[PATCH] kernel/perf: correct return code of rb_alloc_aux() if !has_aux(ev)

[PATCH] kernel/perf: correct return code of rb_alloc_aux() if !has_aux(ev)

[Hendrik Brueckner]

If the event for which an AUX area is about to be allocated, does
not support setting up an AUX area, rb_alloc_aux() return -ENOTSUPP.

This error condition is being returned unfiltered to the user space,
and, for example, the perf tools fails with:

  failed to mmap with 524 (INTERNAL ERROR: strerror_r(524, 0x3fff497a1c8, 512)=22)

This error can be easily seen with "perf record -m 128,256 -e cpu-clock".

The 524 error code maps to -ENOTSUPP (in rb_alloc_aux()). The -ENOTSUPP
error code shall be only used within the kernel.  So the correct error
code would then be -EOPNOTSUPP.

With this commit, the perf tool then reports:

  failed to mmap with 95 (Operation not supported)

which is more clear.

Cc: Pu Hou <bjhoupu@linux.vnet.ibm.com>
Cc: Thomas-Mich Richter <tmricht@linux.vnet.ibm.com>
Signed-off-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
---
 kernel/events/ring_buffer.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
index 2831480..ee97196 100644
--- a/kernel/events/ring_buffer.c
+++ b/kernel/events/ring_buffer.c
@@ -580,7 +580,7 @@ int rb_alloc_aux(struct ring_buffer *rb, struct perf_event *event,
 	int ret = -ENOMEM, max_order = 0;
 
 	if (!has_aux(event))
-		return -ENOTSUPP;
+		return -EOPNOTSUPP;
 
 	if (event->pmu->capabilities & PERF_PMU_CAP_AUX_NO_SG) {
 		/*
-- 
1.8.3.1

Re: [PATCH] kernel/perf: correct return code of rb_alloc_aux() if !has_aux(ev)

[Alexander Shishkin]

Hendrik Brueckner <brueckner@linux.vnet.ibm.com> writes:

> If the event for which an AUX area is about to be allocated, does
> not support setting up an AUX area, rb_alloc_aux() return -ENOTSUPP.
>
> This error condition is being returned unfiltered to the user space,
> and, for example, the perf tools fails with:
>
>   failed to mmap with 524 (INTERNAL ERROR: strerror_r(524, 0x3fff497a1c8, 512)=22)
>
> This error can be easily seen with "perf record -m 128,256 -e cpu-clock".
>
> The 524 error code maps to -ENOTSUPP (in rb_alloc_aux()). The -ENOTSUPP
> error code shall be only used within the kernel.  So the correct error
> code would then be -EOPNOTSUPP.
>
> With this commit, the perf tool then reports:
>
>   failed to mmap with 95 (Operation not supported)
>
> which is more clear.

Acked-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>

Curious as to why does the tool allow this.

Regards,
--
Alex

[tip:perf/urgent] perf/aux: Correct return code of rb_alloc_aux() if !has_aux(ev)

[tip-bot for Hendrik Brueckner]

Commit-ID:  8a1898db51a3390241cd5fae267dc8aaa9db0f8b
Gitweb:     http://git.kernel.org/tip/8a1898db51a3390241cd5fae267dc8aaa9db0f8b
Author:     Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
AuthorDate: Tue, 20 Jun 2017 12:26:39 +0200
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 21 Jun 2017 11:58:30 +0200

perf/aux: Correct return code of rb_alloc_aux() if !has_aux(ev)

If the event for which an AUX area is about to be allocated, does
not support setting up an AUX area, rb_alloc_aux() return -ENOTSUPP.

This error condition is being returned unfiltered to the user space,
and, for example, the perf tools fails with:

  failed to mmap with 524 (INTERNAL ERROR: strerror_r(524, 0x3fff497a1c8, 512)=22)

This error can be easily seen with "perf record -m 128,256 -e cpu-clock".

The 524 error code maps to -ENOTSUPP (in rb_alloc_aux()). The -ENOTSUPP
error code shall be only used within the kernel.  So the correct error
code would then be -EOPNOTSUPP.

With this commit, the perf tool then reports:

  failed to mmap with 95 (Operation not supported)

which is more clear.

Signed-off-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Acked-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Pu Hou <bjhoupu@linux.vnet.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Thomas-Mich Richter <tmricht@linux.vnet.ibm.com>
Cc: acme@kernel.org
Cc: linux-s390@vger.kernel.org
Link: http://lkml.kernel.org/r/1497954399-6355-1-git-send-email-brueckner@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 kernel/events/ring_buffer.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
index 2831480..ee97196 100644
--- a/kernel/events/ring_buffer.c
+++ b/kernel/events/ring_buffer.c
@@ -580,7 +580,7 @@ int rb_alloc_aux(struct ring_buffer *rb, struct perf_event *event,
 	int ret = -ENOMEM, max_order = 0;
 
 	if (!has_aux(event))
-		return -ENOTSUPP;
+		return -EOPNOTSUPP;
 
 	if (event->pmu->capabilities & PERF_PMU_CAP_AUX_NO_SG) {
 		/*