From: Joao Moreira <joao@overdrivepizza.com>
To: Kees Cook <keescook@chromium.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
Sami Tolvanen <samitolvanen@google.com>, X86 ML <x86@kernel.org>,
hjl.tools@gmail.com, Josh Poimboeuf <jpoimboe@redhat.com>,
andrew.cooper3@citrix.com, LKML <linux-kernel@vger.kernel.org>,
Nick Desaulniers <ndesaulniers@google.com>,
llvm@lists.linux.dev
Subject: Re: [RFC][PATCH 6/6] objtool: Add IBT validation / fixups
Date: Tue, 15 Feb 2022 15:38:33 -0800 [thread overview]
Message-ID: <4553dfb68285a686737969e117bf48cc@overdrivepizza.com> (raw)
In-Reply-To: <202202151503.91E9B76B@keescook>
>>
>> Mostly so that we can deduce the address of the trap from the
>> retpoline
>> site, also the above has a fairly high chance of using jcc.d32 which
>> is
>> actually larger than jcc.d8+ud2.
>
> Ah, yeah, that's an interesting point.
>
> Still, I worry about finding ways to convinces Clang to emit precisely
> cmp/je/trap/call, but I guess we'll catch it immediately if it doesn't.
> :P
This can probably be done more easily/precisely if implemented directly
in the compiler's arch-specific backend. At least for x86 it wasn't a
hassle to emit a defined sequence of instructions in the past. The price
is that it will require a pass specific to each supported architecture,
but I guess this isn't that bad.
Perhaps this is discussion for a different mailing list, idk... but
just pointing that it is not a huge wall.
next prev parent reply other threads:[~2022-02-15 23:38 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20211122170301.764232470@infradead.org>
[not found] ` <20211122170805.338489412@infradead.org>
[not found] ` <6ebb0ab131c522f20c094294d49091fc@overdrivepizza.com>
[not found] ` <202202081541.900F9E1B@keescook>
[not found] ` <ad6c2633f39e39583bc5c5eaf7ccbe52@overdrivepizza.com>
2022-02-09 4:05 ` [RFC][PATCH 6/6] objtool: Add IBT validation / fixups Kees Cook
2022-02-09 5:18 ` Joao Moreira
2022-02-11 13:38 ` Peter Zijlstra
2022-02-14 21:38 ` Sami Tolvanen
2022-02-14 22:25 ` Peter Zijlstra
2022-02-15 16:56 ` Sami Tolvanen
2022-02-15 20:03 ` Kees Cook
2022-02-15 21:05 ` Peter Zijlstra
2022-02-15 23:05 ` Kees Cook
2022-02-15 23:38 ` Joao Moreira [this message]
2022-02-16 12:24 ` Peter Zijlstra
2022-02-15 20:53 ` Peter Zijlstra
2022-02-15 22:45 ` Joao Moreira
2022-02-16 0:57 ` Andrew Cooper
2022-03-02 3:06 ` Peter Collingbourne
2022-03-02 3:32 ` Joao Moreira
2022-06-08 17:53 ` Fāng-ruì Sòng
2022-06-09 0:05 ` Sami Tolvanen
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