linux-kernel - Re: Print long messages to console from kernel module

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:	Mon, 25 Feb 2008 17:27:37 -0500
From:	"linux-os (Dick Johnson)" <linux-os@...logic.com>
To:	"Arvid Brodin" <arvid.brodin@...a.com>
Cc:	<linux-kernel@...r.kernel.org>
Subject: Re: Print long messages to console from kernel module

On Mon, 25 Feb 2008, Arvid Brodin wrote:

> I need to write messages > 1023 characters long to the console from a module*. printk() is limited to 1023 characters, and splitting the message over several printk()'s results in a line break and "Month hh:mm:ss host kernel:" being inserted in my text.
>
> I tried including <linux/console.h> and using the console_drivers declared there, but get
> "WARNING: "console_drivers" [<path>/log.ko] undefined!" when compiling and
> "insmod: error inserting 'log.ko': -1 Unknown symbol in module" when insmodding.
>
> I guess this is because non EXPORT_SYMBOL'd symbols are only accessible to statically linked code, and not to modules? I see in printk.c that console_drivers is set up there, and I haven't been able to find any other interface to console_drivers.
>
> In short: is there any way to print messages to the console from a kernel module, except printk()? Is opening /dev/tty and writing to it the way to go?
>
>
> * I'm writing an in-memory logger to be included in a module. The log can be several megabytes. The idea is to use SysRq to print the contents of the log to console after a kernel panic or otherwise when writing to disk might not work.
>
> -- 
> Arvid Brodin
> Enea LCC

Write the data to a kernel buffer. Impliment read() or ioctl() and
poll(). Have a user-mode task sleep in poll, waiting for data to
become available. That user-mode task can do anything it wants,
unrestricted, with the data including writing it to files or any
tty it wants to open.

Cheers,
Dick Johnson
Penguin : Linux version 2.6.22.1 on an i686 machine (5588.28 BogoMips).
My book : http://www.AbominableFirebug.com/
_

****************************************************************
The information transmitted in this message is confidential and may be privileged.  Any review, retransmission, dissemination, or other use of this information by persons or entities other than the intended recipient is prohibited.  If you are not the intended recipient, please notify Analogic Corporation immediately - by replying to this message or by sending an email to DeliveryErrors@...logic.com - and destroy all copies of this information, including any attachments, without reading or disclosing them.

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/