62 lines · cpp
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-exception6//7//===----------------------------------------------------------------------===//8//9// This file implements an ABI-stable string hash based on SipHash, used to10// 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.data(), In.size(), K, 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.data(), In.size(), K, 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(arrayRefFromStringRef(Str), K, RawHashBytes);45 return endian::read64le(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