netdev - Re: [PATCH bpf-next v3 2/3] libbpf: add bpf_object__load_xattr() API function to pass log

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Date:   Fri, 24 May 2019 13:22:15 +0200
From:   Jesper Dangaard Brouer <brouer@...hat.com>
To:     Quentin Monnet <quentin.monnet@...ronome.com>
Cc:     brouer@...hat.com, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>, bpf@...r.kernel.org,
        netdev@...r.kernel.org, oss-drivers@...ronome.com,
        Yonghong Song <yhs@...com>, Andrii Nakryiko <andriin@...com>
Subject: Re: [PATCH bpf-next v3 2/3] libbpf: add bpf_object__load_xattr()
 API function to pass log_level

On Fri, 24 May 2019 11:36:47 +0100
Quentin Monnet <quentin.monnet@...ronome.com> wrote:

> libbpf was recently made aware of the log_level attribute for programs,
> used to specify the level of information expected to be dumped by the
> verifier. Function bpf_prog_load_xattr() got support for this log_level
> parameter.
> 
> But some applications using libbpf rely on another function to load
> programs, bpf_object__load(), which does accept any parameter for log
> level. Create an API function based on bpf_object__load(), but accepting
> an "attr" object as a parameter. Then add a log_level field to that
> object, so that applications calling the new bpf_object__load_xattr()
> can pick the desired log level.

Does this allow us to extend struct bpf_object_load_attr later?

> v3:
> - Rewrite commit log.
> 
> v2:
> - We are in a new cycle, bump libbpf extraversion number.
> 
> Signed-off-by: Quentin Monnet <quentin.monnet@...ronome.com>
> Reviewed-by: Jakub Kicinski <jakub.kicinski@...ronome.com>
> ---
>  tools/lib/bpf/Makefile   |  2 +-
>  tools/lib/bpf/libbpf.c   | 20 +++++++++++++++++---
>  tools/lib/bpf/libbpf.h   |  6 ++++++
>  tools/lib/bpf/libbpf.map |  5 +++++
>  4 files changed, 29 insertions(+), 4 deletions(-)
> 
> diff --git a/tools/lib/bpf/Makefile b/tools/lib/bpf/Makefile
> index a2aceadf68db..9312066a1ae3 100644
> --- a/tools/lib/bpf/Makefile
> +++ b/tools/lib/bpf/Makefile
> @@ -3,7 +3,7 @@
>  
>  BPF_VERSION = 0
>  BPF_PATCHLEVEL = 0
> -BPF_EXTRAVERSION = 3
> +BPF_EXTRAVERSION = 4
>  
>  MAKEFLAGS += --no-print-directory
>  
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index 197b574406b3..1c6fb7a3201e 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -2222,7 +2222,7 @@ static bool bpf_program__is_function_storage(struct bpf_program *prog,
>  }
>  
>  static int
> -bpf_object__load_progs(struct bpf_object *obj)
> +bpf_object__load_progs(struct bpf_object *obj, int log_level)
>  {
>  	size_t i;
>  	int err;
> @@ -2230,6 +2230,7 @@ bpf_object__load_progs(struct bpf_object *obj)
>  	for (i = 0; i < obj->nr_programs; i++) {
>  		if (bpf_program__is_function_storage(&obj->programs[i], obj))
>  			continue;
> +		obj->programs[i].log_level = log_level;
>  		err = bpf_program__load(&obj->programs[i],
>  					obj->license,
>  					obj->kern_version);
> @@ -2381,10 +2382,14 @@ int bpf_object__unload(struct bpf_object *obj)
>  	return 0;
>  }
>  
> -int bpf_object__load(struct bpf_object *obj)
> +int bpf_object__load_xattr(struct bpf_object_load_attr *attr)
>  {
> +	struct bpf_object *obj;
>  	int err;
>  
> +	if (!attr)
> +		return -EINVAL;
> +	obj = attr->obj;
>  	if (!obj)
>  		return -EINVAL;
>  
> @@ -2397,7 +2402,7 @@ int bpf_object__load(struct bpf_object *obj)
>  
>  	CHECK_ERR(bpf_object__create_maps(obj), err, out);
>  	CHECK_ERR(bpf_object__relocate(obj), err, out);
> -	CHECK_ERR(bpf_object__load_progs(obj), err, out);
> +	CHECK_ERR(bpf_object__load_progs(obj, attr->log_level), err, out);
>  
>  	return 0;
>  out:
> @@ -2406,6 +2411,15 @@ int bpf_object__load(struct bpf_object *obj)
>  	return err;
>  }
>  
> +int bpf_object__load(struct bpf_object *obj)
> +{
> +	struct bpf_object_load_attr attr = {
> +		.obj = obj,
> +	};
> +
> +	return bpf_object__load_xattr(&attr);
> +}
> +
>  static int check_path(const char *path)
>  {
>  	char *cp, errmsg[STRERR_BUFSIZE];
> diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
> index c5ff00515ce7..e1c748db44f6 100644
> --- a/tools/lib/bpf/libbpf.h
> +++ b/tools/lib/bpf/libbpf.h
> @@ -89,8 +89,14 @@ LIBBPF_API int bpf_object__unpin_programs(struct bpf_object *obj,
>  LIBBPF_API int bpf_object__pin(struct bpf_object *object, const char *path);
>  LIBBPF_API void bpf_object__close(struct bpf_object *object);
>  
> +struct bpf_object_load_attr {
> +	struct bpf_object *obj;
> +	int log_level;
> +};

Can this be extended later?

>  /* Load/unload object into/from kernel */
>  LIBBPF_API int bpf_object__load(struct bpf_object *obj);
> +LIBBPF_API int bpf_object__load_xattr(struct bpf_object_load_attr *attr);
>  LIBBPF_API int bpf_object__unload(struct bpf_object *obj);
>  LIBBPF_API const char *bpf_object__name(struct bpf_object *obj);
>  LIBBPF_API unsigned int bpf_object__kversion(struct bpf_object *obj);
> diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
> index 673001787cba..6ce61fa0baf3 100644
> --- a/tools/lib/bpf/libbpf.map
> +++ b/tools/lib/bpf/libbpf.map
> @@ -164,3 +164,8 @@ LIBBPF_0.0.3 {
>  		bpf_map_freeze;
>  		btf__finalize_data;
>  } LIBBPF_0.0.2;
> +
> +LIBBPF_0.0.4 {
> +	global:
> +		bpf_object__load_xattr;
> +} LIBBPF_0.0.3;



-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer