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[TSan] Make Shadow/Meta region inclusive-exclusive #144647

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Merged
merged 2 commits into from
Jun 19, 2025
Merged

[TSan] Make Shadow/Meta region inclusive-exclusive #144647

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5d8750f
[TSan] Make Shadow/Meta region inclusive-exclusive
Camsyn Jun 14, 2025
2e26762
Add a DCHECK adhering to the suggestion
Camsyn Jun 18, 2025
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4 changes: 2 additions & 2 deletions compiler-rt/lib/tsan/rtl/tsan_platform.h
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Original file line number Diff line number Diff line change
Expand Up @@ -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;
}
};

Expand All @@ -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;
}
};

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6 changes: 3 additions & 3 deletions compiler-rt/lib/tsan/rtl/tsan_rtl_access.cpp
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Expand Up @@ -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);
Expand Down Expand Up @@ -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)) {
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@melver melver Jun 18, 2025

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This is called from MemoryAccessRange, which checks if size==0, and since size is uptr size will always be > 0. Therefore this check is pointless.

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@Camsyn Camsyn Jun 18, 2025 •
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I understand this.
But MemoryAccessRangeT did not guarantee size != 0 in its context -- is it possible for MemoryAccessRangeT to be called in the future without checking for size == 0?

It just so happens that these checks are wrapped in SANITIZER_DEBUG macro, so I think adding this check is better than adding an assertion DCHECK(size != 0).

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@melver melver Jun 18, 2025

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But MemoryAccessRangeT did not guarantee size != 0 in its context -- is it possible for MemoryAccessRangeT to be called in the future without checking for size == 0?

We don't know.

But it's clear currently an invariant here is size != 0, so why not add a DCHECK and catch if that assumption changes in future?

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@Camsyn Camsyn Jun 18, 2025

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But it's clear currently an invariant here is size != 0, so why not add a DCHECK and catch if that assumption changes in future?

Done.

Printf("Access to non app mem end: %p\n", (void*)(addr + size - 1));
DCHECK(IsAppMem(addr + size - 1));
}
Expand All @@ -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(
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