linux-kernel - [tip: perf/core] perf: Capture branch privilege information

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Date:   Fri, 26 Aug 2022 22:15:48 -0000
From:   "tip-bot2 for Anshuman Khandual" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Anshuman Khandual <anshuman.khandual@....com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        James Clark <james.clark@....com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: perf/core] perf: Capture branch privilege information

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

Commit-ID:     7203d4a5c19fc13c5229c4c1a08a5f9222207230
Gitweb:        https://git.kernel.org/tip/7203d4a5c19fc13c5229c4c1a08a5f9222207230
Author:        Anshuman Khandual <anshuman.khandual@....com>
AuthorDate:    Wed, 24 Aug 2022 10:18:17 +05:30
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Sat, 27 Aug 2022 00:05:47 +02:00

perf: Capture branch privilege information

Platforms like arm64 could capture privilege level information for all the
branch records. Hence this adds a new element in the struct branch_entry to
record the privilege level information, which could be requested through a
new event.attr.branch_sample_type based flag PERF_SAMPLE_BRANCH_PRIV_SAVE.
This flag helps user choose whether privilege information is captured.

Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Reviewed-by: James Clark <james.clark@....com>
Link: https://lkml.kernel.org/r/20220824044822.70230-4-anshuman.khandual@arm.com
---
 include/uapi/linux/perf_event.h | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index fed60e6..1a258d4 100644
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -204,6 +204,8 @@ enum perf_branch_sample_type_shift {
 
 	PERF_SAMPLE_BRANCH_HW_INDEX_SHIFT	= 17, /* save low level index of raw branch records */
 
+	PERF_SAMPLE_BRANCH_PRIV_SAVE_SHIFT	= 18, /* save privilege mode */
+
 	PERF_SAMPLE_BRANCH_MAX_SHIFT		/* non-ABI */
 };
 
@@ -233,6 +235,8 @@ enum perf_branch_sample_type {
 
 	PERF_SAMPLE_BRANCH_HW_INDEX	= 1U << PERF_SAMPLE_BRANCH_HW_INDEX_SHIFT,
 
+	PERF_SAMPLE_BRANCH_PRIV_SAVE	= 1U << PERF_SAMPLE_BRANCH_PRIV_SAVE_SHIFT,
+
 	PERF_SAMPLE_BRANCH_MAX		= 1U << PERF_SAMPLE_BRANCH_MAX_SHIFT,
 };
 
@@ -282,6 +286,13 @@ enum {
 	PERF_BR_NEW_MAX,
 };
 
+enum {
+	PERF_BR_PRIV_UNKNOWN	= 0,
+	PERF_BR_PRIV_USER	= 1,
+	PERF_BR_PRIV_KERNEL	= 2,
+	PERF_BR_PRIV_HV		= 3,
+};
+
 #define PERF_SAMPLE_BRANCH_PLM_ALL \
 	(PERF_SAMPLE_BRANCH_USER|\
 	 PERF_SAMPLE_BRANCH_KERNEL|\
@@ -1402,7 +1413,8 @@ struct perf_branch_entry {
 		type:4,     /* branch type */
 		spec:2,     /* branch speculation info */
 		new_type:4, /* additional branch type */
-		reserved:34;
+		priv:3,     /* privilege level */
+		reserved:31;
 };
 
 union perf_sample_weight {