[PATCH bpf-next v3 1/8] btf: Add a new kfunc set which allows to mark a function to be sleepable

Yosry Ahmed
2022-07-09T00:05:00Z

From: Benjamin Tissoires <benjamin.tissoires@redhat.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@redhat.com>
Signed-off-by: Yosry Ahmed <yosryahmed@google.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 1bfed7fa04287..6e7517573d9e4 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 4f2408a4df08b..2a4b4e50b6fb7 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -6172,7 +6172,7 @@ 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;
@@ -6203,11 +6203,13 @@ 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
@@ -6405,6 +6407,13 @@ 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;
}
--
2.37.0.rc0.161.g10f37bed90-goog