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1//===------------------------ nsan_platform.h -------------------*- C++ -*-===//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// Platform specific information for NSan.10//11//===----------------------------------------------------------------------===//12 13#ifndef NSAN_PLATFORM_H14#define NSAN_PLATFORM_H15 16namespace __nsan {17 18// NSan uses two regions of memory to store information:19// - 'shadow memory' stores the shadow copies of numerical values stored in20// application memory.21// - 'shadow types' is used to determine which value type each byte of memory22// belongs to. This makes sure that we always know whether a shadow value is23// valid. Shadow values may be tampered with using access through other24// pointer types (type punning). Each byte stores:25// - bit 1-0: whether the corresponding value is of unknown (00),26// float (01), double (10), or long double (11) type.27// - bit 5-2: the index of this byte in the value, or 0000 if type is28// unknown.29// This allows handling unaligned loat load/stores by checking that a load30// with a given alignment corresponds to the alignment of the store.31// Any store of a non-floating point type invalidates the corresponding32// bytes, so that subsequent overlapping loads (aligned or not) know that33// the corresponding shadow value is no longer valid.34 35// On Linux/x86_64, memory is laid out as follows:36//37// +--------------------+ 0x800000000000 (top of memory)38// | application memory |39// +--------------------+ 0x700000008000 (kAppAddr)40// | |41// | unused |42// | |43// +--------------------+ 0x44000000800044// | allocator |45// +--------------------+ 0x400000000000 (kHeapMemBeg)46// | shadow memory |47// +--------------------+ 0x200000000000 (kShadowAddr)48// | shadow types |49// +--------------------+ 0x100000000000 (kTypesAddr)50// | reserved by kernel |51// +--------------------+ 0x00000000000052//53//54// To derive a shadow memory address from an application memory address,55// bits 44-46 are cleared to bring the address into the range56// [0x000000000000,0x100000000000). We scale to account for the fact that a57// shadow value takes twice as much space as the original value.58// Then we add kShadowAddr to put the shadow relative offset into the shadow59// memory. See getShadowAddrFor().60// The process is similar for the shadow types.61 62// The ratio of app to shadow memory.63enum { kShadowScale = 2 };64 65// The original value type of a byte in app memory. Uses LLVM terminology:66// https://llvm.org/docs/LangRef.html#floating-point-types67// FIXME: support half and bfloat.68enum ValueType {69 kUnknownValueType = 0,70 kFloatValueType = 1, // LLVM float, shadow type double.71 kDoubleValueType = 2, // LLVM double, shadow type fp128.72 kFp80ValueType = 3, // LLVM x86_fp80, shadow type fp128.73};74 75// The size of ValueType encoding, in bits.76enum {77 kValueSizeSizeBits = 2,78};79 80#if defined(__x86_64__)81struct Mapping {82 // FIXME: kAppAddr == 0x700000000000 ?83 static const uptr kAppAddr = 0x700000008000;84 static const uptr kHeapMemBeg = 0x400000000000;85 static const uptr kShadowAddr = 0x200000000000;86 static const uptr kTypesAddr = 0x100000000000;87 static const uptr kShadowMask = ~0x700000000000;88};89#else90#error "NSan not supported for this platform!"91#endif92 93enum MappingType {94 MAPPING_APP_ADDR,95 MAPPING_ALLOCATOR_ADDR,96 MAPPING_SHADOW_ADDR,97 MAPPING_TYPES_ADDR,98 MAPPING_SHADOW_MASK99};100 101template <typename Mapping, int Type> uptr MappingImpl() {102 switch (Type) {103 case MAPPING_APP_ADDR:104 return Mapping::kAppAddr;105 case MAPPING_ALLOCATOR_ADDR:106 return Mapping::kHeapMemBeg;107 case MAPPING_SHADOW_ADDR:108 return Mapping::kShadowAddr;109 case MAPPING_TYPES_ADDR:110 return Mapping::kTypesAddr;111 case MAPPING_SHADOW_MASK:112 return Mapping::kShadowMask;113 }114}115 116template <int Type> uptr MappingArchImpl() {117 return MappingImpl<Mapping, Type>();118}119 120ALWAYS_INLINE121uptr AppAddr() { return MappingArchImpl<MAPPING_APP_ADDR>(); }122 123ALWAYS_INLINE124uptr AllocatorAddr() { return MappingArchImpl<MAPPING_ALLOCATOR_ADDR>(); }125 126ALWAYS_INLINE127uptr ShadowAddr() { return MappingArchImpl<MAPPING_SHADOW_ADDR>(); }128 129ALWAYS_INLINE130uptr TypesAddr() { return MappingArchImpl<MAPPING_TYPES_ADDR>(); }131 132ALWAYS_INLINE133uptr ShadowMask() { return MappingArchImpl<MAPPING_SHADOW_MASK>(); }134 135} // end namespace __nsan136 137#endif138