linux-kernel - Re: [PATCH v2 2/9] perf script: Add options for custom vdso path

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Date:	Tue, 10 May 2016 10:44:27 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	He Kuang <hekuang@...wei.com>
Cc:	peterz@...radead.org, mingo@...hat.com,
	alexander.shishkin@...ux.intel.com, jolsa@...hat.com,
	wangnan0@...wei.com, jpoimboe@...hat.com, ak@...ux.intel.com,
	eranian@...gle.com, namhyung@...nel.org, adrian.hunter@...el.com,
	sukadev@...ux.vnet.ibm.com, masami.hiramatsu.pt@...achi.com,
	tumanova@...ux.vnet.ibm.com, kan.liang@...el.com,
	penberg@...nel.org, dsahern@...il.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/9] perf script: Add options for custom vdso path

Em Tue, May 10, 2016 at 07:40:30AM +0000, He Kuang escreveu:
> When unwinding callchains on a different machine, vdso info should be
> provided so the unwind process won't be interrupted if address falls
> into vdso region.
> 
> Currently, perf does try to read vdso binary in '.debug' folder, but
> the filename of the vdso file is generated randomly based on
> VDSO__TEMP_FILE_NAME template, such a filename is not reliable and
> users need a way to provide the path of their own vdso binary file.

But this becomes one more burden to the user :-\ Why not calculate a
build-id from the VDSO file contents, copy it to
~/.debug/.build-id/ab/cdef01020304 and insert that into the perf.data
file so that at analysis time we do all this automatically?

We can of course have a way to manually provide it, but having it as the
main way for users doesn't seem a good interface. Am I missing
something?

- Arnaldo
 
> Signed-off-by: He Kuang <hekuang@...wei.com>
> ---
>  tools/perf/builtin-script.c | 2 ++
>  tools/perf/util/dso.c       | 7 +++++++
>  tools/perf/util/dso.h       | 1 +
>  tools/perf/util/symbol.c    | 1 +
>  tools/perf/util/symbol.h    | 1 +
>  5 files changed, 12 insertions(+)
> 
> diff --git a/tools/perf/builtin-script.c b/tools/perf/builtin-script.c
> index 8f6ab2a..c88b547 100644
> --- a/tools/perf/builtin-script.c
> +++ b/tools/perf/builtin-script.c
> @@ -2001,6 +2001,8 @@ int cmd_script(int argc, const char **argv, const char *prefix __maybe_unused)
>  		   "file", "vmlinux pathname"),
>  	OPT_STRING(0, "kallsyms", &symbol_conf.kallsyms_name,
>  		   "file", "kallsyms pathname"),
> +	OPT_STRING(0, "vdso", &symbol_conf.vdso_name,
> +		   "file", "vdso pathname"),
>  	OPT_BOOLEAN('G', "hide-call-graph", &no_callchain,
>  		    "When printing symbols do not display call chain"),
>  	OPT_STRING(0, "symfs", &symbol_conf.symfs, "directory",
> diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c
> index 8e639543..6ed1cce 100644
> --- a/tools/perf/util/dso.c
> +++ b/tools/perf/util/dso.c
> @@ -13,6 +13,7 @@ char dso__symtab_origin(const struct dso *dso)
>  	static const char origin[] = {
>  		[DSO_BINARY_TYPE__KALLSYMS]			= 'k',
>  		[DSO_BINARY_TYPE__VMLINUX]			= 'v',
> +		[DSO_BINARY_TYPE__VDSO]				= 'D',
>  		[DSO_BINARY_TYPE__JAVA_JIT]			= 'j',
>  		[DSO_BINARY_TYPE__DEBUGLINK]			= 'l',
>  		[DSO_BINARY_TYPE__BUILD_ID_CACHE]		= 'B',
> @@ -113,6 +114,11 @@ int dso__read_binary_type_filename(const struct dso *dso,
>  			 build_id_hex, build_id_hex + 2);
>  		break;
>  
> +	case DSO_BINARY_TYPE__VDSO:
> +	{
> +		snprintf(filename, size, "%s", symbol_conf.vdso_name);
> +		break;
> +	}
>  	case DSO_BINARY_TYPE__VMLINUX:
>  	case DSO_BINARY_TYPE__GUEST_VMLINUX:
>  	case DSO_BINARY_TYPE__SYSTEM_PATH_DSO:
> @@ -487,6 +493,7 @@ static void try_to_open_dso(struct dso *dso, struct machine *machine)
>  	enum dso_binary_type binary_type_data[] = {
>  		DSO_BINARY_TYPE__BUILD_ID_CACHE,
>  		DSO_BINARY_TYPE__SYSTEM_PATH_DSO,
> +		DSO_BINARY_TYPE__VDSO,
>  		DSO_BINARY_TYPE__NOT_FOUND,
>  	};
>  	int i = 0;
> diff --git a/tools/perf/util/dso.h b/tools/perf/util/dso.h
> index 0953280..05fac98 100644
> --- a/tools/perf/util/dso.h
> +++ b/tools/perf/util/dso.h
> @@ -30,6 +30,7 @@ enum dso_binary_type {
>  	DSO_BINARY_TYPE__KCORE,
>  	DSO_BINARY_TYPE__GUEST_KCORE,
>  	DSO_BINARY_TYPE__OPENEMBEDDED_DEBUGINFO,
> +	DSO_BINARY_TYPE__VDSO,
>  	DSO_BINARY_TYPE__NOT_FOUND,
>  };
>  
> diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
> index e7588dc..4630751 100644
> --- a/tools/perf/util/symbol.c
> +++ b/tools/perf/util/symbol.c
> @@ -1363,6 +1363,7 @@ static bool dso__is_compatible_symtab_type(struct dso *dso, bool kmod,
>  	case DSO_BINARY_TYPE__UBUNTU_DEBUGINFO:
>  	case DSO_BINARY_TYPE__BUILDID_DEBUGINFO:
>  	case DSO_BINARY_TYPE__OPENEMBEDDED_DEBUGINFO:
> +	case DSO_BINARY_TYPE__VDSO:
>  		return !kmod && dso->kernel == DSO_TYPE_USER;
>  
>  	case DSO_BINARY_TYPE__KALLSYMS:
> diff --git a/tools/perf/util/symbol.h b/tools/perf/util/symbol.h
> index c8b7544..4e6910e 100644
> --- a/tools/perf/util/symbol.h
> +++ b/tools/perf/util/symbol.h
> @@ -114,6 +114,7 @@ struct symbol_conf {
>  			report_hierarchy;
>  	const char	*vmlinux_name,
>  			*kallsyms_name,
> +			*vdso_name,
>  			*source_prefix,
>  			*field_sep;
>  	const char	*default_guest_vmlinux_name,
> -- 
> 1.8.5.2