Re: kern/55958: pciback.hide parsing error

[Aleksey Arens <aza.sea.agenda%gmail.com@localhost>]

by Manuel Bouyer:
> When started as dom0 (or as domU, the code path is the same), the kernel
> command line (which is the module command line in multiboot, when started
> as dom0) is in start_info.cmd_line as is a plain text string, not a
> btinfo_modulelist or bi_modulelist_entry.
> See xen_parse_cmdline() in xen_machdep.c
>

Ok.

> This is not exactly how it works. Yes, the load command is parsed the
> same way for both native and multiboot case, using the same structure. But
> then the exec_multiboot1() function will convert the native structure
> to multiboot format. mmo_string points to bim->path, not the bim
> structure itself.
>
> So to fix the problem no change to bootinfo.h is needed; only the
> boot loader needs to be changed to pass the full string to exec_multiboot1().
>
> For example, instead of reusing bi_modulelist to represent the module,
> module_init() could use a private structure, which is then converted
> to the appropriate interface depending on the boot mode.
>

Thank you for clarifying these details to me.  I have not tracked the
codepath to that point, and was wondering what those functions were
doing.

Your suggestion about handling this problem does sound good to me.

I was concerned initially, if bi_modulelist_entry struct had played a
special role in further processing.  I noticed the field name has been
changed from "path" to 'kmod".  Does it reflect its purpose?  Is there
a detailed documentation on NetBSD's boot protocol, aside from the
source code itself?

One question remains.  Since now the exec.c:module_init() would
potentially fill out an intermediate struct with a long buffer, how
should the code constructing the module image for native
(non-multiboot) bootloading handle the argument buffer length?  Would
doing sizeof() on the corresponding bi_modulelist_entry struct's entry
be sufficient?  Perhaps, there should be a const defined in the
bootinfo.h for this purpose?