Messages in this thread | | | Date | Tue, 21 Feb 2023 12:50:32 -0500 | From | Steven Rostedt <> | Subject | Re: Official documentation from Intel stating that poking INT3 (single-byte) concurrently is OK ? |
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On Tue, 21 Feb 2023 11:44:42 -0500 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> wrote:
> 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 ? >
The fact that we have been using it for over 10 years without issue should be a good guarantee ;-)
I know you probably prefer an official statement, and I thought they actually gave one, but can't seem to find it. Anyway. how does the dynamic linker do this? Doesn't it update code on the fly as well?
-- Steve
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