linux-kernel - Re: [PATCH 20/31] perf tools: Allow BPF program attach to uprobe events

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Date:	Tue, 27 Oct 2015 10:28:09 +0800
From:	"Wangnan (F)" <wangnan0@...wei.com>
To:	<acme@...nel.org>, <ast@...mgrid.com>, <brendan.d.gregg@...il.com>
CC:	<a.p.zijlstra@...llo.nl>, <daniel@...earbox.net>,
	<dsahern@...il.com>, <hekuang@...wei.com>, <jolsa@...nel.org>,
	<lizefan@...wei.com>, <masami.hiramatsu.pt@...achi.com>,
	<namhyung@...nel.org>, <paulus@...ba.org>,
	<linux-kernel@...r.kernel.org>, <pi3orama@....com>,
	<xiakaixu@...wei.com>, Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: Re: [PATCH 20/31] perf tools: Allow BPF program attach to uprobe
 events



On 2015/10/14 20:41, Wang Nan wrote:
> This patch appends new syntax to BPF object section name to support
> probing at uprobe event. Now we can use BPF program like this:
>
>   SEC(
>   "target=/lib64/libc.so.6\n"
>   "libcwrite=__write"
>   )
>   int libcwrite(void *ctx)
>   {
>       return 1;
>   }
>
> Where, in section name of a program, before the main config string,
> we can use 'key=value' style options. Now the only option key "target"
> is for uprobe probing.
>
> Signed-off-by: Wang Nan <wangnan0@...wei.com>
> Cc: Alexei Starovoitov <ast@...mgrid.com>
> Cc: Brendan Gregg <brendan.d.gregg@...il.com>
> Cc: Daniel Borkmann <daniel@...earbox.net>
> Cc: David Ahern <dsahern@...il.com>
> Cc: He Kuang <hekuang@...wei.com>
> Cc: Jiri Olsa <jolsa@...nel.org>
> Cc: Kaixu Xia <xiakaixu@...wei.com>
> Cc: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
> Cc: Namhyung Kim <namhyung@...nel.org>
> Cc: Paul Mackerras <paulus@...ba.org>
> Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> Cc: Zefan Li <lizefan@...wei.com>
> Cc: pi3orama@....com
> Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
> Link: http://lkml.kernel.org/n/ebpf-6yw9eg0ej3l4jnqhinngkw86@git.kernel.org
> ---
>   tools/perf/util/bpf-loader.c | 86 ++++++++++++++++++++++++++++++++++++++++----
>   1 file changed, 80 insertions(+), 6 deletions(-)
>
> diff --git a/tools/perf/util/bpf-loader.c b/tools/perf/util/bpf-loader.c
> index af549ea..73ff9a9 100644
> --- a/tools/perf/util/bpf-loader.c
> +++ b/tools/perf/util/bpf-loader.c
> @@ -111,6 +111,84 @@ bpf_prog_priv__clear(struct bpf_program *prog __maybe_unused,
>   }
>   
>   static int
> +do_config(const char *key, const char *value,
> +	  struct perf_probe_event *pev)
> +{
> +	pr_debug("config bpf program: %s=%s\n", key, value);
> +	if (strcmp(key, "target") == 0) {
> +		pev->uprobes = true;
> +		pev->target = strdup(value);
> +		return 0;
> +	}
> +
> +	pr_warning("BPF: WARNING: invalid config option in object: %s=%s\n",
> +		   key, value);
> +	pr_warning("\tHint: Currently only valid option is 'target=<file>'\n");
> +	return 0;
> +}
>

This part is very easy to be extended to support probing at modules.
I'd like to change "target" to "exec" to make it unify with perf probe,
then add another patch to support module probing in next pull request.

Thank you.

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