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 
29 namespace scudo {
30 
31 enum 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.
40 inline 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 
49 bool hasHardwareCRC32();
50 WEAK u32 computeHardwareCRC32(u32 Crc, uptr Data);
51 
52 } // namespace scudo
53 
54 #endif // SCUDO_CHECKSUM_H_
55