Re: [Crash-utility] [RFC PATCH] struct: Fix handing of percpu symbols
----- Original Message -----
----- Original Message -----
> On Mon 2016-04-18 11:22 -0400, Dave Anderson wrote:
>
> Hi Dave,
>
> > I may be missing something, but it seems like you just need it to calculate
> > cpuaddr each time through the loop, and then you're done with it. But
then
> > you rewind() it, store it, and keep tmpfp open across the do_datatype_addr()
> > call? What am I missing?
>
> sure -- but I'd prefer to avoid the use of tmpfile()/fclose() in the for loop.
> Albeit since we set OPEN_ONLY_ONCE, the following should be fine:
Yep, much better...
Thanks,
Dave
Hi Aaron,
Sorry for the delay in getting around to testing this patch.
Anyway, the tmpfile() portion certainly looks better, but I didn't have
any luck with my testing of the patch functionality.
My first test attempt was with the kmalloc-32 slab freelist corruption vmcores
that I'm looking at, just because they involve the kmem_cache data structure,
which contains a per-cpu pointer to each cpu's the kmem_cache_cpu structure:
struct kmem_cache {
struct kmem_cache_cpu __percpu *cpu_slab;
...
First -- looking at it without your patch -- here is the kmem_cache.cpu_slab
per-cpu pointer:
crash> kmem_cache.cpu_slab ffff880333001c00
cpu_slab = 0x163c0
crash>
Taking that percpu address, I can look at each cpu's instance of the
kmem_cache_cpu structure like so, and can see the corruptio of cpu 3's
freelist pointer:
crash> kmem_cache_cpu 0x163c0:a
[0]: ffff88033fc163c0
struct kmem_cache_cpu {
freelist = 0xffff88031c028fa0,
tid = 31034440,
page = 0xffffea000c700a00,
partial = 0xffffea000ca5d380
}
[1]: ffff88033fc963c0
struct kmem_cache_cpu {
freelist = 0xffff8802d44c91c0,
tid = 28218351,
page = 0xffffea000b513240,
partial = 0x0
}
[2]: ffff88033fd163c0
struct kmem_cache_cpu {
freelist = 0xffff8802d442ba80,
tid = 25768102,
page = 0xffffea000b510ac0,
partial = 0xffffea000c9bce40
}
[3]: ffff88033fd963c0
struct kmem_cache_cpu {
freelist = 0xffff001090e33f80,
tid = 26298247,
page = 0xffffea0006438cc0,
partial = 0xffffea0002ec8b80
}
crash>
Now, with your patch applied, I get this:
crash> kmem_cache_cpu 163c0:a
struct: invalid percpu symbol value: 163c0
crash>
I tried it both with your original patch, and with your original patch
with your updated open_tmpfile() segment jammed in.
Dave