[llvm] r248897 - Add support for sub-byte aligned writes to lib/Support/Endian.h
Teresa Johnson via llvm-commits
llvm-commits at lists.llvm.org
Thu Oct 8 13:55:25 PDT 2015
Just committed follow-on fix r249745, this time with an expanded
unittest for overflow conditions, and I made sure the test passed with
UBSan. Hopefully that takes care of it!
Teresa
On Thu, Oct 8, 2015 at 8:14 AM, Adrian Prantl <aprantl at apple.com> wrote:
> 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
>
--
Teresa Johnson | Software Engineer | tejohnson at google.com | 408-460-2413
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