libsanitizer/asan/asan_poisoning.h

   1 //===-- asan_poisoning.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-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This file is a part of AddressSanitizer, an address sanity checker.
  10 //
  11 // Shadow memory poisoning by ASan RTL and by user application.
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "asan_interceptors.h"
  15 #include "asan_internal.h"
  16 #include "asan_mapping.h"
  17 #include "sanitizer_common/sanitizer_flags.h"
  18 #include "sanitizer_common/sanitizer_platform.h"
  19
  20 namespace __asan {
  21
  22 // Enable/disable memory poisoning.
  23 void SetCanPoisonMemory(bool value);
  24 bool CanPoisonMemory();
  25
  26 // Poisons the shadow memory for "size" bytes starting from "addr".
  27 void PoisonShadow(uptr addr, uptr size, u8 value);
  28
  29 // Poisons the shadow memory for "redzone_size" bytes starting from
  30 // "addr + size".
  31 void PoisonShadowPartialRightRedzone(uptr addr,
  32                                      uptr size,
  33                                      uptr redzone_size,
  34                                      u8 value);
  35
  36 // Fast versions of PoisonShadow and PoisonShadowPartialRightRedzone that
  37 // assume that memory addresses are properly aligned. Use in
  38 // performance-critical code with care.
  39 ALWAYS_INLINE void FastPoisonShadow(uptr aligned_beg, uptr aligned_size,
  40                                     u8 value) {
  41   DCHECK(!value || CanPoisonMemory());
  42 #if SANITIZER_FUCHSIA
  43   __sanitizer_fill_shadow(aligned_beg, aligned_size, value,
  44                           common_flags()->clear_shadow_mmap_threshold);
  45 #else
  46   uptr shadow_beg = MEM_TO_SHADOW(aligned_beg);
  47   uptr shadow_end =
  48       MEM_TO_SHADOW(aligned_beg + aligned_size - ASAN_SHADOW_GRANULARITY) + 1;
  49   // FIXME: Page states are different on Windows, so using the same interface
  50   // for mapping shadow and zeroing out pages doesn't "just work", so we should
  51   // probably provide higher-level interface for these operations.
  52   // For now, just memset on Windows.
  53   if (value || SANITIZER_WINDOWS == 1 ||
  54       shadow_end - shadow_beg < common_flags()->clear_shadow_mmap_threshold) {
  55     REAL(memset)((void*)shadow_beg, value, shadow_end - shadow_beg);
  56   } else {
  57     uptr page_size = GetPageSizeCached();
  58     uptr page_beg = RoundUpTo(shadow_beg, page_size);
  59     uptr page_end = RoundDownTo(shadow_end, page_size);
  60
  61     if (page_beg >= page_end) {
  62       REAL(memset)((void *)shadow_beg, 0, shadow_end - shadow_beg);
  63     } else {
  64       if (page_beg != shadow_beg) {
  65         REAL(memset)((void *)shadow_beg, 0, page_beg - shadow_beg);
  66       }
  67       if (page_end != shadow_end) {
  68         REAL(memset)((void *)page_end, 0, shadow_end - page_end);
  69       }
  70       ReserveShadowMemoryRange(page_beg, page_end - 1, nullptr);
  71     }
  72   }
  73 #endif // SANITIZER_FUCHSIA
  74 }
  75
  76 ALWAYS_INLINE void FastPoisonShadowPartialRightRedzone(
  77     uptr aligned_addr, uptr size, uptr redzone_size, u8 value) {
  78   DCHECK(CanPoisonMemory());
  79   bool poison_partial = flags()->poison_partial;
  80   u8 *shadow = (u8*)MEM_TO_SHADOW(aligned_addr);
  81   for (uptr i = 0; i < redzone_size; i += ASAN_SHADOW_GRANULARITY, shadow++) {
  82     if (i + ASAN_SHADOW_GRANULARITY <= size) {
  83       *shadow = 0;  // fully addressable
  84     } else if (i >= size) {
  85       *shadow =
  86           (ASAN_SHADOW_GRANULARITY == 128) ? 0xff : value;  // unaddressable
  87     } else {
  88       // first size-i bytes are addressable
  89       *shadow = poison_partial ? static_cast<u8>(size - i) : 0;
  90     }
  91   }
  92 }
  93
  94 // Calls __sanitizer::ReleaseMemoryPagesToOS() on
  95 // [MemToShadow(p), MemToShadow(p+size)].
  96 void FlushUnneededASanShadowMemory(uptr p, uptr size);
  97
  98 }  // namespace __asan