linux-kernel - Re: [PATCH v3 -next 11/11] serial: 8250_early: Remove setup_early_serial8250

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <551EDB92.9070008@hurleysoftware.com>
Date:	Fri, 03 Apr 2015 14:27:30 -0400
From:	Peter Hurley <peter@...leysoftware.com>
To:	Yinghai Lu <yinghai@...nel.org>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Jiri Slaby <jslaby@...e.cz>, Rob Herring <robh@...nel.org>,
	"linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>
Subject: Re: [PATCH v3 -next 11/11] serial: 8250_early: Remove setup_early_serial8250_console()

On 04/03/2015 01:44 PM, Yinghai Lu wrote:
> On Fri, Apr 3, 2015 at 10:38 AM, Peter Hurley <peter@...leysoftware.com> wrote:
>> On 04/03/2015 12:57 PM, Yinghai Lu wrote:
>>
>> Wait -- you have earlycon in a product??
> 
> What do you mean?

I mean, what will happen if I put in a big debug banner like Steven
did for ftrace?

Kernel developers need earlycon for debugging arch code; often the earlycon
is just hacked together especially when it requires fixmap support.

Putting it in a product and _relying on undocumented behavior_ is a bad idea.

> when you are using "console=uart8250,io,0x3f8"
> you will have earlycon at first, and handover to console.

which means you have to have CONFIG_SERIAL_EARLYCON to get a serial console
at all.

I have no problem fixing this _if this is causing actual regressions_,
and not simply some minor inconvenience that can be fixed by editing your
grub command line.

However, I see this undocumented behavior as a cautionary tale for why not
every kernel command line hack should be accepted in mainline.

Regards,
Peter Hurley
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/