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selftests: livepatch: test livepatching a kprobed function

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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.

Note that the conflicting kprobe could not be created using the
tracefs interface, see Documentation/trace/kprobetrace.rst.
This interface uses only the pre_handler(), see alloc_trace_kprobe().
But FTRACE_OPS_FL_IPMODIFY is used only when the kprobe is using a
post_handler, see arm_kprobe_ftrace().

Signed-off-by: Michael Vetter <mvetter@suse.com>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Reviewed-by: Joe Lawrence <joe.lawrence@redhat.com>
Tested-by: Marcos Paulo de Souza <mpdesouza@suse.com>
Reviewed-by: Marcos Paulo de Souza <mpdesouza@suse.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Tested-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20241017200132.21946-4-mvetter@suse.com
Signed-off-by: Petr Mladek <pmladek@suse.com>
This commit is contained in:
Michael Vetter 2024-10-17 22:01:32 +02:00 committed by Petr Mladek
parent 59766286b6
commit 62597edf63
4 changed files with 104 additions and 2 deletions
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3
tools/testing/selftests/livepatch/Makefile
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@ -10,7 +10,8 @@ TEST_PROGS := \
test-state.sh \
test-ftrace.sh \
test-sysfs.sh \
test-syscall.sh
test-syscall.sh \
test-kprobe.sh
TEST_FILES := settings

62
tools/testing/selftests/livepatch/test-kprobe.sh Executable file
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@ -0,0 +1,62 @@
#!/bin/bash
# SPDX-License-Identifier: GPL-2.0
# Copyright (C) 2024 SUSE
# Author: Michael Vetter <mvetter@suse.com>
. $(dirname $0)/functions.sh
MOD_LIVEPATCH=test_klp_livepatch
MOD_KPROBE=test_klp_kprobe
setup_config
# Kprobe a function and verify that we can't livepatch that same function
# when it uses a post_handler since only one IPMODIFY maybe be registered
# to any given function at a time.
start_test "livepatch interaction with kprobed function with post_handler"
echo 1 > "$SYSFS_KPROBES_DIR/enabled"
load_mod $MOD_KPROBE has_post_handler=true
load_failing_mod $MOD_LIVEPATCH
unload_mod $MOD_KPROBE
check_result "% insmod test_modules/test_klp_kprobe.ko has_post_handler=true
% insmod test_modules/$MOD_LIVEPATCH.ko
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
insmod: ERROR: could not insert module test_modules/$MOD_LIVEPATCH.ko: Device or resource busy
% rmmod test_klp_kprobe"
start_test "livepatch interaction with kprobed function without post_handler"
load_mod $MOD_KPROBE has_post_handler=false
load_lp $MOD_LIVEPATCH
unload_mod $MOD_KPROBE
disable_lp $MOD_LIVEPATCH
unload_lp $MOD_LIVEPATCH
check_result "% insmod test_modules/test_klp_kprobe.ko has_post_handler=false
% insmod test_modules/$MOD_LIVEPATCH.ko
livepatch: enabling patch '$MOD_LIVEPATCH'
livepatch: '$MOD_LIVEPATCH': initializing patching transition
livepatch: '$MOD_LIVEPATCH': starting patching transition
livepatch: '$MOD_LIVEPATCH': completing patching transition
livepatch: '$MOD_LIVEPATCH': patching complete
% rmmod test_klp_kprobe
% echo 0 > /sys/kernel/livepatch/$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

3
tools/testing/selftests/livepatch/test_modules/Makefile
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@ -6,11 +6,12 @@ obj-m += test_klp_atomic_replace.o \
test_klp_callbacks_demo.o \
test_klp_callbacks_demo2.o \
test_klp_callbacks_mod.o \
test_klp_kprobe.o \
test_klp_livepatch.o \
test_klp_shadow_vars.o \
test_klp_state.o \
test_klp_state2.o \
test_klp_state3.o \
test_klp_shadow_vars.o \
test_klp_syscall.o
# Ensure that KDIR exists, otherwise skip the compilation

38
tools/testing/selftests/livepatch/test_modules/test_klp_kprobe.c Normal file
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@ -0,0 +1,38 @@
// SPDX-License-Identifier: GPL-2.0
// Copyright (C) 2024 Marcos Paulo de Souza <mpdesouza@suse.com>
// Copyright (C) 2024 Michael Vetter <mvetter@suse.com>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/kprobes.h>
static bool has_post_handler = true;
module_param(has_post_handler, bool, 0444);
static void __kprobes post_handler(struct kprobe *p, struct pt_regs *regs,
unsigned long flags)
{
}
static struct kprobe kp = {
.symbol_name = "cmdline_proc_show",
};
static int __init kprobe_init(void)
{
if (has_post_handler)
kp.post_handler = post_handler;
return register_kprobe(&kp);
}
static void __exit kprobe_exit(void)
{
unregister_kprobe(&kp);
}
module_init(kprobe_init)
module_exit(kprobe_exit)
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Michael Vetter <mvetter@suse.com>");
MODULE_DESCRIPTION("Livepatch test: kprobe function");