linux-kernel - Re: [PATCH v11 3/5] x86/earlyprintk: Allocate early log

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]

Date:	Wed, 10 Jun 2015 15:25:54 +0600
From:	Alexander Kuleshov <kuleshovmail@...il.com>
To:	Borislav Petkov <bp@...e.de>
Cc:	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Mark Rustad <mark.d.rustad@...el.com>,
	Yinghai Lu <yinghai@...nel.org>
Subject: Re: [PATCH v11 3/5] x86/earlyprintk: Allocate early log_buf as early
 as possible

2015-06-10 15:04 GMT+06:00 Borislav Petkov <bp@...e.de>:
> Yes, so this whole approach and what you're trying to achieve
> seems kinda confusing and wrong. First of all, the early_printk()
> machinery prints to a special console driver, i.e., I'm looking at the
> registration fun in setup_early_printk().
>
> So using early_printk() to print to dmesg is the wrong tool for the
> job. Actually, if you want to do that, you can just as well use plain
> printk() and try to make it work much earlier. Which is basically what
> you did by using the printk_func per_cpu ptr, but that was hacky and
> ugly.
>
> In order to do that right, you need to slow down first, think hard
> and look hard and long at printk(), log_buf, the statically allocated
> smaller __log_buf and the whole machinery behind it. Whether it can be
> used that early or not. And to explain why it can or why it cannot in
> your commit messages. Then test your stuff a *lot* on the hw you have
> access to because printk() is not a joke. It needs to be very reliable
> and to work.
>

That's right, I thought this too. But when you answered on 10th
(https://lkml.org/lkml/2015/6/8/157) revision that you do not see
earlyprintk messages in the dmesg output and I thought that he
should be there, but didint research printk/log_buf and related
stuff properly.

I will try to learn all earlyprintk related things in more clear way and
resend the patch.

Thank you.
--
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/