[llvm-branch-commits] [compiler-rt] [ASan][Darwin] Support gapless shadow layout for iOS 27.0 (PR #217530)

[Andrew Haberlandt via llvm-branch-commits]

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@@ -314,6 +314,15 @@ extern uptr kHighMemEnd, kMidMemBeg, kMidMemEnd;  // Initialized in __asan_init.
 #    define kMidShadowBeg MEM_TO_SHADOW(kMidMemBeg)
 #    define kMidShadowEnd MEM_TO_SHADOW(kMidMemEnd)
 
+// If the first byte of shadow can be placed after the last byte of app mem,
+// we don't need a gap since the shadow's shadow won't be in the middle
+// of app mem.
+#    if SANITIZER_APPLE
+#      define kGaplessShadow (kLowShadowBeg > kHighMemEnd)
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ndrewh wrote:

IMO, it's clearer to have this define here in a header (which also contains many other platform-specific defines) rather than having to wrap a big if case with`#if SANITIZER_APPLE` in .asan_shadow_setup.cpp.

https://github.com/llvm/llvm-project/pull/217530