Commit 6c4a8bc0 authored by Hans Wennborg's avatar Hans Wennborg
Browse files

Make llvm::crc32() work also for input sizes larger than 32 bits. 

The problem was noticed by the Chrome OS toolchain folks
(crbug.com/1048445) because llvm-objcopy --add-gnu-debuglink would
insert the wrong checksum when processing a binary larger than 4 GB.
That use case regressed in 1e1e3ba2 when we started using
llvm::crc32() in more places.

Differential revision: https://reviews.llvm.org/D74039
parent 364326ce

llvm/lib/Support/CRC.cpp

+9 −1
Original line number Diff line number Diff line
@@ -85,7 +85,15 @@ uint32_t llvm::crc32(uint32_t CRC, ArrayRef<uint8_t> Data) { 


#include <zlib.h>

uint32_t llvm::crc32(uint32_t CRC, ArrayRef<uint8_t> Data) {

  return ::crc32(CRC, (const Bytef *)Data.data(), Data.size());

  // Zlib's crc32() only takes a 32-bit length, so we have to iterate for larger

  // sizes. One could use crc32_z() instead, but that's a recent (2017) addition

  // and may not be available on all systems.

  do {

    ArrayRef<uint8_t> Slice = Data.take_front(UINT32_MAX);

    CRC = ::crc32(CRC, (const Bytef *)Slice.data(), (uInt)Slice.size());

    Data = Data.drop_front(Slice.size());

  } while (Data.size() > 0);

  return CRC;

}



#endif

llvm/unittests/Support/CRCTest.cpp

+20 −0
Original line number Diff line number Diff line
@@ -13,6 +13,7 @@ 
#include "llvm/Support/CRC.h"

#include "llvm/ADT/StringExtras.h"

#include "gtest/gtest.h"

#include <stdlib.h>



using namespace llvm;
@@ -39,6 +40,25 @@ TEST(CRCTest, CRC32) { 
    uint8_t byte = i;

    EXPECT_EQ(crc, ~llvm::crc32(0xFFFFFFFFU, byte));

  }



  EXPECT_EQ(0x00000000U, llvm::crc32(arrayRefFromStringRef("")));

}



#if (SIZE_MAX > UINT32_MAX) && defined(EXPENSIVE_CHECKS)

TEST(CRCTest, LargeCRC32) {

  // Check that crc32 can handle inputs with sizes larger than 32 bits.

  size_t TestSize = (size_t)UINT32_MAX + 42;

  uint8_t *TestData = (uint8_t*)calloc(TestSize, 1);

  if (!TestData)

    return;



  // Test expectation generated with:

  // $ truncate --size=`echo 2^32-1+42 | bc` /tmp/foo

  // $ crc32 /tmp/foo

  EXPECT_EQ(0xE46F28FBU, llvm::crc32(makeArrayRef(TestData, TestSize)));



  free(TestData);

}

#endif



} // end anonymous namespace