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Commit c71e0a65 authored by Peter Collingbourne's avatar Peter Collingbourne Committed by Christopher Ferris
Browse files

libunwindstack: Add Memory::ReadTag() function for reading memory tags. 

This uses an experimental Linux kernel API for reading the tags across
processes using ptrace.

Bug: 135772972

Test: Unit tests pass.
Change-Id: Ib1a09d9219166011de80cf250b756bb8a4bcdb0a
parent 585ff019

libunwindstack/Android.bp

+22 −0
Original line number Diff line number Diff line
@@ -57,6 +57,7 @@ cc_defaults { 
        "MapInfo.cpp",

        "Maps.cpp",

        "Memory.cpp",

        "MemoryMte.cpp",

        "LocalUnwinder.cpp",

        "Regs.cpp",

        "RegsArm.cpp",
@@ -101,6 +102,16 @@ cc_defaults { 
        "liblog",

        "liblzma",

    ],



    header_libs: [

        "bionic_libc_platform_headers",

    ],



    product_variables: {

        experimental_mte: {

            cflags: ["-DANDROID_EXPERIMENTAL_MTE"],

        },

    },

}



cc_library {
@@ -213,6 +224,7 @@ cc_defaults { 
        "tests/MemoryRangesTest.cpp",

        "tests/MemoryRemoteTest.cpp",

        "tests/MemoryTest.cpp",

        "tests/MemoryMteTest.cpp",

        "tests/RegsInfoTest.cpp",

        "tests/RegsIterateTest.cpp",

        "tests/RegsStepIfSignalHandlerTest.cpp",
@@ -268,6 +280,16 @@ cc_defaults { 
        "tests/files/offline/straddle_arm/*",

        "tests/files/offline/straddle_arm64/*",

    ],



    header_libs: [

        "bionic_libc_platform_headers",

    ],



    product_variables: {

        experimental_mte: {

            cflags: ["-DANDROID_EXPERIMENTAL_MTE"],

        },

    },

}



cc_test {

libunwindstack/Memory.cpp

+10 −0
Original line number Diff line number Diff line
@@ -324,6 +324,16 @@ size_t MemoryLocal::Read(uint64_t addr, void* dst, size_t size) { 
  return ProcessVmRead(getpid(), addr, dst, size);

}



#if !defined(ANDROID_EXPERIMENTAL_MTE)

long MemoryRemote::ReadTag(uint64_t) {

  return -1;

}



long MemoryLocal::ReadTag(uint64_t) {

  return -1;

}

#endif



MemoryRange::MemoryRange(const std::shared_ptr<Memory>& memory, uint64_t begin, uint64_t length,

                         uint64_t offset)

    : memory_(memory), begin_(begin), length_(length), offset_(offset) {}

libunwindstack/MemoryCache.h

+1 −0
Original line number Diff line number Diff line
@@ -33,6 +33,7 @@ class MemoryCache : public Memory { 
  virtual ~MemoryCache() = default;



  size_t Read(uint64_t addr, void* dst, size_t size) override;

  long ReadTag(uint64_t addr) override { return impl_->ReadTag(addr); }



  void Clear() override { cache_.clear(); }

libunwindstack/MemoryLocal.h

+1 −0
Original line number Diff line number Diff line
@@ -31,6 +31,7 @@ class MemoryLocal : public Memory { 
  bool IsLocal() const override { return true; }



  size_t Read(uint64_t addr, void* dst, size_t size) override;

  long ReadTag(uint64_t addr) override;

};



}  // namespace unwindstack

libunwindstack/MemoryMte.cpp

0 → 100644
+57 −0
Original line number Diff line number Diff line 
/*

 * Copyright (C) 2020 The Android Open Source Project

 *

 * Licensed under the Apache License, Version 2.0 (the "License");

 * you may not use this file except in compliance with the License.

 * You may obtain a copy of the License at

 *

 *      http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */



#if defined(ANDROID_EXPERIMENTAL_MTE)



#include <sys/ptrace.h>



#include <bionic/mte.h>

#include <bionic/mte_kernel.h>



#include "MemoryLocal.h"

#include "MemoryRemote.h"



namespace unwindstack {



long MemoryRemote::ReadTag(uint64_t addr) {

#if defined(__aarch64__)

  return ptrace(PTRACE_PEEKTAG, pid_, (void*)addr, nullptr);

#else

  (void)addr;

  return -1;

#endif

}



long MemoryLocal::ReadTag(uint64_t addr) {

#if defined(__aarch64__)

  // Check that the memory is readable first. This is racy with the ldg but there's not much

  // we can do about it.

  char data;

  if (!mte_supported() || !Read(addr, &data, 1)) {

    return -1;

  }



  __asm__ __volatile__(".arch_extension mte; ldg %0, [%0]" : "+r"(addr) : : "memory");

  return (addr >> 56) & 0xf;

#else

  (void)addr;

  return -1;

#endif

}



}  // namespace unwindstack



#endif