linux-kernel - Re: [08/36] AArch64: Kernel booting and initialisation

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: <500F2DB7.50403@am.sony.com>
Date:	Tue, 24 Jul 2012 16:20:23 -0700
From:	Frank Rowand <frank.rowand@...sony.com>
To:	Arnd Bergmann <arnd@...db.de>
CC:	Catalin Marinas <catalin.marinas@....com>,
	Christopher Covington <cov@...eaurora.org>,
	Stephen Warren <swarren@...dotorg.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Will Deacon <Will.Deacon@....com>,
	Domenico Andreoli <cavokz@...il.com>
Subject: Re: [08/36] AArch64: Kernel booting and initialisation

On 07/24/12 11:53, Arnd Bergmann wrote:
> On Tuesday 24 July 2012, Catalin Marinas wrote:
>> On Mon, Jul 23, 2012 at 09:52:22PM +0100, Christopher Covington wrote:
>>> Hi Catalin and Stephen,
>>>
>>> Catalin Marinas - July 8, 2012, 9:18 a.m.
>>>> On Fri, Jul 06, 2012 at 10:32:54PM +0100, Stephen Warren wrote:
>>>>
>>>>> Also, on Tegra at least and perhaps OMAP too, there are a few parts
>>>>> of earlyprintk serial port setup (i.e. port selection) which happen
>>>>> as part of the decompressor rather than the main kernel image, so
>>>>> we'd have to re-jig that too.
>>>>
>>>> Whatever we did on AArch32, if it was useful and we want to follow a
>>>> similar model it needs porting given that the code cannot be shared. So
>>>> there is nothing to re-jig but rather implement.
>>>>
>>>> As for earlyprintk, you can initialise it in the decompressed kernel
>>>> anyway. But even though it's a useful debugging tool, it goes against
>>>> the single Image aim (at least the current printascii/addruart
>>>> implementation). I don't have a proper implementation yet.
>>>
>>> Would DCC [1] be a reasonably commonly available early printk mechanism
>>> for the single image to provide?
>>
>> Yes, this can be implemented but I think it has its own restrictions,
>> requiring a JTAG connection.
> 
> Right, which means that it's not generic and we still need to make
> a decision for a how we want to solve the underlying problem. The
> options I see are:
> 
> 1. Have no earlyprintk before loading the console drivers
> 2. Make the series from Domenico architecture independent code
> 3. Reimplement a layer like that, differently
> 4. Make it a compile-time option and allow this only for
>    low level debugging purposes but disable it in distro kernels.

I have found earlyprintk to be very valuable for debugging the many
times that boot fails for me.

Not having earlyprintk does not seem a good idea to me.  Option 4 is
perfectly acceptable for my use cases.

-Frank

--
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/