From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Borkmann Subject: Re: [PATCH bpf] bpf: fix bpffs non-array map seq_show issue Date: Thu, 9 Aug 2018 19:02:16 +0200 Message-ID: <2adc84c4-2e92-db75-ba27-7e23eb9c95ad@iogearbox.net> References: <20180809012519.3534824-1-yhs@fb.com> <20180809022530.yprizizentv7frmt@ast-mbp> <9b44c0d6-d236-75ed-abb6-2d945ceb6b81@iogearbox.net> <99a17600-57c8-06fc-c555-83dc8793f174@fb.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Cc: ast@fb.com, netdev@vger.kernel.org, kernel-team@fb.com, jakub.kicinski@netronome.com To: Yonghong Song , Alexei Starovoitov Return-path: Received: from www62.your-server.de ([213.133.104.62]:54792 "EHLO www62.your-server.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732624AbeHIT2F (ORCPT ); Thu, 9 Aug 2018 15:28:05 -0400 In-Reply-To: <99a17600-57c8-06fc-c555-83dc8793f174@fb.com> Content-Language: en-US Sender: netdev-owner@vger.kernel.org List-ID: On 08/09/2018 06:55 PM, Yonghong Song wrote: > On 8/9/18 8:59 AM, Daniel Borkmann wrote: >> On 08/09/2018 05:15 PM, Yonghong Song wrote: >>> On 8/9/18 7:24 AM, Daniel Borkmann wrote: >>>> On 08/09/2018 05:55 AM, Yonghong Song wrote: >>>>> On 8/8/18 7:25 PM, Alexei Starovoitov wrote: >>>>>> On Wed, Aug 08, 2018 at 06:25:19PM -0700, Yonghong Song wrote: >>>>>>> In function map_seq_next() of kernel/bpf/inode.c, >>>>>>> the first key will be the "0" regardless of the map type. >>>>>>> This works for array. But for hash type, if it happens >>>>>>> key "0" is in the map, the bpffs map show will miss >>>>>>> some items if the key "0" is not the first element of >>>>>>> the first bucket. >>>>>>> >>>>>>> This patch fixed the issue by guaranteeing to get >>>>>>> the first element, if the seq_show is just started, >>>>>>> by passing NULL pointer key to map_get_next_key() callback. >>>>>>> This way, no missing elements will occur for >>>>>>> bpffs hash table show even if key "0" is in the map. >>>>> >>>>> Currently, map_seq_show_elem callback is only implemented >>>>> for arraymap. So the problem actually is not exposed. >>>>> >>>>> The issue is discovered when I tried to implement >>>>> map_seq_show_elem for hash maps, and I will have followup >>>>> patches for it. >> >> Btw, on that note, I would also prefer if we could decouple >> BTF from the map_seq_show_elem() as there is really no reason >> to have it on a per-map. I had a patch below which would enable >> it for all map types generically, and bpftool works out of the >> box for it. Also, array doesn't really have to be 'int' type >> enforced as long as it's some data structure with 4 bytes, it's >> all fine, so this can be made fully generic (we only eventually >> care about the match in size). > > I agree with a generic map_check_btf as mostly we only care about size > and this change should enable btftool btf based pretty print for hash/lru_hash tables. Yep, agree, the below output from bpftool is from test_xdp_noinline.o where both work with it. >>  From 0a8be27cbc2ac0c6fc2632865b5afe37222a1fc7 Mon Sep 17 00:00:00 2001 >> Message-Id: <0a8be27cbc2ac0c6fc2632865b5afe37222a1fc7.1533830053.git.daniel@iogearbox.net> >> From: Daniel Borkmann >> Date: Thu, 9 Aug 2018 16:50:21 +0200 >> Subject: [PATCH bpf-next] bpf, btf: enable for all maps >> >> # bpftool m dump id 19 >> [{ >>          "key": { >>              "": { >>                  "vip": 0, >>                  "vipv6": [] >>              }, >>              "port": 0, >>              "family": 0, >>              "proto": 0 >>          }, >>          "value": { >>              "flags": 0, >>              "vip_num": 0 >>          } >>      } >> ] >> >> Signed-off-by: Daniel Borkmann >> --- >>   include/linux/bpf.h   |  4 +--- >>   kernel/bpf/arraymap.c | 27 --------------------------- >>   kernel/bpf/inode.c    |  3 ++- >>   kernel/bpf/syscall.c  | 24 ++++++++++++++++++++---- >>   4 files changed, 23 insertions(+), 35 deletions(-) >> >> diff --git a/include/linux/bpf.h b/include/linux/bpf.h >> index cd8790d..91aa4be 100644 >> --- a/include/linux/bpf.h >> +++ b/include/linux/bpf.h >> @@ -48,8 +48,6 @@ struct bpf_map_ops { >>       u32 (*map_fd_sys_lookup_elem)(void *ptr); >>       void (*map_seq_show_elem)(struct bpf_map *map, void *key, >>                     struct seq_file *m); >> -    int (*map_check_btf)(const struct bpf_map *map, const struct btf *btf, >> -                 u32 key_type_id, u32 value_type_id); >>   }; >> >>   struct bpf_map { >> @@ -118,7 +116,7 @@ static inline bool bpf_map_offload_neutral(const struct bpf_map *map) >> >>   static inline bool bpf_map_support_seq_show(const struct bpf_map *map) >>   { >> -    return map->ops->map_seq_show_elem && map->ops->map_check_btf; >> +    return map->ops->map_seq_show_elem; >>   } >> >>   extern const struct bpf_map_ops bpf_map_offload_ops; >> diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c >> index 2aa55d030..67f0bdf 100644 >> --- a/kernel/bpf/arraymap.c >> +++ b/kernel/bpf/arraymap.c >> @@ -358,32 +358,6 @@ static void array_map_seq_show_elem(struct bpf_map *map, void *key, >>       rcu_read_unlock(); >>   } >> >> -static int array_map_check_btf(const struct bpf_map *map, const struct btf *btf, >> -                   u32 btf_key_id, u32 btf_value_id) >> -{ >> -    const struct btf_type *key_type, *value_type; >> -    u32 key_size, value_size; >> -    u32 int_data; >> - >> -    key_type = btf_type_id_size(btf, &btf_key_id, &key_size); >> -    if (!key_type || BTF_INFO_KIND(key_type->info) != BTF_KIND_INT) >> -        return -EINVAL; >> - >> -    int_data = *(u32 *)(key_type + 1); >> -    /* bpf array can only take a u32 key.  This check makes >> -     * sure that the btf matches the attr used during map_create. >> -     */ >> -    if (BTF_INT_BITS(int_data) != 32 || key_size != 4 || >> -        BTF_INT_OFFSET(int_data)) >> -        return -EINVAL; >> - >> -    value_type = btf_type_id_size(btf, &btf_value_id, &value_size); >> -    if (!value_type || value_size != map->value_size) >> -        return -EINVAL; >> - >> -    return 0; >> -} >> - >>   const struct bpf_map_ops array_map_ops = { >>       .map_alloc_check = array_map_alloc_check, >>       .map_alloc = array_map_alloc, >> @@ -394,7 +368,6 @@ const struct bpf_map_ops array_map_ops = { >>       .map_delete_elem = array_map_delete_elem, >>       .map_gen_lookup = array_map_gen_lookup, >>       .map_seq_show_elem = array_map_seq_show_elem, >> -    .map_check_btf = array_map_check_btf, >>   }; >> >>   const struct bpf_map_ops percpu_array_map_ops = { >> diff --git a/kernel/bpf/inode.c b/kernel/bpf/inode.c >> index 76efe9a..400f27d 100644 >> --- a/kernel/bpf/inode.c >> +++ b/kernel/bpf/inode.c >> @@ -332,7 +332,8 @@ static int bpf_mkmap(struct dentry *dentry, umode_t mode, void *arg) >>       struct bpf_map *map = arg; >> >>       return bpf_mkobj_ops(dentry, mode, arg, &bpf_map_iops, >> -                 map->btf ? &bpffs_map_fops : &bpffs_obj_fops); >> +                 bpf_map_support_seq_show(map) ? >> +                 &bpffs_map_fops : &bpffs_obj_fops); > > There are an issue here, the condition bpf_map_support_seq_show(map) may not be enough since the map specific implementation assumes availability of btf and proper map key/value btf_type_id's. > We can either use >     map->btf && bpf_map_support_seq_show(map) > condition here, or check map->btf in each individual implementation > of map_support_seq_show(). Good, point, agree. Will fix and cook proper patch later today. Thanks Yonghong! >>   } >> >>   static struct dentry * >> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c >> index 5af4e9e..0b6f6e8 100644 >> --- a/kernel/bpf/syscall.c >> +++ b/kernel/bpf/syscall.c >> @@ -455,6 +455,23 @@ static int bpf_obj_name_cpy(char *dst, const char *src) >>       return 0; >>   } >> >> +static int map_check_btf(const struct bpf_map *map, const struct btf *btf, >> +             u32 btf_key_id, u32 btf_value_id) >> +{ >> +    const struct btf_type *key_type, *value_type; >> +    u32 key_size, value_size; >> + >> +    key_type = btf_type_id_size(btf, &btf_key_id, &key_size); >> +    if (!key_type || key_size != map->key_size) >> +        return -EINVAL; >> + >> +    value_type = btf_type_id_size(btf, &btf_value_id, &value_size); >> +    if (!value_type || value_size != map->value_size) >> +        return -EINVAL; >> + >> +    return 0; >> +} >> + >>   #define BPF_MAP_CREATE_LAST_FIELD btf_value_type_id >>   /* called via syscall */ >>   static int map_create(union bpf_attr *attr) >> @@ -489,8 +506,7 @@ static int map_create(union bpf_attr *attr) >>       atomic_set(&map->refcnt, 1); >>       atomic_set(&map->usercnt, 1); >> >> -    if (bpf_map_support_seq_show(map) && >> -        (attr->btf_key_type_id || attr->btf_value_type_id)) { >> +    if (attr->btf_key_type_id || attr->btf_value_type_id) { >>           struct btf *btf; >> >>           if (!attr->btf_key_type_id || !attr->btf_value_type_id) { >> @@ -504,8 +520,8 @@ static int map_create(union bpf_attr *attr) >>               goto free_map_nouncharge; >>           } >> >> -        err = map->ops->map_check_btf(map, btf, attr->btf_key_type_id, >> -                          attr->btf_value_type_id); >> +        err = map_check_btf(map, btf, attr->btf_key_type_id, >> +                    attr->btf_value_type_id); >>           if (err) { >>               btf_put(btf); >>               goto free_map_nouncharge; >>