Re: [PATCH] tracing: Fix align of static buffer

From: Greg KH
Date: Thu Nov 26 2020 - 00:56:21 EST


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@xxxxxxxxxx
?

thanks,

greg k-h