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To: Alexei Starovoitov , CC: , , , , References: <20210624022518.57875-1-alexei.starovoitov@gmail.com> <20210624022518.57875-3-alexei.starovoitov@gmail.com> From: Yonghong Song Message-ID: <2c523078-cb24-e1ca-2439-27be37cfe90b@fb.com> Date: Fri, 25 Jun 2021 12:46:03 -0700 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 In-Reply-To: <20210624022518.57875-3-alexei.starovoitov@gmail.com> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [2620:10d:c090:400::5:4ed3] X-ClientProxiedBy: MW4PR03CA0242.namprd03.prod.outlook.com (2603:10b6:303:b4::7) To SN6PR1501MB2064.namprd15.prod.outlook.com (2603:10b6:805:d::27) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from [IPv6:2620:10d:c085:21e1::1328] (2620:10d:c090:400::5:4ed3) by MW4PR03CA0242.namprd03.prod.outlook.com (2603:10b6:303:b4::7) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4264.18 via Frontend Transport; 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The per-cpu maps with timers don't make sense, since 'struct > bpf_timer' is a part of map value. bpf timers in per-cpu maps would mean that > the number of timers depends on number of possible cpus and timers would not be > accessible from all cpus. lpm map support can be added in the future. > The timers in inner maps are supported. > > The bpf_map_update/delete_elem() helpers and sys_bpf commands cancel and free > bpf_timer in a given map element. > > Similar to 'struct bpf_spin_lock' BTF is required and it is used to validate > that map element indeed contains 'struct bpf_timer'. > > Make check_and_init_map_value() init both bpf_spin_lock and bpf_timer when > map element data is reused in preallocated htab and lru maps. > > Teach copy_map_value() to support both bpf_spin_lock and bpf_timer in a single > map element. There could be one of each, but not more than one. Due to 'one > bpf_timer in one element' restriction do not support timers in global data, > since global data is a map of single element, but from bpf program side it's > seen as many global variables and restriction of single global timer would be > odd. The sys_bpf map_freeze and sys_mmap syscalls are not allowed on maps with > timers, since user space could have corrupted mmap element and crashed the > kernel. The maps with timers cannot be readonly. Due to these restrictions > search for bpf_timer in datasec BTF in case it was placed in the global data to > report clear error. > > The previous patch allowed 'struct bpf_timer' as a first field in a map > element only. Relax this restriction. > > Refactor lru map to s/bpf_lru_push_free/htab_lru_push_free/ to cancel and free > the timer when lru map deletes an element as a part of it eviction algorithm. > > Make sure that bpf program cannot access 'struct bpf_timer' via direct load/store. > The timer operation are done through helpers only. > This is similar to 'struct bpf_spin_lock'. > > Signed-off-by: Alexei Starovoitov I didn't find major issues. Only one minor comment below. I do a race during map_update where updated map elements will have timer removed but at the same time the timer might still be used after update. But irq spinlock should handle this properly. Acked-by: Yonghong Song > --- > include/linux/bpf.h | 44 ++++++++++++----- > include/linux/btf.h | 1 + > kernel/bpf/arraymap.c | 22 +++++++++ > kernel/bpf/btf.c | 77 ++++++++++++++++++++++++------ > kernel/bpf/hashtab.c | 96 +++++++++++++++++++++++++++++++++----- > kernel/bpf/local_storage.c | 4 +- > kernel/bpf/map_in_map.c | 1 + > kernel/bpf/syscall.c | 21 +++++++-- > kernel/bpf/verifier.c | 30 ++++++++++-- > 9 files changed, 251 insertions(+), 45 deletions(-) > > diff --git a/include/linux/bpf.h b/include/linux/bpf.h > index 72da9d4d070c..90e6c6d1404c 100644 > --- a/include/linux/bpf.h > +++ b/include/linux/bpf.h > @@ -198,24 +198,46 @@ static inline bool map_value_has_spin_lock(const struct bpf_map *map) > return map->spin_lock_off >= 0; > } > > -static inline void check_and_init_map_lock(struct bpf_map *map, void *dst) > +static inline bool map_value_has_timer(const struct bpf_map *map) > { > - if (likely(!map_value_has_spin_lock(map))) > - return; > - *(struct bpf_spin_lock *)(dst + map->spin_lock_off) = > - (struct bpf_spin_lock){}; > + return map->timer_off >= 0; > } > > -/* copy everything but bpf_spin_lock */ > +static inline void check_and_init_map_value(struct bpf_map *map, void *dst) > +{ > + if (unlikely(map_value_has_spin_lock(map))) > + *(struct bpf_spin_lock *)(dst + map->spin_lock_off) = > + (struct bpf_spin_lock){}; > + if (unlikely(map_value_has_timer(map))) > + *(struct bpf_timer *)(dst + map->timer_off) = > + (struct bpf_timer){}; > +} > + [...] > diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c > index 6f6681b07364..e85a5839ffe8 100644 > --- a/kernel/bpf/hashtab.c > +++ b/kernel/bpf/hashtab.c > @@ -228,6 +228,28 @@ static struct htab_elem *get_htab_elem(struct bpf_htab *htab, int i) > return (struct htab_elem *) (htab->elems + i * (u64)htab->elem_size); > } > > +static void htab_free_prealloced_timers(struct bpf_htab *htab) > +{ > + u32 num_entries = htab->map.max_entries; > + int i; > + > + if (likely(!map_value_has_timer(&htab->map))) > + return; > + if (!htab_is_percpu(htab) && !htab_is_lru(htab)) Is !htab_is_percpu(htab) needed? I think we already checked if map_value has timer it can only be hash/lruhash/array? > + /* htab has extra_elems */ > + num_entries += num_possible_cpus(); > + > + for (i = 0; i < num_entries; i++) { > + struct htab_elem *elem; > + > + elem = get_htab_elem(htab, i); > + bpf_timer_cancel_and_free(elem->key + > + round_up(htab->map.key_size, 8) + > + htab->map.timer_off); > + cond_resched(); > + } > +} > + [...]