tsan: unify all shadow mappings

[dvyukov]

Summary

Currently we have ifdef's for Go/C++ and Windows/non-Windows
in MemToShadow, MemToMeta, ShadowToMem. This does not allow
to test all mappings on a single platform.
Make all these functions support a superset of mappings for
all platforms by defining missing mapping consts to 0.
E.g. we always do ^A+B, but if A and B are defined to 0,
then these operations become no-op.

Depends on D107739.

[dvyukov]

changed SelectMapping to use template Arg and rebased

compiler-rt/lib/tsan/rtl/tsan_platform.h

struct Mapping48AddressSpace {
   static const uptr kHeapMemBeg    = 0x7b0000000000ull;
   static const uptr kHeapMemEnd    = 0x7c0000000000ull;
   static const uptr kLoAppMemBeg   = 0x000000001000ull;
   static const uptr kLoAppMemEnd   = 0x008000000000ull;
   static const uptr kMidAppMemBeg  = 0x550000000000ull;
   static const uptr kMidAppMemEnd  = 0x568000000000ull;
   static const uptr kHiAppMemBeg   = 0x7e8000000000ull;
   static const uptr kHiAppMemEnd   = 0x800000000000ull;
-  static const uptr kAppMemMsk     = 0x780000000000ull;
-  static const uptr kAppMemXor     = 0x040000000000ull;
+  static const uptr kShadowMsk = 0x780000000000ull;
+  static const uptr kShadowXor = 0x040000000000ull;
+  static const uptr kShadowAdd = 0x000000000000ull;
   static const uptr kVdsoBeg       = 0xf000000000000000ull;
 };
 
 /*
 C/C++ on linux/mips64 (40-bit VMA)
 0000 0000 00 - 0100 0000 00: -                                           (4 GB)
 0100 0000 00 - 0200 0000 00: main binary                                 (4 GB)
 0200 0000 00 - 2000 0000 00: -                                         (120 GB)
struct MappingMips64_40 {
   static const uptr kHeapMemBeg    = 0xfe00000000ull;
   static const uptr kHeapMemEnd    = 0xff00000000ull;
   static const uptr kLoAppMemBeg   = 0x0100000000ull;
   static const uptr kLoAppMemEnd   = 0x0200000000ull;
   static const uptr kMidAppMemBeg  = 0xaa00000000ull;
   static const uptr kMidAppMemEnd  = 0xab00000000ull;
   static const uptr kHiAppMemBeg   = 0xff80000000ull;
   static const uptr kHiAppMemEnd   = 0xffffffffffull;
-  static const uptr kAppMemMsk     = 0xf800000000ull;
-  static const uptr kAppMemXor     = 0x0800000000ull;
+  static const uptr kShadowMsk = 0xf800000000ull;
+  static const uptr kShadowXor = 0x0800000000ull;
+  static const uptr kShadowAdd = 0x0000000000ull;
   static const uptr kVdsoBeg       = 0xfffff00000ull;
 };
 
 /*
 C/C++ on Darwin/iOS/ARM64 (36-bit VMA, 64 GB VM)
 0000 0000 00 - 0100 0000 00: -                                    (4 GB)
 0100 0000 00 - 0200 0000 00: main binary, modules, thread stacks  (4 GB)
 0200 0000 00 - 0300 0000 00: heap                                 (4 GB)
struct MappingAppleAarch64 {
   static const uptr kShadowBeg     = 0x0400000000ull;
   static const uptr kShadowEnd     = 0x0c00000000ull;
   static const uptr kMetaShadowBeg = 0x0d00000000ull;
   static const uptr kMetaShadowEnd = 0x0e00000000ull;
   static const uptr kTraceMemBeg   = 0x0f00000000ull;
   static const uptr kTraceMemEnd   = 0x0fc0000000ull;
   static const uptr kHiAppMemBeg   = 0x0fc0000000ull;
   static const uptr kHiAppMemEnd   = 0x0fc0000000ull;
-  static const uptr kAppMemMsk     =          0x0ull;
-  static const uptr kAppMemXor     =          0x0ull;
+  static const uptr kShadowMsk = 0x0ull;
+  static const uptr kShadowXor = 0x0ull;
+  static const uptr kShadowAdd = 0x0ull;
   static const uptr kVdsoBeg       = 0x7000000000000000ull;
   static const uptr kMidAppMemBeg = 0;
   static const uptr kMidAppMemEnd = 0;
 };
 
 /*
 C/C++ on linux/aarch64 (39-bit VMA)
 0000 0010 00 - 0100 0000 00: main binary
struct MappingAarch64_39 {
   static const uptr kMidAppMemBeg  = 0x5500000000ull;
   static const uptr kMidAppMemEnd  = 0x5600000000ull;
   static const uptr kTraceMemBeg   = 0x6000000000ull;
   static const uptr kTraceMemEnd   = 0x6200000000ull;
   static const uptr kHeapMemBeg    = 0x7c00000000ull;
   static const uptr kHeapMemEnd    = 0x7d00000000ull;
   static const uptr kHiAppMemBeg   = 0x7e00000000ull;
   static const uptr kHiAppMemEnd   = 0x7fffffffffull;
-  static const uptr kAppMemMsk     = 0x7800000000ull;
-  static const uptr kAppMemXor     = 0x0200000000ull;
+  static const uptr kShadowMsk = 0x7800000000ull;
+  static const uptr kShadowXor = 0x0200000000ull;
+  static const uptr kShadowAdd = 0x0000000000ull;
   static const uptr kVdsoBeg       = 0x7f00000000ull;
 };
 
 /*
 C/C++ on linux/aarch64 (42-bit VMA)
 00000 0010 00 - 01000 0000 00: main binary
 01000 0000 00 - 10000 0000 00: -
 10000 0000 00 - 20000 0000 00: shadow memory
struct MappingAarch64_42 {
   static const uptr kMidAppMemBeg  = 0x2aa00000000ull;
   static const uptr kMidAppMemEnd  = 0x2ab00000000ull;
   static const uptr kTraceMemBeg   = 0x36200000000ull;
   static const uptr kTraceMemEnd   = 0x36400000000ull;
   static const uptr kHeapMemBeg    = 0x3e000000000ull;
   static const uptr kHeapMemEnd    = 0x3f000000000ull;
   static const uptr kHiAppMemBeg   = 0x3f000000000ull;
   static const uptr kHiAppMemEnd   = 0x3ffffffffffull;
-  static const uptr kAppMemMsk     = 0x3c000000000ull;
-  static const uptr kAppMemXor     = 0x04000000000ull;
+  static const uptr kShadowMsk = 0x3c000000000ull;
+  static const uptr kShadowXor = 0x04000000000ull;
+  static const uptr kShadowAdd = 0x00000000000ull;
   static const uptr kVdsoBeg       = 0x37f00000000ull;
 };
 
 struct MappingAarch64_48 {
   static const uptr kLoAppMemBeg   = 0x0000000001000ull;
   static const uptr kLoAppMemEnd   = 0x0000200000000ull;
   static const uptr kShadowBeg     = 0x0002000000000ull;
   static const uptr kShadowEnd     = 0x0004000000000ull;
   static const uptr kMetaShadowBeg = 0x0005000000000ull;
   static const uptr kMetaShadowEnd = 0x0006000000000ull;
   static const uptr kMidAppMemBeg  = 0x0aaaa00000000ull;
   static const uptr kMidAppMemEnd  = 0x0aaaf00000000ull;
   static const uptr kTraceMemBeg   = 0x0f06000000000ull;
   static const uptr kTraceMemEnd   = 0x0f06200000000ull;
   static const uptr kHeapMemBeg    = 0x0ffff00000000ull;
   static const uptr kHeapMemEnd    = 0x0ffff00000000ull;
   static const uptr kHiAppMemBeg   = 0x0ffff00000000ull;
   static const uptr kHiAppMemEnd   = 0x1000000000000ull;
-  static const uptr kAppMemMsk     = 0x0fff800000000ull;
-  static const uptr kAppMemXor     = 0x0000800000000ull;
+  static const uptr kShadowMsk = 0x0fff800000000ull;
+  static const uptr kShadowXor = 0x0000800000000ull;
+  static const uptr kShadowAdd = 0x0000000000000ull;
   static const uptr kVdsoBeg       = 0xffff000000000ull;
 };
 
 /*
 C/C++ on linux/powerpc64 (44-bit VMA)
 0000 0000 0100 - 0001 0000 0000: main binary
 0001 0000 0000 - 0001 0000 0000: -
 0001 0000 0000 - 0b00 0000 0000: shadow
struct MappingPPC64_44 {
   static const uptr kShadowBeg     = 0x000100000000ull;
   static const uptr kShadowEnd     = 0x0b0000000000ull;
   static const uptr kLoAppMemBeg   = 0x000000000100ull;
   static const uptr kLoAppMemEnd   = 0x000100000000ull;
   static const uptr kHeapMemBeg    = 0x0f0000000000ull;
   static const uptr kHeapMemEnd    = 0x0f5000000000ull;
   static const uptr kHiAppMemBeg   = 0x0f6000000000ull;
   static const uptr kHiAppMemEnd   = 0x100000000000ull; // 44 bits
-  static const uptr kAppMemMsk     = 0x0f0000000000ull;
-  static const uptr kAppMemXor     = 0x002100000000ull;
+  static const uptr kShadowMsk = 0x0f0000000000ull;
+  static const uptr kShadowXor = 0x002100000000ull;
+  static const uptr kShadowAdd = 0x000000000000ull;
   static const uptr kVdsoBeg       = 0x3c0000000000000ull;
   static const uptr kMidAppMemBeg = 0;
   static const uptr kMidAppMemEnd = 0;
 };
 
 /*
 C/C++ on linux/powerpc64 (46-bit VMA)
 0000 0000 1000 - 0100 0000 0000: main binary
struct MappingPPC64_46 {
   static const uptr kShadowBeg     = 0x010000000000ull;
   static const uptr kShadowEnd     = 0x100000000000ull;
   static const uptr kHeapMemBeg    = 0x3d0000000000ull;
   static const uptr kHeapMemEnd    = 0x3e0000000000ull;
   static const uptr kLoAppMemBeg   = 0x000000001000ull;
   static const uptr kLoAppMemEnd   = 0x010000000000ull;
   static const uptr kHiAppMemBeg   = 0x3e8000000000ull;
   static const uptr kHiAppMemEnd   = 0x400000000000ull; // 46 bits
-  static const uptr kAppMemMsk     = 0x3c0000000000ull;
-  static const uptr kAppMemXor     = 0x020000000000ull;
+  static const uptr kShadowMsk = 0x3c0000000000ull;
+  static const uptr kShadowXor = 0x020000000000ull;
+  static const uptr kShadowAdd = 0x000000000000ull;
   static const uptr kVdsoBeg       = 0x7800000000000000ull;
   static const uptr kMidAppMemBeg = 0;
   static const uptr kMidAppMemEnd = 0;
 };
 
 /*
 C/C++ on linux/powerpc64 (47-bit VMA)
 0000 0000 1000 - 0100 0000 0000: main binary
struct MappingPPC64_47 {
   static const uptr kShadowBeg     = 0x010000000000ull;
   static const uptr kShadowEnd     = 0x100000000000ull;
   static const uptr kHeapMemBeg    = 0x7d0000000000ull;
   static const uptr kHeapMemEnd    = 0x7e0000000000ull;
   static const uptr kLoAppMemBeg   = 0x000000001000ull;
   static const uptr kLoAppMemEnd   = 0x010000000000ull;
   static const uptr kHiAppMemBeg   = 0x7e8000000000ull;
   static const uptr kHiAppMemEnd   = 0x800000000000ull; // 47 bits
-  static const uptr kAppMemMsk     = 0x7c0000000000ull;
-  static const uptr kAppMemXor     = 0x020000000000ull;
+  static const uptr kShadowMsk = 0x7c0000000000ull;
+  static const uptr kShadowXor = 0x020000000000ull;
+  static const uptr kShadowAdd = 0x000000000000ull;
   static const uptr kVdsoBeg       = 0x7800000000000000ull;
   static const uptr kMidAppMemBeg = 0;
   static const uptr kMidAppMemEnd = 0;
 };
 
 /*
 C/C++ on linux/s390x
 While the kernel provides a 64-bit address space, we have to restrict ourselves
struct MappingS390x {
   static const uptr kShadowBeg     = 0x400000000000ull;
   static const uptr kShadowEnd     = 0x800000000000ull;
   static const uptr kHeapMemBeg    = 0xbe0000000000ull;
   static const uptr kHeapMemEnd    = 0xc00000000000ull;
   static const uptr kLoAppMemBeg   = 0x000000001000ull;
   static const uptr kLoAppMemEnd   = 0x0e0000000000ull;
   static const uptr kHiAppMemBeg   = 0xc00000004000ull;
   static const uptr kHiAppMemEnd   = 0xc00000004000ull;
-  static const uptr kAppMemMsk     = 0xb00000000000ull;
-  static const uptr kAppMemXor     = 0x100000000000ull;
+  static const uptr kShadowMsk = 0xb00000000000ull;
+  static const uptr kShadowXor = 0x100000000000ull;
+  static const uptr kShadowAdd = 0x000000000000ull;
   static const uptr kVdsoBeg       = 0xfffffffff000ull;
   static const uptr kMidAppMemBeg = 0;
   static const uptr kMidAppMemEnd = 0;
 };
 
 /* Go on linux, darwin and freebsd on x86_64
 0000 0000 1000 - 0000 1000 0000: executable
 0000 1000 0000 - 00c0 0000 0000: -
struct MappingGo48 {
   static const uptr kLoAppMemEnd = 0x00e000000000ull;
   static const uptr kMidAppMemBeg = 0;
   static const uptr kMidAppMemEnd = 0;
   static const uptr kHiAppMemBeg = 0;
   static const uptr kHiAppMemEnd = 0;
   static const uptr kHeapMemBeg = 0;
   static const uptr kHeapMemEnd = 0;
   static const uptr kVdsoBeg = 0;
+  static const uptr kShadowMsk = 0;
+  static const uptr kShadowXor = 0;
+  static const uptr kShadowAdd = 0x200000000000ull;
 };
 
 /* Go on windows
 0000 0000 1000 - 0000 1000 0000: executable
 0000 1000 0000 - 00f8 0000 0000: -
 00c0 0000 0000 - 00e0 0000 0000: heap
 00e0 0000 0000 - 0100 0000 0000: -
 0100 0000 0000 - 0500 0000 0000: shadow
-0500 0000 0000 - 0560 0000 0000: -
-0560 0000 0000 - 0760 0000 0000: traces
-0760 0000 0000 - 07d0 0000 0000: metainfo (memory blocks and sync objects)
+0500 0000 0000 - 0700 0000 0000: traces
+0700 0000 0000 - 0770 0000 0000: metainfo (memory blocks and sync objects)
 07d0 0000 0000 - 8000 0000 0000: -
 */
 
 struct MappingGoWindows {
-  static const uptr kMetaShadowBeg = 0x076000000000ull;
-  static const uptr kMetaShadowEnd = 0x07d000000000ull;
-  static const uptr kTraceMemBeg   = 0x056000000000ull;
-  static const uptr kTraceMemEnd   = 0x076000000000ull;
+  static const uptr kMetaShadowBeg = 0x070000000000ull;
+  static const uptr kMetaShadowEnd = 0x077000000000ull;
+  static const uptr kTraceMemBeg = 0x050000000000ull;
+  static const uptr kTraceMemEnd = 0x070000000000ull;
   static const uptr kShadowBeg     = 0x010000000000ull;
   static const uptr kShadowEnd     = 0x050000000000ull;
   static const uptr kLoAppMemBeg = 0x000000001000ull;
   static const uptr kLoAppMemEnd = 0x00e000000000ull;
   static const uptr kMidAppMemBeg = 0;
   static const uptr kMidAppMemEnd = 0;
   static const uptr kHiAppMemBeg = 0;
   static const uptr kHiAppMemEnd = 0;
   static const uptr kHeapMemBeg = 0;
   static const uptr kHeapMemEnd = 0;
   static const uptr kVdsoBeg = 0;
+  static const uptr kShadowMsk = 0;
+  static const uptr kShadowXor = 0;
+  static const uptr kShadowAdd = 0x010000000000ull;
 };
 
 /* Go on linux/powerpc64 (46-bit VMA)
 0000 0000 1000 - 0000 1000 0000: executable
 0000 1000 0000 - 00c0 0000 0000: -
 00c0 0000 0000 - 00e0 0000 0000: heap
 00e0 0000 0000 - 2000 0000 0000: -
 2000 0000 0000 - 2380 0000 0000: shadow
struct MappingGoPPC64_46 {
   static const uptr kLoAppMemEnd = 0x00e000000000ull;
   static const uptr kMidAppMemBeg = 0;
   static const uptr kMidAppMemEnd = 0;
   static const uptr kHiAppMemBeg = 0;
   static const uptr kHiAppMemEnd = 0;
   static const uptr kHeapMemBeg = 0;
   static const uptr kHeapMemEnd = 0;
   static const uptr kVdsoBeg = 0;
+  static const uptr kShadowMsk = 0;
+  static const uptr kShadowXor = 0;
+  static const uptr kShadowAdd = 0x200000000000ull;
 };
 
 /* Go on linux/powerpc64 (47-bit VMA)
 0000 0000 1000 - 0000 1000 0000: executable
 0000 1000 0000 - 00c0 0000 0000: -
 00c0 0000 0000 - 00e0 0000 0000: heap
 00e0 0000 0000 - 2000 0000 0000: -
 2000 0000 0000 - 3000 0000 0000: shadow
struct MappingGoPPC64_47 {
   static const uptr kLoAppMemEnd = 0x00e000000000ull;
   static const uptr kMidAppMemBeg = 0;
   static const uptr kMidAppMemEnd = 0;
   static const uptr kHiAppMemBeg = 0;
   static const uptr kHiAppMemEnd = 0;
   static const uptr kHeapMemBeg = 0;
   static const uptr kHeapMemEnd = 0;
   static const uptr kVdsoBeg = 0;
+  static const uptr kShadowMsk = 0;
+  static const uptr kShadowXor = 0;
+  static const uptr kShadowAdd = 0x200000000000ull;
 };
 
 /* Go on linux/aarch64 (48-bit VMA) and darwin/aarch64 (47-bit VMA)
 0000 0000 1000 - 0000 1000 0000: executable
 0000 1000 0000 - 00c0 0000 0000: -
 00c0 0000 0000 - 00e0 0000 0000: heap
 00e0 0000 0000 - 2000 0000 0000: -
 2000 0000 0000 - 3000 0000 0000: shadow
struct MappingGoAarch64 {
   static const uptr kLoAppMemEnd = 0x00e000000000ull;
   static const uptr kMidAppMemBeg = 0;
   static const uptr kMidAppMemEnd = 0;
   static const uptr kHiAppMemBeg = 0;
   static const uptr kHiAppMemEnd = 0;
   static const uptr kHeapMemBeg = 0;
   static const uptr kHeapMemEnd = 0;
   static const uptr kVdsoBeg = 0;
+  static const uptr kShadowMsk = 0;
+  static const uptr kShadowXor = 0;
+  static const uptr kShadowAdd = 0x200000000000ull;
 };
 
 /*
 Go on linux/mips64 (47-bit VMA)
 0000 0000 1000 - 0000 1000 0000: executable
 0000 1000 0000 - 00c0 0000 0000: -
 00c0 0000 0000 - 00e0 0000 0000: heap
 00e0 0000 0000 - 2000 0000 0000: -
struct MappingGoMips64_47 {
   static const uptr kLoAppMemEnd = 0x00e000000000ull;
   static const uptr kMidAppMemBeg = 0;
   static const uptr kMidAppMemEnd = 0;
   static const uptr kHiAppMemBeg = 0;
   static const uptr kHiAppMemEnd = 0;
   static const uptr kHeapMemBeg = 0;
   static const uptr kHeapMemEnd = 0;
   static const uptr kVdsoBeg = 0;
+  static const uptr kShadowMsk = 0;
+  static const uptr kShadowXor = 0;
+  static const uptr kShadowAdd = 0x200000000000ull;
 };
 
 /*
 Go on linux/s390x
 0000 0000 1000 - 1000 0000 0000: executable and heap - 16 TiB
 1000 0000 0000 - 4000 0000 0000: -
 4000 0000 0000 - 8000 0000 0000: shadow - 64TiB (4 * app)
 8000 0000 0000 - 9000 0000 0000: -
struct MappingGoS390x {
   static const uptr kLoAppMemEnd = 0x100000000000ull;
   static const uptr kMidAppMemBeg = 0;
   static const uptr kMidAppMemEnd = 0;
   static const uptr kHiAppMemBeg = 0;
   static const uptr kHiAppMemEnd = 0;
   static const uptr kHeapMemBeg = 0;
   static const uptr kHeapMemEnd = 0;
   static const uptr kVdsoBeg = 0;
+  static const uptr kShadowMsk = 0;
+  static const uptr kShadowXor = 0;
+  static const uptr kShadowAdd = 0x400000000000ull;
 };
 
 #if defined(__x86_64__)
 #  define HAS_48_BIT_ADDRESS_SPACE 1
 #elif SANITIZER_IOSSIM  // arm64 iOS simulators (order of #if matters)
 #  define HAS_48_BIT_ADDRESS_SPACE 1
 #elif SANITIZER_IOS  // arm64 iOS devices (order of #if matters)
 #  define HAS_48_BIT_ADDRESS_SPACE 0

 bool IsMetaMem(const u32 *p) {
   return SelectMapping<IsMetaMemImpl>(reinterpret_cast<uptr>(p));
 }
 
 struct MemToShadowImpl {
   template <typename Mapping>
   static uptr Apply(uptr x) {
     DCHECK(IsAppMemImpl::Apply<Mapping>(x));
-#if !SANITIZER_GO
-    return (((x) & ~(Mapping::kAppMemMsk | (kShadowCell - 1))) ^
-            Mapping::kAppMemXor) *
-           kShadowCnt;
-#else
-# ifndef SANITIZER_WINDOWS
-    return ((x & ~(kShadowCell - 1)) * kShadowCnt) | Mapping::kShadowBeg;
-# else
-    return ((x & ~(kShadowCell - 1)) * kShadowCnt) + Mapping::kShadowBeg;
-# endif
-#endif
+    return (((x) & ~(Mapping::kShadowMsk | (kShadowCell - 1))) ^
+            Mapping::kShadowXor) *
+               kShadowCnt +
+           Mapping::kShadowAdd;
   }
 };
 
 ALWAYS_INLINE
 RawShadow *MemToShadow(uptr x) {
   return reinterpret_cast<RawShadow *>(SelectMapping<MemToShadowImpl>(x));
 }
 
 struct MemToMetaImpl {
   template <typename Mapping>
   static u32 *Apply(uptr x) {
     DCHECK(IsAppMemImpl::Apply<Mapping>(x));
-#if !SANITIZER_GO
-  return (u32*)(((((x) & ~(Mapping::kAppMemMsk | (kMetaShadowCell - 1)))) /
-      kMetaShadowCell * kMetaShadowSize) | Mapping::kMetaShadowBeg);
-#else
-# ifndef SANITIZER_WINDOWS
-  return (u32*)(((x & ~(kMetaShadowCell - 1)) / \
-      kMetaShadowCell * kMetaShadowSize) | Mapping::kMetaShadowBeg);
-# else
-  return (u32*)(((x & ~(kMetaShadowCell - 1)) / \
-      kMetaShadowCell * kMetaShadowSize) + Mapping::kMetaShadowBeg);
-# endif
-#endif
+    return (u32 *)(((((x) & ~(Mapping::kShadowMsk | (kMetaShadowCell - 1)))) /
+                    kMetaShadowCell * kMetaShadowSize) |
+                   Mapping::kMetaShadowBeg);
   }
 };
 
 ALWAYS_INLINE
 u32 *MemToMeta(uptr x) { return SelectMapping<MemToMetaImpl>(x); }
 
 struct ShadowToMemImpl {
   template <typename Mapping>
   static uptr Apply(uptr sp) {
     DCHECK(IsShadowMemImpl::Apply<Mapping>(sp));
-#if !SANITIZER_GO
   // The shadow mapping is non-linear and we've lost some bits, so we don't have
   // an easy way to restore the original app address. But the mapping is a
   // bijection, so we try to restore the address as belonging to low/mid/high
   // range consecutively and see if shadow->app->shadow mapping gives us the
   // same address.
-  uptr p = (sp / kShadowCnt) ^ Mapping::kAppMemXor;
+    uptr p = ((sp - Mapping::kShadowAdd) / kShadowCnt) ^ Mapping::kShadowXor;
     if (p >= Mapping::kLoAppMemBeg && p < Mapping::kLoAppMemEnd &&
         MemToShadowImpl::Apply<Mapping>(p) == sp)
       return p;
     if (Mapping::kMidAppMemBeg) {
-    p = ((sp / kShadowCnt) ^ Mapping::kAppMemXor) +
-        (Mapping::kMidAppMemBeg & Mapping::kAppMemMsk);
-    if (p >= Mapping::kMidAppMemBeg && p < Mapping::kMidAppMemEnd &&
-        MemToShadowImpl::Apply<Mapping>(p) == sp)
-      return p;
+      uptr p_mid = p + (Mapping::kMidAppMemBeg & Mapping::kShadowMsk);
+      if (p_mid >= Mapping::kMidAppMemBeg && p_mid < Mapping::kMidAppMemEnd &&
+          MemToShadowImpl::Apply<Mapping>(p_mid) == sp)
+        return p_mid;
     }
-  return ((sp / kShadowCnt) ^ Mapping::kAppMemXor) | Mapping::kAppMemMsk;
-#else  // #if !SANITIZER_GO
-# ifndef SANITIZER_WINDOWS
-  return (sp & ~Mapping::kShadowBeg) / kShadowCnt;
-# else
-  return (sp - Mapping::kShadowBeg) / kShadowCnt;
-# endif // SANITIZER_WINDOWS
-#endif
+    return p | Mapping::kShadowMsk;
   }
 };
 
 ALWAYS_INLINE
 uptr ShadowToMem(RawShadow *s) {
   return SelectMapping<ShadowToMemImpl>(reinterpret_cast<uptr>(s));
 }