checksum.h revision 360784 
1//===-- checksum.h ----------------------------------------------*- C++ -*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8
9#ifndef SCUDO_CHECKSUM_H_
10#define SCUDO_CHECKSUM_H_
11
12#include "internal_defs.h"
13
14// Hardware CRC32 is supported at compilation via the following:
15// - for i386 & x86_64: -msse4.2
16// - for ARM & AArch64: -march=armv8-a+crc or -mcrc
17// An additional check must be performed at runtime as well to make sure the
18// emitted instructions are valid on the target host.
19
20#ifdef __SSE4_2__
21#include <smmintrin.h>
22#define CRC32_INTRINSIC FIRST_32_SECOND_64(_mm_crc32_u32, _mm_crc32_u64)
23#endif
24#ifdef __ARM_FEATURE_CRC32
25#include <arm_acle.h>
26#define CRC32_INTRINSIC FIRST_32_SECOND_64(__crc32cw, __crc32cd)
27#endif
28
29namespace scudo {
30
31enum class Checksum : u8 {
32  BSD = 0,
33  HardwareCRC32 = 1,
34};
35
36// BSD checksum, unlike a software CRC32, doesn't use any array lookup. We save
37// significantly on memory accesses, as well as 1K of CRC32 table, on platforms
38// that do no support hardware CRC32. The checksum itself is 16-bit, which is at
39// odds with CRC32, but enough for our needs.
40inline u16 computeBSDChecksum(u16 Sum, uptr Data) {
41  for (u8 I = 0; I < sizeof(Data); I++) {
42    Sum = static_cast<u16>((Sum >> 1) | ((Sum & 1) << 15));
43    Sum = static_cast<u16>(Sum + (Data & 0xff));
44    Data >>= 8;
45  }
46  return Sum;
47}
48
49bool hasHardwareCRC32();
50WEAK u32 computeHardwareCRC32(u32 Crc, uptr Data);
51
52} // namespace scudo
53
54#endif // SCUDO_CHECKSUM_H_
55