linux-kernel - [PATCH v3 1/3] perf: Add perf_event_attr::bp

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Message-ID: <20240709095506.9691-2-yangtiezhu@loongson.cn>
Date: Tue,  9 Jul 2024 17:55:04 +0800
From: Tiezhu Yang <yangtiezhu@...ngson.cn>
To: Will Deacon <will@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Russell King <linux@...linux.org.uk>,
	Catalin Marinas <catalin.marinas@....com>,
	Oleg Nesterov <oleg@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>
Cc: linux-arm-kernel@...ts.infradead.org,
	linux-perf-users@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH v3 1/3] perf: Add perf_event_attr::bp_priv

When developing hardware watchpoint on LoongArch, we want to set the
same privilege passed by the ptrace user data, but there is no bridge
to save this value like bp_addr, bp_type and bp_len. This is a common
issue for the archs which have privilege level of breakpoint.

Add a member "bp_priv" which lives in a union on config3 at the end
of the uapi struct perf_event_attr to make a bridge between ptrace
and hardware breakpoint.

This is preparation for later patch on some archs such as ARM, ARM64
and LoongArch which have privilege level of breakpoint.

Signed-off-by: Tiezhu Yang <yangtiezhu@...ngson.cn>
---
 include/uapi/linux/perf_event.h | 5 ++++-
 kernel/events/hw_breakpoint.c   | 1 +
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index 3a64499b0f5d..abe8da7a1f60 100644
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -521,7 +521,10 @@ struct perf_event_attr {
 	 */
 	__u64	sig_data;
 
-	__u64	config3; /* extension of config2 */
+	union {
+		__u8	bp_priv; /* privilege level of breakpoint */
+		__u64	config3; /* extension of config2 */
+	};
 };
 
 /*
diff --git a/kernel/events/hw_breakpoint.c b/kernel/events/hw_breakpoint.c
index 6c2cb4e4f48d..3ad16b226e4f 100644
--- a/kernel/events/hw_breakpoint.c
+++ b/kernel/events/hw_breakpoint.c
@@ -754,6 +754,7 @@ static void hw_breakpoint_copy_attr(struct perf_event_attr *to,
 	to->bp_addr = from->bp_addr;
 	to->bp_type = from->bp_type;
 	to->bp_len  = from->bp_len;
+	to->bp_priv = from->bp_priv;
 	to->disabled = from->disabled;
 }
 
-- 
2.42.0