linux-kernel - Re: [PATCH] x86/cpu: replacing the open-coded shift with BIT(x)

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Message-ID: <Y2DdQwVfU2jFjMRX@hirez.programming.kicks-ass.net>
Date:   Tue, 1 Nov 2022 09:48:03 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Gaosheng Cui <cuigaosheng1@...wei.com>
Cc:     tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...ux.intel.com, x86@...nel.org, hpa@...or.com,
        puwen@...on.cn, TonyWWang-oc@...oxin.com, Jason@...c4.com,
        hca@...ux.ibm.com, mika.westerberg@...ux.intel.com,
        mario.limonciello@....com, tony.luck@...el.com,
        andrew.cooper3@...rix.com, pawan.kumar.gupta@...ux.intel.com,
        rdunlap@...radead.org, jithu.joseph@...el.com,
        chenyi.qiang@...el.com, rafael.j.wysocki@...el.com,
        paulmck@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/cpu: replacing the open-coded shift with BIT(x)

On Tue, Nov 01, 2022 at 02:09:45PM +0800, Gaosheng Cui wrote:
> Replace the open-coded shift with BIT(x) for x86_power to make the
> code a bit more self-documenting, and we will get a UBSAN issue in
> arch/x86/kernel/cpu/proc.c, fix it.
> 
> The UBSAN warning calltrace like below:
> 
> UBSAN: shift-out-of-bounds in arch/x86/kernel/cpu/proc.c:138:25
> left shift of 1 by 31 places cannot be represented in type 'int'

Same as to the other case; UBSAN is broken garbage, stop quoting it.