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Fix another UBSan test error from r248897 and follow on fix r249689

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While here fix a few more issues with potential overflow and add
new tests for these cases. Ensured that test now passes with UBSan.

llvm-svn: 249745
This commit is contained in:
Teresa Johnson 2015-10-08 20:52:23 +00:00
parent e7748def6e
commit d96ee5bedd
2 changed files with 101 additions and 11 deletions
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28
include/llvm/Support/Endian.h
View File

@ -78,6 +78,9 @@ inline void write(void *memory, value_type value) {
sizeof(value_type));
}
template <typename value_type>
using make_unsigned_t = typename std::make_unsigned<value_type>::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>
@ -96,13 +99,15 @@ inline value_type readAtBitAlignment(const void *memory, uint64_t startBit) {
val[1] = byte_swap<value_type, endian>(val[1]);
// Shift bits from the lower value into place.
unsigned lowerVal = val[0] >> startBit;
make_unsigned_t<value_type> 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;
make_unsigned_t<value_type> numBitsFirstVal =
(sizeof(value_type) * 8) - startBit;
lowerVal &= ((make_unsigned_t<value_type>)1 << numBitsFirstVal) - 1;
// Get the bits from the upper value.
unsigned upperVal = val[1] & ((1 << startBit) - 1);
make_unsigned_t<value_type> upperVal =
val[1] & (((make_unsigned_t<value_type>)1 << startBit) - 1);
// Shift them in to place.
upperVal <<= numBitsFirstVal;
@ -130,14 +135,15 @@ inline void writeAtBitAlignment(void *memory, value_type value,
// Mask off any existing bits in the upper part of the lower value that
// we want to replace.
val[0] &= (1 << startBit) - 1;
unsigned numBitsFirstVal = (sizeof(value_type) * 8) - startBit;
unsigned lowerVal = value;
val[0] &= ((make_unsigned_t<value_type>)1 << startBit) - 1;
make_unsigned_t<value_type> numBitsFirstVal =
(sizeof(value_type) * 8) - startBit;
make_unsigned_t<value_type> lowerVal = value;
if (startBit > 0) {
// Mask off the upper bits in the new value that are not going to go into
// the lower value. This avoids a left shift of a negative value, which
// is undefined behavior.
lowerVal &= ((1 << numBitsFirstVal) - 1);
lowerVal &= (((make_unsigned_t<value_type>)1 << numBitsFirstVal) - 1);
// Now shift the new bits into place
lowerVal <<= startBit;
}
@ -145,11 +151,11 @@ inline void writeAtBitAlignment(void *memory, value_type value,
// Mask off any existing bits in the lower part of the upper value that
// we want to replace.
val[1] &= ~((1 << startBit) - 1);
val[1] &= ~(((make_unsigned_t<value_type>)1 << startBit) - 1);
// Next shift the bits that go into the upper value into position.
unsigned upperVal = value >> numBitsFirstVal;
make_unsigned_t<value_type> upperVal = value >> numBitsFirstVal;
// Mask off upper bits after right shift in case of signed type.
upperVal &= (1 << startBit) - 1;
upperVal &= ((make_unsigned_t<value_type>)1 << startBit) - 1;
val[1] |= upperVal;
// Finally, rewrite values.

84
unittests/Support/EndianTest.cpp
View File

@ -50,6 +50,23 @@ TEST(Endian, ReadBitAligned) {
0x0f000000);
EXPECT_EQ((endian::readAtBitAlignment<int, big, unaligned>(&bigval2[0], 4)),
0x0f000000);
// Test to make sure left shift of start bit doesn't overflow.
EXPECT_EQ(
(endian::readAtBitAlignment<int, little, unaligned>(&littleval2[0], 1)),
0x78000000);
EXPECT_EQ((endian::readAtBitAlignment<int, big, unaligned>(&bigval2[0], 1)),
0x78000000);
// Test to make sure 64-bit int doesn't overflow.
unsigned char littleval3[] = {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xf0,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};
unsigned char bigval3[] = {0xf0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};
EXPECT_EQ((endian::readAtBitAlignment<int64_t, little, unaligned>(
&littleval3[0], 4)),
0x0f00000000000000);
EXPECT_EQ(
(endian::readAtBitAlignment<int64_t, big, unaligned>(&bigval3[0], 4)),
0x0f00000000000000);
}
TEST(Endian, WriteBitAligned) {
@ -78,6 +95,73 @@ TEST(Endian, WriteBitAligned) {
EXPECT_EQ(littleval[5], 0x00);
EXPECT_EQ(littleval[6], 0x00);
EXPECT_EQ(littleval[7], 0x00);
// This test makes sure 1<<31 doesn't overflow.
// Test to make sure left shift of start bit doesn't overflow.
unsigned char bigval2[8] = {0x00};
endian::writeAtBitAlignment<int32_t, big, unaligned>(bigval2, (int)0xffffffff,
1);
EXPECT_EQ(bigval2[0], 0xff);
EXPECT_EQ(bigval2[1], 0xff);
EXPECT_EQ(bigval2[2], 0xff);
EXPECT_EQ(bigval2[3], 0xfe);
EXPECT_EQ(bigval2[4], 0x00);
EXPECT_EQ(bigval2[5], 0x00);
EXPECT_EQ(bigval2[6], 0x00);
EXPECT_EQ(bigval2[7], 0x01);
unsigned char littleval2[8] = {0x00};
endian::writeAtBitAlignment<int32_t, little, unaligned>(littleval2,
(int)0xffffffff, 1);
EXPECT_EQ(littleval2[0], 0xfe);
EXPECT_EQ(littleval2[1], 0xff);
EXPECT_EQ(littleval2[2], 0xff);
EXPECT_EQ(littleval2[3], 0xff);
EXPECT_EQ(littleval2[4], 0x01);
EXPECT_EQ(littleval2[5], 0x00);
EXPECT_EQ(littleval2[6], 0x00);
EXPECT_EQ(littleval2[7], 0x00);
// Test to make sure 64-bit int doesn't overflow.
unsigned char bigval64[16] = {0x00};
endian::writeAtBitAlignment<int64_t, big, unaligned>(
bigval64, (int64_t)0xffffffffffffffff, 1);
EXPECT_EQ(bigval64[0], 0xff);
EXPECT_EQ(bigval64[1], 0xff);
EXPECT_EQ(bigval64[2], 0xff);
EXPECT_EQ(bigval64[3], 0xff);
EXPECT_EQ(bigval64[4], 0xff);
EXPECT_EQ(bigval64[5], 0xff);
EXPECT_EQ(bigval64[6], 0xff);
EXPECT_EQ(bigval64[7], 0xfe);
EXPECT_EQ(bigval64[8], 0x00);
EXPECT_EQ(bigval64[9], 0x00);
EXPECT_EQ(bigval64[10], 0x00);
EXPECT_EQ(bigval64[11], 0x00);
EXPECT_EQ(bigval64[12], 0x00);
EXPECT_EQ(bigval64[13], 0x00);
EXPECT_EQ(bigval64[14], 0x00);
EXPECT_EQ(bigval64[15], 0x01);
unsigned char littleval64[16] = {0x00};
endian::writeAtBitAlignment<int64_t, little, unaligned>(
littleval64, (int64_t)0xffffffffffffffff, 1);
EXPECT_EQ(littleval64[0], 0xfe);
EXPECT_EQ(littleval64[1], 0xff);
EXPECT_EQ(littleval64[2], 0xff);
EXPECT_EQ(littleval64[3], 0xff);
EXPECT_EQ(littleval64[4], 0xff);
EXPECT_EQ(littleval64[5], 0xff);
EXPECT_EQ(littleval64[6], 0xff);
EXPECT_EQ(littleval64[7], 0xff);
EXPECT_EQ(littleval64[8], 0x01);
EXPECT_EQ(littleval64[9], 0x00);
EXPECT_EQ(littleval64[10], 0x00);
EXPECT_EQ(littleval64[11], 0x00);
EXPECT_EQ(littleval64[12], 0x00);
EXPECT_EQ(littleval64[13], 0x00);
EXPECT_EQ(littleval64[14], 0x00);
EXPECT_EQ(littleval64[15], 0x00);
}
TEST(Endian, Write) {