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Date: Wed, 22 Nov 2023 18:32:00 -0500
From: Steven Rostedt <rostedt@goodmis.org>
To: Ilya Leoshkevich <iii@linux.ibm.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>, Alexander Potapenko
 <glider@google.com>, Andrew Morton <akpm@linux-foundation.org>, Christoph
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 Elver <elver@google.com>, Masami Hiramatsu <mhiramat@kernel.org>, Pekka
 Enberg <penberg@kernel.org>, Vasily Gorbik <gor@linux.ibm.com>, Vlastimil
 Babka <vbabka@suse.cz>, Christian Borntraeger <borntraeger@linux.ibm.com>,
 Dmitry Vyukov <dvyukov@google.com>, Hyeonggon Yoo <42.hyeyoo@gmail.com>,
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 <svens@linux.ibm.com>
Subject: Re: [PATCH v2 01/33] ftrace: Unpoison ftrace_regs in
 ftrace_ops_list_func()
Message-ID: <20231122183200.409e982b@gandalf.local.home>
In-Reply-To: <20231121220155.1217090-2-iii@linux.ibm.com>
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	<20231121220155.1217090-2-iii@linux.ibm.com>
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On Tue, 21 Nov 2023 23:00:55 +0100
Ilya Leoshkevich <iii@linux.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@goodmis.org>

-- Steve


> 
> Signed-off-by: Ilya Leoshkevich <iii@linux.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