Re: [next] arm64: boot failed - next-20220606

[Kefeng Wang <wangkefeng.wang@huawei.com>]

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.