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

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  Re: [PATCH 20/31] perf tools: Allow BPF program attach to uprobe  events "Wangnan (F)" <wangnan0@huawei.com> - 2015-10-27 03:30 +0100
    [PATCH] perf tools: Allow BPF program attach to modules Wang Nan <wangnan0@huawei.com> - 2015-10-27 04:10 +0100

#1256411 — 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@huawei.com>
> Cc: Alexei Starovoitov <ast@plumgrid.com>
> Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
> Cc: Daniel Borkmann <daniel@iogearbox.net>
> Cc: David Ahern <dsahern@gmail.com>
> Cc: He Kuang <hekuang@huawei.com>
> Cc: Jiri Olsa <jolsa@kernel.org>
> Cc: Kaixu Xia <xiakaixu@huawei.com>
> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
> Cc: Namhyung Kim <namhyung@kernel.org>
> Cc: Paul Mackerras <paulus@samba.org>
> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
> Cc: Zefan Li <lizefan@huawei.com>
> Cc: pi3orama@163.com
> Cc: Arnaldo Carvalho de Melo <acme@redhat.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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#1256436 — [PATCH] perf tools: Allow BPF program attach to modules

By extending the syntax of BPF object section names, this patch allows
user to attach BPF programs to symbol in modules. For example:

 SEC("module=i915\n"
     "parse_cmds=i915_parse_cmds")
 int parse_cmds(void *ctx)
 {
     return 1;
 }

Implementation is very simple: like what 'perf probe' does, for module,
fill 'uprobe' field in 'struct perf_probe_event'. Other parts would be
done automatically.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: David Ahern <dsahern@gmail.com>
Cc: He Kuang <hekuang@huawei.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kaixu Xia <xiakaixu@huawei.com>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Link: http://lkml.kernel.org/n/ebpf-x1mxko3tby054o573zd575qp@git.kernel.org
---

This patch is based on commit ad14ba45236a496a7ce25f4ea947d245b1406e40
in my git tree[1], and will be appear in the next pull request of this
perf eBPF support patchset.

[1] https://git.kernel.org/cgit/linux/kernel/git/pi3orama/linux.git

---
 tools/perf/util/bpf-loader.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/bpf-loader.c b/tools/perf/util/bpf-loader.c
index b14aff4..a85caae 100644
--- a/tools/perf/util/bpf-loader.c
+++ b/tools/perf/util/bpf-loader.c
@@ -120,10 +120,17 @@ do_config(const char *key, const char *value,
 		pev->target = strdup(value);
 		return 0;
 	}
+	if (strcmp(key, "module") == 0) {
+		pev->uprobes = false;
+		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 'exec=<full patch of file>'\n");
+	pr_warning("\tHint: Currently valid options are:\n");
+	pr_warning("\t          'exec=<full patch of file>'\n");
+	pr_warning("\t          'module=<module name>'\n");
 	return 0;
 }
 
-- 
1.8.3.4

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