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//===--- StableHash.cpp - Context to hold long-lived AST nodes ------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file implements an ABI-stable string hash based on SipHash.
//
//===----------------------------------------------------------------------===//
#include "clang/AST/StableHash.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/Support/Debug.h"
#include <cstdint>
#include <cstring>
using namespace clang;
#define DEBUG_TYPE "clang-stable-hash"
#define SIPHASH_ROTL(x, b) (uint64_t)(((x) << (b)) | ((x) >> (64 - (b))))
#define SIPHASH_U8TO64_LE(p) \
(((uint64_t)((p)[0])) | ((uint64_t)((p)[1]) << 8) | \
((uint64_t)((p)[2]) << 16) | ((uint64_t)((p)[3]) << 24) | \
((uint64_t)((p)[4]) << 32) | ((uint64_t)((p)[5]) << 40) | \
((uint64_t)((p)[6]) << 48) | ((uint64_t)((p)[7]) << 56))
#define SIPHASH_SIPROUND \
do { \
v0 += v1; \
v1 = SIPHASH_ROTL(v1, 13); \
v1 ^= v0; \
v0 = SIPHASH_ROTL(v0, 32); \
v2 += v3; \
v3 = SIPHASH_ROTL(v3, 16); \
v3 ^= v2; \
v0 += v3; \
v3 = SIPHASH_ROTL(v3, 21); \
v3 ^= v0; \
v2 += v1; \
v1 = SIPHASH_ROTL(v1, 17); \
v1 ^= v2; \
v2 = SIPHASH_ROTL(v2, 32); \
} while (0)
template <int cROUNDS, int dROUNDS, class ResultTy>
static inline ResultTy siphash(const uint8_t *in, uint64_t inlen,
const uint8_t (&k)[16]) {
static_assert(sizeof(ResultTy) == 8 || sizeof(ResultTy) == 16,
"result type should be uint64_t or uint128_t");
uint64_t v0 = 0x736f6d6570736575ULL;
uint64_t v1 = 0x646f72616e646f6dULL;
uint64_t v2 = 0x6c7967656e657261ULL;
uint64_t v3 = 0x7465646279746573ULL;
uint64_t b;
uint64_t k0 = SIPHASH_U8TO64_LE(k);
uint64_t k1 = SIPHASH_U8TO64_LE(k + 8);
uint64_t m;
int i;
const uint8_t *end = in + inlen - (inlen % sizeof(uint64_t));
const int left = inlen & 7;
b = ((uint64_t)inlen) << 56;
v3 ^= k1;
v2 ^= k0;
v1 ^= k1;
v0 ^= k0;
if (sizeof(ResultTy) == 16) {
v1 ^= 0xee;
}
for (; in != end; in += 8) {
m = SIPHASH_U8TO64_LE(in);
v3 ^= m;
for (i = 0; i < cROUNDS; ++i)
SIPHASH_SIPROUND;
v0 ^= m;
}
switch (left) {
case 7:
b |= ((uint64_t)in[6]) << 48;
LLVM_FALLTHROUGH;
case 6:
b |= ((uint64_t)in[5]) << 40;
LLVM_FALLTHROUGH;
case 5:
b |= ((uint64_t)in[4]) << 32;
LLVM_FALLTHROUGH;
case 4:
b |= ((uint64_t)in[3]) << 24;
LLVM_FALLTHROUGH;
case 3:
b |= ((uint64_t)in[2]) << 16;
LLVM_FALLTHROUGH;
case 2:
b |= ((uint64_t)in[1]) << 8;
LLVM_FALLTHROUGH;
case 1:
b |= ((uint64_t)in[0]);
break;
case 0:
break;
}
v3 ^= b;
for (i = 0; i < cROUNDS; ++i)
SIPHASH_SIPROUND;
v0 ^= b;
if (sizeof(ResultTy) == 8) {
v2 ^= 0xff;
} else {
v2 ^= 0xee;
}
for (i = 0; i < dROUNDS; ++i)
SIPHASH_SIPROUND;
b = v0 ^ v1 ^ v2 ^ v3;
// This mess with the result type would be easier with 'if constexpr'.
uint64_t firstHalf = b;
if (sizeof(ResultTy) == 8)
return firstHalf;
v1 ^= 0xdd;
for (i = 0; i < dROUNDS; ++i)
SIPHASH_SIPROUND;
b = v0 ^ v1 ^ v2 ^ v3;
uint64_t secondHalf = b;
return firstHalf
| (ResultTy(secondHalf) << (sizeof(ResultTy) == 8 ? 0 : 64));
}
/// Compute an ABI-stable hash of the given string.
uint64_t clang::getStableStringHash(llvm::StringRef string) {
static const uint8_t K[16] = {0xb5, 0xd4, 0xc9, 0xeb, 0x79, 0x10, 0x4a, 0x79,
0x6f, 0xec, 0x8b, 0x1b, 0x42, 0x87, 0x81, 0xd4};
// The aliasing is fine here because of omnipotent char.
auto data = reinterpret_cast<const uint8_t*>(string.data());
return siphash<2, 4, uint64_t>(data, string.size(), K);
}
uint64_t clang::getPointerAuthStringDiscriminator(const ASTContext &ctxt,
llvm::StringRef string) {
auto rawHash = getStableStringHash(string);
// Don't do anything target-specific yet.
// Produce a non-zero 16-bit discriminator.
// We use a 16-bit discriminator because ARM64 can efficiently load
// a 16-bit immediate into the high bits of a register without disturbing
// the remainder of the value, which serves as a nice blend operation.
// 16 bits is also sufficiently compact to not inflate a loader relocation.
// We disallow zero to guarantee a different discriminator from the places
// in the ABI that use a constant zero.
uint64_t discriminator = (rawHash % 0xFFFF) + 1;
LLVM_DEBUG(
llvm::dbgs() << "Ptrauth string disc: " << llvm::utostr(discriminator)
<< " (0x" << llvm::utohexstr(discriminator) << ")"
<< " of: " << string << "\n");
return discriminator;
}
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