[all-commits] [llvm/llvm-project] 681db0: [TSan] Make Shadow/Meta region inclusive-exclusive...

[Kunqiu Chen via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 681db064d221e9eef024ce0aef6165caa37fbfd2
      https://github.com/llvm/llvm-project/commit/681db064d221e9eef024ce0aef6165caa37fbfd2
  Author: Kunqiu Chen <camsyn at foxmail.com>
  Date:   2025-06-19 (Thu, 19 Jun 2025)

  Changed paths:
    M compiler-rt/lib/tsan/rtl/tsan_platform.h
    M compiler-rt/lib/tsan/rtl/tsan_rtl_access.cpp

  Log Message:
  -----------
  [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.



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