On Tue 2024-09-17 15:50:53, Michael Vetter wrote:
The test proves that a function that is being kprobed and uses a post_handler cannot be livepatched.
Only one ftrace_ops with FTRACE_OPS_FL_IPMODIFY set may be registered to any given function at a time.
--- /dev/null +++ b/tools/testing/selftests/livepatch/test-kprobe.sh @@ -0,0 +1,65 @@ +#!/bin/bash +# SPDX-License-Identifier: GPL-2.0 +# Copyright (C) 2024 SUSE +# Author: Michael Vetter mvetter@suse.com
+. $(dirname $0)/functions.sh
+MOD_LIVEPATCH=test_klp_livepatch +MOD_KPROBE=test_klp_kprobe
+setup_config
+# Kprobe a function and verify that we can't livepatch that same function +# when it uses a post_handler since only one IPMODIFY maybe be registered +# to any given function at a time.
+start_test "livepatch interaction with kprobed function with post_handler"
+STATE=$(cat /sys/kernel/debug/kprobes/enabled) +echo 1 > /sys/kernel/debug/kprobes/enabled
+load_mod $MOD_KPROBE has_post_handler=true +load_failing_mod $MOD_LIVEPATCH +unload_mod $MOD_KPROBE
[...]
+echo $STATE > /sys/kernel/debug/kprobes/enabled
The original state won't get restored when the test fails.
A better solution would be to integrate this into setup_config() and cleanup() in /tools/testing/selftests/livepatch/functions.sh
Also it would be great to avoid hard-coding /sys/kernel/debug. See KLP_SYSFS_DIR="/sys/kernel/livepatch" in /tools/testing/selftests/livepatch/functions.sh
I would replace it with:
KERNEL_SYSFS_DIR="/sys/kernel" KLP_SYSFS_DIR="$KERNEL_SYSFS_DIR/livepatch" DEBUG_SYSFS_DIR="$KERNEL_SYSFS_DIR/debug" KPROBES_SYSFS_DIR="$DEBUG_SYSFS_DIR/kprobes"
It would actually look better with switched ordering:
SYSFS_KERNEL_DIR="/sys/kernel" SYSFS_KLP_DIR="$SYSFS_KERNEL_DIR/livepatch" SYSFS_DEBUG_DIR="$SYSFS_KERNEL_DIR/debug" SYSFS_KPROBES_DIR="$SYSFS_DEBUG_DIR/kprobes"
But this would require renaming KLP_SYSFS_DIR everywhere in a separate (prerequisite) patch. It would be nice but I do not want to force you to do it ;-)
--- a/tools/testing/selftests/livepatch/test_modules/Makefile +++ b/tools/testing/selftests/livepatch/test_modules/Makefile @@ -11,7 +11,8 @@ obj-m += test_klp_atomic_replace.o \ test_klp_state2.o \ test_klp_state3.o \ test_klp_shadow_vars.o \
- test_klp_syscall.o
- test_klp_syscall.o \
- test_klp_kprobe.o
Nit: Please, put it in alphabetical order. It is not a big deal. The ordering helps searching. The list already is almost sorted. And the patch needs to be updated anyway.
# Ensure that KDIR exists, otherwise skip the compilation modules: diff --git a/tools/testing/selftests/livepatch/test_modules/test_klp_kprobe.c b/tools/testing/selftests/livepatch/test_modules/test_klp_kprobe.c new file mode 100644 index 000000000000..49b579ea1054 --- /dev/null +++ b/tools/testing/selftests/livepatch/test_modules/test_klp_kprobe.c @@ -0,0 +1,38 @@
[...]
+module_init(kprobe_init) +module_exit(kprobe_exit) +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("Michael Vetter mvetter@suse.com"); +MODULE_DESCRIPTION("Livepatch test: livepatch kprobed function");
Nit: The module adds a kprobe. I would invert the logic:
MODULE_DESCRIPTION("Livepatch test: kprobe livepatched function");
Best Regards, Petr