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

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Date:	Tue, 14 Jul 2015 11:59:25 +0800
From:	"Wangnan (F)" <wangnan0@...wei.com>
To:	Arnaldo Carvalho de Melo <acme@...nel.org>
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



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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