//===-- asan_poisoning.cc -------------------------------------------------===// // // The LLVM Compiler Infrastructure // // This file is distributed under the University of Illinois Open Source // License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// // // This file is a part of AddressSanitizer, an address sanity checker. // // Shadow memory poisoning by ASan RTL and by user application. //===----------------------------------------------------------------------===// #include "asan_interceptors.h" #include "asan_internal.h" #include "asan_mapping.h" #include "sanitizer/asan_interface.h" namespace __asan { void PoisonShadow(uptr addr, uptr size, u8 value) { CHECK(AddrIsAlignedByGranularity(addr)); CHECK(AddrIsAlignedByGranularity(addr + size)); uptr shadow_beg = MemToShadow(addr); uptr shadow_end = MemToShadow(addr + size); CHECK(REAL(memset) != 0); REAL(memset)((void*)shadow_beg, value, shadow_end - shadow_beg); } void PoisonShadowPartialRightRedzone(uptr addr, uptr size, uptr redzone_size, u8 value) { CHECK(AddrIsAlignedByGranularity(addr)); u8 *shadow = (u8*)MemToShadow(addr); for (uptr i = 0; i < redzone_size; i += SHADOW_GRANULARITY, shadow++) { if (i + SHADOW_GRANULARITY <= size) { *shadow = 0; // fully addressable } else if (i >= size) { *shadow = (SHADOW_GRANULARITY == 128) ? 0xff : value; // unaddressable } else { *shadow = size - i; // first size-i bytes are addressable } } } struct ShadowSegmentEndpoint { u8 *chunk; s8 offset; // in [0, SHADOW_GRANULARITY) s8 value; // = *chunk; explicit ShadowSegmentEndpoint(uptr address) { chunk = (u8*)MemToShadow(address); offset = address & (SHADOW_GRANULARITY - 1); value = *chunk; } }; } // namespace __asan // ---------------------- Interface ---------------- {{{1 using namespace __asan; // NOLINT // Current implementation of __asan_(un)poison_memory_region doesn't check // that user program (un)poisons the memory it owns. It poisons memory // conservatively, and unpoisons progressively to make sure asan shadow // mapping invariant is preserved (see detailed mapping description here: // http://code.google.com/p/address-sanitizer/wiki/AddressSanitizerAlgorithm). // // * if user asks to poison region [left, right), the program poisons // at least [left, AlignDown(right)). // * if user asks to unpoison region [left, right), the program unpoisons // at most [AlignDown(left), right). void __asan_poison_memory_region(void const volatile *addr, uptr size) { if (!flags()->allow_user_poisoning || size == 0) return; uptr beg_addr = (uptr)addr; uptr end_addr = beg_addr + size; if (flags()->verbosity >= 1) { Printf("Trying to poison memory region [%p, %p)\n", (void*)beg_addr, (void*)end_addr); } ShadowSegmentEndpoint beg(beg_addr); ShadowSegmentEndpoint end(end_addr); if (beg.chunk == end.chunk) { CHECK(beg.offset < end.offset); s8 value = beg.value; CHECK(value == end.value); // We can only poison memory if the byte in end.offset is unaddressable. // No need to re-poison memory if it is poisoned already. if (value > 0 && value <= end.offset) { if (beg.offset > 0) { *beg.chunk = Min(value, beg.offset); } else { *beg.chunk = kAsanUserPoisonedMemoryMagic; } } return; } CHECK(beg.chunk < end.chunk); if (beg.offset > 0) { // Mark bytes from beg.offset as unaddressable. if (beg.value == 0) { *beg.chunk = beg.offset; } else { *beg.chunk = Min(beg.value, beg.offset); } beg.chunk++; } REAL(memset)(beg.chunk, kAsanUserPoisonedMemoryMagic, end.chunk - beg.chunk); // Poison if byte in end.offset is unaddressable. if (end.value > 0 && end.value <= end.offset) { *end.chunk = kAsanUserPoisonedMemoryMagic; } } void __asan_unpoison_memory_region(void const volatile *addr, uptr size) { if (!flags()->allow_user_poisoning || size == 0) return; uptr beg_addr = (uptr)addr; uptr end_addr = beg_addr + size; if (flags()->verbosity >= 1) { Printf("Trying to unpoison memory region [%p, %p)\n", (void*)beg_addr, (void*)end_addr); } ShadowSegmentEndpoint beg(beg_addr); ShadowSegmentEndpoint end(end_addr); if (beg.chunk == end.chunk) { CHECK(beg.offset < end.offset); s8 value = beg.value; CHECK(value == end.value); // We unpoison memory bytes up to enbytes up to end.offset if it is not // unpoisoned already. if (value != 0) { *beg.chunk = Max(value, end.offset); } return; } CHECK(beg.chunk < end.chunk); if (beg.offset > 0) { *beg.chunk = 0; beg.chunk++; } REAL(memset)(beg.chunk, 0, end.chunk - beg.chunk); if (end.offset > 0 && end.value != 0) { *end.chunk = Max(end.value, end.offset); } } bool __asan_address_is_poisoned(void const volatile *addr) { return __asan::AddressIsPoisoned((uptr)addr); }