libsanitizer/asan/asan_shadow_setup.cpp

   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
  25 // ---------------------- mmap -------------------- {{{1
  26 // Reserve memory range [beg, end].
  27 // We need to use inclusive range because end+1 may not be representable.
  28 void ReserveShadowMemoryRange(uptr beg, uptr end, const char *name) {
  29   CHECK_EQ((beg % GetMmapGranularity()), 0);
  30   CHECK_EQ(((end + 1) % GetMmapGranularity()), 0);
  31   uptr size = end - beg + 1;
  32   DecreaseTotalMmap(size);  // Don't count the shadow against mmap_limit_mb.
  33   if (!MmapFixedSuperNoReserve(beg, size, name)) {
  34     Report(
  35         "ReserveShadowMemoryRange failed while trying to map 0x%zx bytes. "
  36         "Perhaps you're using ulimit -v\n",
  37         size);
  38     Abort();
  39   }
  40   if (common_flags()->use_madv_dontdump) DontDumpShadowMemory(beg, size);
  41 }
  42
  43 static void ProtectGap(uptr addr, uptr size) {
  44   if (!flags()->protect_shadow_gap) {
  45     // The shadow gap is unprotected, so there is a chance that someone
  46     // is actually using this memory. Which means it needs a shadow...
  47     uptr GapShadowBeg = RoundDownTo(MEM_TO_SHADOW(addr), GetPageSizeCached());
  48     uptr GapShadowEnd =
  49         RoundUpTo(MEM_TO_SHADOW(addr + size), GetPageSizeCached()) - 1;
  50     if (Verbosity())
  51       Printf(
  52           "protect_shadow_gap=0:"
  53           " not protecting shadow gap, allocating gap's shadow\n"
  54           "|| `[%p, %p]` || ShadowGap's shadow ||\n",
  55           GapShadowBeg, GapShadowEnd);
  56     ReserveShadowMemoryRange(GapShadowBeg, GapShadowEnd,
  57                              "unprotected gap shadow");
  58     return;
  59   }
  60   void *res = MmapFixedNoAccess(addr, size, "shadow gap");
  61   if (addr == (uptr)res) return;
  62   // A few pages at the start of the address space can not be protected.
  63   // But we really want to protect as much as possible, to prevent this memory
  64   // being returned as a result of a non-FIXED mmap().
  65   if (addr == kZeroBaseShadowStart) {
  66     uptr step = GetMmapGranularity();
  67     while (size > step && addr < kZeroBaseMaxShadowStart) {
  68       addr += step;
  69       size -= step;
  70       void *res = MmapFixedNoAccess(addr, size, "shadow gap");
  71       if (addr == (uptr)res) return;
  72     }
  73   }
  74
  75   Report(
  76       "ERROR: Failed to protect the shadow gap. "
  77       "ASan cannot proceed correctly. ABORTING.\n");
  78   DumpProcessMap();
  79   Die();
  80 }
  81
  82 static void MaybeReportLinuxPIEBug() {
  83 #if SANITIZER_LINUX && (defined(__x86_64__) || defined(__aarch64__))
  84   Report("This might be related to ELF_ET_DYN_BASE change in Linux 4.12.\n");
  85   Report(
  86       "See https://github.com/google/sanitizers/issues/856 for possible "
  87       "workarounds.\n");
  88 #endif
  89 }
  90
  91 void InitializeShadowMemory() {
  92   // Set the shadow memory address to uninitialized.
  93   __asan_shadow_memory_dynamic_address = kDefaultShadowSentinel;
  94
  95   uptr shadow_start = kLowShadowBeg;
  96   // Detect if a dynamic shadow address must used and find a available location
  97   // when necessary. When dynamic address is used, the macro |kLowShadowBeg|
  98   // expands to |__asan_shadow_memory_dynamic_address| which is
  99   // |kDefaultShadowSentinel|.
 100   bool full_shadow_is_available = false;
 101   if (shadow_start == kDefaultShadowSentinel) {
 102     __asan_shadow_memory_dynamic_address = 0;
 103     CHECK_EQ(0, kLowShadowBeg);
 104     shadow_start = FindDynamicShadowStart();
 105     if (SANITIZER_LINUX) full_shadow_is_available = true;
 106   }
 107   // Update the shadow memory address (potentially) used by instrumentation.
 108   __asan_shadow_memory_dynamic_address = shadow_start;
 109
 110   if (kLowShadowBeg) shadow_start -= GetMmapGranularity();
 111
 112   if (!full_shadow_is_available)
 113     full_shadow_is_available =
 114         MemoryRangeIsAvailable(shadow_start, kHighShadowEnd);
 115
 116 #if SANITIZER_LINUX && defined(__x86_64__) && defined(_LP64) && \
 117     !ASAN_FIXED_MAPPING
 118   if (!full_shadow_is_available) {
 119     kMidMemBeg = kLowMemEnd < 0x3000000000ULL ? 0x3000000000ULL : 0;
 120     kMidMemEnd = kLowMemEnd < 0x3000000000ULL ? 0x4fffffffffULL : 0;
 121   }
 122 #endif
 123
 124   if (Verbosity()) PrintAddressSpaceLayout();
 125
 126   if (full_shadow_is_available) {
 127     // mmap the low shadow plus at least one page at the left.
 128     if (kLowShadowBeg)
 129       ReserveShadowMemoryRange(shadow_start, kLowShadowEnd, "low shadow");
 130     // mmap the high shadow.
 131     ReserveShadowMemoryRange(kHighShadowBeg, kHighShadowEnd, "high shadow");
 132     // protect the gap.
 133     ProtectGap(kShadowGapBeg, kShadowGapEnd - kShadowGapBeg + 1);
 134     CHECK_EQ(kShadowGapEnd, kHighShadowBeg - 1);
 135   } else if (kMidMemBeg &&
 136              MemoryRangeIsAvailable(shadow_start, kMidMemBeg - 1) &&
 137              MemoryRangeIsAvailable(kMidMemEnd + 1, kHighShadowEnd)) {
 138     CHECK(kLowShadowBeg != kLowShadowEnd);
 139     // mmap the low shadow plus at least one page at the left.
 140     ReserveShadowMemoryRange(shadow_start, kLowShadowEnd, "low shadow");
 141     // mmap the mid shadow.
 142     ReserveShadowMemoryRange(kMidShadowBeg, kMidShadowEnd, "mid shadow");
 143     // mmap the high shadow.
 144     ReserveShadowMemoryRange(kHighShadowBeg, kHighShadowEnd, "high shadow");
 145     // protect the gaps.
 146     ProtectGap(kShadowGapBeg, kShadowGapEnd - kShadowGapBeg + 1);
 147     ProtectGap(kShadowGap2Beg, kShadowGap2End - kShadowGap2Beg + 1);
 148     ProtectGap(kShadowGap3Beg, kShadowGap3End - kShadowGap3Beg + 1);
 149   } else {
 150     Report(
 151         "Shadow memory range interleaves with an existing memory mapping. "
 152         "ASan cannot proceed correctly. ABORTING.\n");
 153     Report("ASan shadow was supposed to be located in the [%p-%p] range.\n",
 154            shadow_start, kHighShadowEnd);
 155     MaybeReportLinuxPIEBug();
 156     DumpProcessMap();
 157     Die();
 158   }
 159 }
 160
 161 }  // namespace __asan
 162
 163 #endif  // !SANITIZER_FUCHSIA && !SANITIZER_RTEMS