linux-kernel - Re: [PATCH v2 01/33] ftrace: Unpoison ftrace_regs in ftrace_ops_list

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Message-ID: <20231208093133.62aae274@gandalf.local.home>
Date:   Fri, 8 Dec 2023 09:31:33 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Alexander Potapenko <glider@...gle.com>
Cc:     Ilya Leoshkevich <iii@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Christoph Lameter <cl@...ux.com>,
        David Rientjes <rientjes@...gle.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Marco Elver <elver@...gle.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Pekka Enberg <penberg@...nel.org>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Hyeonggon Yoo <42.hyeyoo@...il.com>,
        kasan-dev@...glegroups.com, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linux-s390@...r.kernel.org,
        linux-trace-kernel@...r.kernel.org,
        Mark Rutland <mark.rutland@....com>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Sven Schnelle <svens@...ux.ibm.com>
Subject: Re: [PATCH v2 01/33] ftrace: Unpoison ftrace_regs in
 ftrace_ops_list_func()

On Fri, 8 Dec 2023 15:16:10 +0100
Alexander Potapenko <glider@...gle.com> wrote:

> On Tue, Nov 21, 2023 at 11:02 PM Ilya Leoshkevich <iii@...ux.ibm.com> wrote:
> >
> > Architectures use assembly code to initialize ftrace_regs and call
> > ftrace_ops_list_func(). Therefore, from the KMSAN's point of view,
> > ftrace_regs is poisoned on ftrace_ops_list_func entry(). This causes
> > KMSAN warnings when running the ftrace testsuite.  
> 
> I couldn't reproduce these warnings on x86, hope you really need this
> change on s390 :)

On x86, ftrace_regs sits on the stack. And IIUC, s390 doesn't have the same
concept of a "stack" as other architectures. Perhaps that's the reason s390
needs this?

-- Steve