linux-kernel - Re: [PATCH] tracing: Fix align of static buffer

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Message-ID: <X79Ch+WDwYwqWGk8@kroah.com>
Date:   Thu, 26 Nov 2020 06:52:07 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Minchan Kim <minchan@...nel.org>
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        LKML <linux-kernel@...r.kernel.org>, stable@...r.kernel.org,
        Namhyung Kim <namhyung@...nel.org>
Subject: Re: [PATCH] tracing: Fix align of static buffer

On Wed, Nov 25, 2020 at 02:56:54PM -0800, Minchan Kim wrote:
> With 5.9 kernel on ARM64, I found ftrace_dump output was broken but
> it had no problem with normal output "cat /sys/kernel/debug/tracing/trace".
> 
> With investigation, it seems coping the data into temporal buffer seems to
> break the align binary printf expects if the static buffer is not aligned
> with 4-byte. IIUC, get_arg in bstr_printf expects that args has already
> right align to be decoded and seq_buf_bprintf says ``the arguments are saved
> in a 32bit word array that is defined by the format string constraints``.
> So if we don't keep the align under copy to temporal buffer, the output
> will be broken by shifting some bytes.
> 
> This patch fixes it.

Does this resolve the issue reported at:
	https://lore.kernel.org/r/20201124223917.795844-1-elavila@google.com
?

thanks,

greg k-h