From: Peter Zijlstra <peterz@infradead•org>
To: Christophe Leroy <christophe.leroy@csgroup•eu>
Cc: x86@kernel•org, linux-kernel@vger•kernel.org,
Steven Rostedt <rostedt@goodmis•org>,
Jason Baron <jbaron@akamai•com>,
Josh Poimboeuf <jpoimboe@redhat•com>,
linuxppc-dev@lists•ozlabs.org, Ard Biesheuvel <ardb@kernel•org>
Subject: Re: [PATCH v2] static_call: Don't make __static_call_return0 static
Date: Fri, 18 Mar 2022 18:40:27 +0100 [thread overview]
Message-ID: <20220318174027.GS8939@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <30821468a0e7d28251954b578e5051dc09300d04.1647258493.git.christophe.leroy@csgroup.eu>
On Mon, Mar 14, 2022 at 12:49:36PM +0100, Christophe Leroy wrote:
> System.map shows that vmlinux contains several instances of
> __static_call_return0():
>
> c0004fc0 t __static_call_return0
> c0011518 t __static_call_return0
> c00d8160 t __static_call_return0
>
> arch_static_call_transform() uses the middle one to check whether we are
> setting a call to __static_call_return0 or not:
>
> c0011520 <arch_static_call_transform>:
> c0011520: 3d 20 c0 01 lis r9,-16383 <== r9 = 0xc001 << 16
> c0011524: 39 29 15 18 addi r9,r9,5400 <== r9 += 0x1518
> c0011528: 7c 05 48 00 cmpw r5,r9 <== r9 has value 0xc0011518 here
>
> So if static_call_update() is called with one of the other instances of
> __static_call_return0(), arch_static_call_transform() won't recognise it.
>
> In order to work properly, global single instance of __static_call_return0() is required.
>
> Fixes: 3f2a8fc4b15d ("static_call/x86: Add __static_call_return0()")
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup•eu>
Thanks! I've transferred Josh' ack from v1 in the presumption he's fine
with this one too :-)
prev parent reply other threads:[~2022-03-18 17:41 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-14 11:49 [PATCH v2] static_call: Don't make __static_call_return0 static Christophe Leroy
2022-03-18 17:40 ` Peter Zijlstra [this message]
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