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

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-compiler-rt-sanitizer

Author: Kunqiu Chen (Camsyn)

<details>
<summary>Changes</summary>

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.

---
Full diff: https://github.com/llvm/llvm-project/pull/144647.diff


2 Files Affected:

- (modified) compiler-rt/lib/tsan/rtl/tsan_platform.h (+2-2) 
- (modified) compiler-rt/lib/tsan/rtl/tsan_rtl_access.cpp (+3-3) 


``````````diff
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..b0ce5680c95c1 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);
@@ -675,7 +675,7 @@ void MemoryAccessRangeT(ThreadState* thr, uptr pc, uptr addr, uptr size) {
     Printf("Access to non app mem start: %p\n", (void*)addr);
     DCHECK(IsAppMem(addr));
   }
-  if (!IsAppMem(addr + size - 1)) {
+  if (size > 0 && !IsAppMem(addr + size - 1)) {
     Printf("Access to non app mem end: %p\n", (void*)(addr + size - 1));
     DCHECK(IsAppMem(addr + size - 1));
   }
@@ -686,7 +686,7 @@ void MemoryAccessRangeT(ThreadState* thr, uptr pc, uptr addr, uptr size) {
 
   RawShadow* shadow_mem_end = reinterpret_cast<RawShadow*>(
       reinterpret_cast<uptr>(shadow_mem) + size * kShadowMultiplier - 1);
-  if (!IsShadowMem(shadow_mem_end)) {
+  if (size > 0 && !IsShadowMem(shadow_mem_end)) {
     Printf("Bad shadow end addr: %p (%p)\n", shadow_mem_end,
            (void*)(addr + size - 1));
     Printf(

``````````

</details>


https://github.com/llvm/llvm-project/pull/144647