[PATCH] D39471: [asan] Fix small X86_64 ShadowOffset for non-default shadow scale

[Walter Lee via Phabricator via llvm-commits]

waltl updated this revision to Diff 122137.
waltl added a comment.

Simplify offset computation


https://reviews.llvm.org/D39471

Files:
  compiler-rt/lib/asan/asan_mapping.h
  llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp


Index: llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
===================================================================
--- llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
+++ llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
@@ -101,7 +101,6 @@
 static const uint64_t kIOSShadowOffset32 = 1ULL << 30;
 static const uint64_t kIOSSimShadowOffset32 = 1ULL << 30;
 static const uint64_t kIOSSimShadowOffset64 = kDefaultShadowOffset64;
-static const uint64_t kSmallX86_64ShadowOffset = 0x7FFF8000;  // < 2G.
 static const uint64_t kLinuxKasan_ShadowOffset64 = 0xdffffc0000000000;
 static const uint64_t kPPC64_ShadowOffset64 = 1ULL << 41;
 static const uint64_t kSystemZ_ShadowOffset64 = 1ULL << 52;
@@ -482,6 +481,11 @@
 
   ShadowMapping Mapping;
 
+  Mapping.Scale = kDefaultShadowScale;
+  if (ClMappingScale.getNumOccurrences() > 0) {
+    Mapping.Scale = ClMappingScale;
+  }
+
   if (LongSize == 32) {
     // Android is always PIE, which means that the beginning of the address
     // space is always available.
@@ -517,7 +521,7 @@
       if (IsKasan)
         Mapping.Offset = kLinuxKasan_ShadowOffset64;
       else
-        Mapping.Offset = kSmallX86_64ShadowOffset;
+        Mapping.Offset = 0x7FFFFFFF & (0xFFFFF000 << Mapping.Scale);
     } else if (IsWindows && IsX86_64) {
       Mapping.Offset = kWindowsShadowOffset64;
     } else if (IsMIPS64)
@@ -537,11 +541,6 @@
     Mapping.Offset = kDynamicShadowSentinel;
   }
 
-  Mapping.Scale = kDefaultShadowScale;
-  if (ClMappingScale.getNumOccurrences() > 0) {
-    Mapping.Scale = ClMappingScale;
-  }
-
   if (ClMappingOffset.getNumOccurrences() > 0) {
     Mapping.Offset = ClMappingOffset;
   }
Index: compiler-rt/lib/asan/asan_mapping.h
===================================================================
--- compiler-rt/lib/asan/asan_mapping.h
+++ compiler-rt/lib/asan/asan_mapping.h
@@ -139,7 +139,8 @@
 static const u64 kDefaultShadowSentinel = ~(uptr)0;
 static const u64 kDefaultShadowOffset32 = 1ULL << 29;  // 0x20000000
 static const u64 kDefaultShadowOffset64 = 1ULL << 44;
-static const u64 kDefaultShort64bitShadowOffset = 0x7FFF8000;  // < 2G.
+static const u64 kDefaultShort64bitShadowOffset =
+    0x7FFFFFFF & (0xFFFFF000 << kDefaultShadowScale);  // < 2G.
 static const u64 kIosShadowOffset32 = 1ULL << 30;  // 0x40000000
 static const u64 kIosShadowOffset64 = 0x120200000;
 static const u64 kIosSimShadowOffset32 = 1ULL << 30;


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