lkml.org 
[lkml]   [2018]   [Sep]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [PATCH v8 09/20] kasan: preassign tags to objects with ctors or SLAB_TYPESAFE_BY_RCU
On Fri, Sep 21, 2018 at 2:24 PM, Andrey Konovalov <andreyknvl@google.com> wrote:
> On Fri, Sep 21, 2018 at 1:25 PM, Dmitry Vyukov <dvyukov@google.com> wrote:
>> On Wed, Sep 19, 2018 at 8:54 PM, Andrey Konovalov <andreyknvl@google.com> wrote:
>
>>> if (!shuffle) {
>>> for_each_object_idx(p, idx, s, start, page->objects) {
>>> - setup_object(s, page, p);
>>> - if (likely(idx < page->objects))
>>> - set_freepointer(s, p, p + s->size);
>>> - else
>>> + if (likely(idx < page->objects)) {
>>> + next = p + s->size;
>>> + next = setup_object(s, page, next);
>>> + set_freepointer(s, p, next);
>>> + } else
>>> set_freepointer(s, p, NULL);
>>> }
>>> - page->freelist = fixup_red_left(s, start);
>>> + start = fixup_red_left(s, start);
>>> + start = setup_object(s, page, start);
>>> + page->freelist = start;
>>> }
>>
>> Just want to double-check that this is correct.
>> We now do an additional setup_object call after the loop, but we do 1
>> less in the loop. So total number of calls should be the same, right?
>> However, after the loop we call setup_object for the first object (?),
>> but inside of the loop we skip the call for the last object (?). Am I
>> missing something, or we call ctor twice for the last object and don't
>> call it for the first one?
>
> Inside the loop we call setup_object for the "next" object. So we
> start iterating on the first one, but call setup_object for the
> second. Then the loop moves on to the second one and calls
> setup_object for the third. And so on. So the loop calls setup_object
> for every object (including the last one) except for the first one.
>
> The idea is that we want the freelist pointer that is stored in the
> current object to have a tagged pointer to the next one, so we need to
> assign a tag to the next object before storing the pointer in the
> current one.

Ah, OK, then false alarm.

\
 
 \ /
  Last update: 2018-09-24 11:20    [W:0.075 / U:19.580 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site