linux-kernel - Re: [RFC PATCH 09/22] perf bpf: collect map definitions.

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Date:	Mon, 11 May 2015 15:32:10 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	Wang Nan <wangnan0@...wei.com>
Cc:	ast@...mgrid.com, davem@...emloft.net, acme@...nel.org,
	mingo@...hat.com, a.p.zijlstra@...llo.nl,
	masami.hiramatsu.pt@...achi.com, jolsa@...nel.org,
	lizefan@...nel.org, linux-kernel@...r.kernel.org, pi3orama@....com,
	hekuang@...wei.com
Subject: Re: [RFC PATCH 09/22] perf bpf: collect map definitions.

On Thu, Apr 30, 2015 at 10:52:32AM +0000, Wang Nan wrote:
> If maps are used by eBPF programs, corresponding object file(s) should
> contain a section named 'map'. Which contains map definitions, one for
> each map to describe its format. 'struct perf_bpf_map_def' is
> introduced as part of protocol between perf and eBPF programs. All map
> definitions are copied to obj->maps.
> 
> bpf.h is introduced for common bpf operations.
> 
> Signed-off-by: Wang Nan <wangnan0@...wei.com>
> ---
>  tools/perf/util/bpf-loader.c | 31 +++++++++++++++++++++++++++++++
>  tools/perf/util/bpf-loader.h |  3 +++
>  2 files changed, 34 insertions(+)
> 
> diff --git a/tools/perf/util/bpf-loader.c b/tools/perf/util/bpf-loader.c
> index 296fb06..bf3b793 100644
> --- a/tools/perf/util/bpf-loader.c
> +++ b/tools/perf/util/bpf-loader.c
> @@ -65,6 +65,8 @@ static void bpf_obj_close(struct bpf_obj *obj)
>  
>  	if (obj->path)
>  		free(obj->path);
> +	if (obj->maps)
> +		free(obj->maps);
>  	free(obj);
>  }
>  
> @@ -183,6 +185,32 @@ static int bpf_obj_kver_init(struct bpf_obj *obj,
>  	return 0;
>  }
>  
> +static int bpf_obj_maps_init(struct bpf_obj *obj, void *data,
> +			     size_t size)
> +{
> +	size_t map_def_sz = sizeof(struct bpf_map_def);
> +	int nr_maps = size / map_def_sz;
> +
> +	if (nr_maps == 0) {
> +		pr_debug("bpf: %s doesn't need map definition\n",
> +			 obj->path);
> +		return 0;
> +	}
> +
> +	obj->maps = malloc(nr_maps * map_def_sz);
> +	if (!obj->maps) {
> +		pr_err("bpf: malloc maps failed: %s\n", obj->path);
> +		return -ENOMEM;
> +	}
> +
> +	obj->nr_maps = nr_maps;
> +	memcpy(obj->maps, data, nr_maps * map_def_sz);

Doesn't it need to swap the data as it's binary?

Thanks,
Namhyung


> +	pr_debug("bpf: %d map%s in %s\n", nr_maps,
> +			nr_maps > 1 ? "s" : "",
> +			obj->path);
> +	return 0;
> +}
> +
>  static int bpf_obj_elf_collect(struct bpf_obj *obj)
>  {
>  	Elf *elf = obj->elf.elf;
> @@ -237,6 +265,9 @@ static int bpf_obj_elf_collect(struct bpf_obj *obj)
>  		else if (strcmp(name, "version") == 0)
>  			err = bpf_obj_kver_init(obj, data->d_buf,
>  						data->d_size);
> +		else if (strcmp(name, "maps") == 0)
> +			err = bpf_obj_maps_init(obj, data->d_buf,
> +						data->d_size);
>  		if (err)
>  			goto out;
>  	}
> diff --git a/tools/perf/util/bpf-loader.h b/tools/perf/util/bpf-loader.h
> index e1d5c42..6c5c8d6 100644
> --- a/tools/perf/util/bpf-loader.h
> +++ b/tools/perf/util/bpf-loader.h
> @@ -14,6 +14,7 @@
>  #include "perf.h"
>  #include "symbol.h"
>  #include "probe-event.h"
> +#include "bpf.h"
>  
>  int bpf__load(const char *path);
>  int bpf__run(void);
> @@ -25,6 +26,8 @@ struct bpf_obj {
>  	bool needs_swap;
>  	char license[64];
>  	u32 kern_version;
> +	struct bpf_map_def *maps;
> +	size_t nr_maps;
>  
>  	/*
>  	 * Information when doing elf related work. Only valid if fd
> -- 
> 1.8.3.4
> 
> --
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