There had been an issue with interactions between tracing and live patching
due to how x86' CONFIG_DYNAMIC_FTRACE used to handle the breakpoints at the
updated instructions from its ftrace_int3_handler().
More specifically, starting to trace a live patched function caused a short
period in time where the live patching redirection became ineffective. In
particular, the guarantees from the consistency model couldn't be held up
in this situation.
Implement a testcase for verifying that a function's live patch replacement
is kept effective when enabling tracing on it.
Reuse the existing 'test_klp_livepatch' live patch module which patches
cmdline_proc_show(), the handler for /proc/cmdline.
Let the testcase in a loop
- apply this live patch,
- launch a background shell job enabling tracing on that function
- while continuously verifying that the contents of /proc/cmdline still
match what would be expected when the live patch is applied.
Signed-off-by: Nicolai Stange <nsta...@suse.de>
---
tools/testing/selftests/livepatch/Makefile | 3 +-
.../livepatch/test-livepatch-vs-ftrace.sh | 44 ++++++++++++++++++++++
2 files changed, 46 insertions(+), 1 deletion(-)
create mode 100755
tools/testing/selftests/livepatch/test-livepatch-vs-ftrace.sh
diff --git a/tools/testing/selftests/livepatch/Makefile
b/tools/testing/selftests/livepatch/Makefile
index af4aee79bebb..bfa5353f6d17 100644
--- a/tools/testing/selftests/livepatch/Makefile
+++ b/tools/testing/selftests/livepatch/Makefile
@@ -3,6 +3,7 @@
TEST_GEN_PROGS := \
test-livepatch.sh \
test-callbacks.sh \
- test-shadow-vars.sh
+ test-shadow-vars.sh \
+ test-livepatch-vs-ftrace.sh
include ../lib.mk
diff --git a/tools/testing/selftests/livepatch/test-livepatch-vs-ftrace.sh
b/tools/testing/selftests/livepatch/test-livepatch-vs-ftrace.sh
new file mode 100755
index 000000000000..5c982ec56373
--- /dev/null
+++ b/tools/testing/selftests/livepatch/test-livepatch-vs-ftrace.sh
@@ -0,0 +1,44 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (C) 2019 SUSE Linux GmbH
+
+. $(dirname $0)/functions.sh
+
+set -e
+
+MOD_LIVEPATCH=test_klp_livepatch
+
+# TEST: ftrace a live patched function
+# - load a livepatch that modifies the output from /proc/cmdline
+# - install a function tracer at the live patched function
+# - verify that the function is still patched by reading /proc/cmdline
+# - unload the livepatch and make sure the patch was removed
+
+echo -n "TEST: ftrace a live patched function ... "
+dmesg -C
+
+for i in $(seq 1 3); do
+ load_lp $MOD_LIVEPATCH
+
+ ( echo cmdline_proc_show > /sys/kernel/debug/tracing/set_ftrace_filter;
+ echo function > /sys/kernel/debug/tracing/current_tracer ) &
+
+ for j in $(seq 1 200); do
+ if [[ "$(cat /proc/cmdline)" != \
+ "$MOD_LIVEPATCH: this has been live patched" ]] ; then
+ echo -e "FAIL\n\n"
+ die "livepatch kselftest(s) failed"
+ fi
+ done
+
+ wait %1
+
+ echo nop > /sys/kernel/debug/tracing/current_tracer
+ echo > /sys/kernel/debug/tracing/set_ftrace_filter
+
+ disable_lp $MOD_LIVEPATCH
+ unload_lp $MOD_LIVEPATCH
+done
+
+echo "ok"
+exit 0
--
2.13.7
