linux-kernel - Re: [PATCH] perf test: Enable Symbols test to work with a current module dso

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Date: Wed, 31 Jan 2024 12:58:12 -0800
From: Ian Rogers <irogers@...gle.com>
To: Adrian Hunter <adrian.hunter@...el.com>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>, Jiri Olsa <jolsa@...nel.org>, 
	Namhyung Kim <namhyung@...nel.org>, linux-kernel@...r.kernel.org, 
	linux-perf-users@...r.kernel.org
Subject: Re: [PATCH] perf test: Enable Symbols test to work with a current
 module dso

On Wed, Jan 31, 2024 at 11:24 AM Adrian Hunter <adrian.hunter@...elcom> wrote:
>
> The test needs a struct machine and creates one for the current host,
> but a side-effect is that struct machine has set up kernel maps
> including module maps.
>
> If the 'Symbols' test --dso option specifies a current kernel module,
> it will already be present as a kernel dso, and a map with kmaps needs
> to be used otherwise there will be a segfault - see below.
>
> For that case, find the existing map and use that. In that case also,
> the dso is split by section into multiple dsos, so test those dsos
> also. That in turn, shows up that those dsos have not had overlapping
> symbols removed, so the test fails.
>
> Example:
>
>   Before:
>
>     $ perf test -F -v Symbols --dso /lib/modules/$(uname -r)/kernel/arch/x86/kvm/kvm-intel.ko
>      70: Symbols                                                         :
>     --- start ---
>     Testing /lib/modules/6.7.2-local/kernel/arch/x86/kvm/kvm-intel.ko
>     Segmentation fault (core dumped)
>
>   After:
>
>     $ perf test -F -v Symbols --dso /lib/modules/$(uname -r)/kernel/arch/x86/kvm/kvm-intel.ko
>      70: Symbols                                                         :
>     --- start ---
>     Testing /lib/modules/6.7.2-local/kernel/arch/x86/kvm/kvm-intel.ko
>     Overlapping symbols:
>      41d30-41fbb l vmx_init
>      41d30-41fbb g init_module
>     ---- end ----
>     Symbols: FAILED!
>
> Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>

Reviewed-by: Ian Rogers <irogers@...gle.com>

Thanks,
Ian

> ---
>  tools/perf/tests/symbols.c | 68 ++++++++++++++++++++++++++++++++++++++
>  1 file changed, 68 insertions(+)
>
> diff --git a/tools/perf/tests/symbols.c b/tools/perf/tests/symbols.c
> index 16e1c5502b09..2fed6d67f50f 100644
> --- a/tools/perf/tests/symbols.c
> +++ b/tools/perf/tests/symbols.c
> @@ -41,6 +41,30 @@ static void exit_test_info(struct test_info *ti)
>         machine__delete(ti->machine);
>  }
>
> +struct dso_map {
> +       struct dso *dso;
> +       struct map *map;
> +};
> +
> +static int find_map_cb(struct map *map, void *d)
> +{
> +       struct dso_map *data = d;
> +
> +       if (map__dso(map) != data->dso)
> +               return 0;
> +       data->map = map;
> +       return 1;
> +}
> +
> +static struct map *find_module_map(struct machine *machine, struct dso *dso)
> +{
> +       struct dso_map data = { .dso = dso };
> +
> +       machine__for_each_kernel_map(machine, find_map_cb, &data);
> +
> +       return data.map;
> +}
> +
>  static void get_test_dso_filename(char *filename, size_t max_sz)
>  {
>         if (dso_to_test)
> @@ -51,6 +75,26 @@ static void get_test_dso_filename(char *filename, size_t max_sz)
>
>  static int create_map(struct test_info *ti, char *filename, struct map **map_p)
>  {
> +       struct dso *dso = machine__findnew_dso(ti->machine, filename);
> +
> +       /*
> +        * If 'filename' matches a current kernel module, must use a kernel
> +        * map. Find the one that already exists.
> +        */
> +       if (dso && dso->kernel) {
> +               *map_p = find_module_map(ti->machine, dso);
> +               dso__put(dso);
> +               if (!*map_p) {
> +                       pr_debug("Failed to find map for curent kernel module %s",
> +                                filename);
> +                       return TEST_FAIL;
> +               }
> +               map__get(*map_p);
> +               return TEST_OK;
> +       }
> +
> +       dso__put(dso);
> +
>         /* Create a dummy map at 0x100000 */
>         *map_p = map__new(ti->machine, 0x100000, 0xffffffff, 0, NULL,
>                           PROT_EXEC, 0, NULL, filename, ti->thread);
> @@ -97,6 +141,26 @@ static int test_dso(struct dso *dso)
>         return ret;
>  }
>
> +static int subdivided_dso_cb(struct dso *dso, struct machine *machine __maybe_unused, void *d)
> +{
> +       struct dso *text_dso = d;
> +
> +       if (dso != text_dso && strstarts(dso->short_name, text_dso->short_name))
> +               if (test_dso(dso) != TEST_OK)
> +                       return -1;
> +
> +       return 0;
> +}
> +
> +static int process_subdivided_dso(struct machine *machine, struct dso *dso)
> +{
> +       int ret;
> +
> +       ret = machine__for_each_dso(machine, subdivided_dso_cb, dso);
> +
> +       return ret < 0 ? TEST_FAIL : TEST_OK;
> +}
> +
>  static int test_file(struct test_info *ti, char *filename)
>  {
>         struct map *map = NULL;
> @@ -124,6 +188,10 @@ static int test_file(struct test_info *ti, char *filename)
>         }
>
>         ret = test_dso(dso);
> +
> +       /* Module dso is split into many dsos by section */
> +       if (ret == TEST_OK && dso->kernel)
> +               ret = process_subdivided_dso(ti->machine, dso);
>  out_put:
>         map__put(map);
>
> --
> 2.34.1
>