linux-kernel - Re: [PATCH] perf buildid-cache: recognize vdso when adding files

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Message-ID: <096d999a-780b-446d-aaed-0415411003a8@intel.com>
Date: Thu, 12 Sep 2024 14:56:49 +0300
From: Adrian Hunter <adrian.hunter@...el.com>
To: Changbin Du <changbin.du@...wei.com>,
 Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
 Arnaldo Carvalho de Melo <acme@...nel.org>,
 Namhyung Kim <namhyung@...nel.org>
Cc: Mark Rutland <mark.rutland@....com>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
 Jiri Olsa <jolsa@...nel.org>, Ian Rogers <irogers@...gle.com>,
 "Liang, Kan" <kan.liang@...ux.intel.com>, linux-perf-users@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perf buildid-cache: recognize vdso when adding files

On 12/09/24 14:16, Changbin Du wrote:
> Identify vdso by file name matching. The vdso objects have name
> as vdso[32,64].so[.dbg].
> 
> $ perf buildid-cache -a /work/linux/arch/x86/entry/vdso/vdso64.so.dbg
> 
> Without this change, added vdso using above command actually will never
> be used.
> 
> Cc: Adrian Hunter <adrian.hunter@...el.com>
> Signed-off-by: Changbin Du <changbin.du@...wei.com>

I realized my example was overly convoluted since to
overwrite the existing buildid cache entry the --update
option could simply be used.  However, that needs another
change:

diff --git a/tools/perf/builtin-buildid-cache.c
b/tools/perf/builtin-buildid-cache.c
index 08de05e2aaae3..69f43460d007f 100644
--- a/tools/perf/builtin-buildid-cache.c
+++ b/tools/perf/builtin-buildid-cache.c
@@ -353,7 +353,7 @@ static int build_id_cache__update_file(const char
*filename, struct nsinfo *nsi)

 	if (!err)
 		err = build_id_cache__add_s(sbuild_id, filename, nsi, false,
-					    false);
+					    filename_is_vdso(filename));

 	pr_debug("Updating %s %s: %s\n", sbuild_id, filename,
 		 err ? "FAIL" : "Ok");

With that you can add:

Reviewed-by: Adrian Hunter <adrian.hunter@...el.com>
Tested-by: Adrian Hunter <adrian.hunter@...el.com>


> 
> ---
> This patch is separated from the series "perf: Support searching local
> debugging vdso or specify vdso path in cmdline".
> ---
>  tools/perf/builtin-buildid-cache.c | 32 +++++++++++++++++++++++++++++-
>  1 file changed, 31 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/perf/builtin-buildid-cache.c b/tools/perf/builtin-buildid-cache.c
> index b0511d16aeb6..08de05e2aaae 100644
> --- a/tools/perf/builtin-buildid-cache.c
> +++ b/tools/perf/builtin-buildid-cache.c
> @@ -172,6 +172,36 @@ static int build_id_cache__add_kcore(const char *filename, bool force)
>  	return 0;
>  }
>  
> +static bool filename_is_vdso(const char *filename)
> +{
> +	bool is_vdso = false;
> +	char *fname, *bname;
> +	static const char * const vdso_names[] = {
> +		"vdso.so", "vdso32.so", "vdso64.so", "vdsox32.so"
> +	};
> +
> +	fname = strdup(filename);
> +	if (!fname) {
> +		pr_err("no memory\n");
> +		return false;
> +	}
> +
> +	bname = basename(fname);
> +	if (!bname)
> +		goto out;
> +
> +	for (unsigned int i = 0; i < ARRAY_SIZE(vdso_names); i++) {
> +		if (strstarts(bname, vdso_names[i])) {
> +			is_vdso = true;
> +			break;
> +		}
> +	}
> +
> +out:
> +	free(fname);
> +	return is_vdso;
> +}
> +
>  static int build_id_cache__add_file(const char *filename, struct nsinfo *nsi)
>  {
>  	char sbuild_id[SBUILD_ID_SIZE];
> @@ -189,7 +219,7 @@ static int build_id_cache__add_file(const char *filename, struct nsinfo *nsi)
>  
>  	build_id__sprintf(&bid, sbuild_id);
>  	err = build_id_cache__add_s(sbuild_id, filename, nsi,
> -				    false, false);
> +				    false, filename_is_vdso(filename));
>  	pr_debug("Adding %s %s: %s\n", sbuild_id, filename,
>  		 err ? "FAIL" : "Ok");
>  	return err;