From: Christophe Leroy <christophe.leroy@csgroup.eu>
To: Segher Boessenkool <segher@kernel.crashing.org>
Cc: linux-kernel@vger.kernel.org, npiggin@gmail.com,
Paul Mackerras <paulus@samba.org>,
linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH] powerpc/bug: Remove specific powerpc BUG_ON()
Date: Thu, 11 Feb 2021 15:09:43 +0100 [thread overview]
Message-ID: <6126ca14-419a-9e15-7ffa-b295f26a552e@csgroup.eu> (raw)
In-Reply-To: <20210211114910.GA28121@gate.crashing.org>
Le 11/02/2021 à 12:49, Segher Boessenkool a écrit :
> On Thu, Feb 11, 2021 at 07:41:52AM +0000, Christophe Leroy wrote:
>> powerpc BUG_ON() is based on using twnei or tdnei instruction,
>> which obliges gcc to format the condition into a 0 or 1 value
>> in a register.
>
> Huh? Why is that?
>
> Will it work better if this used __builtin_trap? Or does the kernel only
> detect very specific forms of trap instructions?
We already made a try with __builtin_trap() 1,5 year ago, see
https://patchwork.ozlabs.org/project/linuxppc-dev/patch/20510ce03cc9463f1c9e743c1d93b939de501b53.1566219503.git.christophe.leroy@c-s.fr/
The main problems encountered are:
- It is only possible to use it for BUG_ON, not for WARN_ON because GCC considers it as noreturn. Is
there any workaround ?
- The kernel (With CONFIG_DEBUG_BUGVERBOSE) needs to be able to identify the source file and line
corresponding to the trap. How can that be done with __builtin_trap() ?
Christophe
next prev parent reply other threads:[~2021-02-11 14:25 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-11 7:41 [PATCH] powerpc/bug: Remove specific powerpc BUG_ON() Christophe Leroy
2021-02-11 10:04 ` Nicholas Piggin
2021-02-11 11:50 ` Segher Boessenkool
2021-02-11 22:47 ` Nicholas Piggin
2021-02-11 12:22 ` Segher Boessenkool
2021-02-11 11:49 ` Segher Boessenkool
2021-02-11 12:26 ` Christophe Leroy
2021-02-11 12:39 ` Segher Boessenkool
2021-02-11 14:09 ` Christophe Leroy [this message]
2021-02-11 14:30 ` Segher Boessenkool
2021-02-11 15:30 ` Christophe Leroy
2021-02-27 10:31 ` Christophe Leroy
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