netdev - [PATCH bpf-next v4 1/8] btf: Add a new kfunc set which allows to mark a function to be sleepable

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Message-Id: <20220722021313.3150035-2-yosryahmed@google.com>
Date:   Fri, 22 Jul 2022 02:13:06 +0000
From:   Yosry Ahmed <yosryahmed@...gle.com>
To:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Hao Luo <haoluo@...gle.com>, Tejun Heo <tj@...nel.org>,
        Zefan Li <lizefan.x@...edance.com>
Cc:     Johannes Weiner <hannes@...xchg.org>,
        Shuah Khan <shuah@...nel.org>,
        Michal Hocko <mhocko@...nel.org>,
        KP Singh <kpsingh@...nel.org>,
        Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        John Fastabend <john.fastabend@...il.com>,
        "Michal Koutný" <mkoutny@...e.com>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        David Rientjes <rientjes@...gle.com>,
        Stanislav Fomichev <sdf@...gle.com>,
        Greg Thelen <gthelen@...gle.com>,
        Shakeel Butt <shakeelb@...gle.com>,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        bpf@...r.kernel.org, cgroups@...r.kernel.org,
        Yosry Ahmed <yosryahmed@...gle.com>
Subject: [PATCH bpf-next v4 1/8] btf: Add a new kfunc set which allows to mark
 a function to be sleepable

From: Benjamin Tissoires <benjamin.tissoires@...hat.com>

This allows to declare a kfunc as sleepable and prevents its use in
a non sleepable program.

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@...hat.com>
Signed-off-by: Yosry Ahmed <yosryahmed@...gle.com>
---
 include/linux/btf.h |  2 ++
 kernel/bpf/btf.c    | 13 +++++++++++--
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/include/linux/btf.h b/include/linux/btf.h
index 1bfed7fa0428..6e7517573d9e 100644
--- a/include/linux/btf.h
+++ b/include/linux/btf.h
@@ -18,6 +18,7 @@ enum btf_kfunc_type {
 	BTF_KFUNC_TYPE_RELEASE,
 	BTF_KFUNC_TYPE_RET_NULL,
 	BTF_KFUNC_TYPE_KPTR_ACQUIRE,
+	BTF_KFUNC_TYPE_SLEEPABLE,
 	BTF_KFUNC_TYPE_MAX,
 };
 
@@ -37,6 +38,7 @@ struct btf_kfunc_id_set {
 			struct btf_id_set *release_set;
 			struct btf_id_set *ret_null_set;
 			struct btf_id_set *kptr_acquire_set;
+			struct btf_id_set *sleepable_set;
 		};
 		struct btf_id_set *sets[BTF_KFUNC_TYPE_MAX];
 	};
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 5869f03bcb6e..2040e440f347 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -6178,7 +6178,7 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
 	struct bpf_verifier_log *log = &env->log;
 	u32 i, nargs, ref_id, ref_obj_id = 0;
 	bool is_kfunc = btf_is_kernel(btf);
-	bool rel = false, kptr_get = false;
+	bool rel = false, kptr_get = false, sleepable = false;
 	const char *func_name, *ref_tname;
 	const struct btf_type *t, *ref_t;
 	const struct btf_param *args;
@@ -6209,11 +6209,13 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
 	}
 
 	if (is_kfunc) {
-		/* Only kfunc can be release func */
+		/* Only kfunc can be release, kptr acquire, or sleepable func */
 		rel = btf_kfunc_id_set_contains(btf, resolve_prog_type(env->prog),
 						BTF_KFUNC_TYPE_RELEASE, func_id);
 		kptr_get = btf_kfunc_id_set_contains(btf, resolve_prog_type(env->prog),
 						     BTF_KFUNC_TYPE_KPTR_ACQUIRE, func_id);
+		sleepable = btf_kfunc_id_set_contains(btf, resolve_prog_type(env->prog),
+						      BTF_KFUNC_TYPE_SLEEPABLE, func_id);
 	}
 
 	/* check that BTF function arguments match actual types that the
@@ -6411,6 +6413,13 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
 			func_name);
 		return -EINVAL;
 	}
+
+	if (sleepable && !env->prog->aux->sleepable) {
+		bpf_log(log, "kernel function %s is sleepable but the program is not\n",
+			func_name);
+		return -EINVAL;
+	}
+
 	/* returns argument register number > 0 in case of reference release kfunc */
 	return rel ? ref_regno : 0;
 }
-- 
2.37.1.359.gd136c6c3e2-goog