[PATCH] tools/perf/tests: Fix compilation error with strncpy in tests/tool_pmu

perf fails to compile on systems with GCC version11
as below:

In file included from /usr/include/string.h:519,
                 from /home/athir/perf-tools-next/tools/include/linux/bitmap.h:5,
                 from /home/athir/perf-tools-next/tools/perf/util/pmu.h:5,
                 from /home/athir/perf-tools-next/tools/perf/util/evsel.h:14,
                 from /home/athir/perf-tools-next/tools/perf/util/evlist.h:14,
                 from tests/tool_pmu.c:3:
In function ‘strncpy’,
    inlined from ‘do_test’ at tests/tool_pmu.c:25:3:
/usr/include/bits/string_fortified.h:95:10: error: ‘__builtin_strncpy’ specified bound 128 equals destination size [-Werror=stringop-truncation]
   95 |   return __builtin___strncpy_chk (__dest, __src, __len,
      |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   96 |                                   __glibc_objsize (__dest));
      |                                   ~~~~~~~~~~~~~~~~~~~~~~~~~

The compile error is from strncpy refernce in do_test:
	strncpy(str, tool_pmu__event_to_str(ev), sizeof(str));

This behaviour is not observed with GCC version 8, but observed
with GCC version 11 . This is message from gcc for detecting
truncation while using strncpu. Use snprintf instead of strncpy
here to be safe.

Signed-off-by: Athira Rajeev <redacted>
---
 tools/perf/tests/tool_pmu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/tests/tool_pmu.c b/tools/perf/tests/tool_pmu.c
index 94d0dd8fd3cb..297cc8c55579 100644
--- a/tools/perf/tests/tool_pmu.c
+++ b/tools/perf/tests/tool_pmu.c

@@ -22,7 +22,7 @@ static int do_test(enum tool_pmu_event ev, bool with_pmu)
 	if (with_pmu)
 		snprintf(str, sizeof(str), "tool/%s/", tool_pmu__event_to_str(ev));
 	else
-		strncpy(str, tool_pmu__event_to_str(ev), sizeof(str));
+		snprintf(str, sizeof(str), "%s", tool_pmu__event_to_str(ev));
 
 	parse_events_error__init(&err);
 	ret = parse_events(evlist, str, &err);

-- 
2.43.5

Hello Athira,

On Sun, Oct 13, 2024 at 11:07:42PM +0530, Athira Rajeev wrote:

perf fails to compile on systems with GCC version11
as below:

In file included from /usr/include/string.h:519,
                 from /home/athir/perf-tools-next/tools/include/linux/bitmap.h:5,
                 from /home/athir/perf-tools-next/tools/perf/util/pmu.h:5,
                 from /home/athir/perf-tools-next/tools/perf/util/evsel.h:14,
                 from /home/athir/perf-tools-next/tools/perf/util/evlist.h:14,
                 from tests/tool_pmu.c:3:
In function ‘strncpy’,
    inlined from ‘do_test’ at tests/tool_pmu.c:25:3:
/usr/include/bits/string_fortified.h:95:10: error: ‘__builtin_strncpy’ specified bound 128 equals destination size [-Werror=stringop-truncation]
   95 |   return __builtin___strncpy_chk (__dest, __src, __len,
      |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   96 |                                   __glibc_objsize (__dest));
      |                                   ~~~~~~~~~~~~~~~~~~~~~~~~~

The compile error is from strncpy refernce in do_test:
	strncpy(str, tool_pmu__event_to_str(ev), sizeof(str));

This behaviour is not observed with GCC version 8, but observed
with GCC version 11 . This is message from gcc for detecting
truncation while using strncpu. Use snprintf instead of strncpy
here to be safe.

Signed-off-by: Athira Rajeev <redacted>

I found this issue now and thanks for the quick fix.  I will push to
perf-tools-next soon.

Thanks,
Namhyung

On Sun, Oct 13, 2024 at 11:07:42PM +0530, Athira Rajeev wrote:

perf fails to compile on systems with GCC version11
as below:

I have one more build failure on 32 bit systems.  I'll carry this as
well.

Thanks,
Namhyung

---8<---
From 2e2c7ca3691d223d94ea383a6b688e35579d14d5 Mon Sep 17 00:00:00 2001
From: Namhyung Kim <namhyung@kernel.org>
Date: Mon, 14 Oct 2024 10:34:17 -0700
Subject: [PATCH] perf tools: Fix compiler error in util/tool_pmu.c

  util/tool_pmu.c: In function 'evsel__tool_pmu_read':
  util/tool_pmu.c:419:55: error: passing argument 2 of 'tool_pmu__read_event' from incompatible pointer type [-Werror=incompatible-pointer-types]
    419 |                         if (!tool_pmu__read_event(ev, &val)) {
        |                                                       ^~~~
        |                                                       |
        |                                                       long unsigned int *
  util/tool_pmu.c:335:56: note: expected 'u64 *' {aka 'long long unsigned int *'} but argument is of type 'long unsigned int *'
    335 | bool tool_pmu__read_event(enum tool_pmu_event ev, u64 *result)
        |                                                   ~~~~~^~~~~~

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
---
 tools/perf/util/tool_pmu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/util/tool_pmu.c b/tools/perf/util/tool_pmu.c
index ea9d50f0252023dc..bd1cee643eb506df 100644
--- a/tools/perf/util/tool_pmu.c
+++ b/tools/perf/util/tool_pmu.c

@@ -394,7 +394,7 @@ bool tool_pmu__read_event(enum tool_pmu_event ev, u64 *result)
 int evsel__tool_pmu_read(struct evsel *evsel, int cpu_map_idx, int thread)
 {
 	__u64 *start_time, cur_time, delta_start;
-	unsigned long val;
+	u64 val;
 	int fd, err = 0;
 	struct perf_counts_values *count, *old_count = NULL;
 	bool adjust = false;

-- 
2.47.0.rc1.288.g06298d1525-goog

On Sun, 13 Oct 2024 23:07:42 +0530, Athira Rajeev wrote:

perf fails to compile on systems with GCC version11
as below:

In file included from /usr/include/string.h:519,
                 from /home/athir/perf-tools-next/tools/include/linux/bitmap.h:5,
                 from /home/athir/perf-tools-next/tools/perf/util/pmu.h:5,
                 from /home/athir/perf-tools-next/tools/perf/util/evsel.h:14,
                 from /home/athir/perf-tools-next/tools/perf/util/evlist.h:14,
                 from tests/tool_pmu.c:3:
In function ‘strncpy’,
    inlined from ‘do_test’ at tests/tool_pmu.c:25:3:
/usr/include/bits/string_fortified.h:95:10: error: ‘__builtin_strncpy’ specified bound 128 equals destination size [-Werror=stringop-truncation]
   95 |   return __builtin___strncpy_chk (__dest, __src, __len,
      |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   96 |                                   __glibc_objsize (__dest));
      |                                   ~~~~~~~~~~~~~~~~~~~~~~~~~

[...]

Applied to perf-tools-next, thanks!

Best regards,
Namhyung

On 14 Oct 2024, at 10:56 PM, Namhyung Kim [off-list ref] wrote:

Hello Athira,

On Sun, Oct 13, 2024 at 11:07:42PM +0530, Athira Rajeev wrote:

quoted

perf fails to compile on systems with GCC version11
as below:

In file included from /usr/include/string.h:519,
                from /home/athir/perf-tools-next/tools/include/linux/bitmap.h:5,
                from /home/athir/perf-tools-next/tools/perf/util/pmu.h:5,
                from /home/athir/perf-tools-next/tools/perf/util/evsel.h:14,
                from /home/athir/perf-tools-next/tools/perf/util/evlist.h:14,
                from tests/tool_pmu.c:3:
In function ‘strncpy’,
   inlined from ‘do_test’ at tests/tool_pmu.c:25:3:
/usr/include/bits/string_fortified.h:95:10: error: ‘__builtin_strncpy’ specified bound 128 equals destination size [-Werror=stringop-truncation]
  95 |   return __builtin___strncpy_chk (__dest, __src, __len,
     |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  96 |                                   __glibc_objsize (__dest));
     |                                   ~~~~~~~~~~~~~~~~~~~~~~~~~

The compile error is from strncpy refernce in do_test:
strncpy(str, tool_pmu__event_to_str(ev), sizeof(str));

This behaviour is not observed with GCC version 8, but observed
with GCC version 11 . This is message from gcc for detecting
truncation while using strncpu. Use snprintf instead of strncpy
here to be safe.

Signed-off-by: Athira Rajeev <redacted>

I found this issue now and thanks for the quick fix.  I will push to
perf-tools-next soon.

Thanks,
Namhyung

Sure

Thanks Namhyung for pulling in the change

Athira

quoted

---
tools/perf/tests/tool_pmu.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/tests/tool_pmu.c b/tools/perf/tests/tool_pmu.c
index 94d0dd8fd3cb..297cc8c55579 100644
--- a/tools/perf/tests/tool_pmu.c
+++ b/tools/perf/tests/tool_pmu.c

@@ -22,7 +22,7 @@ static int do_test(enum tool_pmu_event ev, bool with_pmu)

if (with_pmu)
snprintf(str, sizeof(str), "tool/%s/", tool_pmu__event_to_str(ev));
else
- strncpy(str, tool_pmu__event_to_str(ev), sizeof(str));
+ snprintf(str, sizeof(str), "%s", tool_pmu__event_to_str(ev));

parse_events_error__init(&err);
ret = parse_events(evlist, str, &err);
-- 
2.43.5

On Wed, Oct 16, 2024 at 5:30 AM Athira Rajeev
[off-list ref] wrote:

quoted

On 14 Oct 2024, at 10:56 PM, Namhyung Kim [off-list ref] wrote:

Hello Athira,

On Sun, Oct 13, 2024 at 11:07:42PM +0530, Athira Rajeev wrote:

quoted

perf fails to compile on systems with GCC version11
as below:

In file included from /usr/include/string.h:519,
                from /home/athir/perf-tools-next/tools/include/linux/bitmap.h:5,
                from /home/athir/perf-tools-next/tools/perf/util/pmu.h:5,
                from /home/athir/perf-tools-next/tools/perf/util/evsel.h:14,
                from /home/athir/perf-tools-next/tools/perf/util/evlist.h:14,
                from tests/tool_pmu.c:3:
In function ‘strncpy’,
   inlined from ‘do_test’ at tests/tool_pmu.c:25:3:
/usr/include/bits/string_fortified.h:95:10: error: ‘__builtin_strncpy’ specified bound 128 equals destination size [-Werror=stringop-truncation]
  95 |   return __builtin___strncpy_chk (__dest, __src, __len,
     |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  96 |                                   __glibc_objsize (__dest));
     |                                   ~~~~~~~~~~~~~~~~~~~~~~~~~

The compile error is from strncpy refernce in do_test:
strncpy(str, tool_pmu__event_to_str(ev), sizeof(str));

This behaviour is not observed with GCC version 8, but observed
with GCC version 11 . This is message from gcc for detecting
truncation while using strncpu. Use snprintf instead of strncpy
here to be safe.

Signed-off-by: Athira Rajeev <redacted>

I found this issue now and thanks for the quick fix.  I will push to
perf-tools-next soon.

Thanks,
Namhyung

Sure

Thanks Namhyung for pulling in the change

Athira

Thanks for the fixes. As this is test code I don't think performance,
style, etc. matter much. The GCC strncpy warnings are annoying imo,
I'm not sure it makes sense for them to be enabled. I see in the
kernel lots of "sizeof(foo)-1" as a workaround. strlcpy looks like a
better alternative but it gets a checkpatch warning as in the kernel
strscpy is preferred. Perhaps we should create a strscpy shim.

Thanks,
Ian

quoted

quoted

---
tools/perf/tests/tool_pmu.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/tests/tool_pmu.c b/tools/perf/tests/tool_pmu.c
index 94d0dd8fd3cb..297cc8c55579 100644
--- a/tools/perf/tests/tool_pmu.c
+++ b/tools/perf/tests/tool_pmu.c

@@ -22,7 +22,7 @@ static int do_test(enum tool_pmu_event ev, bool with_pmu)

if (with_pmu)
snprintf(str, sizeof(str), "tool/%s/", tool_pmu__event_to_str(ev));
else
- strncpy(str, tool_pmu__event_to_str(ev), sizeof(str));
+ snprintf(str, sizeof(str), "%s", tool_pmu__event_to_str(ev));

parse_events_error__init(&err);
ret = parse_events(evlist, str, &err);
--
2.43.5

On 16 Oct 2024, at 8:36 PM, Ian Rogers [off-list ref] wrote:

On Wed, Oct 16, 2024 at 5:30 AM Athira Rajeev
[off-list ref] wrote:

quoted

quoted

On 14 Oct 2024, at 10:56 PM, Namhyung Kim [off-list ref] wrote:

Hello Athira,

On Sun, Oct 13, 2024 at 11:07:42PM +0530, Athira Rajeev wrote:

quoted

perf fails to compile on systems with GCC version11
as below:

In file included from /usr/include/string.h:519,
               from /home/athir/perf-tools-next/tools/include/linux/bitmap.h:5,
               from /home/athir/perf-tools-next/tools/perf/util/pmu.h:5,
               from /home/athir/perf-tools-next/tools/perf/util/evsel.h:14,
               from /home/athir/perf-tools-next/tools/perf/util/evlist.h:14,
               from tests/tool_pmu.c:3:
In function ‘strncpy’,
  inlined from ‘do_test’ at tests/tool_pmu.c:25:3:
/usr/include/bits/string_fortified.h:95:10: error: ‘__builtin_strncpy’ specified bound 128 equals destination size [-Werror=stringop-truncation]
 95 |   return __builtin___strncpy_chk (__dest, __src, __len,
    |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 96 |                                   __glibc_objsize (__dest));
    |                                   ~~~~~~~~~~~~~~~~~~~~~~~~~

The compile error is from strncpy refernce in do_test:
strncpy(str, tool_pmu__event_to_str(ev), sizeof(str));

This behaviour is not observed with GCC version 8, but observed
with GCC version 11 . This is message from gcc for detecting
truncation while using strncpu. Use snprintf instead of strncpy
here to be safe.

Signed-off-by: Athira Rajeev <redacted>

I found this issue now and thanks for the quick fix.  I will push to
perf-tools-next soon.

Thanks,
Namhyung

Sure

Thanks Namhyung for pulling in the change

Athira

Thanks for the fixes. As this is test code I don't think performance,
style, etc. matter much. The GCC strncpy warnings are annoying imo,
I'm not sure it makes sense for them to be enabled. I see in the
kernel lots of "sizeof(foo)-1" as a workaround. strlcpy looks like a
better alternative but it gets a checkpatch warning as in the kernel
strscpy is preferred. Perhaps we should create a strscpy shim.

IIUC, strscpy is defined in kernel source and is currently not used in tools side.

Ian,
Your point here is that we can create an interface in tools side so that we can later safely use strscpy in cases like this ?

Thanks
Athira

Thanks,
Ian

quoted

quoted

quoted

---
tools/perf/tests/tool_pmu.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/tests/tool_pmu.c b/tools/perf/tests/tool_pmu.c
index 94d0dd8fd3cb..297cc8c55579 100644
--- a/tools/perf/tests/tool_pmu.c
+++ b/tools/perf/tests/tool_pmu.c

@@ -22,7 +22,7 @@ static int do_test(enum tool_pmu_event ev, bool with_pmu)

if (with_pmu)
snprintf(str, sizeof(str), "tool/%s/", tool_pmu__event_to_str(ev));
else
- strncpy(str, tool_pmu__event_to_str(ev), sizeof(str));
+ snprintf(str, sizeof(str), "%s", tool_pmu__event_to_str(ev));

parse_events_error__init(&err);
ret = parse_events(evlist, str, &err);
--
2.43.5

On Wed, Oct 16, 2024 at 11:23 AM Athira Rajeev
[off-list ref] wrote:

quoted

On 16 Oct 2024, at 8:36 PM, Ian Rogers [off-list ref] wrote:

On Wed, Oct 16, 2024 at 5:30 AM Athira Rajeev
[off-list ref] wrote:

quoted

quoted

On 14 Oct 2024, at 10:56 PM, Namhyung Kim [off-list ref] wrote:

Hello Athira,

On Sun, Oct 13, 2024 at 11:07:42PM +0530, Athira Rajeev wrote:

quoted

perf fails to compile on systems with GCC version11
as below:

In file included from /usr/include/string.h:519,
               from /home/athir/perf-tools-next/tools/include/linux/bitmap.h:5,
               from /home/athir/perf-tools-next/tools/perf/util/pmu.h:5,
               from /home/athir/perf-tools-next/tools/perf/util/evsel.h:14,
               from /home/athir/perf-tools-next/tools/perf/util/evlist.h:14,
               from tests/tool_pmu.c:3:
In function ‘strncpy’,
  inlined from ‘do_test’ at tests/tool_pmu.c:25:3:
/usr/include/bits/string_fortified.h:95:10: error: ‘__builtin_strncpy’ specified bound 128 equals destination size [-Werror=stringop-truncation]
 95 |   return __builtin___strncpy_chk (__dest, __src, __len,
    |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 96 |                                   __glibc_objsize (__dest));
    |                                   ~~~~~~~~~~~~~~~~~~~~~~~~~

The compile error is from strncpy refernce in do_test:
strncpy(str, tool_pmu__event_to_str(ev), sizeof(str));

This behaviour is not observed with GCC version 8, but observed
with GCC version 11 . This is message from gcc for detecting
truncation while using strncpu. Use snprintf instead of strncpy
here to be safe.

Signed-off-by: Athira Rajeev <redacted>

I found this issue now and thanks for the quick fix.  I will push to
perf-tools-next soon.

Thanks,
Namhyung

Sure

Thanks Namhyung for pulling in the change

Athira

Thanks for the fixes. As this is test code I don't think performance,
style, etc. matter much. The GCC strncpy warnings are annoying imo,
I'm not sure it makes sense for them to be enabled. I see in the
kernel lots of "sizeof(foo)-1" as a workaround. strlcpy looks like a
better alternative but it gets a checkpatch warning as in the kernel
strscpy is preferred. Perhaps we should create a strscpy shim.

IIUC, strscpy is defined in kernel source and is currently not used in tools side.

Ian,
Your point here is that we can create an interface in tools side so that we can later safely use strscpy in cases like this ?

Yeah. Tbh the string code is a bit chaotic in the code base. There's
some stuff using char*s, some asprintf, there's strbuf then there all
the kernel ways of doing things. I lose track of why strscpy is
superior to strlcpy, but strlcpy will get you a checkpath warning.

The standard kernel solution to the GCC strncpy warning I've seen,
changing "strncpy(a, b, sizeof(a))" to "strncpy(a, b, sizeof(a) - 1)",
looks dodgy and possibly worse to me. The point of the warning I think
relates to strncpy not necessarily \0 terminating the string and you
need to reserve at least 1 character for this, while strlcpy
guarantees the \0 termination. Doing "sizeof(..) - 1" likely confuses
the checker making it give up, but now you have less space to copy a
potential \0 as well as not getting a \0.

Thanks,
Ian

Thanks
Athira

quoted

Thanks,
Ian

quoted

quoted

quoted

---
tools/perf/tests/tool_pmu.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/tests/tool_pmu.c b/tools/perf/tests/tool_pmu.c
index 94d0dd8fd3cb..297cc8c55579 100644
--- a/tools/perf/tests/tool_pmu.c
+++ b/tools/perf/tests/tool_pmu.c

@@ -22,7 +22,7 @@ static int do_test(enum tool_pmu_event ev, bool with_pmu)

if (with_pmu)
snprintf(str, sizeof(str), "tool/%s/", tool_pmu__event_to_str(ev));
else
- strncpy(str, tool_pmu__event_to_str(ev), sizeof(str));
+ snprintf(str, sizeof(str), "%s", tool_pmu__event_to_str(ev));

parse_events_error__init(&err);
ret = parse_events(evlist, str, &err);
--
2.43.5