1 files changed, 159 insertions, 0 deletions
diff --git a/libsanitizer/asan/asan_shadow_setup.cc b/libsanitizer/asan/asan_shadow_setup.cc
new file mode 100644
index 00000000000..9629b36798f
--- /dev/null
+++ b/libsanitizer/asan/asan_shadow_setup.cc
@@ -0,0 +1,159 @@
+//===-- asan_shadow_setup.cc ----------------------------------------------===//
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file is a part of AddressSanitizer, an address sanity checker.
+//
+// Set up the shadow memory.
+//===----------------------------------------------------------------------===//
+
+#include "sanitizer_common/sanitizer_platform.h"
+
+// asan_fuchsia.cc has its own InitializeShadowMemory implementation.
+#if !SANITIZER_FUCHSIA
+
+#include "asan_internal.h"
+#include "asan_mapping.h"
+
+namespace __asan {
+
+// ---------------------- mmap -------------------- {{{1
+// Reserve memory range [beg, end].
+// We need to use inclusive range because end+1 may not be representable.
+void ReserveShadowMemoryRange(uptr beg, uptr end, const char *name) {
+  CHECK_EQ((beg % GetMmapGranularity()), 0);
+  CHECK_EQ(((end + 1) % GetMmapGranularity()), 0);
+  uptr size = end - beg + 1;
+  DecreaseTotalMmap(size);  // Don't count the shadow against mmap_limit_mb.
+  void *res = MmapFixedNoReserve(beg, size, name);
+  if (res != (void *)beg) {
+    Report(
+        "ReserveShadowMemoryRange failed while trying to map 0x%zx bytes. "
+        "Perhaps you're using ulimit -v\n",
+        size);
+    Abort();
+  }
+  if (common_flags()->no_huge_pages_for_shadow) NoHugePagesInRegion(beg, size);
+  if (common_flags()->use_madv_dontdump) DontDumpShadowMemory(beg, size);
+}
+
+static void ProtectGap(uptr addr, uptr size) {
+  if (!flags()->protect_shadow_gap) {
+    // The shadow gap is unprotected, so there is a chance that someone
+    // is actually using this memory. Which means it needs a shadow...
+    uptr GapShadowBeg = RoundDownTo(MEM_TO_SHADOW(addr), GetPageSizeCached());
+    uptr GapShadowEnd =
+        RoundUpTo(MEM_TO_SHADOW(addr + size), GetPageSizeCached()) - 1;
+    if (Verbosity())
+      Printf(
+          "protect_shadow_gap=0:"
+          " not protecting shadow gap, allocating gap's shadow\n"
+          "|| `[%p, %p]` || ShadowGap's shadow ||\n",
+          GapShadowBeg, GapShadowEnd);
+    ReserveShadowMemoryRange(GapShadowBeg, GapShadowEnd,
+                             "unprotected gap shadow");
+    return;
+  }
+  void *res = MmapFixedNoAccess(addr, size, "shadow gap");
+  if (addr == (uptr)res) return;
+  // A few pages at the start of the address space can not be protected.
+  // But we really want to protect as much as possible, to prevent this memory
+  // being returned as a result of a non-FIXED mmap().
+  if (addr == kZeroBaseShadowStart) {
+    uptr step = GetMmapGranularity();
+    while (size > step && addr < kZeroBaseMaxShadowStart) {
+      addr += step;
+      size -= step;
+      void *res = MmapFixedNoAccess(addr, size, "shadow gap");
+      if (addr == (uptr)res) return;
+    }
+  }
+
+  Report(
+      "ERROR: Failed to protect the shadow gap. "
+      "ASan cannot proceed correctly. ABORTING.\n");
+  DumpProcessMap();
+  Die();
+}
+
+static void MaybeReportLinuxPIEBug() {
+#if SANITIZER_LINUX && (defined(__x86_64__) || defined(__aarch64__))
+  Report("This might be related to ELF_ET_DYN_BASE change in Linux 4.12.\n");
+  Report(
+      "See https://github.com/google/sanitizers/issues/856 for possible "
+      "workarounds.\n");
+#endif
+}
+
+void InitializeShadowMemory() {
+  // Set the shadow memory address to uninitialized.
+  __asan_shadow_memory_dynamic_address = kDefaultShadowSentinel;
+
+  uptr shadow_start = kLowShadowBeg;
+  // Detect if a dynamic shadow address must used and find a available location
+  // when necessary. When dynamic address is used, the macro |kLowShadowBeg|
+  // expands to |__asan_shadow_memory_dynamic_address| which is
+  // |kDefaultShadowSentinel|.
+  if (shadow_start == kDefaultShadowSentinel) {
+    __asan_shadow_memory_dynamic_address = 0;
+    CHECK_EQ(0, kLowShadowBeg);
+    shadow_start = FindDynamicShadowStart();
+  }
+  // Update the shadow memory address (potentially) used by instrumentation.
+  __asan_shadow_memory_dynamic_address = shadow_start;
+
+  if (kLowShadowBeg) shadow_start -= GetMmapGranularity();
+  bool full_shadow_is_available =
+      MemoryRangeIsAvailable(shadow_start, kHighShadowEnd);
+
+#if SANITIZER_LINUX && defined(__x86_64__) && defined(_LP64) && \
+    !ASAN_FIXED_MAPPING
+  if (!full_shadow_is_available) {
+    kMidMemBeg = kLowMemEnd < 0x3000000000ULL ? 0x3000000000ULL : 0;
+    kMidMemEnd = kLowMemEnd < 0x3000000000ULL ? 0x4fffffffffULL : 0;
+  }
+#endif
+
+  if (Verbosity()) PrintAddressSpaceLayout();
+
+  if (full_shadow_is_available) {
+    // mmap the low shadow plus at least one page at the left.
+    if (kLowShadowBeg)
+      ReserveShadowMemoryRange(shadow_start, kLowShadowEnd, "low shadow");
+    // mmap the high shadow.
+    ReserveShadowMemoryRange(kHighShadowBeg, kHighShadowEnd, "high shadow");
+    // protect the gap.
+    ProtectGap(kShadowGapBeg, kShadowGapEnd - kShadowGapBeg + 1);
+    CHECK_EQ(kShadowGapEnd, kHighShadowBeg - 1);
+  } else if (kMidMemBeg &&
+             MemoryRangeIsAvailable(shadow_start, kMidMemBeg - 1) &&
+             MemoryRangeIsAvailable(kMidMemEnd + 1, kHighShadowEnd)) {
+    CHECK(kLowShadowBeg != kLowShadowEnd);
+    // mmap the low shadow plus at least one page at the left.
+    ReserveShadowMemoryRange(shadow_start, kLowShadowEnd, "low shadow");
+    // mmap the mid shadow.
+    ReserveShadowMemoryRange(kMidShadowBeg, kMidShadowEnd, "mid shadow");
+    // mmap the high shadow.
+    ReserveShadowMemoryRange(kHighShadowBeg, kHighShadowEnd, "high shadow");
+    // protect the gaps.
+    ProtectGap(kShadowGapBeg, kShadowGapEnd - kShadowGapBeg + 1);
+    ProtectGap(kShadowGap2Beg, kShadowGap2End - kShadowGap2Beg + 1);
+    ProtectGap(kShadowGap3Beg, kShadowGap3End - kShadowGap3Beg + 1);
+  } else {
+    Report(
+        "Shadow memory range interleaves with an existing memory mapping. "
+        "ASan cannot proceed correctly. ABORTING.\n");
+    Report("ASan shadow was supposed to be located in the [%p-%p] range.\n",
+           shadow_start, kHighShadowEnd);
+    MaybeReportLinuxPIEBug();
+    DumpProcessMap();
+    Die();
+  }
+}
+
+}  // namespace __asan
+
+#endif  // !SANITIZER_FUCHSIA