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SubjectOfficial documentation from Intel stating that poking INT3 (single-byte) concurrently is OK ?
Hi Peter,

I have emails from you dating from a few years back unofficially stating
that it's OK to update the first byte of an instruction with a single-byte
int3 concurrently:

https://lkml.indiana.edu/hypermail/linux/kernel/1001.1/01530.html

It is referred in the original implementation of text_poke_bp():
commit fd4363fff3d9 ("x86: Introduce int3 (breakpoint)-based instruction patching")

Olivier Dion is working on the libpatch [1,2] project aiming to use this
property for low-latency/low-overhead live code patching in user-space as
well, but we cannot find an official statement from Intel that guarantees
this breakpoint-bypass technique is indeed OK without stopping the world
while patching.

Do you know where I could find an official statement of this guarantee ?

Thanks!

Mathieu

[1] https://www.dorsal.polymtl.ca/files/may2022/odion_may2022_libpatch_binary_patcher.pdf
[2] https://git.sr.ht/~old/libpatch

--
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com

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