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From: Arvid Brodin <>
Subject: Print long messages to console from kernel module
Date: Mon, 25 Feb 2008 18:30:33 +0100	[thread overview]
Message-ID: <> (raw)

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

             reply	other threads:[~2008-02-25 17:45 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-02-25 17:30 Arvid Brodin [this message]
2008-02-25 22:27 ` linux-os (Dick Johnson)
2008-02-26 12:58   ` Arvid Brodin
2008-02-29 14:58 ` Arvid Brodin

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