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Differential D58195

[HWASAN] Updated HWASAN design document to better portray the chance of missing a bug.
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Authored by hctim on Feb 13 2019, 10:46 AM.

Details

Reviewers
kcc
Commits
rGb5fe6fdbc436: [HWASAN] Updated HWASAN design document to better portray the chance of missing…
rL353990: [HWASAN] Updated HWASAN design document to better portray the chance of missing…
rC353990: [HWASAN] Updated HWASAN design document to better portray the chance of missing…
Summary

Provided rule of thumb percentage chances of miss for 4 and 8 bit tag sizes.

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Repository
rC Clang

Event Timeline

hctim created this revision.Feb 13 2019, 10:46 AM
Herald added a project: Restricted Project. · View Herald TranscriptFeb 13 2019, 10:46 AM
Herald added a subscriber: cfe-commits. · View Herald Transcript
Harbormaster completed remote builds in B28108: Diff 186695.Feb 13 2019, 10:46 AM
hctim added a reviewer: kcc.Feb 13 2019, 10:49 AM
kcc accepted this revision.Feb 13 2019, 2:23 PM

LGTM
and welcome back to the project! :)

This revision is now accepted and ready to land.Feb 13 2019, 2:23 PM
Closed by commit rC353990: [HWASAN] Updated HWASAN design document to better portray the chance of missing… (authored by hctim). · Explain WhyFeb 13 2019, 3:14 PM
This revision was automatically updated to reflect the committed changes.

Revision Contents

Diff 186754

docs/HardwareAssistedAddressSanitizerDesign.rst

Show First 20 Lines • Show All 125 Lines • ▼ Show 20 Lines * Is less portable than :doc:`AddressSanitizer`
that contains non-instrumented code. that contains non-instrumented code.
* May have compatibility problems if the target code uses higher * May have compatibility problems if the target code uses higher
pointer bits for other purposes. pointer bits for other purposes.
* May require changes in the OS kernels (e.g. Linux seems to dislike * May require changes in the OS kernels (e.g. Linux seems to dislike
tagged pointers passed from address space: tagged pointers passed from address space:
https://www.kernel.org/doc/Documentation/arm64/tagged-pointers.txt). https://www.kernel.org/doc/Documentation/arm64/tagged-pointers.txt).
* **Does not require redzones to detect buffer overflows**, * **Does not require redzones to detect buffer overflows**,
but the buffer overflow detection is probabilistic, with roughly but the buffer overflow detection is probabilistic, with roughly
`(2**TS-1)/(2**TS)` probability of catching a bug. `1/(2**TS)` chance of missing a bug (6.25% or 0.39% with 4 and 8-bit TS
respectively).
* **Does not require quarantine to detect heap-use-after-free, * **Does not require quarantine to detect heap-use-after-free,
or stack-use-after-return**. or stack-use-after-return**.
The detection is similarly probabilistic. The detection is similarly probabilistic.
The memory overhead of HWASAN is expected to be much smaller The memory overhead of HWASAN is expected to be much smaller
than that of AddressSanitizer: than that of AddressSanitizer:
`1/TG` extra memory for the shadow `1/TG` extra memory for the shadow
and some overhead due to `TG`-aligning all objects. and some overhead due to `TG`-aligning all objects.
Show All 28 Lines