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Make sure that VDSO patch code is properly aligned #22

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Make sure that VDSO patch code is properly aligned #22

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bjoernd
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@bjoernd bjoernd commented Sep 8, 2023

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:
facebookexperimental/hermit#41. Use an explicitly aligned data structure to enforce this.

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bjoernd commented Sep 8, 2023

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

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

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bjoernd commented Sep 8, 2023

Ack, will check AARCH64, too.

@facebook-github-bot facebook-github-bot added the CLA Signed This label is managed by the Facebook bot. Authors need to sign the CLA before a PR can be reviewed. label Sep 8, 2023
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bjoernd commented Sep 11, 2023 •
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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

jasonwhite
jasonwhite requested changes Sep 11, 2023
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reverie-ptrace/src/vdso.rs Outdated Show resolved Hide resolved
@bjoernd
Make sure that VDSO patch code is properly aligned
c93c470 
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:
facebookexperimental/hermit#41. Use an
explicitly aligned data structure to enforce this.

Signed-off-by: Bjoern Doebel <bjoern.doeel@gmail.com>
jasonwhite
jasonwhite approved these changes Sep 12, 2023
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Looks good! Thanks for fixing this!

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

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@jasonwhite merged this pull request in 9b54803.

@jasonwhite jasonwhite mentioned this pull request Oct 18, 2023
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