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

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Date:   Wed, 22 Nov 2023 18:32:00 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Ilya Leoshkevich <iii@...ux.ibm.com>
Cc:     Alexander Gordeev <agordeev@...ux.ibm.com>,
        Alexander Potapenko <glider@...gle.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 Tue, 21 Nov 2023 23:00:55 +0100
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.
> 
> Fix by trusting the architecture-specific assembly code and always
> unpoisoning ftrace_regs in ftrace_ops_list_func.

You must be very trusting to trust architecture-specific assembly code ;-)

Acked-by: Steven Rostedt (Google) <rostedt@...dmis.org>

-- Steve


> 
> Signed-off-by: Ilya Leoshkevich <iii@...ux.ibm.com>
> ---
>  kernel/trace/ftrace.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index 8de8bec5f366..dfb8b26966aa 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -7399,6 +7399,7 @@ __ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip,
>  void arch_ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip,
>  			       struct ftrace_ops *op, struct ftrace_regs *fregs)
>  {
> +	kmsan_unpoison_memory(fregs, sizeof(*fregs));
>  	__ftrace_ops_list_func(ip, parent_ip, NULL, fregs);
>  }
>  #else