/*
 * livepatch.h - Kernel Live Patching Core
 *
 * Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>
 * Copyright (C) 2014 SUSE
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, see <http://www.gnu.org/licenses/>.
 */

#ifndef _LINUX_LIVEPATCH_H_
#define _LINUX_LIVEPATCH_H_

#include <linux/module.h>
#include <linux/ftrace.h>
#include <linux/completion.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)
 * @immediate:  patch the func immediately, bypassing safety mechanisms
 * @old_addr:   the address of the function being patched
 * @kobj:       kobject for sysfs resources
 * @stack_node: list node for klp_ops func_stack list
 * @old_size:   size of the old function
 * @new_size:   size of the new function
 * @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;
        bool immediate;

        /* internal */
        unsigned long old_addr;
        struct kobject kobj;
        struct list_head stack_node;
        unsigned long old_size, new_size;
        bool patched;
        bool transition;
};

/**
 * 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
 * @kobj:       kobject for sysfs resources
 * @mod:        kernel module associated with the patched object
 *              (NULL for vmlinux)
 * @patched:    the object's funcs have been added to the klp_ops list
 */
struct klp_object {
        /* external */
        const char *name;
        struct klp_func *funcs;

        /* internal */
        struct kobject kobj;
        struct module *mod;
        bool patched;
};

/**
 * struct klp_patch - patch structure for live patching
 * @mod:        reference to the live patch module
 * @objs:       object entries for kernel objects to be patched
 * @immediate:  patch all funcs immediately, bypassing safety mechanisms
 * @list:       list node for global list of registered patches
 * @kobj:       kobject for sysfs resources
 * @enabled:    the patch is enabled (but operation may be incomplete)
 * @finish:     for waiting till it is safe to remove the patch module
 */
struct klp_patch {
        /* external */
        struct module *mod;
        struct klp_object *objs;
        bool immediate;

        /* internal */
        struct list_head list;
        struct kobject kobj;
        bool enabled;
        struct completion finish;
};

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

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

int klp_register_patch(struct klp_patch *);
int klp_unregister_patch(struct klp_patch *);
int klp_enable_patch(struct klp_patch *);
int klp_disable_patch(struct klp_patch *);

void arch_klp_init_object_loaded(struct klp_patch *patch,
                                 struct klp_object *obj);

/* 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);
}

#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) {}

#endif /* CONFIG_LIVEPATCH */

#endif /* _LINUX_LIVEPATCH_H_ */