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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: 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>
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‎tools/testing/selftests/livepatch/Makefile

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@@ -10,7 +10,8 @@ TEST_PROGS := \
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test-state.sh \
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test-ftrace.sh \
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test-sysfs.sh \
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test-syscall.sh
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test-syscall.sh \
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test-kprobe.sh
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TEST_FILES := settings
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‎tools/testing/selftests/livepatch/test-kprobe.sh

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#!/bin/bash
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# SPDX-License-Identifier: GPL-2.0
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# Copyright (C) 2024 SUSE
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# Author: Michael Vetter <mvetter@suse.com>
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. $(dirname $0)/functions.sh
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MOD_LIVEPATCH=test_klp_livepatch
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MOD_KPROBE=test_klp_kprobe
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setup_config
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# Kprobe a function and verify that we can't livepatch that same function
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# when it uses a post_handler since only one IPMODIFY maybe be registered
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# to any given function at a time.
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start_test "livepatch interaction with kprobed function with post_handler"
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echo 1 > "$SYSFS_KPROBES_DIR/enabled"
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load_mod $MOD_KPROBE has_post_handler=true
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load_failing_mod $MOD_LIVEPATCH
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unload_mod $MOD_KPROBE
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check_result "% insmod test_modules/test_klp_kprobe.ko has_post_handler=true
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% insmod test_modules/$MOD_LIVEPATCH.ko
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livepatch: enabling patch '$MOD_LIVEPATCH'
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livepatch: '$MOD_LIVEPATCH': initializing patching transition
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livepatch: failed to register ftrace handler for function 'cmdline_proc_show' (-16)
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livepatch: failed to patch object 'vmlinux'
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livepatch: failed to enable patch '$MOD_LIVEPATCH'
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livepatch: '$MOD_LIVEPATCH': canceling patching transition, going to unpatch
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livepatch: '$MOD_LIVEPATCH': completing unpatching transition
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livepatch: '$MOD_LIVEPATCH': unpatching complete
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insmod: ERROR: could not insert module test_modules/$MOD_LIVEPATCH.ko: Device or resource busy
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% rmmod test_klp_kprobe"
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start_test "livepatch interaction with kprobed function without post_handler"
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load_mod $MOD_KPROBE has_post_handler=false
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load_lp $MOD_LIVEPATCH
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unload_mod $MOD_KPROBE
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disable_lp $MOD_LIVEPATCH
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unload_lp $MOD_LIVEPATCH
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check_result "% insmod test_modules/test_klp_kprobe.ko has_post_handler=false
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% insmod test_modules/$MOD_LIVEPATCH.ko
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livepatch: enabling patch '$MOD_LIVEPATCH'
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livepatch: '$MOD_LIVEPATCH': initializing patching transition
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livepatch: '$MOD_LIVEPATCH': starting patching transition
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livepatch: '$MOD_LIVEPATCH': completing patching transition
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livepatch: '$MOD_LIVEPATCH': patching complete
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% rmmod test_klp_kprobe
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% echo 0 > /sys/kernel/livepatch/$MOD_LIVEPATCH/enabled
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livepatch: '$MOD_LIVEPATCH': initializing unpatching transition
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livepatch: '$MOD_LIVEPATCH': starting unpatching transition
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livepatch: '$MOD_LIVEPATCH': completing unpatching transition
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livepatch: '$MOD_LIVEPATCH': unpatching complete
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% rmmod $MOD_LIVEPATCH"
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exit 0

‎tools/testing/selftests/livepatch/test_modules/Makefile

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@@ -6,11 +6,12 @@ obj-m += test_klp_atomic_replace.o \
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test_klp_callbacks_demo.o \
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test_klp_callbacks_demo2.o \
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test_klp_callbacks_mod.o \
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test_klp_kprobe.o \
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test_klp_livepatch.o \
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test_klp_shadow_vars.o \
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test_klp_state.o \
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test_klp_state2.o \
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test_klp_state3.o \
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test_klp_shadow_vars.o \
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test_klp_syscall.o
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# 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
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// Copyright (C) 2024 Marcos Paulo de Souza <mpdesouza@suse.com>
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// Copyright (C) 2024 Michael Vetter <mvetter@suse.com>
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/kprobes.h>
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static bool has_post_handler = true;
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module_param(has_post_handler, bool, 0444);
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static void __kprobes post_handler(struct kprobe *p, struct pt_regs *regs,
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unsigned long flags)
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{
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}
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static struct kprobe kp = {
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.symbol_name = "cmdline_proc_show",
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};
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static int __init kprobe_init(void)
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{
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if (has_post_handler)
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kp.post_handler = post_handler;
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return register_kprobe(&kp);
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}
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static void __exit kprobe_exit(void)
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{
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unregister_kprobe(&kp);
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}
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module_init(kprobe_init)
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module_exit(kprobe_exit)
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Michael Vetter <mvetter@suse.com>");
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MODULE_DESCRIPTION("Livepatch test: kprobe function");

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