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: -mcrc32 (earlier: -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 #if defined(__CRC32__)
21 // NB: clang has <crc32intrin.h> but GCC does not
22 #include <smmintrin.h>
23 #define CRC32_INTRINSIC                                                        \
24   FIRST_32_SECOND_64(__builtin_ia32_crc32si, __builtin_ia32_crc32di)
25 #elif defined(__SSE4_2__)
26 #include <smmintrin.h>
27 #define CRC32_INTRINSIC FIRST_32_SECOND_64(_mm_crc32_u32, _mm_crc32_u64)
28 #endif
29 #ifdef __ARM_FEATURE_CRC32
30 #include <arm_acle.h>
31 #define CRC32_INTRINSIC FIRST_32_SECOND_64(__crc32cw, __crc32cd)
32 #endif
33 
34 namespace scudo {
35 
36 enum class Checksum : u8 {
37   BSD = 0,
38   HardwareCRC32 = 1,
39 };
40 
41 // BSD checksum, unlike a software CRC32, doesn't use any array lookup. We save
42 // significantly on memory accesses, as well as 1K of CRC32 table, on platforms
43 // that do no support hardware CRC32. The checksum itself is 16-bit, which is at
44 // odds with CRC32, but enough for our needs.
45 inline u16 computeBSDChecksum(u16 Sum, uptr Data) {
46   for (u8 I = 0; I < sizeof(Data); I++) {
47     Sum = static_cast<u16>((Sum >> 1) | ((Sum & 1) << 15));
48     Sum = static_cast<u16>(Sum + (Data & 0xff));
49     Data >>= 8;
50   }
51   return Sum;
52 }
53 
54 bool hasHardwareCRC32();
55 WEAK u32 computeHardwareCRC32(u32 Crc, uptr Data);
56 
57 } // namespace scudo
58 
59 #endif // SCUDO_CHECKSUM_H_
60