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
20namespace __asan {
21
22// Enable/disable memory poisoning.
23void SetCanPoisonMemory(bool value);
24bool CanPoisonMemory();
25
26// Poisons the shadow memory for "size" bytes starting from "addr".
27void PoisonShadow(uptr addr, uptr size, u8 value);
28
29// Poisons the shadow memory for "redzone_size" bytes starting from
30// "addr + size".
31void 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.
39ALWAYS_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 = MEM_TO_SHADOW(
48      aligned_beg + aligned_size - 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      // RTEMS doesn't have have pages, let alone a fast way to zero
55      // them, so default to memset.
56      SANITIZER_RTEMS == 1 ||
57      shadow_end - shadow_beg < common_flags()->clear_shadow_mmap_threshold) {
58    REAL(memset)((void*)shadow_beg, value, shadow_end - shadow_beg);
59  } else {
60    uptr page_size = GetPageSizeCached();
61    uptr page_beg = RoundUpTo(shadow_beg, page_size);
62    uptr page_end = RoundDownTo(shadow_end, page_size);
63
64    if (page_beg >= page_end) {
65      REAL(memset)((void *)shadow_beg, 0, shadow_end - shadow_beg);
66    } else {
67      if (page_beg != shadow_beg) {
68        REAL(memset)((void *)shadow_beg, 0, page_beg - shadow_beg);
69      }
70      if (page_end != shadow_end) {
71        REAL(memset)((void *)page_end, 0, shadow_end - page_end);
72      }
73      ReserveShadowMemoryRange(page_beg, page_end - 1, nullptr);
74    }
75  }
76#endif // SANITIZER_FUCHSIA
77}
78
79ALWAYS_INLINE void FastPoisonShadowPartialRightRedzone(
80    uptr aligned_addr, uptr size, uptr redzone_size, u8 value) {
81  DCHECK(CanPoisonMemory());
82  bool poison_partial = flags()->poison_partial;
83  u8 *shadow = (u8*)MEM_TO_SHADOW(aligned_addr);
84  for (uptr i = 0; i < redzone_size; i += SHADOW_GRANULARITY, shadow++) {
85    if (i + SHADOW_GRANULARITY <= size) {
86      *shadow = 0;  // fully addressable
87    } else if (i >= size) {
88      *shadow = (SHADOW_GRANULARITY == 128) ? 0xff : value;  // unaddressable
89    } else {
90      // first size-i bytes are addressable
91      *shadow = poison_partial ? static_cast<u8>(size - i) : 0;
92    }
93  }
94}
95
96// Calls __sanitizer::ReleaseMemoryPagesToOS() on
97// [MemToShadow(p), MemToShadow(p+size)].
98void FlushUnneededASanShadowMemory(uptr p, uptr size);
99
100}  // namespace __asan
101