firmware discussion

Johannes Hofmann johannes.hofmann at
Tue May 4 12:11:59 PDT 2010

Joe Talbott <josepht at> wrote:
> On Tue, May 04, 2010 at 12:13:50PM +0300, Aggelos Economopoulos wrote:
>> Johannes Hofmann wrote:
>> > Matthew Dillon <dillon at> wrote:
>> >>    Well, the DFly kernel has some very easy-to-use file access functions
>> >>    ala fp_open() and friends (see kern_checkpoint.c for a use case), so
>> >>    accessing the firmware file directly is easy enough.
>> > 
>> > I thought about writing a generic firmware module using the new
>> > FreeBSD API which reads firmware files from a certain directory
>> > using fp_open().
>> > However, it seems that available firmware images need to be announced
>> > with firmware_register() to make them available, so I would need some
>> > sort of opendir() in kernel to scan the firmware directory and
>> > register the available files with firmware_register().
>> ... and also to monitor the directory for changes :)
>> > Alternatively we could adjust subr_firmware.c to trigger a file read
>> > attempt in case the requested image has not yet been registered.
>> Yah, in firmware_get(), it already handles the case where the module
>> containing the firmware isn't loaded yet. You can add the directory
>> search in loadimage() or better yet in a separate function (i.e. have
>> loadimage() call load_image_module() and load_image_blob()). This makes
>> much more sense IMO.
> I think this is a good idea with the one caveat that I don't fully
> understand the security implications of arbitrarily loading blobs into
> kernel memory.  I was thinking of something along the lines of
> /etc/firmware.conf that maps a short name as used by the FreeBSD API
> to a filename in /etc/firmware.

I was thinking about a sysctl interface, like:

kern.firmwares = "ath_bss:/boot/firmware/ath_bss.fw, ath_ibss:/boot/firmware/ath_ibss.fw"

or so. In which case the kernel module would register the images under
the provided short names.

> Johannes, feel free to implement this if you'd like.  I am pretty busy
> with real life at the moment.

Same here :)


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