linux-kernel - [tip: perf/core] perf/hw_breakpoint: Return EOPNOTSUPP for unsupported breakpoint type

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Message-ID: <174107862797.14745.7983428300069881325.tip-bot2@tip-bot2>
Date: Tue, 04 Mar 2025 08:57:07 -0000
From: "tip-bot2 for Saket Kumar Bhaskar" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Saket Kumar Bhaskar <skb99@...ux.ibm.com>, Ingo Molnar <mingo@...nel.org>,
 Marco Elver <elver@...gle.com>, Dmitry Vyukov <dvyukov@...gle.com>,
 Ian Rogers <irogers@...gle.com>, Frederic Weisbecker <fweisbec@...il.com>,
 x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [tip: perf/core] perf/hw_breakpoint: Return EOPNOTSUPP for
 unsupported breakpoint type

The following commit has been merged into the perf/core branch of tip:

Commit-ID:     061c991697062f3bf87b72ed553d1d33a0e370dd
Gitweb:        https://git.kernel.org/tip/061c991697062f3bf87b72ed553d1d33a0e370dd
Author:        Saket Kumar Bhaskar <skb99@...ux.ibm.com>
AuthorDate:    Mon, 03 Mar 2025 14:54:51 +05:30
Committer:     Ingo Molnar <mingo@...nel.org>
CommitterDate: Tue, 04 Mar 2025 09:42:13 +01:00

perf/hw_breakpoint: Return EOPNOTSUPP for unsupported breakpoint type

Currently, __reserve_bp_slot() returns -ENOSPC for unsupported
breakpoint types on the architecture. For example, powerpc
does not support hardware instruction breakpoints. This causes
the perf_skip BPF selftest to fail, as neither ENOENT nor
EOPNOTSUPP is returned by perf_event_open for unsupported
breakpoint types. As a result, the test that should be skipped
for this arch is not correctly identified.

To resolve this, hw_breakpoint_event_init() should exit early by
checking for unsupported breakpoint types using
hw_breakpoint_slots_cached() and return the appropriate error
(-EOPNOTSUPP).

Signed-off-by: Saket Kumar Bhaskar <skb99@...ux.ibm.com>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Cc: Marco Elver <elver@...gle.com>
Cc: Dmitry Vyukov <dvyukov@...gle.com>
Cc: Ian Rogers <irogers@...gle.com>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Link: https://lore.kernel.org/r/20250303092451.1862862-1-skb99@linux.ibm.com
---
 kernel/events/hw_breakpoint.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/kernel/events/hw_breakpoint.c b/kernel/events/hw_breakpoint.c
index bc4a610..8ec2cb6 100644
--- a/kernel/events/hw_breakpoint.c
+++ b/kernel/events/hw_breakpoint.c
@@ -950,9 +950,10 @@ static int hw_breakpoint_event_init(struct perf_event *bp)
 		return -ENOENT;
 
 	/*
-	 * no branch sampling for breakpoint events
+	 * Check if breakpoint type is supported before proceeding.
+	 * Also, no branch sampling for breakpoint events.
 	 */
-	if (has_branch_stack(bp))
+	if (!hw_breakpoint_slots_cached(find_slot_idx(bp->attr.bp_type)) || has_branch_stack(bp))
 		return -EOPNOTSUPP;
 
 	err = register_perf_hw_breakpoint(bp);