[asan] Fix small X86_64 ShadowOffset for non-default shadow scale
The requirement is that shadow memory must be aligned to page
boundaries (4k in this case). Use a closed form equation that always
satisfies this requirement.
Differential Revision: https://reviews.llvm.org/D39471
llvm-svn: 318421
diff --git a/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp b/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
index 190efce2..c707dfc 100644
--- a/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
+++ b/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
@@ -97,7 +97,8 @@
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 kSmallX86_64ShadowOffsetBase = 0x7FFFFFFF; // < 2G.
+static const uint64_t kSmallX86_64ShadowOffsetAlignMask = ~0xFFFULL;
static const uint64_t kLinuxKasan_ShadowOffset64 = 0xdffffc0000000000;
static const uint64_t kPPC64_ShadowOffset64 = 1ULL << 41;
static const uint64_t kSystemZ_ShadowOffset64 = 1ULL << 52;
@@ -495,6 +496,11 @@
ShadowMapping Mapping;
+ Mapping.Scale = kDefaultShadowScale;
+ if (ClMappingScale.getNumOccurrences() > 0) {
+ Mapping.Scale = ClMappingScale;
+ }
+
if (LongSize == 32) {
if (IsAndroid)
Mapping.Offset = kDynamicShadowSentinel;
@@ -528,7 +534,8 @@
if (IsKasan)
Mapping.Offset = kLinuxKasan_ShadowOffset64;
else
- Mapping.Offset = kSmallX86_64ShadowOffset;
+ Mapping.Offset = (kSmallX86_64ShadowOffsetBase &
+ (kSmallX86_64ShadowOffsetAlignMask << Mapping.Scale));
} else if (IsWindows && IsX86_64) {
Mapping.Offset = kWindowsShadowOffset64;
} else if (IsMIPS64)
@@ -548,11 +555,6 @@
Mapping.Offset = kDynamicShadowSentinel;
}
- Mapping.Scale = kDefaultShadowScale;
- if (ClMappingScale.getNumOccurrences() > 0) {
- Mapping.Scale = ClMappingScale;
- }
-
if (ClMappingOffset.getNumOccurrences() > 0) {
Mapping.Offset = ClMappingOffset;
}