Re: [kvm-unit-tests PATCH v1 2/2] lib/alloc_page: Fix compilation issue on 32bit archs

Sean Christopherson
2020-07-14T14:05:36Z

On Tue, Jul 14, 2020 at 01:41:23PM +0200, Claudio Imbrenda wrote:
> On Tue, 14 Jul 2020 13:20:16 +0200
> Thomas Huth <thuth@redhat.com> wrote:
>
> > On 14/07/2020 13.09, Claudio Imbrenda wrote:
> > > The assert in lib/alloc_page is hardcoded to long, and size_t is
> > > just an int on 32 bit architectures.
> > >
> > > Adding a cast makes the compiler happy.
> > >
> > > Fixes: 73f4b202beb39 ("lib/alloc_page: change some parameter types")
> > > Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
> > > ---
> > > lib/alloc_page.c | 5 +++--
> > > 1 file changed, 3 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/lib/alloc_page.c b/lib/alloc_page.c
> > > index fa3c527..617b003 100644
> > > --- a/lib/alloc_page.c
> > > +++ b/lib/alloc_page.c
> > > @@ -29,11 +29,12 @@ void free_pages(void *mem, size_t size)
> > > assert_msg((unsigned long) mem % PAGE_SIZE == 0,
> > > "mem not page aligned: %p", mem);
> > >
> > > - assert_msg(size % PAGE_SIZE == 0, "size not page aligned:
> > > %#lx", size);
> > > + assert_msg(size % PAGE_SIZE == 0, "size not page aligned:
> > > %#lx",
> > > + (unsigned long)size);
> > >
> > > assert_msg(size == 0 || (uintptr_t)mem == -size ||
> > > (uintptr_t)mem + size > (uintptr_t)mem,
> > > - "mem + size overflow: %p + %#lx", mem, size);
> > > + "mem + size overflow: %p + %#lx", mem,
> > > (unsigned long)size);
> >
> > Looking at lib/printf.c, it seems like it also supports %z ... have
> > you tried?
>
> no, but in hindsight I should have. It's probably a much cleaner
> solution. I'll try and respin.

I'm not opposed to using size_t, but if we go that route then the entirety
of alloc_page.c should be converted to size_t. As is, there is code like:

void free_pages_by_order(void *mem, unsigned int order)
{
free_pages(mem, 1ul << (order + PAGE_SHIFT));
}

and

void *alloc_pages(unsigned int order)
{
...

/* Looking for a run of length (1 << order). */
unsigned long run = 0;
const unsigned long n = 1ul << order;
const unsigned long align_mask = (n << PAGE_SHIFT) - 1;
void *run_start = NULL;
void *run_prev = NULL;
unsigned long run_next_pa = 0;
unsigned long pa;

assert(order < sizeof(unsigned long) * 8);

...
}

that very explicitly uses 'unsigned long' for the size.