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Mon, 21 Sep 2026 19:26:19 +0000 X-Mizu-Trace-ID: c80bc367aa6462a1 X-Migadu-Flow: FLOW_OUT From: Shakeel Butt To: Andrew Morton , Alexei Starovoitov Cc: Johannes Weiner , Michal Hocko , Roman Gushchin , JP Kobryn , Muchun Song , Tejun Heo , Michal Koutny , Amery Hung , Daniel Borkmann , Andrii Nakryiko , Eduard Zingerman , Kumar Kartikeya Dwivedi , Martin KaFai Lau , Song Liu , Yonghong Song , Emil Tsalapatis , Jiri Olsa , Ihor Solodrai , John Fastabend , Jiayuan Chen , hui.zhu@linux.dev, Donet Tom , Greg Thelen , Meta kernel team , linux-mm@kvack.org, bpf@vger.kernel.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [RFC PATCH 1/4] bpf, cgroup: fix cgroup struct_ops query for a second attach type Date: Mon, 21 Sep 2026 12:25:56 -0700 Message-ID: <20260921192559.2619635-2-shakeel.butt@linux.dev> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260921192559.2619635-1-shakeel.butt@linux.dev> References: <20260921192559.2619635-1-shakeel.butt@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 7EEF6A000C X-Stat-Signature: ebfa7x3peymo5mwka7csba9f46bxwrqg X-Rspam-User: X-HE-Tag: 1790018781-129003 X-HE-Meta: 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 SjZgTdOY JELttJuZK1aoXnLeVNeuzc8UBKR/V7wAUhkKmlS3nQ8XyM1Hk0TO8b/TwLP6txDaWWwae5OVnaxiz66Pc7WSjw/2mySmjynyVDM69L9vY/2iDMHcfF+SiZ6qyXE/g3I+Aig1N6+HWcbbqNgxV5/2hWK6V5oQqhn1kZux9X7ziY9tt1CzvfluZC4vguEcqMN43e4MWcAm9J+UrPTg509dTWTQc8YV2ewm7nRPN2tPZpu5zNj3QyTvU3XlZxVHvtDW+7SkcPH0EtlwoW+TFbgpXhbCSPA7uQnrB9kQzwMy7AOQXo8UCloaodcy5In28lLtDzUxRHxVn+2LnrykJ384ox5nAC9TpykPUVs7B Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Two things in __cgroup_bpf_query() work only because CGROUP_TCP_SOCK_OPS is the only one struct_ops attach type. It calls cgroup_bpf_enabled(atype) with an atype that find_atype_by_struct_ops_id() works out at runtime. That macro is an asm goto and needs a constant. Today the compiler can see there is only one value; add a second type and the build breaks with "impossible constraint in 'asm'". Add cgroup_bpf_enabled_runtime(), which reads the key instead, and use it here. This is a syscall path, so the cost does not matter. And find_atype_by_struct_ops_id() matches on type_id alone. An attach type whose subsystem is not built keeps type_id 0, so a query for type 0 finds it and returns success with nothing instead of -ENOENT. Skip such slots. Signed-off-by: Shakeel Butt --- include/linux/bpf-cgroup.h | 9 +++++++++ kernel/bpf/cgroup.c | 3 ++- 2 files changed, 11 insertions(+), 1 deletion(-) diff --git a/include/linux/bpf-cgroup.h b/include/linux/bpf-cgroup.h index 8a75a6cd7309..3b2c127d401d 100644 --- a/include/linux/bpf-cgroup.h +++ b/include/linux/bpf-cgroup.h @@ -76,6 +76,14 @@ to_cgroup_bpf_attach_type(enum bpf_attach_type attach_type) extern struct static_key_false cgroup_bpf_enabled_key[MAX_CGROUP_BPF_ATTACH_TYPE]; #define cgroup_bpf_enabled(atype) static_branch_unlikely(&cgroup_bpf_enabled_key[atype]) +/* + * Same test when @atype is not a constant. cgroup_bpf_enabled() uses + * static_branch_unlikely which creates jump-label site and requires statically + * selected key. Since key is selected dynamically, use static_key_enabled here + * and keep it off fast paths. + */ +#define cgroup_bpf_enabled_runtime(atype) \ + static_key_enabled(&cgroup_bpf_enabled_key[atype]) struct bpf_cgroup_storage_map; @@ -508,6 +516,7 @@ static inline int cgroup_bpf_struct_ops_attach(struct bpf_map *map, } #define cgroup_bpf_enabled(atype) (0) +#define cgroup_bpf_enabled_runtime(atype) (0) #define BPF_CGROUP_RUN_SA_PROG_LOCK(sk, uaddr, uaddrlen, atype, t_ctx) ({ 0; }) #define BPF_CGROUP_RUN_SA_PROG(sk, uaddr, uaddrlen, atype) ({ 0; }) #define BPF_CGROUP_PRE_CONNECT_ENABLED(sk) (0) diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c index 696b27383974..99b4e96f5db7 100644 --- a/kernel/bpf/cgroup.c +++ b/kernel/bpf/cgroup.c @@ -45,6 +45,7 @@ static enum cgroup_bpf_attach_type find_atype_by_struct_ops_id(u32 type_id) for (atype = 0; atype < MAX_CGROUP_BPF_ATTACH_TYPE; atype++) { if (cgroup_bpf_is_struct_ops_atype(atype) && + cgroup_struct_ops[atype].type_id && cgroup_struct_ops[atype].type_id == type_id) return atype; } @@ -1448,7 +1449,7 @@ static int __cgroup_bpf_query(struct cgroup *cgrp, const union bpf_attr *attr, return -ENOENT; from_atype = to_atype = atype; flags = 0; - if (!cgroup_bpf_enabled(atype)) + if (!cgroup_bpf_enabled_runtime(atype)) goto skip_count; } else if (type == BPF_LSM_CGROUP) { if (!effective_query && attr->query.prog_cnt && -- 2.53.0-Meta