[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
Thu Oct 8 08:14:21 PDT 2015
Thanks for fixing the issue! I’ll watch the bots to verify that it worked.
-- adrian
> On Oct 8, 2015, at 6:19 AM, Teresa Johnson <tejohnson at google.com> wrote:
>
> I committed a fix at r249689. I didn't have a chance to validate via a
> UBSan build, but will try to do so now. I did confirm that it
> correctly avoids a negative value going into the left shift for that
> test, however, so I anticipate that it will address the failure.
>
> Thanks,
> Teresa
>
> On Wed, Oct 7, 2015 at 5:07 PM, Adrian Prantl <aprantl at apple.com> wrote:
>>
>>> 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
>>>
>>
>
>
>
> --
> Teresa Johnson | Software Engineer | tejohnson at google.com | 408-460-2413
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