Re: [Crash-utility] [RFC PATCH] struct: Fix handing of percpu symbols
On Thu 2016-04-21 14:59 -0400, Dave Anderson wrote:
Hi Dave,
Sorry for the delay in getting around to testing this patch.
No problem at all.
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;
...
[ ... ]
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.
IIUC, the cpu_slab object is allocated from the dynamic percpu area.
Unfortunately the patch only takes into consideration static in-kernel
percpu symbols i.e. those between the range of __per_cpu_start and
__per_cpu_end.
Not sure how to test for such percpu symbols at the moment.
Looking at the patch again perhaps the following is more suitable for
per_cpu_symbol_value_search():
--- a/symbols.c
+++ b/symbols.c
@@ -5181,7 +5181,8 @@ per_cpu_symbol_value_search(ulong value)
if ((sp = symval_hash_search(value)) == NULL)
sp = st->symtable;
- for (; sp < st->symend; sp++)
+ for (; sp < st->__per_cpu_end; sp++)
+
if (value == sp->value)
return sp = __per_cpu_symbol_search(sp->name);
--
Aaron Tomlin