3408e6af75
Factor out the 64-bit hash calculation in getPointerAuthStableSipHash() as getStableSipHash(). This allows using the full 64-bit hash where we require a stable hash. Similar to getPointerAuthStableSipHash(), the new hash function is meant to be stable across platforms and compiler versions.
62 lines
2.1 KiB
C++
62 lines
2.1 KiB
C++
//===--- SipHash.cpp - An ABI-stable string hash --------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements an ABI-stable string hash based on SipHash, used to
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// compute ptrauth discriminators.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Support/SipHash.h"
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#include "siphash/SipHash.h"
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#include "llvm/ADT/ArrayRef.h"
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#include "llvm/ADT/StringExtras.h"
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#include "llvm/ADT/StringRef.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/Endian.h"
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#include <cstdint>
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using namespace llvm;
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using namespace support;
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#define DEBUG_TYPE "llvm-siphash"
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void llvm::getSipHash_2_4_64(ArrayRef<uint8_t> In, const uint8_t (&K)[16],
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uint8_t (&Out)[8]) {
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siphash<2, 4>(In.data(), In.size(), K, Out);
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}
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void llvm::getSipHash_2_4_128(ArrayRef<uint8_t> In, const uint8_t (&K)[16],
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uint8_t (&Out)[16]) {
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siphash<2, 4>(In.data(), In.size(), K, Out);
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}
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/// Compute an ABI-stable 64-bit hash of the given string.
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uint64_t llvm::getStableSipHash(StringRef Str) {
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static const uint8_t K[16] = {0xb5, 0xd4, 0xc9, 0xeb, 0x79, 0x10, 0x4a, 0x79,
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0x6f, 0xec, 0x8b, 0x1b, 0x42, 0x87, 0x81, 0xd4};
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uint8_t RawHashBytes[8];
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getSipHash_2_4_64(arrayRefFromStringRef(Str), K, RawHashBytes);
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return endian::read64le(RawHashBytes);
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}
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/// Compute an ABI-stable 16-bit hash of the given string.
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uint16_t llvm::getPointerAuthStableSipHash(StringRef Str) {
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uint64_t RawHash = getStableSipHash(Str);
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// Produce a non-zero 16-bit discriminator.
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uint16_t Discriminator = (RawHash % 0xFFFF) + 1;
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LLVM_DEBUG(
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dbgs() << "ptrauth stable hash discriminator: " << utostr(Discriminator)
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<< " (0x"
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<< utohexstr(Discriminator, /*Lowercase=*/false, /*Width=*/4)
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<< ")"
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<< " of: " << Str << "\n");
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return Discriminator;
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}
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