Re: kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression

From: Toke Høiland-Jørgensen
Date: Mon May 23 2022 - 06:30:38 EST

kernel test robot <lkp@xxxxxxxxx> writes:

> tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head: eaea45fc0e7b6ae439526b4a41d91230c8517336
> commit: 782347b6bcad07ddb574422e01e22c92e05928c8 xdp: Add proper __rcu annotations to redirect map entries
> date: 11 months ago
> config: ia64-randconfig-s031-20220522 (https://download.01.org/0day-ci/archive/20220522/202205222029.xpW3PM1y-lkp@xxxxxxxxx/config)
> compiler: ia64-linux-gcc (GCC) 11.3.0

Hmm, so this is ia64-only? Some kind of macro breakage? Paul, any ideas?

-Toke

> reproduce:
> wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
> chmod +x ~/bin/make.cross
> # apt-get install sparse
> # sparse version: v0.6.4-dirty
> # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=782347b6bcad07ddb574422e01e22c92e05928c8
> git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
> git fetch --no-tags linus master
> git checkout 782347b6bcad07ddb574422e01e22c92e05928c8
> # save the config file
> mkdir build_dir && cp config build_dir/.config
> COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.3.0 make.cross C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' O=build_dir ARCH=ia64 SHELL=/bin/bash kernel/bpf/
>
> If you fix the issue, kindly add following tag where applicable
> Reported-by: kernel test robot <lkp@xxxxxxxxx>
>
>
> sparse warnings: (new ones prefixed by >>)
> kernel/bpf/devmap.c:561:29: sparse: sparse: incorrect type in assignment (different address spaces) @@ expected struct bpf_dtab_netdev *dst @@ got struct bpf_dtab_netdev [noderef] __rcu * @@
> kernel/bpf/devmap.c:561:29: sparse: expected struct bpf_dtab_netdev *dst
> kernel/bpf/devmap.c:561:29: sparse: got struct bpf_dtab_netdev [noderef] __rcu *
> kernel/bpf/devmap.c:657:29: sparse: sparse: incorrect type in assignment (different address spaces) @@ expected struct bpf_dtab_netdev *dst @@ got struct bpf_dtab_netdev [noderef] __rcu * @@
> kernel/bpf/devmap.c:657:29: sparse: expected struct bpf_dtab_netdev *dst
> kernel/bpf/devmap.c:657:29: sparse: got struct bpf_dtab_netdev [noderef] __rcu *
>>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
>>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
>>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
>>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
>>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
>>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
>>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
>>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
>>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
>>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
>>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
>>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
>>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
>>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
>>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
>>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
>>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
>>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
>>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
>>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
>>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
>>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
>>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
>>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
>>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
>>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
>>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
>>> kernel/bpf/devmap.c:1030:40: sparse: sparse: cast removes address space '__rcu' of expression
>
> vim +/__rcu +1030 kernel/bpf/devmap.c
>
> 990
> 991 static int dev_map_notification(struct notifier_block *notifier,
> 992 ulong event, void *ptr)
> 993 {
> 994 struct net_device *netdev = netdev_notifier_info_to_dev(ptr);
> 995 struct bpf_dtab *dtab;
> 996 int i, cpu;
> 997
> 998 switch (event) {
> 999 case NETDEV_REGISTER:
> 1000 if (!netdev->netdev_ops->ndo_xdp_xmit || netdev->xdp_bulkq)
> 1001 break;
> 1002
> 1003 /* will be freed in free_netdev() */
> 1004 netdev->xdp_bulkq = alloc_percpu(struct xdp_dev_bulk_queue);
> 1005 if (!netdev->xdp_bulkq)
> 1006 return NOTIFY_BAD;
> 1007
> 1008 for_each_possible_cpu(cpu)
> 1009 per_cpu_ptr(netdev->xdp_bulkq, cpu)->dev = netdev;
> 1010 break;
> 1011 case NETDEV_UNREGISTER:
> 1012 /* This rcu_read_lock/unlock pair is needed because
> 1013 * dev_map_list is an RCU list AND to ensure a delete
> 1014 * operation does not free a netdev_map entry while we
> 1015 * are comparing it against the netdev being unregistered.
> 1016 */
> 1017 rcu_read_lock();
> 1018 list_for_each_entry_rcu(dtab, &dev_map_list, list) {
> 1019 if (dtab->map.map_type == BPF_MAP_TYPE_DEVMAP_HASH) {
> 1020 dev_map_hash_remove_netdev(dtab, netdev);
> 1021 continue;
> 1022 }
> 1023
> 1024 for (i = 0; i < dtab->map.max_entries; i++) {
> 1025 struct bpf_dtab_netdev *dev, *odev;
> 1026
> 1027 dev = rcu_dereference(dtab->netdev_map[i]);
> 1028 if (!dev || netdev != dev->dev)
> 1029 continue;
>> 1030 odev = unrcu_pointer(cmpxchg(&dtab->netdev_map[i], RCU_INITIALIZER(dev), NULL));
> 1031 if (dev == odev)
> 1032 call_rcu(&dev->rcu,
> 1033 __dev_map_entry_free);
> 1034 }
> 1035 }
> 1036 rcu_read_unlock();
> 1037 break;
> 1038 default:
> 1039 break;
> 1040 }
> 1041 return NOTIFY_OK;
> 1042 }
> 1043
>
> --
> 0-DAY CI Kernel Test Service
> https://01.org/lkp