linux-kernel - [PATCH AUTOSEL 6.6 124/294] perf/hw_breakpoint: Return EOPNOTSUPP for unsupported breakpoint type

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Message-Id: <20250505225634.2688578-124-sashal@kernel.org>
Date: Mon,  5 May 2025 18:53:44 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...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>,
	Sasha Levin <sashal@...nel.org>,
	peterz@...radead.org,
	mingo@...hat.com,
	acme@...nel.org,
	namhyung@...nel.org,
	linux-perf-users@...r.kernel.org
Subject: [PATCH AUTOSEL 6.6 124/294] perf/hw_breakpoint: Return EOPNOTSUPP for unsupported breakpoint type

From: Saket Kumar Bhaskar <skb99@...ux.ibm.com>

[ Upstream commit 061c991697062f3bf87b72ed553d1d33a0e370dd ]

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
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 6c2cb4e4f48da..8f3f624419aa9 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);
-- 
2.39.5