1 //===-- asan_shadow_setup.cpp ---------------------------------------------===//
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 // Set up the shadow memory.
12 //===----------------------------------------------------------------------===//
13
14 #include "sanitizer_common/sanitizer_platform.h"
15
16 // asan_fuchsia.cpp and asan_rtems.cpp have their own
17 // InitializeShadowMemory implementation.
18 #if !SANITIZER_FUCHSIA && !SANITIZER_RTEMS
19
20 #include "asan_internal.h"
21 #include "asan_mapping.h"
22
23 namespace __asan {
24
ProtectGap(uptr addr,uptr size)25 static void ProtectGap(uptr addr, uptr size) {
26 if (!flags()->protect_shadow_gap) {
27 // The shadow gap is unprotected, so there is a chance that someone
28 // is actually using this memory. Which means it needs a shadow...
29 uptr GapShadowBeg = RoundDownTo(MEM_TO_SHADOW(addr), GetPageSizeCached());
30 uptr GapShadowEnd =
31 RoundUpTo(MEM_TO_SHADOW(addr + size), GetPageSizeCached()) - 1;
32 if (Verbosity())
33 Printf(
34 "protect_shadow_gap=0:"
35 " not protecting shadow gap, allocating gap's shadow\n"
36 "|| `[%p, %p]` || ShadowGap's shadow ||\n",
37 GapShadowBeg, GapShadowEnd);
38 ReserveShadowMemoryRange(GapShadowBeg, GapShadowEnd,
39 "unprotected gap shadow");
40 return;
41 }
42 __sanitizer::ProtectGap(addr, size, kZeroBaseShadowStart,
43 kZeroBaseMaxShadowStart);
44 }
45
MaybeReportLinuxPIEBug()46 static void MaybeReportLinuxPIEBug() {
47 #if SANITIZER_LINUX && \
48 (defined(__x86_64__) || defined(__aarch64__) || SANITIZER_RISCV64)
49 Report("This might be related to ELF_ET_DYN_BASE change in Linux 4.12.\n");
50 Report(
51 "See https://github.com/google/sanitizers/issues/856 for possible "
52 "workarounds.\n");
53 #endif
54 }
55
InitializeShadowMemory()56 void InitializeShadowMemory() {
57 // Set the shadow memory address to uninitialized.
58 __asan_shadow_memory_dynamic_address = kDefaultShadowSentinel;
59
60 uptr shadow_start = kLowShadowBeg;
61 // Detect if a dynamic shadow address must used and find a available location
62 // when necessary. When dynamic address is used, the macro |kLowShadowBeg|
63 // expands to |__asan_shadow_memory_dynamic_address| which is
64 // |kDefaultShadowSentinel|.
65 bool full_shadow_is_available = false;
66 if (shadow_start == kDefaultShadowSentinel) {
67 shadow_start = FindDynamicShadowStart();
68 if (SANITIZER_LINUX) full_shadow_is_available = true;
69 }
70 // Update the shadow memory address (potentially) used by instrumentation.
71 __asan_shadow_memory_dynamic_address = shadow_start;
72
73 if (kLowShadowBeg) shadow_start -= GetMmapGranularity();
74
75 if (!full_shadow_is_available)
76 full_shadow_is_available =
77 MemoryRangeIsAvailable(shadow_start, kHighShadowEnd);
78
79 #if SANITIZER_LINUX && defined(__x86_64__) && defined(_LP64) && \
80 !ASAN_FIXED_MAPPING
81 if (!full_shadow_is_available) {
82 kMidMemBeg = kLowMemEnd < 0x3000000000ULL ? 0x3000000000ULL : 0;
83 kMidMemEnd = kLowMemEnd < 0x3000000000ULL ? 0x4fffffffffULL : 0;
84 }
85 #endif
86
87 if (Verbosity()) PrintAddressSpaceLayout();
88
89 if (full_shadow_is_available) {
90 // mmap the low shadow plus at least one page at the left.
91 if (kLowShadowBeg)
92 ReserveShadowMemoryRange(shadow_start, kLowShadowEnd, "low shadow");
93 // mmap the high shadow.
94 ReserveShadowMemoryRange(kHighShadowBeg, kHighShadowEnd, "high shadow");
95 // protect the gap.
96 ProtectGap(kShadowGapBeg, kShadowGapEnd - kShadowGapBeg + 1);
97 CHECK_EQ(kShadowGapEnd, kHighShadowBeg - 1);
98 } else if (kMidMemBeg &&
99 MemoryRangeIsAvailable(shadow_start, kMidMemBeg - 1) &&
100 MemoryRangeIsAvailable(kMidMemEnd + 1, kHighShadowEnd)) {
101 CHECK(kLowShadowBeg != kLowShadowEnd);
102 // mmap the low shadow plus at least one page at the left.
103 ReserveShadowMemoryRange(shadow_start, kLowShadowEnd, "low shadow");
104 // mmap the mid shadow.
105 ReserveShadowMemoryRange(kMidShadowBeg, kMidShadowEnd, "mid shadow");
106 // mmap the high shadow.
107 ReserveShadowMemoryRange(kHighShadowBeg, kHighShadowEnd, "high shadow");
108 // protect the gaps.
109 ProtectGap(kShadowGapBeg, kShadowGapEnd - kShadowGapBeg + 1);
110 ProtectGap(kShadowGap2Beg, kShadowGap2End - kShadowGap2Beg + 1);
111 ProtectGap(kShadowGap3Beg, kShadowGap3End - kShadowGap3Beg + 1);
112 } else {
113 Report(
114 "Shadow memory range interleaves with an existing memory mapping. "
115 "ASan cannot proceed correctly. ABORTING.\n");
116 Report("ASan shadow was supposed to be located in the [%p-%p] range.\n",
117 shadow_start, kHighShadowEnd);
118 MaybeReportLinuxPIEBug();
119 DumpProcessMap();
120 Die();
121 }
122 }
123
124 } // namespace __asan
125
126 #endif // !SANITIZER_FUCHSIA && !SANITIZER_RTEMS
127