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Date:	Thu, 26 Nov 2015 17:56:57 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Wang Nan <wangnan0@...wei.com>
Cc:	masami.hiramatsu.pt@...achi.com, ast@...nel.org,
	lizefan@...wei.com, pi3orama@....com, linux-kernel@...r.kernel.org,
	Namhyung Kim <namhyung@...nel.org>
Subject: Re: [PATCH 04/16] bpf tools: Collect map definition in bpf_object

Em Tue, Nov 24, 2015 at 01:36:09PM +0000, Wang Nan escreveu:
>  bpf_object__init_maps(struct bpf_object *obj, void *data,
>  		      size_t size)
>  {
> -	if (size == 0) {
> +	size_t nr_maps;
> +	int i;
> +
> +	nr_maps = size / sizeof(struct bpf_map_def);
> +	if (!data || !nr_maps) {
>  		pr_debug("%s doesn't need map definition\n",
>  			 obj->path);
>  		return 0;
>  	}
>  
> -	obj->maps_buf = malloc(size);
> -	if (!obj->maps_buf) {
> -		pr_warning("malloc maps failed: %s\n", obj->path);
> +	pr_debug("maps in %s: %ld bytes\n", obj->path, (long)size);

We have %zd for these cases, please avoid using cast unnecessarily.

> +
> +	obj->maps = calloc(1, sizeof(obj->maps[0]) * nr_maps);

Hey, calloc does more than just zeroing the allocated memory, that first
member is the number of entries, so you could do it as:

	obj->maps = calloc(nr_maps, sizeof(obj->maps[0]));

To use that 'nmemb' first parameter and to make the whole thing a bit
more compact.

> +	if (!obj->maps) {
> +		pr_warning("alloc maps for object failed\n");
>  		return -ENOMEM;
>  	}
> +	obj->nr_maps = nr_maps;
>  
> -	obj->maps_buf_sz = size;
> -	memcpy(obj->maps_buf, data, size);
> -	pr_debug("maps in %s: %ld bytes\n", obj->path, (long)size);
> +	for (i = 0; i < nr_maps; i++) {
> +		struct bpf_map_def *def = &obj->maps[i].def;
> +
> +		/*
> +		 * fill all fd with -1 so won't close incorrect
> +		 * fd (0, stdin) when failure.
> +		 */
> +		obj->maps[i].fd = -1;
> +
> +		/* Save map definition into obj->maps */
> +		*def = *(struct bpf_map_def *)(data +
> +				i * sizeof(struct bpf_map_def));

This gets more clear/compact as:

		*def = ((struct bpf_map_def *)data)[i];

Testing:

[acme@zoo c]$ cat void_long.c 
#include <stdio.h>

void main(void)
{
	long a[] = { 0, 21, 332, 4443, 5554 };
	void *v = &a;
	int i;

	for (i = 0; i < 5; ++i)
		printf("++((long *)v)[%d]=%ld\n", i, ++((long *)v)[i]);
}
[acme@zoo c]$ make void_long
cc     void_long.c   -o void_long
[acme@zoo c]$ ./void_long 
++((long *)v)[0]=1
++((long *)v)[1]=22
++((long *)v)[2]=333
++((long *)v)[3]=4444
++((long *)v)[4]=5555
[acme@zoo c]$

> +	}
>  	return 0;
>  }
>  
> @@ -688,37 +707,15 @@ 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);

perhaps calloc?

> -	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, -1, sizeof(int) * nr_maps);
> +	for (i = 0; i < obj->nr_maps; i++) {
> +		struct bpf_map_def *def = &obj->maps[i].def;
> +		int *pfd = &obj->maps[i].fd;
>  
> -	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);
> +		*pfd = bpf_create_map(def->type,
> +				      def->key_size,
> +				      def->value_size,
> +				      def->max_entries);
>  		if (*pfd < 0) {
>  			size_t j;
>  			int err = *pfd;
> @@ -726,22 +723,17 @@ bpf_object__create_maps(struct bpf_object *obj)
>  			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);
> +				zclose(obj->maps[j].fd);
>  			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_program__relocate(struct bpf_program *prog, int *map_fds)
> +bpf_program__relocate(struct bpf_program *prog, struct bpf_object *obj)
>  {
>  	int i;
>  
> @@ -761,7 +753,7 @@ bpf_program__relocate(struct bpf_program *prog, int *map_fds)
>  			return -LIBBPF_ERRNO__RELOC;
>  		}
>  		insns[insn_idx].src_reg = BPF_PSEUDO_MAP_FD;
> -		insns[insn_idx].imm = map_fds[map_idx];
> +		insns[insn_idx].imm = obj->maps[map_idx].fd;
>  	}
>  
>  	zfree(&prog->reloc_desc);
> @@ -780,7 +772,7 @@ bpf_object__relocate(struct bpf_object *obj)
>  	for (i = 0; i < obj->nr_programs; i++) {
>  		prog = &obj->programs[i];
>  
> -		err = bpf_program__relocate(prog, obj->map_fds);
> +		err = bpf_program__relocate(prog, obj);
>  		if (err) {
>  			pr_warning("failed to relocate '%s'\n",
>  				   prog->section_name);
> @@ -804,8 +796,7 @@ static int bpf_object__collect_reloc(struct bpf_object *obj)
>  		Elf_Data *data = obj->efile.reloc[i].data;
>  		int idx = shdr->sh_info;
>  		struct bpf_program *prog;
> -		size_t nr_maps = obj->maps_buf_sz /
> -				 sizeof(struct bpf_map_def);
> +		size_t nr_maps = obj->nr_maps;
>  
>  		if (shdr->sh_type != SHT_REL) {
>  			pr_warning("internal error at %d\n", __LINE__);
> @@ -1050,10 +1041,8 @@ int bpf_object__unload(struct bpf_object *obj)
>  	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;
> +	for (i = 0; i < obj->nr_maps; i++)
> +		zclose(obj->maps[i].fd);
>  
>  	for (i = 0; i < obj->nr_programs; i++)
>  		bpf_program__unload(&obj->programs[i]);
> @@ -1096,7 +1085,15 @@ void bpf_object__close(struct bpf_object *obj)
>  	bpf_object__elf_finish(obj);
>  	bpf_object__unload(obj);
>  
> -	zfree(&obj->maps_buf);
> +	for (i = 0; i < obj->nr_maps; i++) {
> +		if (obj->maps[i].clear_priv)
> +			obj->maps[i].clear_priv(&obj->maps[i],
> +						obj->maps[i].priv);
> +		obj->maps[i].priv = NULL;
> +		obj->maps[i].clear_priv = NULL;
> +	}
> +	zfree(&obj->maps);
> +	obj->nr_maps = 0;
>  
>  	if (obj->programs && obj->nr_programs) {
>  		for (i = 0; i < obj->nr_programs; i++)
> @@ -1251,3 +1248,72 @@ int bpf_program__nth_fd(struct bpf_program *prog, int n)
>  
>  	return fd;
>  }
> +
> +int bpf_map__get_fd(struct bpf_map *map)
> +{
> +	if (!map)
> +		return -EINVAL;
> +
> +	return map->fd;
> +}
> +
> +int bpf_map__get_def(struct bpf_map *map, struct bpf_map_def *pdef)
> +{
> +	if (!map || !pdef)
> +		return -EINVAL;
> +
> +	*pdef = map->def;
> +	return 0;
> +}
> +
> +int bpf_map__set_private(struct bpf_map *map, void *priv,
> +			 bpf_map_clear_priv_t clear_priv)
> +{
> +	if (!map)
> +		return -EINVAL;
> +
> +	if (map->priv) {
> +		if (map->clear_priv)
> +			map->clear_priv(map, map->priv);
> +	}
> +
> +	map->priv = priv;
> +	map->clear_priv = clear_priv;
> +	return 0;
> +}
> +
> +int bpf_map__get_private(struct bpf_map *map, void **ppriv)
> +{
> +	if (!map)
> +		return -EINVAL;
> +
> +	if (ppriv)
> +		*ppriv = map->priv;
> +	return 0;
> +}
> +
> +struct bpf_map *
> +bpf_map__next(struct bpf_map *prev, struct bpf_object *obj)
> +{
> +	size_t idx;
> +	struct bpf_map *s, *e;
> +
> +	if (!obj || !obj->maps)
> +		return NULL;
> +
> +	s = obj->maps;
> +	e = obj->maps + obj->nr_maps;
> +
> +	if (prev == NULL)
> +		return s;
> +
> +	if ((prev < s) || (prev >= e)) {
> +		pr_warning("error: map handler doesn't belong to object\n");

I wonder if this shouldn't be made pr_debug, and as well have a function
prefix, otherwise we may think this is related to some other kind of
map, so I suggest:
		pr_debug("%s: error: map handler doesn't belong to object\n", __func__);

Or at least:

		pr_debug("BPF error: map handler doesn't belong to object\n");

> +		return NULL;
> +	}
> +
> +	idx = (prev - obj->maps) + 1;
> +	if (idx >= obj->nr_maps)
> +		return NULL;
> +	return &obj->maps[idx];
> +}
> diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
> index 949df4b..709d2fa 100644
> --- a/tools/lib/bpf/libbpf.h
> +++ b/tools/lib/bpf/libbpf.h
> @@ -165,4 +165,25 @@ struct bpf_map_def {
>  	unsigned int max_entries;
>  };
>  
> +/*
> + * There is another 'struct bpf_map' in include/linux/map.h. However,
> + * it is not a uapi header so no need to consider name confliction.

             s/confliction/conflict/g

But I would use "name clash".

> + */
> +struct bpf_map;
> +
> +struct bpf_map *
> +bpf_map__next(struct bpf_map *map, struct bpf_object *obj);
> +#define bpf_map__for_each(pos, obj)		\
> +	for ((pos) = bpf_map__next(NULL, (obj));	\
> +	     (pos) != NULL;				\
> +	     (pos) = bpf_map__next((pos), (obj)))
> +
> +int bpf_map__get_fd(struct bpf_map *map);
> +int bpf_map__get_def(struct bpf_map *map, struct bpf_map_def *pdef);
> +
> +typedef void (*bpf_map_clear_priv_t)(struct bpf_map *, void *);
> +int bpf_map__set_private(struct bpf_map *map, void *priv,
> +			 bpf_map_clear_priv_t clear_priv);
> +int bpf_map__get_private(struct bpf_map *map, void **ppriv);
> +
>  #endif
> -- 
> 1.8.3.4
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