Index: compiler-rt/trunk/lib/esan/esan.cpp
===================================================================
--- compiler-rt/trunk/lib/esan/esan.cpp
+++ compiler-rt/trunk/lib/esan/esan.cpp
@@ -14,6 +14,7 @@
 
 #include "esan.h"
 #include "esan_interface_internal.h"
+#include "esan_shadow.h"
 #include "sanitizer_common/sanitizer_common.h"
 #include "sanitizer_common/sanitizer_flag_parser.h"
 #include "sanitizer_common/sanitizer_flags.h"
@@ -27,6 +28,7 @@
 
 bool EsanIsInitialized;
 ToolType WhichTool;
+ShadowMapping Mapping;
 
 static const char EsanOptsEnv[] = "ESAN_OPTIONS";
 
@@ -59,6 +61,69 @@
   }
 }
 
+#if SANITIZER_DEBUG
+static bool verifyShadowScheme() {
+  // Sanity checks for our shadow mapping scheme.
+  for (int Scale = 0; Scale < 8; ++Scale) {
+    Mapping.initialize(Scale);
+    uptr AppStart, AppEnd;
+    for (int i = 0; getAppRegion(i, &AppStart, &AppEnd); ++i) {
+      DCHECK(isAppMem(AppStart));
+      DCHECK(!isAppMem(AppStart - 1));
+      DCHECK(isAppMem(AppEnd - 1));
+      DCHECK(!isAppMem(AppEnd));
+      DCHECK(!isShadowMem(AppStart));
+      DCHECK(!isShadowMem(AppEnd - 1));
+      DCHECK(isShadowMem(appToShadow(AppStart)));
+      DCHECK(isShadowMem(appToShadow(AppEnd - 1)));
+      // Double-shadow checks.
+      DCHECK(!isShadowMem(appToShadow(appToShadow(AppStart))));
+      DCHECK(!isShadowMem(appToShadow(appToShadow(AppEnd - 1))));
+    }
+    // Ensure no shadow regions overlap each other.
+    uptr ShadowAStart, ShadowBStart, ShadowAEnd, ShadowBEnd;
+    for (int i = 0; getShadowRegion(i, &ShadowAStart, &ShadowAEnd); ++i) {
+      for (int j = 0; getShadowRegion(j, &ShadowBStart, &ShadowBEnd); ++j) {
+        DCHECK(i == j || ShadowAStart >= ShadowBEnd ||
+               ShadowAEnd <= ShadowBStart);
+      }
+    }
+  }
+  return true;
+}
+#endif
+
+static void initializeShadow() {
+  DCHECK(verifyShadowScheme());
+
+  if (WhichTool == ESAN_CacheFrag)
+    Mapping.initialize(2); // 4B:1B, so 4 to 1 == >>2.
+  else
+    UNREACHABLE("unknown tool shadow mapping");
+
+  VPrintf(1, "Shadow scale=%d offset=%p\n", Mapping.Scale, Mapping.Offset);
+
+  uptr ShadowStart, ShadowEnd;
+  for (int i = 0; getShadowRegion(i, &ShadowStart, &ShadowEnd); ++i) {
+    VPrintf(1, "Shadow #%d: [%zx-%zx) (%zuGB)\n", i, ShadowStart, ShadowEnd,
+            (ShadowEnd - ShadowStart) >> 30);
+
+    uptr Map = (uptr)MmapFixedNoReserve(ShadowStart, ShadowEnd - ShadowStart,
+                                        "shadow");
+    if (Map != ShadowStart) {
+      Printf("FATAL: EfficiencySanitizer failed to map its shadow memory.\n");
+      Die();
+    }
+
+    if (common_flags()->no_huge_pages_for_shadow)
+      NoHugePagesInRegion(ShadowStart, ShadowEnd - ShadowStart);
+    if (common_flags()->use_madv_dontdump)
+      DontDumpShadowMemory(ShadowStart, ShadowEnd - ShadowStart);
+
+    // TODO: Call MmapNoAccess() on in-between regions.
+  }
+}
+
 static void initializeFlags() {
   // Once we add our own flags we'll parse them here.
   // For now the common ones are sufficient.
@@ -95,6 +160,7 @@
     Die();
   }
 
+  initializeShadow();
   initializeInterceptors();
 
   EsanIsInitialized = true;
Index: compiler-rt/trunk/lib/esan/esan_interceptors.cpp
===================================================================
--- compiler-rt/trunk/lib/esan/esan_interceptors.cpp
+++ compiler-rt/trunk/lib/esan/esan_interceptors.cpp
@@ -13,6 +13,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "esan.h"
+#include "esan_shadow.h"
 #include "interception/interception.h"
 #include "sanitizer_common/sanitizer_common.h"
 #include "sanitizer_common/sanitizer_libc.h"
@@ -20,6 +21,19 @@
 
 using namespace __esan; // NOLINT
 
+// FIXME: if this gets more complex as more platforms are added we may
+// want to split pieces into separate platform-specific files.
+#if SANITIZER_LINUX
+// Sanitizer runtimes in general want to avoid including system headers.
+// We define the few constants we need here:
+const int EINVAL = 22; // from /usr/include/asm-generic/errno-base.h
+const int MAP_FIXED = 0x10; // from /usr/include/sys/mman.h
+extern "C" int *__errno_location();
+#define errno (*__errno_location())
+#else
+#error Other platforms are not yet supported.
+#endif
+
 #define CUR_PC() (StackTrace::GetCurrentPc())
 
 //===----------------------------------------------------------------------===//
@@ -388,6 +402,56 @@
   return REAL(rmdir)(path);
 }
 
+//===----------------------------------------------------------------------===//
+// Shadow-related interceptors
+//===----------------------------------------------------------------------===//
+
+// These are candidates for sharing with all sanitizers if shadow memory
+// support is also standardized.
+
+static bool fixMmapAddr(void **addr, SIZE_T sz, int flags) {
+  if (*addr) {
+    uptr AppStart, AppEnd;
+    bool SingleApp = false;
+    for (int i = 0; getAppRegion(i, &AppStart, &AppEnd); ++i) {
+      if ((uptr)*addr >= AppStart && (uptr)*addr + sz - 1 <= AppEnd) {
+        SingleApp = true;
+        break;
+      }
+    }
+    if (!SingleApp) {
+      VPrintf(1, "mmap conflict: [%p-%p) is not in an app region\n",
+              *addr, (uptr)*addr + sz);
+      if (flags & MAP_FIXED) {
+        errno = EINVAL;
+        return false;
+      } else {
+        *addr = 0;
+      }
+    }
+  }
+  return true;
+}
+
+INTERCEPTOR(void *, mmap, void *addr, SIZE_T sz, int prot, int flags,
+                 int fd, OFF_T off) {
+  if (!fixMmapAddr(&addr, sz, flags))
+    return (void *)-1;
+  return REAL(mmap)(addr, sz, prot, flags, fd, off);
+}
+
+#if SANITIZER_LINUX
+INTERCEPTOR(void *, mmap64, void *addr, SIZE_T sz, int prot, int flags,
+                 int fd, OFF64_T off) {
+  if (!fixMmapAddr(&addr, sz, flags))
+    return (void *)-1;
+  return REAL(mmap64)(addr, sz, prot, flags, fd, off);
+}
+#define ESAN_MAYBE_INTERCEPT_MMAP64 INTERCEPT_FUNCTION(mmap64)
+#else
+#define ESAN_MAYBE_INTERCEPT_MMAP64
+#endif
+
 namespace __esan {
 
 void initializeInterceptors() {
@@ -411,6 +475,9 @@
   INTERCEPT_FUNCTION(puts);
   INTERCEPT_FUNCTION(rmdir);
 
+  INTERCEPT_FUNCTION(mmap);
+  ESAN_MAYBE_INTERCEPT_MMAP64;
+
   // TODO(bruening): we should intercept calloc() and other memory allocation
   // routines that zero memory and update our shadow memory appropriately.
 
Index: compiler-rt/trunk/lib/esan/esan_shadow.h
===================================================================
--- compiler-rt/trunk/lib/esan/esan_shadow.h
+++ compiler-rt/trunk/lib/esan/esan_shadow.h
@@ -0,0 +1,197 @@
+//===-- esan_shadow.h -------------------------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file is a part of EfficiencySanitizer, a family of performance tuners.
+//
+// Shadow memory mappings for the esan run-time.
+//===----------------------------------------------------------------------===//
+
+#ifndef ESAN_SHADOW_H
+#define ESAN_SHADOW_H
+
+#include <sanitizer_common/sanitizer_platform.h>
+
+#if SANITIZER_WORDSIZE != 64
+#error Only 64-bit is supported
+#endif
+
+namespace __esan {
+
+#if SANITIZER_LINUX && defined(__x86_64__)
+// Linux x86_64
+//
+// Application memory falls into these 5 regions (ignoring the corner case
+// of PIE with a non-zero PT_LOAD base):
+//
+// [0x00000000'00000000, 0x00000100'00000000) non-PIE + heap
+// [0x00005500'00000000, 0x00005700'00000000) PIE
+// [0x00007f00'00000000, 0x00007fff'ff600000) libraries + stack, part 1
+// [0x00007fff'ff601000, 0x00008000'00000000) libraries + stack, part 2
+// [0xffffffff'ff600000, 0xffffffff'ff601000) vsyscall
+//
+// Although we can ignore the vsyscall for the most part as there are few data
+// references there (other sanitizers ignore it), we enforce a gap inside the
+// library region to distinguish the vsyscall's shadow, considering this gap to
+// be an invalid app region.
+//
+// We disallow application memory outside of those 5 regions.
+//
+// Our shadow memory is scaled from a 1:1 mapping and supports a scale
+// specified at library initialization time that can be any power-of-2
+// scaledown (1x, 2x, 4x, 8x, 16x, etc.).
+//
+// We model our shadow memory after Umbra, a library used by the Dr. Memory
+// tool: https://github.com/DynamoRIO/drmemory/blob/master/umbra/umbra_x64.c.
+// We use Umbra's scheme as it was designed to support different
+// offsets, it supports two different shadow mappings (which we may want to
+// use for future tools), and it ensures that the shadow of a shadow will
+// not overlap either shadow memory or application memory.
+//
+// This formula translates from application memory to shadow memory:
+//
+//   shadow(app) = ((app & 0x00000fff'ffffffff) + offset) >> scale
+//
+// Where the offset for 1:1 is 0x00001200'00000000.  For other scales, the
+// offset is shifted left by the scale, except for scales of 1 and 2 where
+// it must be tweaked in order to pass the double-shadow test
+// (see the "shadow(shadow)" comments below):
+//   scale == 0: 0x0000120'000000000
+//   scale == 1: 0x0000220'000000000
+//   scale == 2: 0x0000440'000000000
+//   scale >= 3: (0x0000120'000000000 << scale)
+//
+// Do not pass in the open-ended end value to the formula as it will fail.
+//
+// The resulting shadow memory regions for a 0 scaling are:
+//
+// [0x00001200'00000000, 0x00001300'00000000)
+// [0x00001700'00000000, 0x00001900'00000000)
+// [0x00002100'00000000, 0x000021ff'ff600000)
+// [0x000021ff'ff601000, 0x00002200'00000000)
+// [0x000021ff'ff600000, 0x000021ff'ff601000]
+//
+// We also want to ensure that a wild access by the application into the shadow
+// regions will not corrupt our own shadow memory.  shadow(shadow) ends up
+// disjoint from shadow(app):
+//
+// [0x00001400'00000000, 0x00001500'00000000)
+// [0x00001900'00000000, 0x00001b00'00000000)
+// [0x00001300'00000000, 0x000013ff'ff600000]
+// [0x000013ff'ff601000, 0x00001400'00000000]
+// [0x000013ff'ff600000, 0x000013ff'ff601000]
+
+struct ApplicationRegion {
+  uptr Start;
+  uptr End;
+  bool ShadowMergedWithPrev;
+};
+
+static const struct ApplicationRegion AppRegions[] = {
+  {0x0000000000000000ull, 0x0000010000000000u, false},
+  {0x0000550000000000u,   0x0000570000000000u, false},
+  // We make one shadow mapping to hold the shadow regions for all 3 of these
+  // app regions, as the mappings interleave, and the gap between the 3rd and
+  // 4th scales down below a page.
+  {0x00007f0000000000u,   0x00007fffff600000u, false},
+  {0x00007fffff601000u,   0x0000800000000000u, true},
+  {0xffffffffff600000u,   0xffffffffff601000u, true},
+};
+static const u32 NumAppRegions = sizeof(AppRegions)/sizeof(AppRegions[0]);
+
+class ShadowMapping {
+public:
+  static const uptr Mask = 0x00000fffffffffffu;
+  // The scale and offset vary by tool.
+  uptr Scale;
+  uptr Offset;
+  void initialize(uptr ShadowScale) {
+    static const uptr OffsetArray[3] = {
+        0x0000120000000000u,
+        0x0000220000000000u,
+        0x0000440000000000u,
+    };
+    Scale = ShadowScale;
+    if (Scale <= 2)
+      Offset = OffsetArray[Scale];
+    else
+      Offset = OffsetArray[0] << Scale;
+  }
+};
+extern ShadowMapping Mapping;
+#else
+// We'll want to use templatized functions over the ShadowMapping once
+// we support more platforms.
+#error Platform not supported
+#endif
+
+static inline bool getAppRegion(u32 i, uptr *Start, uptr *End) {
+  if (i >= NumAppRegions)
+    return false;
+  *Start = AppRegions[i].Start;
+  *End = AppRegions[i].End;
+  return true;
+}
+
+ALWAYS_INLINE
+bool isAppMem(uptr Mem) {
+  for (u32 i = 0; i < NumAppRegions; ++i) {
+    if (Mem >= AppRegions[i].Start && Mem < AppRegions[i].End)
+      return true;
+  }
+  return false;
+}
+
+ALWAYS_INLINE
+uptr appToShadow(uptr App) {
+  DCHECK(isAppMem(App));
+  return (((App & ShadowMapping::Mask) + Mapping.Offset) >> Mapping.Scale);
+}
+
+static inline bool getShadowRegion(u32 i, uptr *Start, uptr *End) {
+  if (i >= NumAppRegions)
+    return false;
+  u32 UnmergedShadowCount = 0;
+  u32 AppIdx;
+  for (AppIdx = 0; AppIdx < NumAppRegions; ++AppIdx) {
+    if (!AppRegions[AppIdx].ShadowMergedWithPrev) {
+      if (UnmergedShadowCount == i)
+        break;
+      UnmergedShadowCount++;
+    }
+  }
+  if (AppIdx >= NumAppRegions || UnmergedShadowCount != i)
+    return false;
+  *Start = appToShadow(AppRegions[AppIdx].Start);
+  // The formula fails for the end itself.
+  *End = appToShadow(AppRegions[AppIdx].End - 1) + 1;
+  // Merge with adjacent shadow regions:
+  for (++AppIdx; AppIdx < NumAppRegions; ++AppIdx) {
+    if (!AppRegions[AppIdx].ShadowMergedWithPrev)
+      break;
+    *Start = Min(*Start, appToShadow(AppRegions[AppIdx].Start));
+    *End = Max(*End, appToShadow(AppRegions[AppIdx].End - 1) + 1);
+  }
+  return true;
+}
+
+ALWAYS_INLINE
+bool isShadowMem(uptr Mem) {
+  // We assume this is not used on any critical performance path and so there's
+  // no need to hardcode the mapping results.
+  for (uptr i = 0; i < NumAppRegions; ++i) {
+    if (Mem >= appToShadow(AppRegions[i].Start) &&
+        Mem < appToShadow(AppRegions[i].End))
+      return true;
+  }
+  return false;
+}
+
+} // namespace __esan
+
+#endif /* ESAN_SHADOW_H */
Index: compiler-rt/trunk/test/esan/TestCases/mmap-shadow-conflict.c
===================================================================
--- compiler-rt/trunk/test/esan/TestCases/mmap-shadow-conflict.c
+++ compiler-rt/trunk/test/esan/TestCases/mmap-shadow-conflict.c
@@ -0,0 +1,29 @@
+// RUN: %clang_esan_frag -O0 %s -o %t 2>&1
+// RUN: %env_esan_opts=verbosity=1 %run %t 2>&1 | FileCheck %s
+
+#include <unistd.h>
+#include <sys/mman.h>
+#include <stdio.h>
+
+int main(int argc, char **argv) {
+  void *Map = mmap((void *)0x0000016000000000ULL, 0x1000, PROT_READ,
+                   MAP_ANON|MAP_PRIVATE|MAP_FIXED, -1, 0);
+  if (Map == (void *)-1)
+    fprintf(stderr, "map failed\n");
+  else
+    fprintf(stderr, "mapped %p\n", Map);
+  Map = mmap((void *)0x0000016000000000ULL, 0x1000, PROT_READ,
+                   MAP_ANON|MAP_PRIVATE, -1, 0);
+  fprintf(stderr, "mapped %p\n", Map);
+  // CHECK:      in esan::initializeLibrary
+  // CHECK-NEXT: Shadow scale=2 offset=0x440000000000
+  // CHECK-NEXT: Shadow #0: [110000000000-114000000000) (256GB)
+  // CHECK-NEXT: Shadow #1: [124000000000-12c000000000) (512GB)
+  // CHECK-NEXT: Shadow #2: [14c000000000-150000000000) (256GB)
+  // CHECK-NEXT: mmap conflict: {{.*}}
+  // CHECK-NEXT: map failed
+  // CHECK-NEXT: mmap conflict: {{.*}}
+  // CHECK-NEXT: mapped {{.*}}
+  // CHECK-NEXT: in esan::finalizeLibrary
+  return 0;
+}
Index: compiler-rt/trunk/test/esan/TestCases/verbose-simple.c
===================================================================
--- compiler-rt/trunk/test/esan/TestCases/verbose-simple.c
+++ compiler-rt/trunk/test/esan/TestCases/verbose-simple.c
@@ -3,6 +3,10 @@
 
 int main(int argc, char **argv) {
   // CHECK:      in esan::initializeLibrary
+  // CHECK-NEXT: Shadow scale=2 offset=0x440000000000
+  // CHECK-NEXT: Shadow #0: [110000000000-114000000000) (256GB)
+  // CHECK-NEXT: Shadow #1: [124000000000-12c000000000) (512GB)
+  // CHECK-NEXT: Shadow #2: [14c000000000-150000000000) (256GB)
   // CHECK-NEXT: in esan::finalizeLibrary
   // CHECK-NEXT: {{.*}}EfficiencySanitizer is not finished: nothing yet to report
   return 0;