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Subject[PATCH v3 3/3] selftests/livepatch: Test interaction with ftrace_enabled
Date
From: Joe Lawrence <joe.lawrence@redhat.com>

Since livepatching depends upon ftrace handlers to implement "patched"
code functionality, verify that the ftrace_enabled sysctl value
interacts with livepatch registration as expected. At the same time,
ensure that ftrace_enabled is set and part of the test environment
configuration that is saved and restored when running the selftests.

Signed-off-by: Joe Lawrence <joe.lawrence@redhat.com>
Signed-off-by: Miroslav Benes <mbenes@suse.cz>
---
tools/testing/selftests/livepatch/Makefile | 3 +-
.../testing/selftests/livepatch/functions.sh | 14 +++-
.../selftests/livepatch/test-ftrace.sh | 65 +++++++++++++++++++
3 files changed, 80 insertions(+), 2 deletions(-)
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 b7e5a67ae434..31eb09e38729 100644
--- a/tools/testing/selftests/livepatch/functions.sh
+++ b/tools/testing/selftests/livepatch/functions.sh
@@ -32,12 +32,16 @@ function die() {
function push_config() {
DYNAMIC_DEBUG=$(grep '^kernel/livepatch' /sys/kernel/debug/dynamic_debug/control | \
awk -F'[: ]' '{print "file " $1 " line " $2 " " $4}')
+ FTRACE_ENABLED=$(sysctl --values kernel.ftrace_enabled)
}

function pop_config() {
if [[ -n "$DYNAMIC_DEBUG" ]]; then
echo -n "$DYNAMIC_DEBUG" > /sys/kernel/debug/dynamic_debug/control
fi
+ if [[ -n "$FTRACE_ENABLED" ]]; then
+ sysctl kernel.ftrace_enabled="$FTRACE_ENABLED" &> /dev/null
+ fi
}

function set_dynamic_debug() {
@@ -47,12 +51,20 @@ function set_dynamic_debug() {
EOF
}

+function set_ftrace_enabled() {
+ local sysctl="$1"
+ result=$(sysctl kernel.ftrace_enabled="$1" 2>&1 | paste --serial --delimiters=' ')
+ echo "livepatch: $result" > /dev/kmsg
+}
+
# setup_config - save the current config and set a script exit trap that
# restores the original config. Setup the dynamic debug
-# for verbose livepatching output.
+# for verbose livepatching output and turn on
+# the ftrace_enabled sysctl.
function setup_config() {
push_config
set_dynamic_debug
+ set_ftrace_enabled 1
trap pop_config EXIT INT TERM HUP
}

diff --git a/tools/testing/selftests/livepatch/test-ftrace.sh b/tools/testing/selftests/livepatch/test-ftrace.sh
new file mode 100755
index 000000000000..e2a76887f40a
--- /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@redhat.com>
+
+. $(dirname $0)/functions.sh
+
+MOD_LIVEPATCH=test_klp_livepatch
+
+setup_config
+
+
+# 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
--
2.23.0
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