Re: [PATCH 03/13] kexec: Move segment verification code in a separate function

Vivek Goyal
2014-06-04T18:48:23Z

On Wed, Jun 04, 2014 at 11:32:55AM +0200, Borislav Petkov wrote:
> On Tue, Jun 03, 2014 at 09:06:52AM -0400, Vivek Goyal wrote:
> > Previously do_kimage_alloc() will allocate a kimage structure, copy
> > segment list from user space and then do the segment list sanity verification.
> >
> > Break down this function in 3 parts. do_kimage_alloc_init() to do actual
> > allocation and basic initialization of kimage structure.
> > copy_user_segment_list() to copy segment list from user space and
> > sanity_check_segment_list() to verify the sanity of segment list as passed
> > by user space.
> >
> > In later patches, I need to only allocate kimage and not copy segment
> > list from user space. So breaking down in smaller functions enables
> > re-use of code at other places.
>
> I haven't seen what's going on further in the patchset but from looking at
> kimage_normal_alloc() and kimage_crash_alloc()'s guts, they look very
> similar and could probably share a common __kimage_alloc which does
> do_kimage_alloc_init, copy_user_segment_list, sanity_check_segment_list
> and kimage_alloc_control_pages...
>
> One probably would have to actually write it down to see whether it
> makes sense though and is not too ugly :-)

Hi Boris,

Agreed. kimage_normal_alloc() and kimage_crash_alloc() are sharing
lot of code and it should make sense to write a common function for
shared code and let both call that function. I will give it a try
and if it makes sense will make it part of next version of posting.

>
> > Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
> > ---
>
> In any case, it looks ok, just two nitpicks below:
>
> Acked-by: Borislav Petkov <bp@suse.de>
>
> > kernel/kexec.c | 182 ++++++++++++++++++++++++++++++++-------------------------
> > 1 file changed, 101 insertions(+), 81 deletions(-)
>
> ...
>
> > +static struct kimage *do_kimage_alloc_init(void)
> > +{
> > + struct kimage *image;
> > +
> > + /* Allocate a controlling structure */
> > + image = kzalloc(sizeof(*image), GFP_KERNEL);
> > + if (!image)
> > + return NULL;
> > +
> > + image->head = 0;
> > + image->entry = &image->head;
> > + image->last_entry = &image->head;
> > + image->control_page = ~0; /* By default this does not apply */
> > + image->type = KEXEC_TYPE_DEFAULT;
> > +
> > + /* Initialize the list of control pages */
> > + INIT_LIST_HEAD(&image->control_pages);
> > +
> > + /* Initialize the list of destination pages */
> > + INIT_LIST_HEAD(&image->dest_pages);
> > +
> > + /* Initialize the list of unusable pages */
> > + INIT_LIST_HEAD(&image->unuseable_pages);
>
> If the "e" in "unuseable" bugs you too, like me, you could add this one
> to your patchset :-)
>
> http://lkml.kernel.org/r/1392819695-24116-1-git-send-email-bp@alien8.de
>

Hmm..., Interesting. I never noticed it. So google search seems to say
that unuseable is also not wrong.

I am not feeling very strongly about it, so I will leave this cleanup
for some other day.

> ...
>
> > @@ -258,22 +292,23 @@ static int kimage_normal_alloc(struct kimage **rimage, unsigned long entry,
> > get_order(KEXEC_CONTROL_PAGE_SIZE));
> > if (!image->control_code_page) {
> > printk(KERN_ERR "Could not allocate control_code_buffer\n");
> > - goto out_free;
> > + goto out_free_image;
> > }
> >
> > image->swap_page = kimage_alloc_control_pages(image, 0);
> > if (!image->swap_page) {
> > printk(KERN_ERR "Could not allocate swap buffer\n");
> > - goto out_free;
> > + goto out_free_control_pages;
> > }
> >
> > *rimage = image;
> > return 0;
> >
> > -out_free:
> > +
>
> Superfluous newline.

Will remove.

Thanks
Vivek