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Commit eb4a6dbf authored by Christopher Ferris's avatar Christopher Ferris
Browse files

Speed up StepIfSignalHandler path. 

The StepIfSignalHandler code reads from the process memory object, which
is currently the slowest way to read memory. Change the code to read from
the elf memory object which will almost always be a memory mapped file and
should be really fast.

Also, move the tests for StepIfSignalHandler to its own file.

Bug: 23762183

Test: Unit tests pass.
Change-Id: I1100b50554e5ef736a87babd484f3f34e9071caa
parent 33913ebf

libunwindstack/Android.bp

+1 −0
Original line number Diff line number Diff line
@@ -115,6 +115,7 @@ cc_test { 
        "tests/MemoryRangeTest.cpp",

        "tests/MemoryRemoteTest.cpp",

        "tests/MemoryTest.cpp",

        "tests/RegsStepIfSignalHandlerTest.cpp",

        "tests/RegsTest.cpp",

        "tests/SymbolsTest.cpp",

        "tests/UnwindTest.cpp",

libunwindstack/Elf.cpp

+1 −1
Original line number Diff line number Diff line
@@ -96,7 +96,7 @@ bool Elf::GetFunctionName(uint64_t addr, std::string* name, uint64_t* func_offse 
}



bool Elf::Step(uint64_t rel_pc, Regs* regs, Memory* process_memory) {

  return valid_ && (regs->StepIfSignalHandler(process_memory) ||

  return valid_ && (regs->StepIfSignalHandler(rel_pc, this, process_memory) ||

                    interface_->Step(rel_pc, regs, process_memory) ||

                    (gnu_debugdata_interface_ &&

                     gnu_debugdata_interface_->Step(rel_pc, regs, process_memory)));

libunwindstack/Regs.cpp

+30 −17
Original line number Diff line number Diff line
@@ -350,9 +350,12 @@ Regs* Regs::CreateFromLocal() { 
  return regs;

}



bool RegsArm::StepIfSignalHandler(Memory* memory) {

bool RegsArm::StepIfSignalHandler(uint64_t rel_pc, Elf* elf, Memory* process_memory) {

  uint32_t data;

  if (!memory->Read(pc(), &data, sizeof(data))) {

  Memory* elf_memory = elf->memory();

  // Read from elf memory since it is usually more expensive to read from

  // process memory.

  if (!elf_memory->Read(rel_pc, &data, sizeof(data))) {

    return false;

  }
@@ -371,7 +374,7 @@ bool RegsArm::StepIfSignalHandler(Memory* memory) { 
    // Form 3 (thumb):

    // 0x77 0x27              movs r7, #77

    // 0x00 0xdf              svc 0

    if (!memory->Read(sp(), &data, sizeof(data))) {

    if (!process_memory->Read(sp(), &data, sizeof(data))) {

      return false;

    }

    if (data == 0x5ac3c35a) {
@@ -395,7 +398,7 @@ bool RegsArm::StepIfSignalHandler(Memory* memory) { 
    // Form 3 (thumb):

    // 0xad 0x27              movs r7, #ad

    // 0x00 0xdf              svc 0

    if (!memory->Read(sp(), &data, sizeof(data))) {

    if (!process_memory->Read(sp(), &data, sizeof(data))) {

      return false;

    }

    if (data == sp() + 8) {
@@ -410,16 +413,19 @@ bool RegsArm::StepIfSignalHandler(Memory* memory) { 
    return false;

  }



  if (!memory->Read(offset, regs_.data(), sizeof(uint32_t) * ARM_REG_LAST)) {

  if (!process_memory->Read(offset, regs_.data(), sizeof(uint32_t) * ARM_REG_LAST)) {

    return false;

  }

  SetFromRaw();

  return true;

}



bool RegsArm64::StepIfSignalHandler(Memory* memory) {

bool RegsArm64::StepIfSignalHandler(uint64_t rel_pc, Elf* elf, Memory* process_memory) {

  uint64_t data;

  if (!memory->Read(pc(), &data, sizeof(data))) {

  Memory* elf_memory = elf->memory();

  // Read from elf memory since it is usually more expensive to read from

  // process memory.

  if (!elf_memory->Read(rel_pc, &data, sizeof(data))) {

    return false;

  }
@@ -432,7 +438,8 @@ bool RegsArm64::StepIfSignalHandler(Memory* memory) { 
  }



  // SP + sizeof(siginfo_t) + uc_mcontext offset + X0 offset.

  if (!memory->Read(sp() + 0x80 + 0xb0 + 0x08, regs_.data(), sizeof(uint64_t) * ARM64_REG_LAST)) {

  if (!process_memory->Read(sp() + 0x80 + 0xb0 + 0x08, regs_.data(),

                            sizeof(uint64_t) * ARM64_REG_LAST)) {

    return false;

  }
@@ -440,9 +447,12 @@ bool RegsArm64::StepIfSignalHandler(Memory* memory) { 
  return true;

}



bool RegsX86::StepIfSignalHandler(Memory* memory) {

bool RegsX86::StepIfSignalHandler(uint64_t rel_pc, Elf* elf, Memory* process_memory) {

  uint64_t data;

  if (!memory->Read(pc(), &data, sizeof(data))) {

  Memory* elf_memory = elf->memory();

  // Read from elf memory since it is usually more expensive to read from

  // process memory.

  if (!elf_memory->Read(rel_pc, &data, sizeof(data))) {

    return false;

  }
@@ -458,7 +468,7 @@ bool RegsX86::StepIfSignalHandler(Memory* memory) { 
    //   int signum

    //   struct sigcontext (same format as mcontext)

    struct x86_mcontext_t context;

    if (!memory->Read(sp() + 4, &context, sizeof(context))) {

    if (!process_memory->Read(sp() + 4, &context, sizeof(context))) {

      return false;

    }

    regs_[X86_REG_EBP] = context.ebp;
@@ -484,12 +494,12 @@ bool RegsX86::StepIfSignalHandler(Memory* memory) { 


    // Get the location of the sigcontext data.

    uint32_t ptr;

    if (!memory->Read(sp() + 8, &ptr, sizeof(ptr))) {

    if (!process_memory->Read(sp() + 8, &ptr, sizeof(ptr))) {

      return false;

    }

    // Only read the portion of the data structure we care about.

    x86_ucontext_t x86_ucontext;

    if (!memory->Read(ptr + 0x14, &x86_ucontext.uc_mcontext, sizeof(x86_mcontext_t))) {

    if (!process_memory->Read(ptr + 0x14, &x86_ucontext.uc_mcontext, sizeof(x86_mcontext_t))) {

      return false;

    }

    SetFromUcontext(&x86_ucontext);
@@ -498,14 +508,17 @@ bool RegsX86::StepIfSignalHandler(Memory* memory) { 
  return false;

}



bool RegsX86_64::StepIfSignalHandler(Memory* memory) {

bool RegsX86_64::StepIfSignalHandler(uint64_t rel_pc, Elf* elf, Memory* process_memory) {

  uint64_t data;

  if (!memory->Read(pc(), &data, sizeof(data)) || data != 0x0f0000000fc0c748) {

  Memory* elf_memory = elf->memory();

  // Read from elf memory since it is usually more expensive to read from

  // process memory.

  if (!elf_memory->Read(rel_pc, &data, sizeof(data)) || data != 0x0f0000000fc0c748) {

    return false;

  }



  uint16_t data2;

  if (!memory->Read(pc() + 8, &data2, sizeof(data2)) || data2 != 0x0f05) {

  if (!elf_memory->Read(rel_pc + 8, &data2, sizeof(data2)) || data2 != 0x0f05) {

    return false;

  }
@@ -517,7 +530,7 @@ bool RegsX86_64::StepIfSignalHandler(Memory* memory) { 
  // Read the mcontext data from the stack.

  // sp points to the ucontext data structure, read only the mcontext part.

  x86_64_ucontext_t x86_64_ucontext;

  if (!memory->Read(sp() + 0x28, &x86_64_ucontext.uc_mcontext, sizeof(x86_64_mcontext_t))) {

  if (!process_memory->Read(sp() + 0x28, &x86_64_ucontext.uc_mcontext, sizeof(x86_64_mcontext_t))) {

    return false;

  }

  SetFromUcontext(&x86_64_ucontext);

libunwindstack/include/unwindstack/Regs.h

+5 −5
Original line number Diff line number Diff line
@@ -57,7 +57,7 @@ class Regs { 


  virtual uint64_t GetAdjustedPc(uint64_t rel_pc, Elf* elf) = 0;



  virtual bool StepIfSignalHandler(Memory*) = 0;

  virtual bool StepIfSignalHandler(uint64_t rel_pc, Elf* elf, Memory* process_memory) = 0;



  virtual void SetFromRaw() = 0;
@@ -109,7 +109,7 @@ class RegsArm : public RegsImpl<uint32_t> { 


  void SetFromRaw() override;



  bool StepIfSignalHandler(Memory* memory) override;

  bool StepIfSignalHandler(uint64_t rel_pc, Elf* elf, Memory* process_memory) override;

};



class RegsArm64 : public RegsImpl<uint64_t> {
@@ -121,7 +121,7 @@ class RegsArm64 : public RegsImpl<uint64_t> { 


  void SetFromRaw() override;



  bool StepIfSignalHandler(Memory* memory) override;

  bool StepIfSignalHandler(uint64_t rel_pc, Elf* elf, Memory* process_memory) override;

};



class RegsX86 : public RegsImpl<uint32_t> {
@@ -133,7 +133,7 @@ class RegsX86 : public RegsImpl<uint32_t> { 


  void SetFromRaw() override;



  bool StepIfSignalHandler(Memory* memory) override;

  bool StepIfSignalHandler(uint64_t rel_pc, Elf* elf, Memory* process_memory) override;



  void SetFromUcontext(x86_ucontext_t* ucontext);

};
@@ -147,7 +147,7 @@ class RegsX86_64 : public RegsImpl<uint64_t> { 


  void SetFromRaw() override;



  bool StepIfSignalHandler(Memory* memory) override;

  bool StepIfSignalHandler(uint64_t rel_pc, Elf* elf, Memory* process_memory) override;



  void SetFromUcontext(x86_64_ucontext_t* ucontext);

};

libunwindstack/tests/RegsFake.h

+1 −1
Original line number Diff line number Diff line
@@ -33,7 +33,7 @@ class RegsFake : public RegsImpl<TypeParam> { 


  uint64_t GetAdjustedPc(uint64_t, Elf*) override { return 0; }

  void SetFromRaw() override {}

  bool StepIfSignalHandler(Memory*) override { return false; }

  bool StepIfSignalHandler(uint64_t, Elf*, Memory*) override { return false; }

  bool GetReturnAddressFromDefault(Memory*, uint64_t*) { return false; }

};