/* 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>

#if IS_ENABLED(CONFIG_LIVEPATCH)

#include <asm/livepatch.h>

/* task patch states */
#define KLP_UNDEFINED   -1
#define KLP_UNPATCHED    0
#define KLP_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_ */