Re: [PATCH] perf tests: Fix false TEST_OK result for 'perf test hist'

[Namhyung Kim <namhyung@kernel.org>]

Hi,

On Tue, Dec 15, 2015 at 04:18:44AM +0000, Wang Nan wrote:
> Commit 71d6de64feddd4b455555326fba2111b3006d9e0 ('perf test: Fix hist
> testcases when kptr_restrict is on') solves a double free problem when
> 'perf test hist' calling setup_fake_machine(). However, the result is
> still incorrect. For example:
> 
>  $ ./perf test -v 'filtering hist entries'
>  25: Test filtering hist entries                              :
>  --- start ---
>  test child forked, pid 4186
>  Cannot create kernel maps
>  test child finished with 0
>  ---- end ----
>  Test filtering hist entries: Ok
> 
> In this case the body of this test is not get executed at all, but the
> result is 'Ok'. I think 'Skip' should be better.

Right, I missed this part.

But on second thought, I think it should not create real kernel maps.
What setup_fake_machine() does is to create/insert fake
dso/mmap/symbols for testing hist functions.  So it has to use the
predefined info not real ones.


> 
> The reason is that *ALL* hists test cases forget to reset err after
> using it to hold an error code.
> 
> This patch ensure err is reset.
> 
> In case when kptr_restrict prevent normal user get kernel address, this
> test should be skipped, not fail. This patch uses linux/err.h to store
> error code in return value of setup_fake_machine(), and let 'EACCES' to
> indicate this problem.

Please just remove the machine__create_kernel_maps() in
setup_fake_machine() and simply return TEST_FAIL if there's an error.

Thanks,
Namhyung


> 
> Signed-off-by: Wang Nan <wangnan0@huawei.com>
> Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
> Cc: Jiri Olsa <jolsa@kernel.org>
> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
> Cc: Namhyung Kim <namhyung@kernel.org>
> ---
>  tools/perf/tests/hists_common.c   | 12 +++++++++---
>  tools/perf/tests/hists_common.h   |  1 +
>  tools/perf/tests/hists_cumulate.c |  6 +++++-
>  tools/perf/tests/hists_filter.c   |  6 +++++-
>  tools/perf/tests/hists_link.c     |  6 +++++-
>  tools/perf/tests/hists_output.c   |  6 +++++-
>  6 files changed, 30 insertions(+), 7 deletions(-)
> 
> diff --git a/tools/perf/tests/hists_common.c b/tools/perf/tests/hists_common.c
> index bcfd081..2eca1b2 100644
> --- a/tools/perf/tests/hists_common.c
> +++ b/tools/perf/tests/hists_common.c
> @@ -81,15 +81,20 @@ struct machine *setup_fake_machine(struct machines *machines)
>  {
>  	struct machine *machine = machines__find(machines, HOST_KERNEL_ID);
>  	size_t i;
> +	int err = -ENOMEM;
>  
>  	if (machine == NULL) {
>  		pr_debug("Not enough memory for machine setup\n");
> -		return NULL;
> +		return ERR_PTR(-ENOMEM);
>  	}
>  
>  	if (machine__create_kernel_maps(machine)) {
>  		pr_debug("Cannot create kernel maps\n");
> -		return NULL;
> +		if (symbol_conf.kptr_restrict) {
> +			pr_debug("Hint: Check /proc/sys/kernel/kptr_restrict.\n");
> +			err = -EACCES;
> +		}
> +		return ERR_PTR(err);
>  	}
>  
>  	for (i = 0; i < ARRAY_SIZE(fake_threads); i++) {
> @@ -155,7 +160,8 @@ struct machine *setup_fake_machine(struct machines *machines)
>  out:
>  	pr_debug("Not enough memory for machine setup\n");
>  	machine__delete_threads(machine);
> -	return NULL;
> +	machine__exit(machine);
> +	return ERR_PTR(err);
>  }
>  
>  void print_hists_in(struct hists *hists)
> diff --git a/tools/perf/tests/hists_common.h b/tools/perf/tests/hists_common.h
> index 888254e..0252eae 100644
> --- a/tools/perf/tests/hists_common.h
> +++ b/tools/perf/tests/hists_common.h
> @@ -1,5 +1,6 @@
>  #ifndef __PERF_TESTS__HISTS_COMMON_H__
>  #define __PERF_TESTS__HISTS_COMMON_H__
> +#include <linux/err.h>
>  
>  struct machine;
>  struct machines;
> diff --git a/tools/perf/tests/hists_cumulate.c b/tools/perf/tests/hists_cumulate.c
> index 8292948..c211075 100644
> --- a/tools/perf/tests/hists_cumulate.c
> +++ b/tools/perf/tests/hists_cumulate.c
> @@ -706,13 +706,17 @@ int test__hists_cumulate(int subtest __maybe_unused)
>  	err = parse_events(evlist, "cpu-clock", NULL);
>  	if (err)
>  		goto out;
> +	err = TEST_FAIL;
>  
>  	machines__init(&machines);
>  
>  	/* setup threads/dso/map/symbols also */
>  	machine = setup_fake_machine(&machines);
> -	if (!machine)
> +	if (IS_ERR(machine)) {
> +		if (PTR_ERR(machine) == -EACCES)
> +			err = TEST_SKIP;
>  		goto out;
> +	}
>  
>  	if (verbose > 1)
>  		machine__fprintf(machine, stderr);
> diff --git a/tools/perf/tests/hists_filter.c b/tools/perf/tests/hists_filter.c
> index ccb5b49..795a04d 100644
> --- a/tools/perf/tests/hists_filter.c
> +++ b/tools/perf/tests/hists_filter.c
> @@ -120,6 +120,7 @@ int test__hists_filter(int subtest __maybe_unused)
>  	err = parse_events(evlist, "task-clock", NULL);
>  	if (err)
>  		goto out;
> +	err = TEST_FAIL;
>  
>  	/* default sort order (comm,dso,sym) will be used */
>  	if (setup_sorting() < 0)
> @@ -129,8 +130,11 @@ int test__hists_filter(int subtest __maybe_unused)
>  
>  	/* setup threads/dso/map/symbols also */
>  	machine = setup_fake_machine(&machines);
> -	if (!machine)
> +	if (IS_ERR(machine)) {
> +		if (PTR_ERR(machine) == -EACCES)
> +			err = TEST_SKIP;
>  		goto out;
> +	}
>  
>  	if (verbose > 1)
>  		machine__fprintf(machine, stderr);
> diff --git a/tools/perf/tests/hists_link.c b/tools/perf/tests/hists_link.c
> index 6243e2b..f5f37ef9 100644
> --- a/tools/perf/tests/hists_link.c
> +++ b/tools/perf/tests/hists_link.c
> @@ -293,6 +293,7 @@ int test__hists_link(int subtest __maybe_unused)
>  	if (err)
>  		goto out;
>  
> +	err = TEST_FAIL;
>  	/* default sort order (comm,dso,sym) will be used */
>  	if (setup_sorting() < 0)
>  		goto out;
> @@ -301,8 +302,11 @@ int test__hists_link(int subtest __maybe_unused)
>  
>  	/* setup threads/dso/map/symbols also */
>  	machine = setup_fake_machine(&machines);
> -	if (!machine)
> +	if (IS_ERR(machine)) {
> +		if (PTR_ERR(machine) == -EACCES)
> +			err = TEST_SKIP;
>  		goto out;
> +	}
>  
>  	if (verbose > 1)
>  		machine__fprintf(machine, stderr);
> diff --git a/tools/perf/tests/hists_output.c b/tools/perf/tests/hists_output.c
> index 248beec..cc570cf 100644
> --- a/tools/perf/tests/hists_output.c
> +++ b/tools/perf/tests/hists_output.c
> @@ -597,13 +597,17 @@ int test__hists_output(int subtest __maybe_unused)
>  	err = parse_events(evlist, "cpu-clock", NULL);
>  	if (err)
>  		goto out;
> +	err = TEST_FAIL;
>  
>  	machines__init(&machines);
>  
>  	/* setup threads/dso/map/symbols also */
>  	machine = setup_fake_machine(&machines);
> -	if (!machine)
> +	if (IS_ERR(machine)) {
> +		if (PTR_ERR(machine) == -EACCES)
> +			err = TEST_SKIP;
>  		goto out;
> +	}
>  
>  	if (verbose > 1)
>  		machine__fprintf(machine, stderr);
> -- 
> 1.8.3.4
>