On 2022/6/9 11:44, Kefeng Wang wrote:
On 2022/6/9 10:49, Vasily Averin wrote:
Dear ARM developers,
could you please help me to find the reason of this problem?
Hi,
mem_cgroup_from_obj():
ffff80000836cf40: d503245f bti c
ffff80000836cf44: d503201f nop
ffff80000836cf48: d503201f nop
ffff80000836cf4c: d503233f paciasp
ffff80000836cf50: d503201f nop
ffff80000836cf54: d2e00021 mov x1,
#0x1000000000000 // #281474976710656
ffff80000836cf58: 8b010001 add x1, x0, x1
ffff80000836cf5c: b25657e4 mov x4,
#0xfffffc0000000000 // #-4398046511104
ffff80000836cf60: d34cfc21 lsr x1, x1, #12
ffff80000836cf64: d37ae421 lsl x1, x1, #6
ffff80000836cf68: 8b040022 add x2, x1, x4
ffff80000836cf6c: f9400443 ldr x3, [x2, #8]
x5 : ffff80000a96f000 x4 : fffffc0000000000 x3 : ffff80000ad5e680
x2 : fffffe00002bc240 x1 : 00000200002bc240 x0 : ffff80000af09740
x0 = 0xffff80000af09740 is an argument of mem_cgroup_from_obj()
according to System.map it is init_net
This issue is caused by calling virt_to_page() on address of static
variable init_net.
Arm64 consider that addresses of static variables are not valid
virtual addresses.
On x86_64 the same API works without any problem.
Unfortunately I do not understand the cause of the problem.
I do not see any bugs in my patch.
I'm using an existing API, mem_cgroup_from_obj(), to find the memory
cgroup used
to account for the specified object.
In particular, in the current case, I wanted to get the memory cgroup
of the
specified network namespace by the name taken from for_each_net().
The first object in this list is the static structure unit_net
root@test:~# cat /proc/kallsyms |grep -w _data
ffff80000a110000 D _data
root@test:~# cat /proc/kallsyms |grep -w _end
ffff80000a500000 B _end
root@test:~# cat /proc/kallsyms |grep -w init_net
ffff80000a4eb980 B init_net
the init_net is located in data section, on arm64, it is allowed by
vmalloc, see
map_kernel_segment(pgdp, _data, _end, PAGE_KERNEL, &vmlinux_data,
0, 0);
and the arm has same behavior.
We could let init_net be allocated dynamically, but I think it could
change a lot.
Any better sugguestion, Catalin?
or add vmalloc check in mem_cgroup_from_obj()?
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 27cebaa53472..fb817e5da5f0 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2860,7 +2860,10 @@ struct mem_cgroup *mem_cgroup_from_obj(void *p)
if (mem_cgroup_disabled())
return NULL;
- folio = virt_to_folio(p);
+ if (unlikely(is_vmalloc_addr(p)))
+ folio = page_folio(vmalloc_to_page(p));
+ else
+ folio = virt_to_folio(p);
/*
* Slab objects are accounted individually, not per-page.
