Re: [PATCH] bpf: add bpf_msleep_interruptible()

[Matt Bobrowski <mattbobrowski@google.com>]

On Mon, May 05, 2025 at 03:38:59PM +0900, Sergey Senozhatsky wrote:
> bpf_msleep_interruptible() puts a calling context into an
> interruptible sleep.  This function is expected to be used
> for testing only (perhaps in conjunction with fault-injection)
> to simulate various execution delays or timeouts.
>
> Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
> ---
>  include/linux/bpf.h            |  1 +
>  include/uapi/linux/bpf.h       |  9 +++++++++
>  kernel/bpf/helpers.c           | 13 +++++++++++++
>  kernel/trace/bpf_trace.c       |  2 ++
>  tools/include/uapi/linux/bpf.h |  9 +++++++++
>  5 files changed, 34 insertions(+)
> 
> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index 3f0cc89c0622..85bd1daaa7df 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -3392,6 +3392,7 @@ extern const struct bpf_func_proto bpf_get_retval_proto;
>  extern const struct bpf_func_proto bpf_user_ringbuf_drain_proto;
>  extern const struct bpf_func_proto bpf_cgrp_storage_get_proto;
>  extern const struct bpf_func_proto bpf_cgrp_storage_delete_proto;
> +extern const struct bpf_func_proto bpf_msleep_interruptible_proto;
>  
>  const struct bpf_func_proto *tracing_prog_func_proto(
>    enum bpf_func_id func_id, const struct bpf_prog *prog);
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 71d5ac83cf5d..cbbb6d70a7a3 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -5814,6 +5814,14 @@ union bpf_attr {
>   *		0 on success.
>   *
>   *		**-ENOENT** if the bpf_local_storage cannot be found.
> + *
> + * long bpf_msleep_interruptible(long timeout)
> + *	Description
> + *		Make the current task sleep until *timeout* milliseconds have
> + *		elapsed or until a signal is received.
> + *
> + *	Return
> + *		The remaining time of the sleep duration in milliseconds.
>   */
>  #define ___BPF_FUNC_MAPPER(FN, ctx...)			\
>  	FN(unspec, 0, ##ctx)				\
> @@ -6028,6 +6036,7 @@ union bpf_attr {
>  	FN(user_ringbuf_drain, 209, ##ctx)		\
>  	FN(cgrp_storage_get, 210, ##ctx)		\
>  	FN(cgrp_storage_delete, 211, ##ctx)		\
> +	FN(msleep_interruptible, 212, ##ctx)		\
>  	/* This helper list is effectively frozen. If you are trying to	\
>  	 * add a new helper, you should add a kfunc instead which has	\
>  	 * less stability guarantees. See Documentation/bpf/kfuncs.rst	\

I noticed that you've written the newly proposed BPF helper in the
legacy BPF helper form, which I believe is now discouraged, as also
stated within the above comment. You probably want to respin this
patch series having written this newly proposed BPF helper in BPF
kfuncs [0] form instead.

Additionally, as part of your patch series I think you'll also want to
include some selftests.

[0] https://docs.kernel.org/bpf/kfuncs.html

> diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
> index e3a2662f4e33..0a3449c282f2 100644
> --- a/kernel/bpf/helpers.c
> +++ b/kernel/bpf/helpers.c
> @@ -1905,6 +1905,19 @@ static const struct bpf_func_proto bpf_dynptr_data_proto = {
>  	.arg3_type	= ARG_CONST_ALLOC_SIZE_OR_ZERO,
>  };
>  
> +BPF_CALL_1(bpf_msleep_interruptible, long, timeout)
> +{
> +	return msleep_interruptible(timeout);
> +}
> +
> +const struct bpf_func_proto bpf_msleep_interruptible_proto = {
> +	.func		= bpf_msleep_interruptible,
> +	.gpl_only	= false,
> +	.might_sleep	= true,
> +	.ret_type	= RET_INTEGER,
> +	.arg1_type	= ARG_ANYTHING,
> +};
> +
>  const struct bpf_func_proto bpf_get_current_task_proto __weak;
>  const struct bpf_func_proto bpf_get_current_task_btf_proto __weak;
>  const struct bpf_func_proto bpf_probe_read_user_proto __weak;
> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> index 52c432a44aeb..8a0b96aed0c0 100644
> --- a/kernel/trace/bpf_trace.c
> +++ b/kernel/trace/bpf_trace.c
> @@ -1475,6 +1475,8 @@ bpf_tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
>  		return &bpf_get_branch_snapshot_proto;
>  	case BPF_FUNC_find_vma:
>  		return &bpf_find_vma_proto;
> +	case BPF_FUNC_msleep_interruptible:
> +		return &bpf_msleep_interruptible_proto;
>  	default:
>  		break;
>  	}
> diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
> index 71d5ac83cf5d..cbbb6d70a7a3 100644
> --- a/tools/include/uapi/linux/bpf.h
> +++ b/tools/include/uapi/linux/bpf.h
> @@ -5814,6 +5814,14 @@ union bpf_attr {
>   *		0 on success.
>   *
>   *		**-ENOENT** if the bpf_local_storage cannot be found.
> + *
> + * long bpf_msleep_interruptible(long timeout)
> + *	Description
> + *		Make the current task sleep until *timeout* milliseconds have
> + *		elapsed or until a signal is received.
> + *
> + *	Return
> + *		The remaining time of the sleep duration in milliseconds.
>   */
>  #define ___BPF_FUNC_MAPPER(FN, ctx...)			\
>  	FN(unspec, 0, ##ctx)				\
> @@ -6028,6 +6036,7 @@ union bpf_attr {
>  	FN(user_ringbuf_drain, 209, ##ctx)		\
>  	FN(cgrp_storage_get, 210, ##ctx)		\
>  	FN(cgrp_storage_delete, 211, ##ctx)		\
> +	FN(msleep_interruptible, 212, ##ctx)		\
>  	/* This helper list is effectively frozen. If you are trying to	\
>  	 * add a new helper, you should add a kfunc instead which has	\
>  	 * less stability guarantees. See Documentation/bpf/kfuncs.rst	\
> -- 
> 2.49.0.906.g1f30a19c02-goog
>