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Work around a Linux arm32 unaligned data issue in SuperPMI #56517

Merged
merged 2 commits into from
Jul 30, 2021
Merged

Work around a Linux arm32 unaligned data issue in SuperPMI #56517

merged 2 commits into from
Jul 30, 2021

Commits on Jul 29, 2021

  1. Work around a Linux arm32 unaligned data issue in SuperPMI 

    impImportStaticReadOnlyField reads the data at the address returned by
getFieldAddress. SuperPMI saves and replays this data, but it doesn't
store it at a naturally aligned address. For int64/double (at least),
this is a problem on Linux arm32, which raises a SIGBUS exception on
such unaligned access.

This works around the problem by copying the potentially unaligned data
to a known aligned spot before reading it. This is only done under DEBUG
and when we know we are replaying under SuperPMI.

A proper fix would be to teach SuperPMI about alignment, but that would be
a large and risky change, compared to this small and isolated workaround.

The fixes the non-determinism of dotnet#56156.
    @BruceForstall
    BruceForstall committed Jul 29, 2021
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  2. Only add alignment adjustment when required

    @BruceForstall
    BruceForstall committed Jul 29, 2021
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