Commit 62597edf authored by Michael Vetter's avatar Michael Vetter Committed by Petr Mladek
Browse files

selftests: livepatch: test livepatching a kprobed function 



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: default avatarMichael Vetter <mvetter@suse.com>
Reviewed-by: default avatarMiroslav Benes <mbenes@suse.cz>
Reviewed-by: default avatarJoe Lawrence <joe.lawrence@redhat.com>
Tested-by: default avatarMarcos Paulo de Souza <mpdesouza@suse.com>
Reviewed-by: default avatarMarcos Paulo de Souza <mpdesouza@suse.com>
Reviewed-by: default avatarPetr Mladek <pmladek@suse.com>
Tested-by: default avatarPetr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20241017200132.21946-4-mvetter@suse.com


Signed-off-by: default avatarPetr Mladek <pmladek@suse.com>
parent 59766286

tools/testing/selftests/livepatch/Makefile

+2 −1
Original line number Diff line number Diff line
@@ -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

tools/testing/selftests/livepatch/test-kprobe.sh

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Original line number Diff line number Diff line 
#!/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

tools/testing/selftests/livepatch/test_modules/Makefile

+2 −1
Original line number Diff line number Diff line
@@ -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

tools/testing/selftests/livepatch/test_modules/test_klp_kprobe.c

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// 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");