Re: [PATCH] drm/tests/drm_buddy: avoid 64-bit calculation

[Christian König]

Am 17.02.24 um 02:31 schrieb Randy Dunlap:
> On 2/16/24 12:24, Arnd Bergmann wrote:
> > From: Arnd Bergmann <arnd@xxxxxxxx>
> >
> > The newly added drm_test_buddy_alloc_contiguous() test fails to link on
> > 32-bit targets because of inadvertent 64-bit calculations:
> >
> > ERROR: modpost: "__aeabi_uldivmod" [drivers/gpu/drm/tests/drm_buddy_test.ko] undefined!
> > ERROR: modpost: "__aeabi_ldivmod" [drivers/gpu/drm/tests/drm_buddy_test.ko] undefined!
> >
> > >From what I can tell, the numbers cannot possibly overflow a 32-bit size,
> > so use different types for these.
> >
> > I noticed that the function has another possible flaw in that is mixes
> > what it calls pages with 4KB units. This is a big confusing at best,
> > or possibly broken when built on machines with larger pages.
> >
> > Fixes: a64056bb5a32 ("drm/tests/drm_buddy: add alloc_contiguous test")
> > Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
> Tested-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>

I've just pushed a similar patch Mathew came up a bit earlier to 
drm-misc-fixes.

Sorry for the noise, I have to catch up on picking up patches for 
misc-fixes and misc-next.

Christian.

> Thanks.
>
> > ---
> >   drivers/gpu/drm/tests/drm_buddy_test.c | 7 ++++---
> >   1 file changed, 4 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/tests/drm_buddy_test.c b/drivers/gpu/drm/tests/drm_buddy_test.c
> > index fee6bec757d1..50a5f98cd5bd 100644
> > --- a/drivers/gpu/drm/tests/drm_buddy_test.c
> > +++ b/drivers/gpu/drm/tests/drm_buddy_test.c
> > @@ -21,7 +21,8 @@ static inline u64 get_size(int order, u64 chunk_size)
> >   
> >   static void drm_test_buddy_alloc_contiguous(struct kunit *test)
> >   {
> > -	u64 mm_size, ps = SZ_4K, i, n_pages, total;
> > +	u64 mm_size, total;
> > +	u32 i, ps = SZ_4K, n_pages;
> >   	struct drm_buddy_block *block;
> >   	struct drm_buddy mm;
> >   	LIST_HEAD(left);
> > @@ -29,7 +30,8 @@ static void drm_test_buddy_alloc_contiguous(struct kunit *test)
> >   	LIST_HEAD(right);
> >   	LIST_HEAD(allocated);
> >   
> > -	mm_size = 16 * 3 * SZ_4K;
> > +	n_pages = 16 * 3;
> > +	mm_size = n_pages * SZ_4K;
> >   
> >   	KUNIT_EXPECT_FALSE(test, drm_buddy_init(&mm, mm_size, ps));
> >   
> > @@ -42,7 +44,6 @@ static void drm_test_buddy_alloc_contiguous(struct kunit *test)
> >   	 */
> >   
> >   	i = 0;
> > -	n_pages = mm_size / ps;
> >   	do {
> >   		struct list_head *list;
> >   		int slot = i % 3;