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

Namhyung Kim
2015-05-11T06:42:16Z

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@huawei.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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