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SubjectRE: [PATCH bpf-next v6 1/8] btf: Add a new kfunc flag which allows to mark a function to be sleepable
Date
> From: Hao Luo [mailto:haoluo@google.com]
> Sent: Monday, August 1, 2022 7:54 PM
> From: Benjamin Tissoires <benjamin.tissoires@redhat.com>
>
> 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>
> Co-developed-by: Yosry Ahmed <yosryahmed@google.com>
> Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
> Signed-off-by: Hao Luo <haoluo@google.com>

Thanks, helpful also for me.

Reviewed-by: Roberto Sassu <roberto.sassu@huawei.com>

Roberto

> ---
> Documentation/bpf/kfuncs.rst | 6 ++++++
> include/linux/btf.h | 1 +
> kernel/bpf/btf.c | 9 +++++++++
> 3 files changed, 16 insertions(+)
>
> diff --git a/Documentation/bpf/kfuncs.rst b/Documentation/bpf/kfuncs.rst
> index c0b7dae6dbf5..c8b21de1c772 100644
> --- a/Documentation/bpf/kfuncs.rst
> +++ b/Documentation/bpf/kfuncs.rst
> @@ -146,6 +146,12 @@ that operate (change some property, perform some
> operation) on an object that
> was obtained using an acquire kfunc. Such kfuncs need an unchanged pointer to
> ensure the integrity of the operation being performed on the expected object.
>
> +2.4.6 KF_SLEEPABLE flag
> +-----------------------
> +
> +The KF_SLEEPABLE flag is used for kfuncs that may sleep. Such kfuncs can only
> +be called by sleepable BPF programs (BPF_F_SLEEPABLE).
> +
> 2.5 Registering the kfuncs
> --------------------------
>
> diff --git a/include/linux/btf.h b/include/linux/btf.h
> index cdb376d53238..976cbdd2981f 100644
> --- a/include/linux/btf.h
> +++ b/include/linux/btf.h
> @@ -49,6 +49,7 @@
> * for this case.
> */
> #define KF_TRUSTED_ARGS (1 << 4) /* kfunc only takes trusted pointer
> arguments */
> +#define KF_SLEEPABLE (1 << 5) /* kfunc may sleep */
>
> struct btf;
> struct btf_member;
> diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
> index 7e64447659f3..d3e4c86b8fcd 100644
> --- a/kernel/bpf/btf.c
> +++ b/kernel/bpf/btf.c
> @@ -6175,6 +6175,7 @@ static int btf_check_func_arg_match(struct
> bpf_verifier_env *env,
> {
> enum bpf_prog_type prog_type = resolve_prog_type(env->prog);
> bool rel = false, kptr_get = false, trusted_arg = false;
> + bool sleepable = false;
> struct bpf_verifier_log *log = &env->log;
> u32 i, nargs, ref_id, ref_obj_id = 0;
> bool is_kfunc = btf_is_kernel(btf);
> @@ -6212,6 +6213,7 @@ static int btf_check_func_arg_match(struct
> bpf_verifier_env *env,
> rel = kfunc_flags & KF_RELEASE;
> kptr_get = kfunc_flags & KF_KPTR_GET;
> trusted_arg = kfunc_flags & KF_TRUSTED_ARGS;
> + sleepable = kfunc_flags & KF_SLEEPABLE;
> }
>
> /* check that BTF function arguments match actual types that the
> @@ -6419,6 +6421,13 @@ 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;
> }
> --
> 2.37.1.455.g008518b4e5-goog

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