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  CHECK(AddrIsAlignedByGranularity(addr));
24  CHECK(AddrIsAlignedByGranularity(addr + size));
25  uptr shadow_beg = MemToShadow(addr);
26  uptr shadow_end = MemToShadow(addr + size);
27  CHECK(REAL(memset) != 0);
28  REAL(memset)((void*)shadow_beg, value, shadow_end - shadow_beg);
29}
30
31void PoisonShadowPartialRightRedzone(uptr addr,
32                                     uptr size,
33                                     uptr redzone_size,
34                                     u8 value) {
35  CHECK(AddrIsAlignedByGranularity(addr));
36  u8 *shadow = (u8*)MemToShadow(addr);
37  for (uptr i = 0; i < redzone_size;
38       i += SHADOW_GRANULARITY, shadow++) {
39    if (i + SHADOW_GRANULARITY <= size) {
40      *shadow = 0;  // fully addressable
41    } else if (i >= size) {
42      *shadow = (SHADOW_GRANULARITY == 128) ? 0xff : value;  // unaddressable
43    } else {
44      *shadow = size - i;  // first size-i bytes are addressable
45    }
46  }
47}
48
49
50struct ShadowSegmentEndpoint {
51  u8 *chunk;
52  s8 offset;  // in [0, SHADOW_GRANULARITY)
53  s8 value;  // = *chunk;
54
55  explicit ShadowSegmentEndpoint(uptr address) {
56    chunk = (u8*)MemToShadow(address);
57    offset = address & (SHADOW_GRANULARITY - 1);
58    value = *chunk;
59  }
60};
61
62}  // namespace __asan
63
64// ---------------------- Interface ---------------- {{{1
65using namespace __asan;  // NOLINT
66
67// Current implementation of __asan_(un)poison_memory_region doesn't check
68// that user program (un)poisons the memory it owns. It poisons memory
69// conservatively, and unpoisons progressively to make sure asan shadow
70// mapping invariant is preserved (see detailed mapping description here:
71// http://code.google.com/p/address-sanitizer/wiki/AddressSanitizerAlgorithm).
72//
73// * if user asks to poison region [left, right), the program poisons
74// at least [left, AlignDown(right)).
75// * if user asks to unpoison region [left, right), the program unpoisons
76// at most [AlignDown(left), right).
77void __asan_poison_memory_region(void const volatile *addr, uptr size) {
78  if (!flags()->allow_user_poisoning || size == 0) return;
79  uptr beg_addr = (uptr)addr;
80  uptr end_addr = beg_addr + size;
81  if (flags()->verbosity >= 1) {
82    Printf("Trying to poison memory region [%p, %p)\n",
83           (void*)beg_addr, (void*)end_addr);
84  }
85  ShadowSegmentEndpoint beg(beg_addr);
86  ShadowSegmentEndpoint end(end_addr);
87  if (beg.chunk == end.chunk) {
88    CHECK(beg.offset < end.offset);
89    s8 value = beg.value;
90    CHECK(value == end.value);
91    // We can only poison memory if the byte in end.offset is unaddressable.
92    // No need to re-poison memory if it is poisoned already.
93    if (value > 0 && value <= end.offset) {
94      if (beg.offset > 0) {
95        *beg.chunk = Min(value, beg.offset);
96      } else {
97        *beg.chunk = kAsanUserPoisonedMemoryMagic;
98      }
99    }
100    return;
101  }
102  CHECK(beg.chunk < end.chunk);
103  if (beg.offset > 0) {
104    // Mark bytes from beg.offset as unaddressable.
105    if (beg.value == 0) {
106      *beg.chunk = beg.offset;
107    } else {
108      *beg.chunk = Min(beg.value, beg.offset);
109    }
110    beg.chunk++;
111  }
112  REAL(memset)(beg.chunk, kAsanUserPoisonedMemoryMagic, end.chunk - beg.chunk);
113  // Poison if byte in end.offset is unaddressable.
114  if (end.value > 0 && end.value <= end.offset) {
115    *end.chunk = kAsanUserPoisonedMemoryMagic;
116  }
117}
118
119void __asan_unpoison_memory_region(void const volatile *addr, uptr size) {
120  if (!flags()->allow_user_poisoning || size == 0) return;
121  uptr beg_addr = (uptr)addr;
122  uptr end_addr = beg_addr + size;
123  if (flags()->verbosity >= 1) {
124    Printf("Trying to unpoison memory region [%p, %p)\n",
125           (void*)beg_addr, (void*)end_addr);
126  }
127  ShadowSegmentEndpoint beg(beg_addr);
128  ShadowSegmentEndpoint end(end_addr);
129  if (beg.chunk == end.chunk) {
130    CHECK(beg.offset < end.offset);
131    s8 value = beg.value;
132    CHECK(value == end.value);
133    // We unpoison memory bytes up to enbytes up to end.offset if it is not
134    // unpoisoned already.
135    if (value != 0) {
136      *beg.chunk = Max(value, end.offset);
137    }
138    return;
139  }
140  CHECK(beg.chunk < end.chunk);
141  if (beg.offset > 0) {
142    *beg.chunk = 0;
143    beg.chunk++;
144  }
145  REAL(memset)(beg.chunk, 0, end.chunk - beg.chunk);
146  if (end.offset > 0 && end.value != 0) {
147    *end.chunk = Max(end.value, end.offset);
148  }
149}
150
151bool __asan_address_is_poisoned(void const volatile *addr) {
152  return __asan::AddressIsPoisoned((uptr)addr);
153}
154