asan_poisoning.cc revision 73bad81febb2a872627c03e579beea1da4b49294
1//===-- asan_poisoning.cc -------------------------------------------------===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This file is a part of AddressSanitizer, an address sanity checker. 11// 12// Shadow memory poisoning by ASan RTL and by user application. 13//===----------------------------------------------------------------------===// 14 15#include "asan_interceptors.h" 16#include "asan_internal.h" 17#include "asan_mapping.h" 18#include "sanitizer/asan_interface.h" 19 20namespace __asan { 21 22void PoisonShadow(uptr addr, uptr size, u8 value) { 23 if (!flags()->poison_heap) return; 24 CHECK(AddrIsAlignedByGranularity(addr)); 25 CHECK(AddrIsAlignedByGranularity(addr + size)); 26 uptr shadow_beg = MemToShadow(addr); 27 uptr shadow_end = MemToShadow(addr + size); 28 CHECK(REAL(memset) != 0); 29 REAL(memset)((void*)shadow_beg, value, shadow_end - shadow_beg); 30} 31 32void PoisonShadowPartialRightRedzone(uptr addr, 33 uptr size, 34 uptr redzone_size, 35 u8 value) { 36 if (!flags()->poison_heap) return; 37 CHECK(AddrIsAlignedByGranularity(addr)); 38 u8 *shadow = (u8*)MemToShadow(addr); 39 for (uptr i = 0; i < redzone_size; 40 i += SHADOW_GRANULARITY, shadow++) { 41 if (i + SHADOW_GRANULARITY <= size) { 42 *shadow = 0; // fully addressable 43 } else if (i >= size) { 44 *shadow = (SHADOW_GRANULARITY == 128) ? 0xff : value; // unaddressable 45 } else { 46 *shadow = size - i; // first size-i bytes are addressable 47 } 48 } 49} 50 51 52struct ShadowSegmentEndpoint { 53 u8 *chunk; 54 s8 offset; // in [0, SHADOW_GRANULARITY) 55 s8 value; // = *chunk; 56 57 explicit ShadowSegmentEndpoint(uptr address) { 58 chunk = (u8*)MemToShadow(address); 59 offset = address & (SHADOW_GRANULARITY - 1); 60 value = *chunk; 61 } 62}; 63 64} // namespace __asan 65 66// ---------------------- Interface ---------------- {{{1 67using namespace __asan; // NOLINT 68 69// Current implementation of __asan_(un)poison_memory_region doesn't check 70// that user program (un)poisons the memory it owns. It poisons memory 71// conservatively, and unpoisons progressively to make sure asan shadow 72// mapping invariant is preserved (see detailed mapping description here: 73// http://code.google.com/p/address-sanitizer/wiki/AddressSanitizerAlgorithm). 74// 75// * if user asks to poison region [left, right), the program poisons 76// at least [left, AlignDown(right)). 77// * if user asks to unpoison region [left, right), the program unpoisons 78// at most [AlignDown(left), right). 79void __asan_poison_memory_region(void const volatile *addr, uptr size) { 80 if (!flags()->allow_user_poisoning || size == 0) return; 81 uptr beg_addr = (uptr)addr; 82 uptr end_addr = beg_addr + size; 83 if (flags()->verbosity >= 1) { 84 Printf("Trying to poison memory region [%p, %p)\n", 85 (void*)beg_addr, (void*)end_addr); 86 } 87 ShadowSegmentEndpoint beg(beg_addr); 88 ShadowSegmentEndpoint end(end_addr); 89 if (beg.chunk == end.chunk) { 90 CHECK(beg.offset < end.offset); 91 s8 value = beg.value; 92 CHECK(value == end.value); 93 // We can only poison memory if the byte in end.offset is unaddressable. 94 // No need to re-poison memory if it is poisoned already. 95 if (value > 0 && value <= end.offset) { 96 if (beg.offset > 0) { 97 *beg.chunk = Min(value, beg.offset); 98 } else { 99 *beg.chunk = kAsanUserPoisonedMemoryMagic; 100 } 101 } 102 return; 103 } 104 CHECK(beg.chunk < end.chunk); 105 if (beg.offset > 0) { 106 // Mark bytes from beg.offset as unaddressable. 107 if (beg.value == 0) { 108 *beg.chunk = beg.offset; 109 } else { 110 *beg.chunk = Min(beg.value, beg.offset); 111 } 112 beg.chunk++; 113 } 114 REAL(memset)(beg.chunk, kAsanUserPoisonedMemoryMagic, end.chunk - beg.chunk); 115 // Poison if byte in end.offset is unaddressable. 116 if (end.value > 0 && end.value <= end.offset) { 117 *end.chunk = kAsanUserPoisonedMemoryMagic; 118 } 119} 120 121void __asan_unpoison_memory_region(void const volatile *addr, uptr size) { 122 if (!flags()->allow_user_poisoning || size == 0) return; 123 uptr beg_addr = (uptr)addr; 124 uptr end_addr = beg_addr + size; 125 if (flags()->verbosity >= 1) { 126 Printf("Trying to unpoison memory region [%p, %p)\n", 127 (void*)beg_addr, (void*)end_addr); 128 } 129 ShadowSegmentEndpoint beg(beg_addr); 130 ShadowSegmentEndpoint end(end_addr); 131 if (beg.chunk == end.chunk) { 132 CHECK(beg.offset < end.offset); 133 s8 value = beg.value; 134 CHECK(value == end.value); 135 // We unpoison memory bytes up to enbytes up to end.offset if it is not 136 // unpoisoned already. 137 if (value != 0) { 138 *beg.chunk = Max(value, end.offset); 139 } 140 return; 141 } 142 CHECK(beg.chunk < end.chunk); 143 if (beg.offset > 0) { 144 *beg.chunk = 0; 145 beg.chunk++; 146 } 147 REAL(memset)(beg.chunk, 0, end.chunk - beg.chunk); 148 if (end.offset > 0 && end.value != 0) { 149 *end.chunk = Max(end.value, end.offset); 150 } 151} 152 153bool __asan_address_is_poisoned(void const volatile *addr) { 154 return __asan::AddressIsPoisoned((uptr)addr); 155} 156 157// This is a simplified version of __asan_(un)poison_memory_region, which 158// assumes that left border of region to be poisoned is properly aligned. 159static void PoisonAlignedStackMemory(uptr addr, uptr size, bool do_poison) { 160 if (size == 0) return; 161 uptr aligned_size = size & ~(SHADOW_GRANULARITY - 1); 162 PoisonShadow(addr, aligned_size, 163 do_poison ? kAsanStackUseAfterScopeMagic : 0); 164 if (size == aligned_size) 165 return; 166 s8 end_offset = (s8)(size - aligned_size); 167 s8* shadow_end = (s8*)MemToShadow(addr + aligned_size); 168 s8 end_value = *shadow_end; 169 if (do_poison) { 170 // If possible, mark all the bytes mapping to last shadow byte as 171 // unaddressable. 172 if (end_value > 0 && end_value <= end_offset) 173 *shadow_end = (s8)kAsanStackUseAfterScopeMagic; 174 } else { 175 // If necessary, mark few first bytes mapping to last shadow byte 176 // as addressable 177 if (end_value != 0) 178 *shadow_end = Max(end_value, end_offset); 179 } 180} 181 182void __asan_poison_stack_memory(uptr addr, uptr size) { 183 if (flags()->verbosity > 0) 184 Report("poisoning: %p %zx\n", (void*)addr, size); 185 PoisonAlignedStackMemory(addr, size, true); 186} 187 188void __asan_unpoison_stack_memory(uptr addr, uptr size) { 189 if (flags()->verbosity > 0) 190 Report("unpoisoning: %p %zx\n", (void*)addr, size); 191 PoisonAlignedStackMemory(addr, size, false); 192} 193