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 nstange@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