2022-04-21 21:17:26

by Benjamin Tissoires

Subject: [RFC bpf-next v4 4/7] btf: Add a new kfunc set which allows to mark a function to be sleepable

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

Signed-off-by: Benjamin Tissoires <[email protected]>

---

new in v4
---
include/linux/btf.h | 2 ++
kernel/bpf/btf.c | 16 +++++++++++++---
2 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/include/linux/btf.h b/include/linux/btf.h
index 76a3ff48ae2a..b8b83dcf86bf 100644
--- a/include/linux/btf.h
+++ b/include/linux/btf.h
@@ -17,6 +17,7 @@ enum btf_kfunc_type {
BTF_KFUNC_TYPE_ACQUIRE,
BTF_KFUNC_TYPE_RELEASE,
BTF_KFUNC_TYPE_RET_NULL,
+ BTF_KFUNC_TYPE_SLEEPABLE,
BTF_KFUNC_TYPE_MAX,
};

@@ -35,6 +36,7 @@ struct btf_kfunc_id_set {
struct btf_id_set *acquire_set;
struct btf_id_set *release_set;
struct btf_id_set *ret_null_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 22e6e3cdc7ee..bf6a82461c58 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -5889,7 +5889,7 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
const struct btf_type *t, *ref_t;
const struct btf_param *args;
int ref_regno = 0, ret;
- bool rel = false;
+ bool rel = false, sleepable = false;

t = btf_type_by_id(btf, func_id);
if (!t || !btf_type_is_func(t)) {
@@ -5915,10 +5915,13 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
return -EINVAL;
}

- /* Only kfunc can be release func */
- if (is_kfunc)
+ /* Only kfunc can be release or sleepable func */
+ if (is_kfunc) {
rel = btf_kfunc_id_set_contains(btf, resolve_prog_type(env->prog),
BTF_KFUNC_TYPE_RELEASE, 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
* verifier sees.
*/
@@ -6092,6 +6095,13 @@ 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;
}
--
2.35.1

2022-04-27 09:42:19

by Alexei Starovoitov

Subject: Re: [RFC bpf-next v4 4/7] btf: Add a new kfunc set which allows to mark a function to be sleepable

On Thu, Apr 21, 2022 at 04:07:37PM +0200, Benjamin Tissoires wrote:
> This allows to declare a kfunc as sleepable and prevents its use in
> a non sleepable program.
>
> Signed-off-by: Benjamin Tissoires <[email protected]>

makes sense.
> @@ -17,6 +17,7 @@ enum btf_kfunc_type {
> BTF_KFUNC_TYPE_ACQUIRE,
> BTF_KFUNC_TYPE_RELEASE,
> BTF_KFUNC_TYPE_RET_NULL,
> + BTF_KFUNC_TYPE_SLEEPABLE,
> BTF_KFUNC_TYPE_MAX,
> };
>
> @@ -35,6 +36,7 @@ struct btf_kfunc_id_set {
> struct btf_id_set *acquire_set;
> struct btf_id_set *release_set;
> struct btf_id_set *ret_null_set;
> + struct btf_id_set *sleepable_set;