[Crash-utility] [PATCH] Add support for SLAB OBJFREELIST_SLAB.

[Thomas Garnier]

That was quick.

Thanks Dave!

On Fri, Dec 2, 2016 at 10:59 AM, Dave Anderson <anderson at redhat.com> wrote:

>
>
> ----- Original Message -----
> > In this mode, the freelist can be an object and if the slab is full,
> > there is no freelist. On the next free, an object is recycled to be used
> > as the freelist but not clean-up. This change will go through only
> > known freed objects to prevent errors of wrong/corrupt freelist entries.
> >
> > Related to the linux kernel commit: b03a017bebc403d40aa53a092e79b3
> 020786537d.
>
> Thanks Thomas -- the patch queued for crash-7.1.8:
>
>   https://github.com/crash-utility/crash/commit/
> 59fbaf3e4b030b150f750f5b0ac7dfc3eafaa78f
>
> Dave
>
>
> > ---
> >  memory.c | 30 ++++++++++++++++++++++++------
> >  1 file changed, 24 insertions(+), 6 deletions(-)
> >
> > diff --git a/memory.c b/memory.c
> > index 4eac413..774d090 100644
> > --- a/memory.c
> > +++ b/memory.c
> > @@ -9880,6 +9880,7 @@ ignore_cache(struct meminfo *si, char *name)
> >  #define SLAB_MAGIC_DESTROYED    0xB2F23C5AUL    /* slab has been
> destroyed
> >  */
> >
> >  #define SLAB_CFLGS_BUFCTL       0x020000UL      /* bufctls in own cache
> */
> > +#define SLAB_CFLGS_OBJFREELIST  0x40000000UL    /* Freelist as an
> object */
> >
> >  #define KMEM_SLAB_ADDR          (1)
> >  #define KMEM_BUFCTL_ADDR        (2)
> > @@ -12439,11 +12440,13 @@ gather_slab_free_list_percpu(struct meminfo
> *si)
> >  static void
> >  gather_slab_free_list_slab_overload_page(struct meminfo *si)
> >  {
> > -     int i, active;
> > +     int i, active, start_offset;
> >       ulong obj, objnr, cnt, freelist;
> >       unsigned char *ucharptr;
> >       unsigned short *ushortptr;
> >       unsigned int *uintptr;
> > +     unsigned int cache_flags, overload_active;
> > +     ulong slab_overload_page;
> >
> >       if (CRASHDEBUG(1))
> >               fprintf(fp, "slab page: %lx active: %ld si->c_num: %ld\n",
> > @@ -12452,12 +12455,19 @@ gather_slab_free_list_slab_
> overload_page(struct
> > meminfo *si)
> >       if (si->s_inuse == si->c_num )
> >               return;
> >
> > -     readmem(si->slab - OFFSET(page_lru) + OFFSET(page_freelist),
> > +     slab_overload_page = si->slab - OFFSET(page_lru);
> > +     readmem(slab_overload_page + OFFSET(page_freelist),
> >               KVADDR, &freelist, sizeof(void *), "page freelist",
> >               FAULT_ON_ERROR);
> >          readmem(freelist, KVADDR, si->freelist,
> >               si->freelist_index_size * si->c_num,
> >                  "freelist array", FAULT_ON_ERROR);
> > +     readmem(si->cache+OFFSET(kmem_cache_s_flags),
> > +             KVADDR, &cache_flags, sizeof(uint),
> > +             "kmem_cache_s flags", FAULT_ON_ERROR);
> > +        readmem(slab_overload_page + OFFSET(page_active),
> > +                KVADDR, &overload_active, sizeof(uint),
> > +                "active", FAULT_ON_ERROR);
> >
> >       BNEG(si->addrlist, sizeof(ulong) * (si->c_num+1));
> >       cnt = objnr = 0;
> > @@ -12466,14 +12476,22 @@ gather_slab_free_list_slab_
> overload_page(struct
> > meminfo *si)
> >       uintptr = NULL;
> >       active = si->s_inuse;
> >
> > +     /*
> > +      * On an OBJFREELIST slab, the object might have been recycled
> > +      * and everything before the active count can be random data.
> > +      */
> > +     start_offset = 0;
> > +     if (cache_flags & SLAB_CFLGS_OBJFREELIST)
> > +             start_offset = overload_active;
> > +
> >       switch (si->freelist_index_size)
> >       {
> > -     case 1: ucharptr = (unsigned char *)si->freelist; break;
> > -     case 2: ushortptr = (unsigned short *)si->freelist; break;
> > -     case 4: uintptr = (unsigned int *)si->freelist; break;
> > +     case 1: ucharptr = (unsigned char *)si->freelist + start_offset;
> break;
> > +     case 2: ushortptr = (unsigned short *)si->freelist + start_offset;
> break;
> > +     case 4: uintptr = (unsigned int *)si->freelist + start_offset;
> break;
> >       }
> >
> > -     for (i = 0; i < si->c_num; i++) {
> > +     for (i = start_offset; i < si->c_num; i++) {
> >               switch (si->freelist_index_size)
> >               {
> >               case 1: objnr = (ulong)*ucharptr++; break;
> > --
> > 2.8.0.rc3.226.g39d4020
> >
> > --
> > Crash-utility mailing list
> > Crash-utility at redhat.com
> > https://www.redhat.com/mailman/listinfo/crash-utility
> >
>



-- 
Thomas
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://listman.redhat.com/archives/crash-utility/attachments/20161202/4024d3d8/attachment.htm>