From: Josh Poimboeuf <jpoimboe@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: alexandre.chartre@oracle.com, linux-kernel@vger.kernel.org,
jthierry@redhat.com, tglx@linutronix.de, x86@kernel.org
Subject: Re: [RFC][PATCH 3/7] objtool: Allow branches within the same alternative.
Date: Sun, 19 Apr 2020 11:32:19 -0500 [thread overview]
Message-ID: <20200419163219.b5dpg246xh6avsci@treble> (raw)
In-Reply-To: <20200416151024.885221682@infradead.org>
On Thu, Apr 16, 2020 at 05:07:55PM +0200, Peter Zijlstra wrote:
> From: Alexandre Chartre <alexandre.chartre@oracle.com>
>
> Currently objtool prevents any branch to an alternative. While preventing
> branching from the outside to the middle of an alternative makes perfect
> sense, branching within the same alternative should be allowed. To do so,
> identify each alternative and check that a branch to an alternative comes
> from the same alternative.
>
> Signed-off-by: Alexandre Chartre <alexandre.chartre@oracle.com>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> Link: https://lkml.kernel.org/r/20200414103618.12657-3-alexandre.chartre@oracle.com
I I think I'd rather just drop this patch. It adds some complexity and
I don't really see a benefit to having the warning in the first place.
Branching to the middle of an alternative group just doesn't seem like a
realistic scenario (can it even be done with the alternative macros?).
Even if it were possible, I'm not sure why somebody would attempt such a
feat. And it seems like it would just wreck the system anyway.
--
Josh
next prev parent reply other threads:[~2020-04-19 16:32 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-16 15:07 [RFC][PATCH 0/7] objtool vs retpoline Peter Zijlstra
2020-04-16 15:07 ` [RFC][PATCH 1/7] objtool: is_fentry_call() crashes if call has no destination Peter Zijlstra
2020-04-16 15:07 ` [RFC][PATCH 2/7] objtool: UNWIND_HINT_RET_OFFSET should not check registers Peter Zijlstra
2020-04-16 15:07 ` [RFC][PATCH 3/7] objtool: Allow branches within the same alternative Peter Zijlstra
2020-04-19 16:32 ` Josh Poimboeuf [this message]
2020-04-19 19:27 ` Peter Zijlstra
2020-04-16 15:07 ` [RFC][PATCH 4/7] objtool: Add support for intra-function calls Peter Zijlstra
2020-04-19 16:41 ` Josh Poimboeuf
2020-04-23 11:40 ` Peter Zijlstra
2020-04-16 15:07 ` [RFC][PATCH 5/7] x86/speculation: Change __FILL_RETURN_BUFFER to work with objtool Peter Zijlstra
2020-04-19 16:51 ` Josh Poimboeuf
2020-04-19 16:55 ` Josh Poimboeuf
2020-04-19 18:58 ` Peter Zijlstra
2020-04-16 15:07 ` [RFC][PATCH 6/7] x86/retpoline: Out-of-line retpoline Peter Zijlstra
2020-04-16 15:22 ` Peter Zijlstra
2020-04-16 15:07 ` [RFC][PATCH 7/7] x86/nospec: Remove ANNOTATE_NOSPEC_ALTERNATIVE Peter Zijlstra
2020-04-16 15:32 ` [RFC][PATCH 0/7] objtool vs retpoline Peter Zijlstra
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