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

[Wangnan (F)]

On 2015/7/14 3:54, Arnaldo Carvalho de Melo wrote:
> 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.

Yes, it should be better.

Thank you,

> - 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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