A possible unbounded loop in moea_sync_icache: why sys/vm/mlock_test:mlock__copy_on_write_vnode fails?

[Justin Hibbits]

On Thu, Jan 9, 2020, 17:31 Mark Millard <marklmi at yahoo.com> wrote:

>
>
> On 2020-Jan-9, at 03:12, Leandro Lupori <leandro.lupori at gmail.com>
> wrote:
>
> > Interesting, this looks like the same issue that was fixed on 64-bit
> some time ago: https://reviews.freebsd.org/D19149.
>
> I changed my local code to use va+1 as in that update
> and can confirm that I now get:
>
> # kyua test -k /usr/tests/Kyuafile sys/vm/mlock_test
> sys/vm/mlock_test:mlock__copy_on_write_anon  ->  passed  [0.018s]
> sys/vm/mlock_test:mlock__copy_on_write_vnode  ->  passed  [0.008s]
> sys/vm/mlock_test:mlock__truncate_and_resize  ->  passed  [0.019s]
> sys/vm/mlock_test:mlock__truncate_and_unlock  ->  passed  [0.019s]
>
>
> > On Thu, Jan 9, 2020 at 3:03 AM Mark Millard via freebsd-ppc <freebsd-ppc
> at freebsd.org> wrote:
> >> . . .
> >> The code in question:
> >>
> >> static void
> >> moea_sync_icache(mmu_t mmu, pmap_t pm, vm_offset_t va, vm_size_t sz)
> >> {
> >>         struct pvo_entry *pvo;
> >>         vm_offset_t lim;
> >>         vm_paddr_t pa;
> >>         vm_size_t len;
> >>
> >>         PMAP_LOCK(pm);
> >>         while (sz > 0) {
> >>                 lim = round_page(va);
>
> The above line is where I changed the va to be
> va+1 .
>
> >>                 len = MIN(lim - va, sz);
> >>                 pvo = moea_pvo_find_va(pm, va & ~ADDR_POFF, NULL);
> >>                 if (pvo != NULL) {
> >>                         pa = (pvo->pvo_pte.pte.pte_lo & PTE_RPGN) |
> >>                             (va & ADDR_POFF);
> >>                         moea_syncicache(pa, len);
> >>                 }
> >>                 va += len;
> >>                 sz -= len;
> >>         }
> >>         PMAP_UNLOCK(pm);
> >> }
> >
>
>
> ===
> Mark Millard
> marklmi at yahoo.com
> ( dsl-only.net went
> away in early 2018-Mar)
>

Hi Mark,

I just committed the fix as r356595.

- Justin

>