linux-kernel - [tip:perf/urgent] perf/aux: Correct return code of rb_alloc_aux() if !has

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Message-ID: <tip-8a1898db51a3390241cd5fae267dc8aaa9db0f8b@git.kernel.org>
Date:   Wed, 21 Jun 2017 09:46:02 -0700
From:   tip-bot for Hendrik Brueckner <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     brueckner@...ux.vnet.ibm.com, bjhoupu@...ux.vnet.ibm.com,
        mingo@...nel.org, hpa@...or.com, linux-kernel@...r.kernel.org,
        alexander.shishkin@...ux.intel.com, torvalds@...ux-foundation.org,
        tmricht@...ux.vnet.ibm.com, peterz@...radead.org,
        tglx@...utronix.de
Subject: [tip:perf/urgent] perf/aux: Correct return code of rb_alloc_aux()
 if !has_aux(ev)

Commit-ID:  8a1898db51a3390241cd5fae267dc8aaa9db0f8b
Gitweb:     http://git.kernel.org/tip/8a1898db51a3390241cd5fae267dc8aaa9db0f8b
Author:     Hendrik Brueckner <brueckner@...ux.vnet.ibm.com>
AuthorDate: Tue, 20 Jun 2017 12:26:39 +0200
Committer:  Ingo Molnar <mingo@...nel.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@...ux.vnet.ibm.com>
Acked-by: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Pu Hou <bjhoupu@...ux.vnet.ibm.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Thomas-Mich Richter <tmricht@...ux.vnet.ibm.com>
Cc: acme@...nel.org
Cc: linux-s390@...r.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@...nel.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) {
 		/*