validity = StackFrameARM64::CONTEXT_VALID_PC |
                            StackFrameARM64::CONTEXT_VALID_SP;

  return frame;
}

StackFrameARM64* StackwalkerARM64::GetCallerByFramePointer(
    const vector<StackFrame*> &frames) {
  StackFrameARM64* last_frame = static_cast<StackFrameARM64*>(frames.back());

  uint64_t last_fp = last_frame->context.iregs[MD_CONTEXT_ARM64_REG_FP];

  uint64_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;
  }

  uint64_t caller_lr = 0;
  if (last_fp && !memory_->GetMemoryAtAddress(last_fp + 8, &caller_lr)) {
    BPLOG(ERROR) << "Unable to read caller_lr from last_fp + 8: 0x"
                 << std::hex << (last_fp + 8);
    return NULL;
  }

  uint64_t caller_sp = last_fp ? last_fp + 16 :
      last_frame->context.iregs[MD_CONTEXT_ARM64_REG_SP];

  // Create a new stack frame (ownership will be transferred to the caller)
  // and fill it in.
  StackFrameARM64* frame = new StackFrameARM64();

  frame->trust = StackFrame::FRAME_TRUST_FP;
  frame->context = last_frame->context;
  frame->context.iregs[MD_CONTEXT_ARM64_REG_FP] = caller_fp;
  frame->context.iregs[MD_CONTEXT_ARM64_REG_SP] = caller_sp;
  frame->context.iregs[MD_CONTEXT_ARM64_REG_PC] =
      last_frame->context.iregs[MD_CONTEXT_ARM64_REG_LR];
  frame->context.iregs[MD_CONTEXT_ARM64_REG_LR] = caller_lr;
  frame->context_validity = StackFrameARM64::CONTEXT_VALID_PC |
                            StackFrameARM64::CONTEXT_VALID_LR |
                            StackFrameARM64::CONTEXT_VALID_FP |
                            StackFrameARM64::CONTEXT_VALID_SP;
  return frame;
}

StackFrame* StackwalkerARM64::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();
  StackFrameARM64* last_frame = static_cast<StackFrameARM64*>(frames.back());
  scoped_ptr<StackFrameARM64> 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 (!frame.get())
    frame.reset(GetCallerByFramePointer(frames));

  // If everything 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_ARM64_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_ARM64_REG_SP]
      < last_frame->context.iregs[MD_CONTEXT_ARM64_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.
  // ARM64 instructions have a uniform 4-byte encoding, so subtracting 4 off
  // the return address gets back to the beginning of the call instruction.
  // Callers that require the exact return address value may access
  // frame->context.iregs[MD_CONTEXT_ARM64_REG_PC].
  frame->instruction = frame->context.iregs[MD_CONTEXT_ARM64_REG_PC] - 4;

  return frame.release();
}


}  // namespace google_breakpad