From: Peter Zijlstra <peterz@infradead.org>
To: Joao Moreira <joao@overdrivepizza.com>
Cc: Kees Cook <keescook@chromium.org>,
x86@kernel.org, Sami Tolvanen <samitolvanen@google.com>,
linux-kernel@vger.kernel.org, Mark Rutland <mark.rutland@arm.com>,
Josh Poimboeuf <jpoimboe@redhat.com>
Subject: Re: [PATCH] x86/ibt: Implement FineIBT
Date: Tue, 18 Oct 2022 22:30:27 +0200 [thread overview]
Message-ID: <Y08M4+GxoqvuZ+bq@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <c561dd8ec384bfc77998a6db6ed824e7@overdrivepizza.com>
On Tue, Oct 18, 2022 at 01:17:28PM -0700, Joao Moreira wrote:
> >
> > > Tangent: why are these nop instead of 0xcc? These bytes aren't
> > > executed
> > > ever are they?
> >
> > Because that's what the compiler gets us through
> > -fpatchable-function-entry.
>
> Is it useful to get the compiler to emit 0xcc with
> -fpatchable-function-entry under any circumstance? I can probably change
> that quickly if needed/useful.
Having it emit 0xcc for the bytes in front of the symbol might be
interesting. It would mean a few kernel changes, but nothing too hard.
That is, -fpatchable-function-entry=N,M gets us N-M bytes in at the
start of the symbol and M bytes in front of it. The N-M bytes at the
start of the function *are* executed and should obviously not become
0xcc (GCC keeps them 0x90 while LLVM makes them large NOPs).
next prev parent reply other threads:[~2022-10-18 20:31 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-18 13:35 [PATCH] x86/ibt: Implement FineIBT Peter Zijlstra
2022-10-18 14:43 ` David Laight
2022-10-18 15:58 ` Joao Moreira
2022-10-18 17:20 ` Kees Cook
2022-10-18 20:09 ` Joao Moreira
2022-10-19 5:33 ` Kees Cook
2022-10-18 21:27 ` David Laight
2022-10-18 14:47 ` Peter Zijlstra
2022-10-18 18:09 ` Kees Cook
2022-10-18 19:56 ` Peter Zijlstra
2022-10-18 23:31 ` Josh Poimboeuf
2022-10-19 5:22 ` Kees Cook
2022-10-19 11:38 ` Peter Zijlstra
2022-10-19 5:14 ` Kees Cook
2022-10-18 19:59 ` Peter Zijlstra
2022-10-18 21:09 ` Peter Zijlstra
2022-10-19 5:05 ` Kees Cook
2022-10-19 12:03 ` Peter Zijlstra
2022-10-19 15:22 ` Sami Tolvanen
2022-10-20 11:04 ` Peter Zijlstra
2022-10-18 19:59 ` Joao Moreira
2022-10-19 5:32 ` Kees Cook
2022-10-19 19:35 ` Joao Moreira
2022-10-18 20:05 ` Peter Zijlstra
2022-10-19 5:00 ` Kees Cook
2022-10-18 20:09 ` Peter Zijlstra
2022-10-18 20:17 ` Joao Moreira
2022-10-18 20:30 ` Peter Zijlstra [this message]
2022-10-19 4:48 ` Joao Moreira
2022-10-19 5:19 ` Kees Cook
2022-10-31 19:13 ` Joao Moreira
2022-11-01 21:39 ` Kees Cook
2022-11-01 21:50 ` Joao Moreira
2022-10-19 5:18 ` Kees Cook
2022-10-19 5:16 ` Kees Cook
2022-10-20 11:05 ` Peter Zijlstra
2022-10-18 23:38 ` Josh Poimboeuf
2022-10-19 7:29 ` Peter Zijlstra
2022-10-21 23:08 ` Josh Poimboeuf
2022-10-22 15:03 ` Peter Zijlstra
2022-10-24 17:15 ` Sami Tolvanen
2022-10-24 18:38 ` Joao Moreira
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