linux-kernel - Re: [PATCH v6 3/8] kmsg: introduce additional kmsg devices support

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Date:	Fri, 26 Feb 2016 15:05:10 +0100
From:	Petr Mladek <pmladek@...e.com>
To:	Kazimierz Krosman <k.krosman@...sung.com>
Cc:	akpm@...ux-foundation.org, peter@...leysoftware.com, tj@...nel.org,
	vvs@...tuozzo.com, corbet@....net, arnd@...db.de,
	gregkh@...uxfoundation.org, daniel@...que.org,
	kay.sievers@...y.org, linux-kernel@...r.kernel.org,
	linux-doc@...r.kernel.org, linux-api@...r.kernel.org,
	k.lewandowsk@...sung.com, m.niesluchow@...sung.com,
	richard.weinberger@...il.com, b.zolnierkie@...sung.com,
	luto@...capital.net, knhoon.baik@...sung.com
Subject: Re: [PATCH v6 3/8] kmsg: introduce additional kmsg devices support

On Wed 2016-02-24 12:53:16, Kazimierz Krosman wrote:
> From: Marcin Niesluchowski <m.niesluchow@...sung.com>
> 
> kmsg device provides operations on cyclic logging buffer used mainly
> by kernel but also in userspace by privileged processes.
> 
> Additional kmsg devices keep the same log format but may be added
> dynamically with custom size.
> 
> Signed-off-by: Marcin Niesluchowski <m.niesluchow@...sung.com>
> Signed-off-by: Paul Osmialowski <p.osmialowsk@...sung.com>
> [Rebased kmsg patch v5 on Linux 4.5-rc5]
> Signed-off-by: Kazimierz Krosman <k.krosman@...sung.com>
> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
> index 3653a8e..b99403b 100644
> --- a/kernel/printk/printk.c
> +++ b/kernel/printk/printk.c
> @@ -584,9 +595,11 @@ ssize_t msg_print_ext_body(char *buf, size_t size,
>  void log_buf_kexec_setup(void)
>  {
>  	VMCOREINFO_SYMBOL(log_buf);
> -	VMCOREINFO_SYMBOL(log_buf_len);
> -	VMCOREINFO_SYMBOL(log_first_idx);
> -	VMCOREINFO_SYMBOL(log_next_idx);
> +	VMCOREINFO_STRUCT_SIZE(log_buffer);
> +	VMCOREINFO_OFFSET(log_buffer, buf);
> +	VMCOREINFO_OFFSET(log_buffer, len);
> +	VMCOREINFO_OFFSET(log_buffer, first_idx);
> +	VMCOREINFO_OFFSET(log_buffer, next_idx);

This breaks makedumpfile, crash and possibly other tools
that use this information to access the log buffer.

Best Regards,
Petr