On Thu, Jun 09, 2022 at 12:43:00PM +0800, Kefeng Wang wrote: > > 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. > It sounds right. Later we can add something like mem_cgroup_from_slab_obj() to use on hot paths and avoid this check.
