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Commit fbca3000 authored by Yong Li's avatar Yong Li
Browse files

Fix GetGlobalVariableOffset with tagged pointer in aarch64 



Tagged pointer for aarch64 since Android R would lead top byte to have
random values. For example of a symbol from libart.so in a hwasan
enabled device in Android R:

1490: 8800000000b094a0   144 OBJECT  GLOBAL 24 __dex_debug_descriptor

We need to mask off the top byte so that the address range comparison
would work as intended.

Test: Ran new unit test

Signed-off-by: default avatarYong Li <yongl0722@gmail.com>
Change-Id: Ia8c638e16baff57740c569e9eaf9cfd1f5bd3fad
parent 451197cb

libunwindstack/Elf.cpp

+6 −0
Original line number Diff line number Diff line
@@ -124,6 +124,12 @@ bool Elf::GetGlobalVariableOffset(const std::string& name, uint64_t* memory_offs 
    return false;

  }



  if (arch() == ARCH_ARM64) {

    // Tagged pointer after Android R would lead top byte to have random values

    // https://source.android.com/devices/tech/debug/tagged-pointers

    vaddr &= (1ULL << 56) - 1;

  }



  // Check the .data section.

  uint64_t vaddr_start = interface_->data_vaddr_start();

  if (vaddr >= vaddr_start && vaddr < interface_->data_vaddr_end()) {

libunwindstack/tests/ElfFake.h

+2 −0
Original line number Diff line number Diff line
@@ -55,6 +55,8 @@ class ElfFake : public Elf { 


  void FakeSetLoadBias(uint64_t load_bias) { load_bias_ = load_bias; }



  void FakeSetArch(ArchEnum arch) { arch_ = arch; }



  void FakeSetInterface(ElfInterface* interface) { interface_.reset(interface); }

  void FakeSetGnuDebugdataInterface(ElfInterface* interface) {

    gnu_debugdata_interface_.reset(interface);

libunwindstack/tests/ElfTest.cpp

+42 −0
Original line number Diff line number Diff line
@@ -438,6 +438,48 @@ TEST_F(ElfTest, get_global_vaddr_in_dynamic_section) { 
  EXPECT_EQ(0xc080U, offset);

}



TEST_F(ElfTest, get_global_vaddr_with_tagged_pointer) {

  ElfFake elf(memory_);

  elf.FakeSetValid(true);

  elf.FakeSetArch(ARCH_ARM64);



  ElfInterfaceMock* interface = new ElfInterfaceMock(memory_);

  elf.FakeSetInterface(interface);

  interface->MockSetDataVaddrStart(0x500);

  interface->MockSetDataVaddrEnd(0x600);

  interface->MockSetDataOffset(0xa000);



  std::string global("something");

  EXPECT_CALL(*interface, GetGlobalVariable(global, ::testing::_))

      .WillOnce(::testing::DoAll(::testing::SetArgPointee<1>(0x8800000000000580),

                                 ::testing::Return(true)));



  uint64_t offset;

  ASSERT_TRUE(elf.GetGlobalVariableOffset(global, &offset));

  EXPECT_EQ(0xa080U, offset);

}



TEST_F(ElfTest, get_global_vaddr_without_tagged_pointer) {

  ElfFake elf(memory_);

  elf.FakeSetValid(true);

  elf.FakeSetArch(ARCH_X86_64);



  ElfInterfaceMock* interface = new ElfInterfaceMock(memory_);

  elf.FakeSetInterface(interface);

  interface->MockSetDataVaddrStart(0x8800000000000500);

  interface->MockSetDataVaddrEnd(0x8800000000000600);

  interface->MockSetDataOffset(0x880000000000a000);



  std::string global("something");

  EXPECT_CALL(*interface, GetGlobalVariable(global, ::testing::_))

      .WillOnce(::testing::DoAll(::testing::SetArgPointee<1>(0x8800000000000580),

                                 ::testing::Return(true)));



  uint64_t offset;

  ASSERT_TRUE(elf.GetGlobalVariableOffset(global, &offset));

  EXPECT_EQ(0x880000000000a080U, offset);

}



TEST_F(ElfTest, is_valid_pc_elf_invalid) {

  ElfFake elf(memory_);

  elf.FakeSetValid(false);