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![Petr Mladek](/assets/img/avatar_default.png)
We might need to do some actions before the shadow variable is freed. For example, we might need to remove it from a list or free some data that it points to. This is already possible now. The user can get the shadow variable by klp_shadow_get(), do the necessary actions, and then call klp_shadow_free(). This patch allows to do it a more elegant way. The user could implement the needed actions in a callback that is passed to klp_shadow_free() as a parameter. The callback usually does reverse operations to the constructor callback that can be called by klp_shadow_*alloc(). It is especially useful for klp_shadow_free_all(). There we need to do these extra actions for each found shadow variable with the given ID. Note that the memory used by the shadow variable itself is still released later by rcu callback. It is needed to protect internal structures that keep all shadow variables. But the destructor is called immediately. The shadow variable must not be access anyway after klp_shadow_free() is called. The user is responsible to protect this any suitable way. Be aware that the destructor is called under klp_shadow_lock. It is the same as for the contructor in klp_shadow_alloc(). Signed-off-by: Petr Mladek <pmladek@suse.com> Acked-by: Josh Poimboeuf <jpoimboe@redhat.com> Acked-by: Miroslav Benes <mbenes@suse.cz> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
214 lines
7 KiB
C
214 lines
7 KiB
C
/*
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* livepatch.h - Kernel Live Patching Core
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*
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* Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>
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* Copyright (C) 2014 SUSE
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef _LINUX_LIVEPATCH_H_
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#define _LINUX_LIVEPATCH_H_
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#include <linux/module.h>
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#include <linux/ftrace.h>
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#include <linux/completion.h>
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#if IS_ENABLED(CONFIG_LIVEPATCH)
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#include <asm/livepatch.h>
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/* task patch states */
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#define KLP_UNDEFINED -1
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#define KLP_UNPATCHED 0
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#define KLP_PATCHED 1
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/**
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* struct klp_func - function structure for live patching
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* @old_name: name of the function to be patched
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* @new_func: pointer to the patched function code
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* @old_sympos: a hint indicating which symbol position the old function
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* can be found (optional)
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* @old_addr: the address of the function being patched
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* @kobj: kobject for sysfs resources
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* @stack_node: list node for klp_ops func_stack list
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* @old_size: size of the old function
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* @new_size: size of the new function
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* @patched: the func has been added to the klp_ops list
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* @transition: the func is currently being applied or reverted
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*
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* The patched and transition variables define the func's patching state. When
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* patching, a func is always in one of the following states:
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*
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* patched=0 transition=0: unpatched
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* patched=0 transition=1: unpatched, temporary starting state
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* patched=1 transition=1: patched, may be visible to some tasks
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* patched=1 transition=0: patched, visible to all tasks
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*
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* And when unpatching, it goes in the reverse order:
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*
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* patched=1 transition=0: patched, visible to all tasks
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* patched=1 transition=1: patched, may be visible to some tasks
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* patched=0 transition=1: unpatched, temporary ending state
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* patched=0 transition=0: unpatched
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*/
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struct klp_func {
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/* external */
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const char *old_name;
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void *new_func;
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/*
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* The old_sympos field is optional and can be used to resolve
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* duplicate symbol names in livepatch objects. If this field is zero,
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* it is expected the symbol is unique, otherwise patching fails. If
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* this value is greater than zero then that occurrence of the symbol
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* in kallsyms for the given object is used.
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*/
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unsigned long old_sympos;
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/* internal */
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unsigned long old_addr;
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struct kobject kobj;
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struct list_head stack_node;
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unsigned long old_size, new_size;
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bool patched;
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bool transition;
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};
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struct klp_object;
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/**
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* struct klp_callbacks - pre/post live-(un)patch callback structure
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* @pre_patch: executed before code patching
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* @post_patch: executed after code patching
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* @pre_unpatch: executed before code unpatching
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* @post_unpatch: executed after code unpatching
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* @post_unpatch_enabled: flag indicating if post-unpatch callback
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* should run
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*
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* All callbacks are optional. Only the pre-patch callback, if provided,
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* will be unconditionally executed. If the parent klp_object fails to
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* patch for any reason, including a non-zero error status returned from
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* the pre-patch callback, no further callbacks will be executed.
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*/
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struct klp_callbacks {
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int (*pre_patch)(struct klp_object *obj);
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void (*post_patch)(struct klp_object *obj);
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void (*pre_unpatch)(struct klp_object *obj);
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void (*post_unpatch)(struct klp_object *obj);
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bool post_unpatch_enabled;
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};
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/**
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* struct klp_object - kernel object structure for live patching
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* @name: module name (or NULL for vmlinux)
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* @funcs: function entries for functions to be patched in the object
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* @callbacks: functions to be executed pre/post (un)patching
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* @kobj: kobject for sysfs resources
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* @mod: kernel module associated with the patched object
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* (NULL for vmlinux)
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* @patched: the object's funcs have been added to the klp_ops list
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*/
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struct klp_object {
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/* external */
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const char *name;
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struct klp_func *funcs;
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struct klp_callbacks callbacks;
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/* internal */
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struct kobject kobj;
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struct module *mod;
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bool patched;
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};
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/**
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* struct klp_patch - patch structure for live patching
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* @mod: reference to the live patch module
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* @objs: object entries for kernel objects to be patched
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* @list: list node for global list of registered patches
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* @kobj: kobject for sysfs resources
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* @enabled: the patch is enabled (but operation may be incomplete)
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* @finish: for waiting till it is safe to remove the patch module
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*/
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struct klp_patch {
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/* external */
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struct module *mod;
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struct klp_object *objs;
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/* internal */
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struct list_head list;
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struct kobject kobj;
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bool enabled;
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struct completion finish;
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};
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#define klp_for_each_object(patch, obj) \
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for (obj = patch->objs; obj->funcs || obj->name; obj++)
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#define klp_for_each_func(obj, func) \
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for (func = obj->funcs; \
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func->old_name || func->new_func || func->old_sympos; \
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func++)
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int klp_register_patch(struct klp_patch *);
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int klp_unregister_patch(struct klp_patch *);
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int klp_enable_patch(struct klp_patch *);
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int klp_disable_patch(struct klp_patch *);
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void arch_klp_init_object_loaded(struct klp_patch *patch,
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struct klp_object *obj);
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/* Called from the module loader during module coming/going states */
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int klp_module_coming(struct module *mod);
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void klp_module_going(struct module *mod);
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void klp_copy_process(struct task_struct *child);
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void klp_update_patch_state(struct task_struct *task);
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static inline bool klp_patch_pending(struct task_struct *task)
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{
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return test_tsk_thread_flag(task, TIF_PATCH_PENDING);
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}
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static inline bool klp_have_reliable_stack(void)
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{
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return IS_ENABLED(CONFIG_STACKTRACE) &&
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IS_ENABLED(CONFIG_HAVE_RELIABLE_STACKTRACE);
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}
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typedef int (*klp_shadow_ctor_t)(void *obj,
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void *shadow_data,
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void *ctor_data);
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typedef void (*klp_shadow_dtor_t)(void *obj, void *shadow_data);
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void *klp_shadow_get(void *obj, unsigned long id);
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void *klp_shadow_alloc(void *obj, unsigned long id,
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size_t size, gfp_t gfp_flags,
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klp_shadow_ctor_t ctor, void *ctor_data);
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void *klp_shadow_get_or_alloc(void *obj, unsigned long id,
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size_t size, gfp_t gfp_flags,
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klp_shadow_ctor_t ctor, void *ctor_data);
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void klp_shadow_free(void *obj, unsigned long id, klp_shadow_dtor_t dtor);
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void klp_shadow_free_all(unsigned long id, klp_shadow_dtor_t dtor);
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#else /* !CONFIG_LIVEPATCH */
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static inline int klp_module_coming(struct module *mod) { return 0; }
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static inline void klp_module_going(struct module *mod) {}
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static inline bool klp_patch_pending(struct task_struct *task) { return false; }
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static inline void klp_update_patch_state(struct task_struct *task) {}
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static inline void klp_copy_process(struct task_struct *child) {}
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#endif /* CONFIG_LIVEPATCH */
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#endif /* _LINUX_LIVEPATCH_H_ */
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