Quelle livepatch.h Sprache: C

/* SPDX-License-Identifier: GPL-2.0-or-later */
/*
* livepatch.h - Kernel Live Patching Core
*
* Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>
* Copyright (C) 2014 SUSE
*/

#ifndef _LINUX_LIVEPATCH_H_
#define _LINUX_LIVEPATCH_H_

#include <linux/module.h>
#include <linux/ftrace.h>
#include <linux/completion.h>
#include <linux/list.h>
#include <linux/livepatch_sched.h>

#if IS_ENABLED(CONFIG_LIVEPATCH)

/* task patch states */
#define KLP_TRANSITION_IDLE  -1
#define KLP_TRANSITION_UNPATCHED  0
#define KLP_TRANSITION_PATCHED   1

/**
* struct klp_func - function structure for live patching
* @old_name: name of the function to be patched
* @new_func: pointer to the patched function code
* @old_sympos: a hint indicating which symbol position the old function
* can be found (optional)
* @old_func: pointer to the function being patched
* @kobj: kobject for sysfs resources
* @node: list node for klp_object func_list
* @stack_node: list node for klp_ops func_stack list
* @old_size: size of the old function
* @new_size: size of the new function
* @nop:        temporary patch to use the original code again; dyn. allocated
* @patched: the func has been added to the klp_ops list
* @transition: the func is currently being applied or reverted
*
* The patched and transition variables define the func's patching state.  When
* patching, a func is always in one of the following states:
*
*   patched=0 transition=0: unpatched
*   patched=0 transition=1: unpatched, temporary starting state
*   patched=1 transition=1: patched, may be visible to some tasks
*   patched=1 transition=0: patched, visible to all tasks
*
* And when unpatching, it goes in the reverse order:
*
*   patched=1 transition=0: patched, visible to all tasks
*   patched=1 transition=1: patched, may be visible to some tasks
*   patched=0 transition=1: unpatched, temporary ending state
*   patched=0 transition=0: unpatched
*/
struct klp_func {
/* external */
const char *old_name;
void *new_func;
/*
* The old_sympos field is optional and can be used to resolve
* duplicate symbol names in livepatch objects. If this field is zero,
* it is expected the symbol is unique, otherwise patching fails. If
* this value is greater than zero then that occurrence of the symbol
* in kallsyms for the given object is used.
*/
unsigned long old_sympos;

/* internal */
void *old_func;
struct kobject kobj;
struct list_head node;
struct list_head stack_node;
unsigned long old_size, new_size;
bool nop;
bool patched;
bool transition;
};

struct klp_object;

/**
* struct klp_callbacks - pre/post live-(un)patch callback structure
* @pre_patch: executed before code patching
* @post_patch: executed after code patching
* @pre_unpatch: executed before code unpatching
* @post_unpatch: executed after code unpatching
* @post_unpatch_enabled: flag indicating if post-unpatch callback
* should run
*
* All callbacks are optional.  Only the pre-patch callback, if provided,
* will be unconditionally executed.  If the parent klp_object fails to
* patch for any reason, including a non-zero error status returned from
* the pre-patch callback, no further callbacks will be executed.
*/
struct klp_callbacks {
int (*pre_patch)(struct klp_object *obj);
void (*post_patch)(struct klp_object *obj);
void (*pre_unpatch)(struct klp_object *obj);
void (*post_unpatch)(struct klp_object *obj);
bool post_unpatch_enabled;
};

/**
* struct klp_object - kernel object structure for live patching
* @name: module name (or NULL for vmlinux)
* @funcs: function entries for functions to be patched in the object
* @callbacks: functions to be executed pre/post (un)patching
* @kobj: kobject for sysfs resources
* @func_list: dynamic list of the function entries
* @node: list node for klp_patch obj_list
* @mod: kernel module associated with the patched object
* (NULL for vmlinux)
* @dynamic:    temporary object for nop functions; dynamically allocated
* @patched: the object's funcs have been added to the klp_ops list
*/
struct klp_object {
/* external */
const char *name;
struct klp_func *funcs;
struct klp_callbacks callbacks;

/* internal */
struct kobject kobj;
struct list_head func_list;
struct list_head node;
struct module *mod;
bool dynamic;
bool patched;
};

/**
* struct klp_state - state of the system modified by the livepatch
* @id: system state identifier (non-zero)
* @version: version of the change
* @data: custom data
*/
struct klp_state {
unsigned long id;
unsigned int version;
void *data;
};

/**
* struct klp_patch - patch structure for live patching
* @mod: reference to the live patch module
* @objs: object entries for kernel objects to be patched
* @states: system states that can get modified
* @replace: replace all actively used patches
* @list: list node for global list of actively used patches
* @kobj: kobject for sysfs resources
* @obj_list: dynamic list of the object entries
* @enabled: the patch is enabled (but operation may be incomplete)
* @forced: was involved in a forced transition
* @free_work: patch cleanup from workqueue-context
* @finish: for waiting till it is safe to remove the patch module
*/
struct klp_patch {
/* external */
struct module *mod;
struct klp_object *objs;
struct klp_state *states;
bool replace;

/* internal */
struct list_head list;
struct kobject kobj;
struct list_head obj_list;
bool enabled;
bool forced;
struct work_struct free_work;
struct completion finish;
};

#define klp_for_each_object_static(patch, obj) \
for (obj = patch->objs; obj->funcs || obj->name; obj++)

#define klp_for_each_object_safe(patch, obj, tmp_obj)  \
list_for_each_entry_safe(obj, tmp_obj, &patch->obj_list, node)

#define klp_for_each_object(patch, obj) \
list_for_each_entry(obj, &patch->obj_list, node)

#define klp_for_each_func_static(obj, func) \
for (func = obj->funcs; \
      func->old_name || func->new_func || func->old_sympos; \
      func++)

#define klp_for_each_func_safe(obj, func, tmp_func)   \
list_for_each_entry_safe(func, tmp_func, &obj->func_list, node)

#define klp_for_each_func(obj, func) \
list_for_each_entry(func, &obj->func_list, node)

int klp_enable_patch(struct klp_patch *);

/* Called from the module loader during module coming/going states */
int klp_module_coming(struct module *mod);
void klp_module_going(struct module *mod);

void klp_copy_process(struct task_struct *child);
void klp_update_patch_state(struct task_struct *task);

static inline bool klp_patch_pending(struct task_struct *task)
{
return test_tsk_thread_flag(task, TIF_PATCH_PENDING);
}

static inline bool klp_have_reliable_stack(void)
{
return IS_ENABLED(CONFIG_STACKTRACE) &&
        IS_ENABLED(CONFIG_HAVE_RELIABLE_STACKTRACE);
}

typedef int (*klp_shadow_ctor_t)(void *obj,
     void *shadow_data,
     void *ctor_data);
typedef void (*klp_shadow_dtor_t)(void *obj, void *shadow_data);

void *klp_shadow_get(void *obj, unsigned long id);
void *klp_shadow_alloc(void *obj, unsigned long id,
         size_t size, gfp_t gfp_flags,
         klp_shadow_ctor_t ctor, void *ctor_data);
void *klp_shadow_get_or_alloc(void *obj, unsigned long id,
         size_t size, gfp_t gfp_flags,
         klp_shadow_ctor_t ctor, void *ctor_data);
void klp_shadow_free(void *obj, unsigned long id, klp_shadow_dtor_t dtor);
void klp_shadow_free_all(unsigned long id, klp_shadow_dtor_t dtor);

struct klp_state *klp_get_state(struct klp_patch *patch, unsigned long id);
struct klp_state *klp_get_prev_state(unsigned long id);

int klp_apply_section_relocs(struct module *pmod, Elf_Shdr *sechdrs,
        const char *shstrtab, const char *strtab,
        unsigned int symindex, unsigned int secindex,
        const char *objname);

#else /* !CONFIG_LIVEPATCH */

static inline int klp_module_coming(struct module *mod) { return 0; }
static inline void klp_module_going(struct module *mod) {}
static inline bool klp_patch_pending(struct task_struct *task) { return false; }
static inline void klp_update_patch_state(struct task_struct *task) {}
static inline void klp_copy_process(struct task_struct *child) {}

static inline
int klp_apply_section_relocs(struct module *pmod, Elf_Shdr *sechdrs,
        const char *shstrtab, const char *strtab,
        unsigned int symindex, unsigned int secindex,
        const char *objname)
{
return 0;
}

#endif /* CONFIG_LIVEPATCH */

#endif /* _LINUX_LIVEPATCH_H_ */

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