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 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
  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
  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