1//===--- SipHash.cpp - An ABI-stable string hash --------------------------===//
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// This file implements an ABI-stable string hash based on SipHash, used to
10// compute ptrauth discriminators.
11//
12//===----------------------------------------------------------------------===//
13
14#include "llvm/Support/SipHash.h"
15#include "siphash/SipHash.h"
16#include "llvm/ADT/ArrayRef.h"
17#include "llvm/ADT/StringExtras.h"
18#include "llvm/ADT/StringRef.h"
19#include "llvm/Support/Debug.h"
20#include "llvm/Support/Endian.h"
21#include <cstdint>
22
23using namespace llvm;
24using namespace support;
25
26#define DEBUG_TYPE "llvm-siphash"
27
28void llvm::getSipHash_2_4_64(ArrayRef<uint8_t> In, const uint8_t (&K)[16],
29 uint8_t (&Out)[8]) {
30 siphash<2, 4>(in: In.data(), inlen: In.size(), k: K, out&: Out);
31}
32
33void llvm::getSipHash_2_4_128(ArrayRef<uint8_t> In, const uint8_t (&K)[16],
34 uint8_t (&Out)[16]) {
35 siphash<2, 4>(in: In.data(), inlen: In.size(), k: K, out&: Out);
36}
37
38/// Compute an ABI-stable 64-bit hash of the given string.
39uint64_t llvm::getStableSipHash(StringRef Str) {
40 static const uint8_t K[16] = {0xb5, 0xd4, 0xc9, 0xeb, 0x79, 0x10, 0x4a, 0x79,
41 0x6f, 0xec, 0x8b, 0x1b, 0x42, 0x87, 0x81, 0xd4};
42
43 uint8_t RawHashBytes[8];
44 getSipHash_2_4_64(In: arrayRefFromStringRef(Input: Str), K, Out&: RawHashBytes);
45 return endian::read64le(P: RawHashBytes);
46}
47
48/// Compute an ABI-stable 16-bit hash of the given string.
49uint16_t llvm::getPointerAuthStableSipHash(StringRef Str) {
50 uint64_t RawHash = getStableSipHash(Str);
51
52 // Produce a non-zero 16-bit discriminator.
53 uint16_t Discriminator = (RawHash % 0xFFFF) + 1;
54 LLVM_DEBUG(
55 dbgs() << "ptrauth stable hash discriminator: " << utostr(Discriminator)
56 << " (0x"
57 << utohexstr(Discriminator, /*Lowercase=*/false, /*Width=*/4)
58 << ")"
59 << " of: " << Str << "\n");
60 return Discriminator;
61}
62