[compiler-rt] 681db06 - [TSan] Make Shadow/Meta region inclusive-exclusive (#144647)

[via llvm-commits]

Author: Kunqiu Chen
Date: 2025-06-19T16:25:51+08:00
New Revision: 681db064d221e9eef024ce0aef6165caa37fbfd2

URL: https://github.com/llvm/llvm-project/commit/681db064d221e9eef024ce0aef6165caa37fbfd2
DIFF: https://github.com/llvm/llvm-project/commit/681db064d221e9eef024ce0aef6165caa37fbfd2.diff

LOG: [TSan] Make Shadow/Meta region inclusive-exclusive (#144647)

This commit changes the interval shadow/meta address check from
inclusive-inclusive ( $[\mathrm{start}, \mathrm{end}]$ ) to
inclusive-exclusive ( $[\mathrm{start}, \mathrm{end})$ ), to resolve the
ambiguity of the end point address. This also aligns the logic with the
check for `isAppMem` (i.e., inclusive-exclusive), ensuring consistent
behavior across all memory classifications.

1. The `isShadowMem` and `isMetaMem` checks previously used an
inclusive-inclusive interval, i.e., $[\mathrm{start}, \mathrm{end}]$,
which could lead to a boundary address being incorrectly classified as
both Shadow and Meta memory, e.g., 0x3000_0000_0000 in
`Mapping48AddressSpace`.
- What's more, even when Shadow doesn't border Meta, `ShadowMem::end`
cannot be considered a legal shadow address, as TSan protects the gap,
i.e., `ProtectRange(ShadowEnd(), MetaShadowBeg());`

2. `ShadowMem`/`MetaMem` addresses are derived from `AppMem` using an
affine-like transformation (`* factor + bias`). This transformation
includes two extra modifications: high- and low-order bits are masked
out, and for Shadow Memory, an optional XOR operation may be applied to
prevent conflicts with certain AppMem regions.
- Given that all AppMem regions are defined as inclusive-exclusive
intervals, $[\mathrm{start}, \mathrm{end})$, the resulting Shadow/Meta
regions should logically also be inclusive-exclusive.

Note: This change is purely for improving code consistency and should
have no functional impact. In practice, the exact endpoint addresses of
the Shadow/Meta regions are generally not reached.

Added: 
    

Modified: 
    compiler-rt/lib/tsan/rtl/tsan_platform.h
    compiler-rt/lib/tsan/rtl/tsan_rtl_access.cpp

Removed: 
    


################################################################################
diff  --git a/compiler-rt/lib/tsan/rtl/tsan_platform.h b/compiler-rt/lib/tsan/rtl/tsan_platform.h
index 354f6da6a64a1..ada594bc11fc7 100644
--- a/compiler-rt/lib/tsan/rtl/tsan_platform.h
+++ b/compiler-rt/lib/tsan/rtl/tsan_platform.h
@@ -931,7 +931,7 @@ bool IsAppMem(uptr mem) { return SelectMapping<IsAppMemImpl>(mem); }
 struct IsShadowMemImpl {
   template <typename Mapping>
   static bool Apply(uptr mem) {
-    return mem >= Mapping::kShadowBeg && mem <= Mapping::kShadowEnd;
+    return mem >= Mapping::kShadowBeg && mem < Mapping::kShadowEnd;
   }
 };
 
@@ -943,7 +943,7 @@ bool IsShadowMem(RawShadow *p) {
 struct IsMetaMemImpl {
   template <typename Mapping>
   static bool Apply(uptr mem) {
-    return mem >= Mapping::kMetaShadowBeg && mem <= Mapping::kMetaShadowEnd;
+    return mem >= Mapping::kMetaShadowBeg && mem < Mapping::kMetaShadowEnd;
   }
 };
 

diff  --git a/compiler-rt/lib/tsan/rtl/tsan_rtl_access.cpp b/compiler-rt/lib/tsan/rtl/tsan_rtl_access.cpp
index cf07686d968dc..dbdc6359d92aa 100644
--- a/compiler-rt/lib/tsan/rtl/tsan_rtl_access.cpp
+++ b/compiler-rt/lib/tsan/rtl/tsan_rtl_access.cpp
@@ -525,7 +525,7 @@ ALWAYS_INLINE USED void UnalignedMemoryAccess(ThreadState* thr, uptr pc,
 void ShadowSet(RawShadow* p, RawShadow* end, RawShadow v) {
   DCHECK_LE(p, end);
   DCHECK(IsShadowMem(p));
-  DCHECK(IsShadowMem(end));
+  DCHECK(p == end || IsShadowMem(end - 1));
   UNUSED const uptr kAlign = kShadowCnt * kShadowSize;
   DCHECK_EQ(reinterpret_cast<uptr>(p) % kAlign, 0);
   DCHECK_EQ(reinterpret_cast<uptr>(end) % kAlign, 0);
@@ -669,7 +669,7 @@ void MemoryAccessRangeT(ThreadState* thr, uptr pc, uptr addr, uptr size) {
   RawShadow* shadow_mem = MemToShadow(addr);
   DPrintf2("#%d: MemoryAccessRange: @%p %p size=%d is_read=%d\n", thr->tid,
            (void*)pc, (void*)addr, (int)size, is_read);
-
+  DCHECK_NE(size, 0);
 #if SANITIZER_DEBUG
   if (!IsAppMem(addr)) {
     Printf("Access to non app mem start: %p\n", (void*)addr);