lkml.org 
[lkml]   [2007]   [Dec]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH -mm -v2] x86 boot : export boot_params via sysfs
Greg KH wrote:
>> This is a binary structure defined by protocol;
>
> What protocol? Is this a "standard" documented somewhere?

Yes, see Documentation/i386/* (although some of it is documented by
reference to include/asm-x86/boot_params.h).

>> in that way it's not significantly different from something passed
>> from the firmware (in fact, it might very well *be* passed from the
>> firmware.) We have in the past found platform bugs by looking at the
>> contents of the whole structure, e.g. to find that part of it has
>> been inappropriately clobbered.
>
> For debugging things, then just export it through debugfs.

Fair enough, however...

>> It is also in the form needed by e.g. kexec to operate.
>
> Does kexec need this today to work properly? Or is this something new?

I believe kexec currently tries to reconstitute it from what data is
available to it. This is incomplete, though, and has been flagged as a
problem for kexec.

> What userspace program is going to know the exact data format of this
> blob, and where is it going to know that format from? The kernel header
> files in sanitized form? Or something else?

It can pick it up from <asm/boot_params.h> (which is now
userspace-safe); or it can decode it itself. Programs like kexec can
pass through most of the data without examining it, this is the main
reason for having it as a blob.

-hpa


\
 
 \ /
  Last update: 2007-12-12 20:09    [W:0.055 / U:2.724 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site