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 23 using namespace llvm; 24 using namespace support; 25 26 #define DEBUG_TYPE "llvm-siphash" 27 28 void llvm::getSipHash_2_4_64(ArrayRef<uint8_t> In, const uint8_t (&K)[16], 29 uint8_t (&Out)[8]) { 30 siphash<2, 4>(In.data(), In.size(), K, Out); 31 } 32 33 void llvm::getSipHash_2_4_128(ArrayRef<uint8_t> In, const uint8_t (&K)[16], 34 uint8_t (&Out)[16]) { 35 siphash<2, 4>(In.data(), In.size(), K, Out); 36 } 37 38 /// Compute an ABI-stable 16-bit hash of the given string. 39 uint16_t llvm::getPointerAuthStableSipHash(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(arrayRefFromStringRef(Str), K, RawHashBytes); 45 uint64_t RawHash = endian::read64le(RawHashBytes); 46 47 // Produce a non-zero 16-bit discriminator. 48 uint16_t Discriminator = (RawHash % 0xFFFF) + 1; 49 LLVM_DEBUG( 50 dbgs() << "ptrauth stable hash discriminator: " << utostr(Discriminator) 51 << " (0x" 52 << utohexstr(Discriminator, /*Lowercase=*/false, /*Width=*/4) 53 << ")" 54 << " of: " << Str << "\n"); 55 return Discriminator; 56 } 57