Re: Saving the kernel log accross boots
On Thu, 25 Jun 2009 17:29:54 +0200, Wolfram Sang wrote: > Before digging any deeper I would like to know if someone as a better > (more general) idea. Could you stuff the output into an MTD device? For that, see CONFIG_MTD_OOPS. Thak's looks great. Right now we have a watchdog without OOPS. Regards, Wolfram -- MM -- To unsubscribe from this list: send the line "unsubscribe linux-embedded" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: Saving the kernel log accross boots
Martin Meuli wrote:
> Hi All
>
> In case of a crash we would like to save the kernel log and retrieve it
> in the next boot.
> There are already several suggestions on how to do it on this and other
> lists.
> (Kernel crashing and log buffers: Robin Getz)
> Unfortunately we don't have extra SRAM to use for it. We need to do it
> in the 'normal' RAM.
>
> ARCH=ARM
>
> What we did:
> - modify kernel/printk.c: use
> __attribute__((__section__(".bss.kringbuf"... to put the log related
> stuf into a separate section
> - modify the linker script to link .bss.kringbuf at the start of the
> .bss section
> - modify arch/arm/kernel/head-common.S to exclude the new section from
> being nulled (if it was a watchdog restart)
> - modify kernel/printk.c to use cach_flush after prink
> - make sure the bootloader does not overwrite that memory
>
> This seems to work.
> After a crash we get the messages from the new boot and the last crash.
> It seems that the decompress code is using memory at the end of the
> kernel and destroys the log. So we have to use the bootloader to
> decompress the image into RAM.
>
> Before digging any deeper I would like to know if someone as a better
> (more general) idea.
>
> Regards, Martin
I submitted for a review a new filesystem for 2.6.30 called pramfs that
it can be useful for your case. You could use a little piece of ram to
store the log.
Marco
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Re: Saving the kernel log accross boots
> > Before digging any deeper I would like to know if someone as a better > > (more general) idea. > > Could you stuff the output into an MTD device? For that, see CONFIG_MTD_OOPS. Regards, Wolfram -- Pengutronix e.K. | Wolfram Sang| Industrial Linux Solutions | http://www.pengutronix.de/ | signature.asc Description: Digital signature
Re: Saving the kernel log accross boots
Martin Meuli wrote: > > Before digging any deeper I would like to know if someone as a better > (more general) idea. Could you stuff the output into an MTD device? What about netconsole, or putting the console on a serial port? Then you could send the log out before and up to the point the crash happens. -- To unsubscribe from this list: send the line "unsubscribe linux-embedded" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
