[llvm] r248897 - Add support for sub-byte aligned writes to lib/Support/Endian.h
Adrian Prantl via llvm-commits
llvm-commits at lists.llvm.org
Wed Oct 7 17:07:10 PDT 2015
> On Oct 7, 2015, at 5:05 PM, Adrian Prantl <aprantl at apple.com> wrote:
>
> It’s a two-stage process. First the stage1 bot builds the compiler and the sanitizer-enabled runtime (you may be able to skip this step if you have one lying around) and then the second stage compiler runs came with '-DLLVM_USE_SANITIZER=Address;Undefined’ and a blacklist for certain C++ stdlib headers.
>
> At the top of this log you can see the full set of options passed to make:
>
> http://lab.llvm.org:8080/green/job/clang-stage2-cmake-RgSan_build/487/consoleFull
>
>
> — adrian
>
>> On Oct 7, 2015, at 5:00 PM, Teresa Johnson <tejohnson at google.com> wrote:
>>
>> How do I get UBSan to run on the unittests? I don't see where the
>> option is being added on the buildbot page, but maybe I missed it.
The jenkins bots run three sub-jobs: Acquire, Build, Check. This is probably why you didn’t see it.
>> Thanks,
>> Teresa
>>
>> On Wed, Oct 7, 2015 at 4:18 PM, Teresa Johnson <tejohnson at google.com> wrote:
>>> Yes, I added that function and see the problem. I will fix the UBSan
>>> error by masking off the upper bits before the shift. It might be
>>> tomorrow morning before I can fix it though as I am going offline
>>> shortly. Will try to get it in today though.
>>> Teresa
>>>
>>> On Wed, Oct 7, 2015 at 2:52 PM, Adrian Prantl <aprantl at apple.com> wrote:
>>>> Hi Teresa,
>>>>
>>>> I’m still working on confirming it, but it looks quite plausible that this commit caused the following UBSan test failure on lab.llvm.org:
>>>>
>>>> http://lab.llvm.org:8080/green/job/clang-stage2-cmake-RgSan_check/477/consoleFull#-1567746458254eaf0-7326-4999-85b0-388101f2d404
>>>>
>>>> FAIL: LLVM-Unit :: Support/SupportTests/Endian.WriteBitAligned (23480 of 23746)
>>>>
>>>> ******************** TEST 'LLVM-Unit :: Support/SupportTests/Endian.WriteBitAligned' FAILED ********************
>>>>
>>>> Note: Google Test filter = Endian.WriteBitAligned
>>>> [==========] Running 1 test from 1 test case.
>>>> [----------] Global test environment set-up.
>>>> [----------] 1 test from Endian
>>>> [ RUN ] Endian.WriteBitAligned
>>>> /Users/buildslave/jenkins/sharedspace/clang-stage2-cmake-RgSan at 2/llvm/include/llvm/Support/Endian.h:135:21: runtime error: left shift of negative value -21846
>>>> SUMMARY: AddressSanitizer: undefined-behavior /Users/buildslave/jenkins/sharedspace/clang-stage2-cmake-RgSan at 2/llvm/include/llvm/Support/Endian.h:135:21 in
>>>> 0 SupportTests 0x00000001009c01c3 llvm::sys::PrintStackTrace(llvm::raw_ostream&) + 339
>>>> 1 SupportTests 0x00000001009beaa5 llvm::sys::RunSignalHandlers() + 213
>>>> 2 SupportTests 0x00000001009c143f SignalHandler(int) + 655
>>>> 3 libsystem_platform.dylib 0x00007fff8b72ef1a _sigtramp + 26
>>>> 4 libclang_rt.asan_osx_dynamic.dylib 0x0000000101c0678d getTypeCacheHashTableBucket(unsigned long)::__ubsan_vptr_hash_set + 532925
>>>> 5 libsystem_c.dylib 0x00007fff853459b3 abort + 129
>>>> 6 libclang_rt.asan_osx_dynamic.dylib 0x0000000100ee5f56 __sanitizer::Abort() + 6
>>>>
>>>>
>>>>
>>>> -- adrian
>>>>
>>>>
>>>>> On Sep 30, 2015, at 6:20 AM, Teresa Johnson via llvm-commits <llvm-commits at lists.llvm.org> wrote:
>>>>>
>>>>> Author: tejohnson
>>>>> Date: Wed Sep 30 08:20:37 2015
>>>>> New Revision: 248897
>>>>>
>>>>> URL: http://llvm.org/viewvc/llvm-project?rev=248897&view=rev
>>>>> Log:
>>>>> Add support for sub-byte aligned writes to lib/Support/Endian.h
>>>>>
>>>>> Summary:
>>>>> As per Duncan's review for D12536, I extracted the sub-byte bit aligned
>>>>> reading and writing code into lib/Support, and generalized it. Added calls from
>>>>> BackpatchWord. Also added unittests.
>>>>>
>>>>> Reviewers: dexonsmith
>>>>>
>>>>> Subscribers: llvm-commits
>>>>>
>>>>> Differential Revision: http://reviews.llvm.org/D13189
>>>>>
>>>>> Modified:
>>>>> llvm/trunk/include/llvm/Bitcode/BitstreamWriter.h
>>>>> llvm/trunk/include/llvm/Support/Endian.h
>>>>> llvm/trunk/unittests/Support/EndianTest.cpp
>>>>>
>>>>> Modified: llvm/trunk/include/llvm/Bitcode/BitstreamWriter.h
>>>>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Bitcode/BitstreamWriter.h?rev=248897&r1=248896&r2=248897&view=diff
>>>>> ==============================================================================
>>>>> --- llvm/trunk/include/llvm/Bitcode/BitstreamWriter.h (original)
>>>>> +++ llvm/trunk/include/llvm/Bitcode/BitstreamWriter.h Wed Sep 30 08:20:37 2015
>>>>> @@ -102,18 +102,13 @@ public:
>>>>> /// Backpatch a 32-bit word in the output at the given bit offset
>>>>> /// with the specified value.
>>>>> void BackpatchWord(uint64_t BitNo, unsigned NewWord) {
>>>>> + using namespace llvm::support;
>>>>> unsigned ByteNo = BitNo / 8;
>>>>> - if ((BitNo & 7) == 0) {
>>>>> - // Already 8-bit aligned
>>>>> - support::endian::write32le(&Out[ByteNo], NewWord);
>>>>> - } else {
>>>>> - uint64_t CurDWord = support::endian::read64le(&Out[ByteNo]);
>>>>> - unsigned StartBit = BitNo & 7;
>>>>> - // Currently expect to backpatch 0-value placeholders.
>>>>> - assert(((CurDWord >> StartBit) & 0xffffffff) == 0);
>>>>> - CurDWord |= NewWord << StartBit;
>>>>> - support::endian::write64le(&Out[ByteNo], CurDWord);
>>>>> - }
>>>>> + assert((!endian::readAtBitAlignment<uint32_t, little, unaligned>(
>>>>> + &Out[ByteNo], BitNo & 7)) &&
>>>>> + "Expected to be patching over 0-value placeholders");
>>>>> + endian::writeAtBitAlignment<uint32_t, little, unaligned>(
>>>>> + &Out[ByteNo], NewWord, BitNo & 7);
>>>>> }
>>>>>
>>>>> void Emit(uint32_t Val, unsigned NumBits) {
>>>>>
>>>>> Modified: llvm/trunk/include/llvm/Support/Endian.h
>>>>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Support/Endian.h?rev=248897&r1=248896&r2=248897&view=diff
>>>>> ==============================================================================
>>>>> --- llvm/trunk/include/llvm/Support/Endian.h (original)
>>>>> +++ llvm/trunk/include/llvm/Support/Endian.h Wed Sep 30 08:20:37 2015
>>>>> @@ -77,6 +77,81 @@ inline void write(void *memory, value_ty
>>>>> &value,
>>>>> sizeof(value_type));
>>>>> }
>>>>> +
>>>>> +/// Read a value of a particular endianness from memory, for a location
>>>>> +/// that starts at the given bit offset within the first byte.
>>>>> +template <typename value_type, endianness endian, std::size_t alignment>
>>>>> +inline value_type readAtBitAlignment(const void *memory, uint64_t startBit) {
>>>>> + assert(startBit < 8);
>>>>> + if (startBit == 0)
>>>>> + return read<value_type, endian, alignment>(memory);
>>>>> + else {
>>>>> + // Read two values and compose the result from them.
>>>>> + value_type val[2];
>>>>> + memcpy(&val[0],
>>>>> + LLVM_ASSUME_ALIGNED(
>>>>> + memory, (detail::PickAlignment<value_type, alignment>::value)),
>>>>> + sizeof(value_type) * 2);
>>>>> + val[0] = byte_swap<value_type, endian>(val[0]);
>>>>> + val[1] = byte_swap<value_type, endian>(val[1]);
>>>>> +
>>>>> + // Shift bits from the lower value into place.
>>>>> + unsigned lowerVal = val[0] >> startBit;
>>>>> + // Mask off upper bits after right shift in case of signed type.
>>>>> + unsigned numBitsFirstVal = (sizeof(value_type) * 8) - startBit;
>>>>> + lowerVal &= (1 << numBitsFirstVal) - 1;
>>>>> +
>>>>> + // Get the bits from the upper value.
>>>>> + unsigned upperVal = val[1] & ((1 << startBit) - 1);
>>>>> + // Shift them in to place.
>>>>> + upperVal <<= numBitsFirstVal;
>>>>> +
>>>>> + return lowerVal | upperVal;
>>>>> + }
>>>>> +}
>>>>> +
>>>>> +/// Write a value to memory with a particular endianness, for a location
>>>>> +/// that starts at the given bit offset within the first byte.
>>>>> +template <typename value_type, endianness endian, std::size_t alignment>
>>>>> +inline void writeAtBitAlignment(void *memory, value_type value,
>>>>> + uint64_t startBit) {
>>>>> + assert(startBit < 8);
>>>>> + if (startBit == 0)
>>>>> + write<value_type, endian, alignment>(memory, value);
>>>>> + else {
>>>>> + // Read two values and shift the result into them.
>>>>> + value_type val[2];
>>>>> + memcpy(&val[0],
>>>>> + LLVM_ASSUME_ALIGNED(
>>>>> + memory, (detail::PickAlignment<value_type, alignment>::value)),
>>>>> + sizeof(value_type) * 2);
>>>>> + val[0] = byte_swap<value_type, endian>(val[0]);
>>>>> + val[1] = byte_swap<value_type, endian>(val[1]);
>>>>> +
>>>>> + // Mask off any existing bits in the upper part of the lower value that
>>>>> + // we want to replace.
>>>>> + val[0] &= (1 << startBit) - 1;
>>>>> + // Now shift in the new bits
>>>>> + val[0] |= value << startBit;
>>>>> +
>>>>> + // Mask off any existing bits in the lower part of the upper value that
>>>>> + // we want to replace.
>>>>> + val[1] &= ~((1 << startBit) - 1);
>>>>> + // Next shift the bits that go into the upper value into position.
>>>>> + unsigned numBitsFirstVal = (sizeof(value_type) * 8) - startBit;
>>>>> + unsigned upperVal = value >> numBitsFirstVal;
>>>>> + // Mask off upper bits after right shift in case of signed type.
>>>>> + upperVal &= (1 << startBit) - 1;
>>>>> + val[1] |= upperVal;
>>>>> +
>>>>> + // Finally, rewrite values.
>>>>> + val[0] = byte_swap<value_type, endian>(val[0]);
>>>>> + val[1] = byte_swap<value_type, endian>(val[1]);
>>>>> + memcpy(LLVM_ASSUME_ALIGNED(
>>>>> + memory, (detail::PickAlignment<value_type, alignment>::value)),
>>>>> + &val[0], sizeof(value_type) * 2);
>>>>> + }
>>>>> +}
>>>>> } // end namespace endian
>>>>>
>>>>> namespace detail {
>>>>>
>>>>> Modified: llvm/trunk/unittests/Support/EndianTest.cpp
>>>>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/unittests/Support/EndianTest.cpp?rev=248897&r1=248896&r2=248897&view=diff
>>>>> ==============================================================================
>>>>> --- llvm/trunk/unittests/Support/EndianTest.cpp (original)
>>>>> +++ llvm/trunk/unittests/Support/EndianTest.cpp Wed Sep 30 08:20:37 2015
>>>>> @@ -32,6 +32,54 @@ TEST(Endian, Read) {
>>>>> (endian::read<int32_t, little, unaligned>(littleval + 1)));
>>>>> }
>>>>>
>>>>> +TEST(Endian, ReadBitAligned) {
>>>>> + // Simple test to make sure we properly pull out the 0x0 word.
>>>>> + unsigned char littleval[] = {0x3f, 0x00, 0x00, 0x00, 0xc0, 0xff, 0xff, 0xff};
>>>>> + unsigned char bigval[] = {0x00, 0x00, 0x00, 0x3f, 0xff, 0xff, 0xff, 0xc0};
>>>>> + EXPECT_EQ(
>>>>> + (endian::readAtBitAlignment<int, little, unaligned>(&littleval[0], 6)),
>>>>> + 0x0);
>>>>> + EXPECT_EQ((endian::readAtBitAlignment<int, big, unaligned>(&bigval[0], 6)),
>>>>> + 0x0);
>>>>> + // Test to make sure that signed right shift of 0xf0000000 is masked
>>>>> + // properly.
>>>>> + unsigned char littleval2[] = {0x00, 0x00, 0x00, 0xf0, 0x00, 0x00, 0x00, 0x00};
>>>>> + unsigned char bigval2[] = {0xf0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};
>>>>> + EXPECT_EQ(
>>>>> + (endian::readAtBitAlignment<int, little, unaligned>(&littleval2[0], 4)),
>>>>> + 0x0f000000);
>>>>> + EXPECT_EQ((endian::readAtBitAlignment<int, big, unaligned>(&bigval2[0], 4)),
>>>>> + 0x0f000000);
>>>>> +}
>>>>> +
>>>>> +TEST(Endian, WriteBitAligned) {
>>>>> + // This test ensures that signed right shift of 0xffffaa is masked
>>>>> + // properly.
>>>>> + unsigned char bigval[8] = {0x00};
>>>>> + endian::writeAtBitAlignment<int32_t, big, unaligned>(bigval, (int)0xffffaaaa,
>>>>> + 4);
>>>>> + EXPECT_EQ(bigval[0], 0xff);
>>>>> + EXPECT_EQ(bigval[1], 0xfa);
>>>>> + EXPECT_EQ(bigval[2], 0xaa);
>>>>> + EXPECT_EQ(bigval[3], 0xa0);
>>>>> + EXPECT_EQ(bigval[4], 0x00);
>>>>> + EXPECT_EQ(bigval[5], 0x00);
>>>>> + EXPECT_EQ(bigval[6], 0x00);
>>>>> + EXPECT_EQ(bigval[7], 0x0f);
>>>>> +
>>>>> + unsigned char littleval[8] = {0x00};
>>>>> + endian::writeAtBitAlignment<int32_t, little, unaligned>(littleval,
>>>>> + (int)0xffffaaaa, 4);
>>>>> + EXPECT_EQ(littleval[0], 0xa0);
>>>>> + EXPECT_EQ(littleval[1], 0xaa);
>>>>> + EXPECT_EQ(littleval[2], 0xfa);
>>>>> + EXPECT_EQ(littleval[3], 0xff);
>>>>> + EXPECT_EQ(littleval[4], 0x0f);
>>>>> + EXPECT_EQ(littleval[5], 0x00);
>>>>> + EXPECT_EQ(littleval[6], 0x00);
>>>>> + EXPECT_EQ(littleval[7], 0x00);
>>>>> +}
>>>>> +
>>>>> TEST(Endian, Write) {
>>>>> unsigned char data[5];
>>>>> endian::write<int32_t, big, unaligned>(data, -1362446643);
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> llvm-commits mailing list
>>>>> llvm-commits at lists.llvm.org
>>>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits
>>>>
>>>
>>>
>>>
>>> --
>>> Teresa Johnson | Software Engineer | tejohnson at google.com | 408-460-2413
>>
>>
>>
>> --
>> Teresa Johnson | Software Engineer | tejohnson at google.com | 408-460-2413
>
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