linux-kernel - Re: [PATCH 06/39] bpf tools: Create eBPF maps defined in an object file

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Date:	Mon, 13 Jul 2015 16:54:53 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Wang Nan <wangnan0@...wei.com>
Cc:	ast@...mgrid.com, linux-kernel@...r.kernel.org, lizefan@...wei.com,
	hekuang@...wei.com, xiakaixu@...wei.com, pi3orama@....com
Subject: Re: [PATCH 06/39] bpf tools: Create eBPF maps defined in an object
 file

Em Thu, Jul 09, 2015 at 12:35:09PM +0000, Wang Nan escreveu:

<SNIP>

> +static int
> +bpf_object__create_maps(struct bpf_object *obj)
> +{
> +	unsigned int i;
> +	size_t nr_maps;
> +	int *pfd;
> +
> +	nr_maps = obj->maps_buf_sz / sizeof(struct bpf_map_def);
> +	if (!obj->maps_buf || !nr_maps) {
> +		pr_debug("don't need create maps for %s\n",
> +			 obj->path);
> +		return 0;
> +	}
> +
> +	obj->map_fds = malloc(sizeof(int) * nr_maps);
> +	if (!obj->map_fds) {
> +		pr_warning("realloc perf_bpf_map_fds failed\n");
> +		return -ENOMEM;
> +	}
> +	obj->nr_map_fds = nr_maps;
> +
> +	/* fill all fd with -1 */
> +	memset(obj->map_fds, 0xff, sizeof(int) * nr_maps);

Huh? Each entry is an int... If you want to set it all to -1, why don't
you do it as:

	memset(obj->map_fds, -1, sizeof(int) * nr_maps);

That way we can even remove that comment :) Doing it, please let me know
if this has some magic twist that makes it be right as-is, if so, please
provide a better comment.

- Arnaldo

> +
> +	pfd = obj->map_fds;
> +	for (i = 0; i < nr_maps; i++) {
> +		struct bpf_map_def def;
> +
> +		def = *(struct bpf_map_def *)(obj->maps_buf +
> +				i * sizeof(struct bpf_map_def));
> +
> +		*pfd = bpf_create_map(def.type,
> +				      def.key_size,
> +				      def.value_size,
> +				      def.max_entries);
> +		if (*pfd < 0) {
> +			size_t j;
> +			int err = *pfd;
> +
> +			pr_warning("failed to create map: %s\n",
> +				   strerror(errno));
> +			for (j = 0; j < i; j++)
> +				zclose(obj->map_fds[j]);
> +			obj->nr_map_fds = 0;
> +			zfree(&obj->map_fds);
> +			return err;
> +		}
> +		pr_debug("create map: fd=%d\n", *pfd);
> +		pfd++;
> +	}
> +
> +	zfree(&obj->maps_buf);
> +	obj->maps_buf_sz = 0;
> +	return 0;
> +}
> +
>  static int bpf_object__collect_reloc(struct bpf_object *obj)
>  {
>  	int i, err;
> @@ -671,6 +736,42 @@ struct bpf_object *bpf_object__open_buffer(void *obj_buf,
>  	return __bpf_object__open("[buffer]", obj_buf, obj_buf_sz);
>  }
>  
> +int bpf_object__unload(struct bpf_object *obj)
> +{
> +	size_t i;
> +
> +	if (!obj)
> +		return -EINVAL;
> +
> +	for (i = 0; i < obj->nr_map_fds; i++)
> +		zclose(obj->map_fds[i]);
> +	zfree(&obj->map_fds);
> +	obj->nr_map_fds = 0;
> +
> +	return 0;
> +}
> +
> +int bpf_object__load(struct bpf_object *obj)
> +{
> +	if (!obj)
> +		return -EINVAL;
> +
> +	if (obj->loaded) {
> +		pr_warning("object should not be loaded twice\n");
> +		return -EINVAL;
> +	}
> +
> +	obj->loaded = true;
> +	if (bpf_object__create_maps(obj))
> +		goto out;
> +
> +	return 0;
> +out:
> +	bpf_object__unload(obj);
> +	pr_warning("failed to load object '%s'\n", obj->path);
> +	return -EINVAL;
> +}
> +
>  void bpf_object__close(struct bpf_object *obj)
>  {
>  	size_t i;
> @@ -679,6 +780,7 @@ void bpf_object__close(struct bpf_object *obj)
>  		return;
>  
>  	bpf_object__elf_finish(obj);
> +	bpf_object__unload(obj);
>  
>  	zfree(&obj->maps_buf);
>  
> diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
> index 6e75acd..3e69600 100644
> --- a/tools/lib/bpf/libbpf.h
> +++ b/tools/lib/bpf/libbpf.h
> @@ -30,6 +30,10 @@ struct bpf_object *bpf_object__open_buffer(void *obj_buf,
>  					   size_t obj_buf_sz);
>  void bpf_object__close(struct bpf_object *object);
>  
> +/* Load/unload object into/from kernel */
> +int bpf_object__load(struct bpf_object *obj);
> +int bpf_object__unload(struct bpf_object *obj);
> +
>  /*
>   * We don't need __attribute__((packed)) now since it is
>   * unnecessary for 'bpf_map_def' because they are all aligned.
> -- 
> 1.8.3.4
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