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facebookexperimental / reverie

An ergonomic and safe syscall interception framework for Linux.
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Make sure that VDSO patch code is properly aligned #22

Closed bjoernd closed 1 year ago

bjoernd commented 1 year ago

The code that is injected into the tracee processes' VDSO needs to be 8 byte aligned in order to satisfy conditions imposed by the ptrace interface on 64 bit architectures. There have been reproducible reports of that not always being the case: https://github.com/facebookexperimental/hermit/issues/41. Use an explicitly aligned data structure to enforce this.

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bjoernd commented 1 year ago

CLA: This is a contribution via Amazon, I am working with the internal team to get added to the CLA we have in place.

jasonwhite commented 1 year ago

Great detective work! aarch64 will likely have the same issue. Do you mind updating the same code for that architecture as well?

bjoernd commented 1 year ago

Ack, will check AARCH64, too.

bjoernd commented 1 year ago

Added the change for AARCH64 and renamed the data structure to a more generic BufferAligned<size>. ARM64 is only compile-tested because my use case (Hermit) doesn't even build on ARM64.

I did run cargo test on ARM, too, and it failed the same tests as without the patch.

test vdso::tests::vdso_can_find_symbols_info ... FAILED
test vdso::tests::vdso_patch_info_is_valid ... FAILED
facebook-github-bot commented 1 year ago

@jasonwhite has imported this pull request. If you are a Meta employee, you can view this diff on Phabricator.

facebook-github-bot commented 1 year ago

@jasonwhite merged this pull request in facebookexperimental/reverie@9b5480352e5de1f73f1039af048f7d48015c6ae9.