linux-kernel - [PATCH 2/3] perf test: Add syscall and address tests to brstack test

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Message-Id: <20250813-james-brbe-test-v1-2-76a0144b73fb@linaro.org>
Date: Wed, 13 Aug 2025 14:38:50 +0100
From: James Clark <james.clark@...aro.org>
To: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
 Arnaldo Carvalho de Melo <acme@...nel.org>, 
 Namhyung Kim <namhyung@...nel.org>, Mark Rutland <mark.rutland@....com>, 
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>, 
 Jiri Olsa <jolsa@...nel.org>, Ian Rogers <irogers@...gle.com>, 
 Adrian Hunter <adrian.hunter@...el.com>, 
 Anshuman Khandual <anshuman.khandual@....com>, 
 Mark Rutland <mark.rutland@....com>, "Rob Herring (Arm)" <robh@...nel.org>, 
 Adam Young <admiyo@...amperecomputing.com>, Will Deacon <will@...nel.org>, 
 German Gomez <german.gomez@....com>
Cc: linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org, 
 James Clark <james.clark@...aro.org>
Subject: [PATCH 2/3] perf test: Add syscall and address tests to brstack
 test

Test that SYSCALL type branches are emitted from the expected 'getppid'
symbol. Test that when only 'k' is used, sources addresses are all in
the kernel. Test that no kernel addresses leak by checking for them in
the 'u' test.

Signed-off-by: James Clark <james.clark@...aro.org>
---
 tools/perf/tests/shell/test_brstack.sh | 61 +++++++++++++++++++++++++++++++++-
 1 file changed, 60 insertions(+), 1 deletion(-)

diff --git a/tools/perf/tests/shell/test_brstack.sh b/tools/perf/tests/shell/test_brstack.sh
index 46e5aa9ce8ee..252d22d39c7b 100755
--- a/tools/perf/tests/shell/test_brstack.sh
+++ b/tools/perf/tests/shell/test_brstack.sh
@@ -64,8 +64,50 @@ test_user_branches() {
 	do
 		check_branches "$x"
 	done
+
+	# Dump addresses only this time
+	perf script -i "$TMPDIR/perf.data" --fields brstack | \
+		tr ' ' '\n' > "$TMPDIR/perf.script"
+
+	# There should be no kernel addresses with the u option, in either
+	# source or target addresses.
+	if grep -E -m1 "0x[89a-f][0-9a-f]{15}" $TMPDIR/perf.script; then
+		echo "ERROR: Kernel address found in user mode"
+		err=1
+	fi
 	# some branch types are still not being tested:
-	# IND COND_CALL COND_RET SYSCALL SYSRET IRQ SERROR NO_TX
+	# IND COND_CALL COND_RET SYSRET IRQ SERROR NO_TX
+}
+
+
+test_kernel_branches() {
+	echo "Testing that k option only includes kernel source addresses"
+
+	if ! perf record --branch-filter any,k -o- -- true > /dev/null; then
+		echo "skip: not enough privileges"
+	else
+		perf record -o $TMPDIR/perf.data --branch-filter any,k -- \
+			perf bench syscall basic --loop 1000
+		perf script -i $TMPDIR/perf.data --fields brstack | \
+			tr ' ' '\n' > $TMPDIR/perf.script
+
+		# Example of branch entries:
+		#       "0xffffffff93bda241/0xffffffff93bda20f/M/-/-/..."
+		# Source addresses come first and target address can be either
+		# userspace or kernel even with k option, as long as the source
+		# is in kernel.
+
+		#Look for source addresses with top bit set
+		if ! grep -E -m1 "^0x[89a-f][0-9a-f]{15}" $TMPDIR/perf.script; then
+			echo "ERROR: Kernel branches missing"
+			err=1
+		fi
+		# Look for no source addresses without top bit set
+		if grep -E -m1 "^0x[0-7][0-9a-f]{0,15}" $TMPDIR/perf.script; then
+			echo "ERROR: User branches found with kernel filter"
+			err=1
+		fi
+	fi
 }
 
 # first argument <arg0> is the argument passed to "--branch-stack <arg0>,save_type,u"
@@ -100,9 +142,26 @@ test_filter() {
 	fi
 }
 
+test_syscall() {
+	echo "Testing syscalls"
+	# skip if perf doesn't have enough privileges
+	if ! perf record --branch-filter any,k -o- -- true > /dev/null; then
+		echo "skip: not enough privileges"
+	else
+		perf record -o $TMPDIR/perf.data --branch-filter \
+			any_call,save_type,u,k -c 10000 -- \
+			perf bench syscall basic --loop 1000
+		perf script -i $TMPDIR/perf.data --fields brstacksym | \
+			tr ' ' '\n' > $TMPDIR/perf.script
+
+		check_branches "getppid[^ ]*/SYSCALL/"
+	fi
+}
 set -e
 
 test_user_branches
+test_syscall
+test_kernel_branches
 
 any_call="CALL|IND_CALL|COND_CALL|SYSCALL|IRQ"
 

-- 
2.34.1