[PATCH] selftests/livepatch: test interaction with ftrace_enabled

[Joe Lawrence]

Since livepatching depends upon ftrace handlers to implement "patched"
functionality, verify that the ftrace_enabled sysctl value interacts
with livepatch registration as expected.

Signed-off-by: Joe Lawrence <joe.lawrence@xxxxxxxxxx>
---
 tools/testing/selftests/livepatch/Makefile    |  3 +-
 .../testing/selftests/livepatch/functions.sh  | 18 +++++
 .../selftests/livepatch/test-ftrace.sh        | 65 +++++++++++++++++++
 3 files changed, 85 insertions(+), 1 deletion(-)
 create mode 100755 tools/testing/selftests/livepatch/test-ftrace.sh

diff --git a/tools/testing/selftests/livepatch/Makefile b/tools/testing/selftests/livepatch/Makefile
index fd405402c3ff..1886d9d94b88 100644
--- a/tools/testing/selftests/livepatch/Makefile
+++ b/tools/testing/selftests/livepatch/Makefile
@@ -4,6 +4,7 @@ TEST_PROGS_EXTENDED := functions.sh
 TEST_PROGS := \
 	test-livepatch.sh \
 	test-callbacks.sh \
-	test-shadow-vars.sh
+	test-shadow-vars.sh \
+	test-ftrace.sh
 
 include ../lib.mk
diff --git a/tools/testing/selftests/livepatch/functions.sh b/tools/testing/selftests/livepatch/functions.sh
index 79b0affd21fb..556252efece0 100644
--- a/tools/testing/selftests/livepatch/functions.sh
+++ b/tools/testing/selftests/livepatch/functions.sh
@@ -52,6 +52,24 @@ function set_dynamic_debug() {
 		EOF
 }
 
+function push_ftrace_enabled() {
+	FTRACE_ENABLED=$(sysctl --values kernel.ftrace_enabled)
+}
+function pop_ftrace_enabled() {
+	if [[ -n "$FTRACE_ENABLED" ]]; then
+		sysctl kernel.ftrace_enabled="$FTRACE_ENABLED"
+	fi
+}
+# set_ftrace_enabled() - save the current ftrace_enabled config and tweak
+# 			 it for the self-tests.  Set a script exit trap
+#			 that restores the original value.
+function set_ftrace_enabled() {
+	local sysctl="$1"
+        trap pop_ftrace_enabled EXIT INT TERM HUP
+	result=$(sysctl kernel.ftrace_enabled="$1" 2>&1 | paste --serial --delimiters=' ')
+	echo "livepatch: $result" > /dev/kmsg
+}
+
 # loop_until(cmd) - loop a command until it is successful or $MAX_RETRIES,
 #		    sleep $RETRY_INTERVAL between attempts
 #	cmd - command and its arguments to run
diff --git a/tools/testing/selftests/livepatch/test-ftrace.sh b/tools/testing/selftests/livepatch/test-ftrace.sh
new file mode 100755
index 000000000000..016576883a33
--- /dev/null
+++ b/tools/testing/selftests/livepatch/test-ftrace.sh
@@ -0,0 +1,65 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (C) 2019 Joe Lawrence <joe.lawrence@xxxxxxxxxx>
+
+. $(dirname $0)/functions.sh
+
+MOD_LIVEPATCH=test_klp_livepatch
+
+set_dynamic_debug
+
+
+# TEST: livepatch interaction with ftrace_enabled sysctl
+# - turn ftrace_enabled OFF and verify livepatches can't load
+# - turn ftrace_enabled ON and verify livepatch can load
+# - verify that ftrace_enabled can't be turned OFF while a livepatch is loaded
+
+echo -n "TEST: livepatch interaction with ftrace_enabled sysctl ... "
+dmesg -C
+
+set_ftrace_enabled 0
+load_failing_mod $MOD_LIVEPATCH
+
+set_ftrace_enabled 1
+load_lp $MOD_LIVEPATCH
+if [[ "$(cat /proc/cmdline)" != "$MOD_LIVEPATCH: this has been live patched" ]] ; then
+	echo -e "FAIL\n\n"
+	die "livepatch kselftest(s) failed"
+fi
+
+set_ftrace_enabled 0
+if [[ "$(cat /proc/cmdline)" != "$MOD_LIVEPATCH: this has been live patched" ]] ; then
+	echo -e "FAIL\n\n"
+	die "livepatch kselftest(s) failed"
+fi
+disable_lp $MOD_LIVEPATCH
+unload_lp $MOD_LIVEPATCH
+
+check_result "livepatch: kernel.ftrace_enabled = 0
+% modprobe $MOD_LIVEPATCH
+livepatch: enabling patch '$MOD_LIVEPATCH'
+livepatch: '$MOD_LIVEPATCH': initializing patching transition
+livepatch: failed to register ftrace handler for function 'cmdline_proc_show' (-16)
+livepatch: failed to patch object 'vmlinux'
+livepatch: failed to enable patch '$MOD_LIVEPATCH'
+livepatch: '$MOD_LIVEPATCH': canceling patching transition, going to unpatch
+livepatch: '$MOD_LIVEPATCH': completing unpatching transition
+livepatch: '$MOD_LIVEPATCH': unpatching complete
+modprobe: ERROR: could not insert '$MOD_LIVEPATCH': Device or resource busy
+livepatch: kernel.ftrace_enabled = 1
+% modprobe $MOD_LIVEPATCH
+livepatch: enabling patch '$MOD_LIVEPATCH'
+livepatch: '$MOD_LIVEPATCH': initializing patching transition
+livepatch: '$MOD_LIVEPATCH': starting patching transition
+livepatch: '$MOD_LIVEPATCH': completing patching transition
+livepatch: '$MOD_LIVEPATCH': patching complete
+livepatch: sysctl: setting key \"kernel.ftrace_enabled\": Device or resource busy kernel.ftrace_enabled = 0
+% echo 0 > /sys/kernel/livepatch/$MOD_LIVEPATCH/enabled
+livepatch: '$MOD_LIVEPATCH': initializing unpatching transition
+livepatch: '$MOD_LIVEPATCH': starting unpatching transition
+livepatch: '$MOD_LIVEPATCH': completing unpatching transition
+livepatch: '$MOD_LIVEPATCH': unpatching complete
+% rmmod $MOD_LIVEPATCH"
+
+
+exit 0
-- 
2.21.0