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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * core.c - Kernel Live Patching Core
  *
  * Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>
  * Copyright (C) 2014 SUSE
  */
 
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 
 #include <linux/module.h>
 #include <linux/kernel.h>
 #include <linux/mutex.h>
 #include <linux/slab.h>
 #include <linux/list.h>
 #include <linux/kallsyms.h>
 #include <linux/livepatch.h>
 #include <linux/elf.h>
 #include <linux/moduleloader.h>
 #include <linux/completion.h>
 #include <linux/memory.h>
 #include <linux/rcupdate.h>
 #include <asm/cacheflush.h>
 #include "core.h"
 #include "patch.h"
 #include "state.h"
 #include "transition.h"
 
 /*
  * klp_mutex is a coarse lock which serializes access to klp data.  All
  * accesses to klp-related variables and structures must have mutex protection,
  * except within the following functions which carefully avoid the need for it:
  *
  * - klp_ftrace_handler()
  * - klp_update_patch_state()
  */
 DEFINE_MUTEX(klp_mutex);
 
 /*
  * Actively used patches: enabled or in transition. Note that replaced
  * or disabled patches are not listed even though the related kernel
  * module still can be loaded.
  */
 LIST_HEAD(klp_patches);
 
 static struct kobject *klp_root_kobj;
 
 static bool klp_is_module(struct klp_object *obj)
 {
     return obj->name;
 }
 
 /* sets obj->mod if object is not vmlinux and module is found */
 static void klp_find_object_module(struct klp_object *obj)
 {
     struct module *mod;
 
     if (!klp_is_module(obj))
         return;
 
     rcu_read_lock_sched();
     /*
      * We do not want to block removal of patched modules and therefore
      * we do not take a reference here. The patches are removed by
      * klp_module_going() instead.
      */
     mod = find_module(obj->name);
     /*
      * Do not mess work of klp_module_coming() and klp_module_going().
      * Note that the patch might still be needed before klp_module_going()
      * is called. Module functions can be called even in the GOING state
      * until mod->exit() finishes. This is especially important for
      * patches that modify semantic of the functions.
      */
     if (mod && mod->klp_alive)
         obj->mod = mod;
 
     rcu_read_unlock_sched();
 }
 
 static bool klp_initialized(void)
 {
     return !!klp_root_kobj;
 }
 
 static struct klp_func *klp_find_func(struct klp_object *obj,
                       struct klp_func *old_func)
 {
     struct klp_func *func;
 
     klp_for_each_func(obj, func) {
         if ((strcmp(old_func->old_name, func->old_name) == 0) &&
             (old_func->old_sympos == func->old_sympos)) {
             return func;
         }
     }
 
     return NULL;
 }
 
 static struct klp_object *klp_find_object(struct klp_patch *patch,
                       struct klp_object *old_obj)
 {
     struct klp_object *obj;
 
     klp_for_each_object(patch, obj) {
         if (klp_is_module(old_obj)) {
             if (klp_is_module(obj) &&
                 strcmp(old_obj->name, obj->name) == 0) {
                 return obj;
             }
         } else if (!klp_is_module(obj)) {
             return obj;
         }
     }
 
     return NULL;
 }
 
 struct klp_find_arg {
     const char *objname;
     const char *name;
     unsigned long addr;
     unsigned long count;
     unsigned long pos;
 };
 
 static int klp_find_callback(void *data, const char *name,
                  struct module *mod, unsigned long addr)
 {
     struct klp_find_arg *args = data;
 
     if ((mod && !args->objname) || (!mod && args->objname))
         return 0;
 
     if (strcmp(args->name, name))
         return 0;
 
     if (args->objname && strcmp(args->objname, mod->name))
         return 0;
 
     args->addr = addr;
     args->count++;
 
     /*
      * Finish the search when the symbol is found for the desired position
      * or the position is not defined for a non-unique symbol.
      */
     if ((args->pos && (args->count == args->pos)) ||
         (!args->pos && (args->count > 1)))
         return 1;
 
     return 0;
 }
 
 static int klp_find_object_symbol(const char *objname, const char *name,
                   unsigned long sympos, unsigned long *addr)
 {
     struct klp_find_arg args = {
         .objname = objname,
         .name = name,
         .addr = 0,
         .count = 0,
         .pos = sympos,
     };
 
     if (objname)
         module_kallsyms_on_each_symbol(klp_find_callback, &args);
     else
         kallsyms_on_each_symbol(klp_find_callback, &args);
 
     /*
      * Ensure an address was found. If sympos is 0, ensure symbol is unique;
      * otherwise ensure the symbol position count matches sympos.
      */
     if (args.addr == 0)
         pr_err("symbol '%s' not found in symbol table\n", name);
     else if (args.count > 1 && sympos == 0) {
         pr_err("unresolvable ambiguity for symbol '%s' in object '%s'\n",
                name, objname);
     } else if (sympos != args.count && sympos > 0) {
         pr_err("symbol position %lu for symbol '%s' in object '%s' not found\n",
                sympos, name, objname ? objname : "vmlinux");
     } else {
         *addr = args.addr;
         return 0;
     }
 
     *addr = 0;
     return -EINVAL;
 }
 
 static int klp_resolve_symbols(Elf_Shdr *sechdrs, const char *strtab,
                    unsigned int symndx, Elf_Shdr *relasec,
                    const char *sec_objname)
 {
     int i, cnt, ret;
     char sym_objname[MODULE_NAME_LEN];
     char sym_name[KSYM_NAME_LEN];
     Elf_Rela *relas;
     Elf_Sym *sym;
     unsigned long sympos, addr;
     bool sym_vmlinux;
     bool sec_vmlinux = !strcmp(sec_objname, "vmlinux");
 
     /*
      * Since the field widths for sym_objname and sym_name in the sscanf()
      * call are hard-coded and correspond to MODULE_NAME_LEN and
      * KSYM_NAME_LEN respectively, we must make sure that MODULE_NAME_LEN
      * and KSYM_NAME_LEN have the values we expect them to have.
      *
      * Because the value of MODULE_NAME_LEN can differ among architectures,
      * we use the smallest/strictest upper bound possible (56, based on
      * the current definition of MODULE_NAME_LEN) to prevent overflows.
      */
     BUILD_BUG_ON(MODULE_NAME_LEN < 56 || KSYM_NAME_LEN != 128);
 
     relas = (Elf_Rela *) relasec->sh_addr;
     /* For each rela in this klp relocation section */
     for (i = 0; i < relasec->sh_size / sizeof(Elf_Rela); i++) {
         sym = (Elf_Sym *)sechdrs[symndx].sh_addr + ELF_R_SYM(relas[i].r_info);
         if (sym->st_shndx != SHN_LIVEPATCH) {
             pr_err("symbol %s is not marked as a livepatch symbol\n",
                    strtab + sym->st_name);
             return -EINVAL;
         }
 
         /* Format: .klp.sym.sym_objname.sym_name,sympos */
         cnt = sscanf(strtab + sym->st_name,
                  ".klp.sym.%55[^.].%127[^,],%lu",
                  sym_objname, sym_name, &sympos);
         if (cnt != 3) {
             pr_err("symbol %s has an incorrectly formatted name\n",
                    strtab + sym->st_name);
             return -EINVAL;
         }
 
         sym_vmlinux = !strcmp(sym_objname, "vmlinux");
 
         /*
          * Prevent module-specific KLP rela sections from referencing
          * vmlinux symbols.  This helps prevent ordering issues with
          * module special section initializations.  Presumably such
          * symbols are exported and normal relas can be used instead.
          */
         if (!sec_vmlinux && sym_vmlinux) {
             pr_err("invalid access to vmlinux symbol '%s' from module-specific livepatch relocation section",
                    sym_name);
             return -EINVAL;
         }
 
         /* klp_find_object_symbol() treats a NULL objname as vmlinux */
         ret = klp_find_object_symbol(sym_vmlinux ? NULL : sym_objname,
                          sym_name, sympos, &addr);
         if (ret)
             return ret;
 
         sym->st_value = addr;
     }
 
     return 0;
 }
 
 /*
  * At a high-level, there are two types of klp relocation sections: those which
  * reference symbols which live in vmlinux; and those which reference symbols
  * which live in other modules.  This function is called for both types:
  *
  * 1) When a klp module itself loads, the module code calls this function to
  *    write vmlinux-specific klp relocations (.klp.rela.vmlinux.* sections).
  *    These relocations are written to the klp module text to allow the patched
  *    code/data to reference unexported vmlinux symbols.  They're written as
  *    early as possible to ensure that other module init code (.e.g.,
  *    jump_label_apply_nops) can access any unexported vmlinux symbols which
  *    might be referenced by the klp module's special sections.
  *
  * 2) When a to-be-patched module loads -- or is already loaded when a
  *    corresponding klp module loads -- klp code calls this function to write
  *    module-specific klp relocations (.klp.rela.{module}.* sections).  These
  *    are written to the klp module text to allow the patched code/data to
  *    reference symbols which live in the to-be-patched module or one of its
  *    module dependencies.  Exported symbols are supported, in addition to
  *    unexported symbols, in order to enable late module patching, which allows
  *    the to-be-patched module to be loaded and patched sometime *after* the
  *    klp module is loaded.
  */
 int klp_apply_section_relocs(struct module *pmod, Elf_Shdr *sechdrs,
                  const char *shstrtab, const char *strtab,
                  unsigned int symndx, unsigned int secndx,
                  const char *objname)
 {
     int cnt, ret;
     char sec_objname[MODULE_NAME_LEN];
     Elf_Shdr *sec = sechdrs + secndx;
 
     /*
      * Format: .klp.rela.sec_objname.section_name
      * See comment in klp_resolve_symbols() for an explanation
      * of the selected field width value.
      */
     cnt = sscanf(shstrtab + sec->sh_name, ".klp.rela.%55[^.]",
              sec_objname);
     if (cnt != 1) {
         pr_err("section %s has an incorrectly formatted name\n",
                shstrtab + sec->sh_name);
         return -EINVAL;
     }
 
     if (strcmp(objname ? objname : "vmlinux", sec_objname))
         return 0;
 
     ret = klp_resolve_symbols(sechdrs, strtab, symndx, sec, sec_objname);
     if (ret)
         return ret;
 
     return apply_relocate_add(sechdrs, strtab, symndx, secndx, pmod);
 }
 
 /*
  * Sysfs Interface
  *
  * /sys/kernel/livepatch
  * /sys/kernel/livepatch/<patch>
  * /sys/kernel/livepatch/<patch>/enabled
  * /sys/kernel/livepatch/<patch>/transition
  * /sys/kernel/livepatch/<patch>/force
  * /sys/kernel/livepatch/<patch>/<object>
  * /sys/kernel/livepatch/<patch>/<object>/<function,sympos>
  */
 static int __klp_disable_patch(struct klp_patch *patch);
 
 static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr,
                  const char *buf, size_t count)
 {
     struct klp_patch *patch;
     int ret;
     bool enabled;
 
     ret = kstrtobool(buf, &enabled);
     if (ret)
         return ret;
 
     patch = container_of(kobj, struct klp_patch, kobj);
 
     mutex_lock(&klp_mutex);
 
     if (patch->enabled == enabled) {
         /* already in requested state */
         ret = -EINVAL;
         goto out;
     }
 
     /*
      * Allow to reverse a pending transition in both ways. It might be
      * necessary to complete the transition without forcing and breaking
      * the system integrity.
      *
      * Do not allow to re-enable a disabled patch.
      */
     if (patch == klp_transition_patch)
         klp_reverse_transition();
     else if (!enabled)
         ret = __klp_disable_patch(patch);
     else
         ret = -EINVAL;
 
 out:
     mutex_unlock(&klp_mutex);
 
     if (ret)
         return ret;
     return count;
 }
 
 static ssize_t enabled_show(struct kobject *kobj,
                 struct kobj_attribute *attr, char *buf)
 {
     struct klp_patch *patch;
 
     patch = container_of(kobj, struct klp_patch, kobj);
     return snprintf(buf, PAGE_SIZE-1, "%d\n", patch->enabled);
 }
 
 static ssize_t transition_show(struct kobject *kobj,
                    struct kobj_attribute *attr, char *buf)
 {
     struct klp_patch *patch;
 
     patch = container_of(kobj, struct klp_patch, kobj);
     return snprintf(buf, PAGE_SIZE-1, "%d\n",
             patch == klp_transition_patch);
 }
 
 static ssize_t force_store(struct kobject *kobj, struct kobj_attribute *attr,
                const char *buf, size_t count)
 {
     struct klp_patch *patch;
     int ret;
     bool val;
 
     ret = kstrtobool(buf, &val);
     if (ret)
         return ret;
 
     if (!val)
         return count;
 
     mutex_lock(&klp_mutex);
 
     patch = container_of(kobj, struct klp_patch, kobj);
     if (patch != klp_transition_patch) {
         mutex_unlock(&klp_mutex);
         return -EINVAL;
     }
 
     klp_force_transition();
 
     mutex_unlock(&klp_mutex);
 
     return count;
 }
 
 static struct kobj_attribute enabled_kobj_attr = __ATTR_RW(enabled);
 static struct kobj_attribute transition_kobj_attr = __ATTR_RO(transition);
 static struct kobj_attribute force_kobj_attr = __ATTR_WO(force);
 static struct attribute *klp_patch_attrs[] = {
     &enabled_kobj_attr.attr,
     &transition_kobj_attr.attr,
     &force_kobj_attr.attr,
     NULL
 };
 ATTRIBUTE_GROUPS(klp_patch);
 
 static void klp_free_object_dynamic(struct klp_object *obj)
 {
     kfree(obj->name);
     kfree(obj);
 }
 
 static void klp_init_func_early(struct klp_object *obj,
                 struct klp_func *func);
 static void klp_init_object_early(struct klp_patch *patch,
                   struct klp_object *obj);
 
 static struct klp_object *klp_alloc_object_dynamic(const char *name,
                            struct klp_patch *patch)
 {
     struct klp_object *obj;
 
     obj = kzalloc(sizeof(*obj), GFP_KERNEL);
     if (!obj)
         return NULL;
 
     if (name) {
         obj->name = kstrdup(name, GFP_KERNEL);
         if (!obj->name) {
             kfree(obj);
             return NULL;
         }
     }
 
     klp_init_object_early(patch, obj);
     obj->dynamic = true;
 
     return obj;
 }
 
 static void klp_free_func_nop(struct klp_func *func)
 {
     kfree(func->old_name);
     kfree(func);
 }
 
 static struct klp_func *klp_alloc_func_nop(struct klp_func *old_func,
                        struct klp_object *obj)
 {
     struct klp_func *func;
 
     func = kzalloc(sizeof(*func), GFP_KERNEL);
     if (!func)
         return NULL;
 
     if (old_func->old_name) {
         func->old_name = kstrdup(old_func->old_name, GFP_KERNEL);
         if (!func->old_name) {
             kfree(func);
             return NULL;
         }
     }
 
     klp_init_func_early(obj, func);
     /*
      * func->new_func is same as func->old_func. These addresses are
      * set when the object is loaded, see klp_init_object_loaded().
      */
     func->old_sympos = old_func->old_sympos;
     func->nop = true;
 
     return func;
 }
 
 static int klp_add_object_nops(struct klp_patch *patch,
                    struct klp_object *old_obj)
 {
     struct klp_object *obj;
     struct klp_func *func, *old_func;
 
     obj = klp_find_object(patch, old_obj);
 
     if (!obj) {
         obj = klp_alloc_object_dynamic(old_obj->name, patch);
         if (!obj)
             return -ENOMEM;
     }
 
     klp_for_each_func(old_obj, old_func) {
         func = klp_find_func(obj, old_func);
         if (func)
             continue;
 
         func = klp_alloc_func_nop(old_func, obj);
         if (!func)
             return -ENOMEM;
     }
 
     return 0;
 }
 
 /*
  * Add 'nop' functions which simply return to the caller to run
  * the original function. The 'nop' functions are added to a
  * patch to facilitate a 'replace' mode.
  */
 static int klp_add_nops(struct klp_patch *patch)
 {
     struct klp_patch *old_patch;
     struct klp_object *old_obj;
 
     klp_for_each_patch(old_patch) {
         klp_for_each_object(old_patch, old_obj) {
             int err;
 
             err = klp_add_object_nops(patch, old_obj);
             if (err)
                 return err;
         }
     }
 
     return 0;
 }
 
 static void klp_kobj_release_patch(struct kobject *kobj)
 {
     struct klp_patch *patch;
 
     patch = container_of(kobj, struct klp_patch, kobj);
     complete(&patch->finish);
 }
 
 static struct kobj_type klp_ktype_patch = {
     .release = klp_kobj_release_patch,
     .sysfs_ops = &kobj_sysfs_ops,
     .default_groups = klp_patch_groups,
 };
 
 static void klp_kobj_release_object(struct kobject *kobj)
 {
     struct klp_object *obj;
 
     obj = container_of(kobj, struct klp_object, kobj);
 
     if (obj->dynamic)
         klp_free_object_dynamic(obj);
 }
 
 static struct kobj_type klp_ktype_object = {
     .release = klp_kobj_release_object,
     .sysfs_ops = &kobj_sysfs_ops,
 };
 
 static void klp_kobj_release_func(struct kobject *kobj)
 {
     struct klp_func *func;
 
     func = container_of(kobj, struct klp_func, kobj);
 
     if (func->nop)
         klp_free_func_nop(func);
 }
 
 static struct kobj_type klp_ktype_func = {
     .release = klp_kobj_release_func,
     .sysfs_ops = &kobj_sysfs_ops,
 };
 
 static void __klp_free_funcs(struct klp_object *obj, bool nops_only)
 {
     struct klp_func *func, *tmp_func;
 
     klp_for_each_func_safe(obj, func, tmp_func) {
         if (nops_only && !func->nop)
             continue;
 
         list_del(&func->node);
         kobject_put(&func->kobj);
     }
 }
 
 /* Clean up when a patched object is unloaded */
 static void klp_free_object_loaded(struct klp_object *obj)
 {
     struct klp_func *func;
 
     obj->mod = NULL;
 
     klp_for_each_func(obj, func) {
         func->old_func = NULL;
 
         if (func->nop)
             func->new_func = NULL;
     }
 }
 
 static void __klp_free_objects(struct klp_patch *patch, bool nops_only)
 {
     struct klp_object *obj, *tmp_obj;
 
     klp_for_each_object_safe(patch, obj, tmp_obj) {
         __klp_free_funcs(obj, nops_only);
 
         if (nops_only && !obj->dynamic)
             continue;
 
         list_del(&obj->node);
         kobject_put(&obj->kobj);
     }
 }
 
 static void klp_free_objects(struct klp_patch *patch)
 {
     __klp_free_objects(patch, false);
 }
 
 static void klp_free_objects_dynamic(struct klp_patch *patch)
 {
     __klp_free_objects(patch, true);
 }
 
 /*
  * This function implements the free operations that can be called safely
  * under klp_mutex.
  *
  * The operation must be completed by calling klp_free_patch_finish()
  * outside klp_mutex.
  */
 static void klp_free_patch_start(struct klp_patch *patch)
 {
     if (!list_empty(&patch->list))
         list_del(&patch->list);
 
     klp_free_objects(patch);
 }
 
 /*
  * This function implements the free part that must be called outside
  * klp_mutex.
  *
  * It must be called after klp_free_patch_start(). And it has to be
  * the last function accessing the livepatch structures when the patch
  * gets disabled.
  */
 static void klp_free_patch_finish(struct klp_patch *patch)
 {
     /*
      * Avoid deadlock with enabled_store() sysfs callback by
      * calling this outside klp_mutex. It is safe because
      * this is called when the patch gets disabled and it
      * cannot get enabled again.
      */
     kobject_put(&patch->kobj);
     wait_for_completion(&patch->finish);
 
     /* Put the module after the last access to struct klp_patch. */
     if (!patch->forced)
         module_put(patch->mod);
 }
 
 /*
  * The livepatch might be freed from sysfs interface created by the patch.
  * This work allows to wait until the interface is destroyed in a separate
  * context.
  */
 static void klp_free_patch_work_fn(struct work_struct *work)
 {
     struct klp_patch *patch =
         container_of(work, struct klp_patch, free_work);
 
     klp_free_patch_finish(patch);
 }
 
 void klp_free_patch_async(struct klp_patch *patch)
 {
     klp_free_patch_start(patch);
     schedule_work(&patch->free_work);
 }
 
 void klp_free_replaced_patches_async(struct klp_patch *new_patch)
 {
     struct klp_patch *old_patch, *tmp_patch;
 
     klp_for_each_patch_safe(old_patch, tmp_patch) {
         if (old_patch == new_patch)
             return;
         klp_free_patch_async(old_patch);
     }
 }
 
 static int klp_init_func(struct klp_object *obj, struct klp_func *func)
 {
     if (!func->old_name)
         return -EINVAL;
 
     /*
      * NOPs get the address later. The patched module must be loaded,
      * see klp_init_object_loaded().
      */
     if (!func->new_func && !func->nop)
         return -EINVAL;
 
     if (strlen(func->old_name) >= KSYM_NAME_LEN)
         return -EINVAL;
 
     INIT_LIST_HEAD(&func->stack_node);
     func->patched = false;
     func->transition = false;
 
     /* The format for the sysfs directory is <function,sympos> where sympos
      * is the nth occurrence of this symbol in kallsyms for the patched
      * object. If the user selects 0 for old_sympos, then 1 will be used
      * since a unique symbol will be the first occurrence.
      */
     return kobject_add(&func->kobj, &obj->kobj, "%s,%lu",
                func->old_name,
                func->old_sympos ? func->old_sympos : 1);
 }
 
 static int klp_apply_object_relocs(struct klp_patch *patch,
                    struct klp_object *obj)
 {
     int i, ret;
     struct klp_modinfo *info = patch->mod->klp_info;
 
     for (i = 1; i < info->hdr.e_shnum; i++) {
         Elf_Shdr *sec = info->sechdrs + i;
 
         if (!(sec->sh_flags & SHF_RELA_LIVEPATCH))
             continue;
 
         ret = klp_apply_section_relocs(patch->mod, info->sechdrs,
                            info->secstrings,
                            patch->mod->core_kallsyms.strtab,
                            info->symndx, i, obj->name);
         if (ret)
             return ret;
     }
 
     return 0;
 }
 
 /* parts of the initialization that is done only when the object is loaded */
 static int klp_init_object_loaded(struct klp_patch *patch,
                   struct klp_object *obj)
 {
     struct klp_func *func;
     int ret;
 
     if (klp_is_module(obj)) {
         /*
          * Only write module-specific relocations here
          * (.klp.rela.{module}.*).  vmlinux-specific relocations were
          * written earlier during the initialization of the klp module
          * itself.
          */
         ret = klp_apply_object_relocs(patch, obj);
         if (ret)
             return ret;
     }
 
     klp_for_each_func(obj, func) {
         ret = klp_find_object_symbol(obj->name, func->old_name,
                          func->old_sympos,
                          (unsigned long *)&func->old_func);
         if (ret)
             return ret;
 
         ret = kallsyms_lookup_size_offset((unsigned long)func->old_func,
                           &func->old_size, NULL);
         if (!ret) {
             pr_err("kallsyms size lookup failed for '%s'\n",
                    func->old_name);
             return -ENOENT;
         }
 
         if (func->nop)
             func->new_func = func->old_func;
 
         ret = kallsyms_lookup_size_offset((unsigned long)func->new_func,
                           &func->new_size, NULL);
         if (!ret) {
             pr_err("kallsyms size lookup failed for '%s' replacement\n",
                    func->old_name);
             return -ENOENT;
         }
     }
 
     return 0;
 }
 
 static int klp_init_object(struct klp_patch *patch, struct klp_object *obj)
 {
     struct klp_func *func;
     int ret;
     const char *name;
 
     if (klp_is_module(obj) && strlen(obj->name) >= MODULE_NAME_LEN)
         return -EINVAL;
 
     obj->patched = false;
     obj->mod = NULL;
 
     klp_find_object_module(obj);
 
     name = klp_is_module(obj) ? obj->name : "vmlinux";
     ret = kobject_add(&obj->kobj, &patch->kobj, "%s", name);
     if (ret)
         return ret;
 
     klp_for_each_func(obj, func) {
         ret = klp_init_func(obj, func);
         if (ret)
             return ret;
     }
 
     if (klp_is_object_loaded(obj))
         ret = klp_init_object_loaded(patch, obj);
 
     return ret;
 }
 
 static void klp_init_func_early(struct klp_object *obj,
                 struct klp_func *func)
 {
     kobject_init(&func->kobj, &klp_ktype_func);
     list_add_tail(&func->node, &obj->func_list);
 }
 
 static void klp_init_object_early(struct klp_patch *patch,
                   struct klp_object *obj)
 {
     INIT_LIST_HEAD(&obj->func_list);
     kobject_init(&obj->kobj, &klp_ktype_object);
     list_add_tail(&obj->node, &patch->obj_list);
 }
 
 static void klp_init_patch_early(struct klp_patch *patch)
 {
     struct klp_object *obj;
     struct klp_func *func;
 
     INIT_LIST_HEAD(&patch->list);
     INIT_LIST_HEAD(&patch->obj_list);
     kobject_init(&patch->kobj, &klp_ktype_patch);
     patch->enabled = false;
     patch->forced = false;
     INIT_WORK(&patch->free_work, klp_free_patch_work_fn);
     init_completion(&patch->finish);
 
     klp_for_each_object_static(patch, obj) {
         klp_init_object_early(patch, obj);
 
         klp_for_each_func_static(obj, func) {
             klp_init_func_early(obj, func);
         }
     }
 }
 
 static int klp_init_patch(struct klp_patch *patch)
 {
     struct klp_object *obj;
     int ret;
 
     ret = kobject_add(&patch->kobj, klp_root_kobj, "%s", patch->mod->name);
     if (ret)
         return ret;
 
     if (patch->replace) {
         ret = klp_add_nops(patch);
         if (ret)
             return ret;
     }
 
     klp_for_each_object(patch, obj) {
         ret = klp_init_object(patch, obj);
         if (ret)
             return ret;
     }
 
     list_add_tail(&patch->list, &klp_patches);
 
     return 0;
 }
 
 static int __klp_disable_patch(struct klp_patch *patch)
 {
     struct klp_object *obj;
 
     if (WARN_ON(!patch->enabled))
         return -EINVAL;
 
     if (klp_transition_patch)
         return -EBUSY;
 
     klp_init_transition(patch, KLP_UNPATCHED);
 
     klp_for_each_object(patch, obj)
         if (obj->patched)
             klp_pre_unpatch_callback(obj);
 
     /*
      * Enforce the order of the func->transition writes in
      * klp_init_transition() and the TIF_PATCH_PENDING writes in
      * klp_start_transition().  In the rare case where klp_ftrace_handler()
      * is called shortly after klp_update_patch_state() switches the task,
      * this ensures the handler sees that func->transition is set.
      */
     smp_wmb();
 
     klp_start_transition();
     patch->enabled = false;
     klp_try_complete_transition();
 
     return 0;
 }
 
 static int __klp_enable_patch(struct klp_patch *patch)
 {
     struct klp_object *obj;
     int ret;
 
     if (klp_transition_patch)
         return -EBUSY;
 
     if (WARN_ON(patch->enabled))
         return -EINVAL;
 
     pr_notice("enabling patch '%s'\n", patch->mod->name);
 
     klp_init_transition(patch, KLP_PATCHED);
 
     /*
      * Enforce the order of the func->transition writes in
      * klp_init_transition() and the ops->func_stack writes in
      * klp_patch_object(), so that klp_ftrace_handler() will see the
      * func->transition updates before the handler is registered and the
      * new funcs become visible to the handler.
      */
     smp_wmb();
 
     klp_for_each_object(patch, obj) {
         if (!klp_is_object_loaded(obj))
             continue;
 
         ret = klp_pre_patch_callback(obj);
         if (ret) {
             pr_warn("pre-patch callback failed for object '%s'\n",
                 klp_is_module(obj) ? obj->name : "vmlinux");
             goto err;
         }
 
         ret = klp_patch_object(obj);
         if (ret) {
             pr_warn("failed to patch object '%s'\n",
                 klp_is_module(obj) ? obj->name : "vmlinux");
             goto err;
         }
     }
 
     klp_start_transition();
     patch->enabled = true;
     klp_try_complete_transition();
 
     return 0;
 err:
     pr_warn("failed to enable patch '%s'\n", patch->mod->name);
 
     klp_cancel_transition();
     return ret;
 }
 
 /**
  * klp_enable_patch() - enable the livepatch
  * @patch:  patch to be enabled
  *
  * Initializes the data structure associated with the patch, creates the sysfs
  * interface, performs the needed symbol lookups and code relocations,
  * registers the patched functions with ftrace.
  *
  * This function is supposed to be called from the livepatch module_init()
  * callback.
  *
  * Return: 0 on success, otherwise error
  */
 int klp_enable_patch(struct klp_patch *patch)
 {
     int ret;
     struct klp_object *obj;
 
     if (!patch || !patch->mod || !patch->objs)
         return -EINVAL;
 
     klp_for_each_object_static(patch, obj) {
         if (!obj->funcs)
             return -EINVAL;
     }
 
 
     if (!is_livepatch_module(patch->mod)) {
         pr_err("module %s is not marked as a livepatch module\n",
                patch->mod->name);
         return -EINVAL;
     }
 
     if (!klp_initialized())
         return -ENODEV;
 
     if (!klp_have_reliable_stack()) {
         pr_warn("This architecture doesn't have support for the livepatch consistency model.\n");
         pr_warn("The livepatch transition may never complete.\n");
     }
 
     mutex_lock(&klp_mutex);
 
     if (!klp_is_patch_compatible(patch)) {
         pr_err("Livepatch patch (%s) is not compatible with the already installed livepatches.\n",
             patch->mod->name);
         mutex_unlock(&klp_mutex);
         return -EINVAL;
     }
 
     if (!try_module_get(patch->mod)) {
         mutex_unlock(&klp_mutex);
         return -ENODEV;
     }
 
     klp_init_patch_early(patch);
 
     ret = klp_init_patch(patch);
     if (ret)
         goto err;
 
     ret = __klp_enable_patch(patch);
     if (ret)
         goto err;
 
     mutex_unlock(&klp_mutex);
 
     return 0;
 
 err:
     klp_free_patch_start(patch);
 
     mutex_unlock(&klp_mutex);
 
     klp_free_patch_finish(patch);
 
     return ret;
 }
 EXPORT_SYMBOL_GPL(klp_enable_patch);
 
 /*
  * This function unpatches objects from the replaced livepatches.
  *
  * We could be pretty aggressive here. It is called in the situation where
  * these structures are no longer accessed from the ftrace handler.
  * All functions are redirected by the klp_transition_patch. They
  * use either a new code or they are in the original code because
  * of the special nop function patches.
  *
  * The only exception is when the transition was forced. In this case,
  * klp_ftrace_handler() might still see the replaced patch on the stack.
  * Fortunately, it is carefully designed to work with removed functions
  * thanks to RCU. We only have to keep the patches on the system. Also
  * this is handled transparently by patch->module_put.
  */
 void klp_unpatch_replaced_patches(struct klp_patch *new_patch)
 {
     struct klp_patch *old_patch;
 
     klp_for_each_patch(old_patch) {
         if (old_patch == new_patch)
             return;
 
         old_patch->enabled = false;
         klp_unpatch_objects(old_patch);
     }
 }
 
 /*
  * This function removes the dynamically allocated 'nop' functions.
  *
  * We could be pretty aggressive. NOPs do not change the existing
  * behavior except for adding unnecessary delay by the ftrace handler.
  *
  * It is safe even when the transition was forced. The ftrace handler
  * will see a valid ops->func_stack entry thanks to RCU.
  *
  * We could even free the NOPs structures. They must be the last entry
  * in ops->func_stack. Therefore unregister_ftrace_function() is called.
  * It does the same as klp_synchronize_transition() to make sure that
  * nobody is inside the ftrace handler once the operation finishes.
  *
  * IMPORTANT: It must be called right after removing the replaced patches!
  */
 void klp_discard_nops(struct klp_patch *new_patch)
 {
     klp_unpatch_objects_dynamic(klp_transition_patch);
     klp_free_objects_dynamic(klp_transition_patch);
 }
 
 /*
  * Remove parts of patches that touch a given kernel module. The list of
  * patches processed might be limited. When limit is NULL, all patches
  * will be handled.
  */
 static void klp_cleanup_module_patches_limited(struct module *mod,
                            struct klp_patch *limit)
 {
     struct klp_patch *patch;
     struct klp_object *obj;
 
     klp_for_each_patch(patch) {
         if (patch == limit)
             break;
 
         klp_for_each_object(patch, obj) {
             if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
                 continue;
 
             if (patch != klp_transition_patch)
                 klp_pre_unpatch_callback(obj);
 
             pr_notice("reverting patch '%s' on unloading module '%s'\n",
                   patch->mod->name, obj->mod->name);
             klp_unpatch_object(obj);
 
             klp_post_unpatch_callback(obj);
 
             klp_free_object_loaded(obj);
             break;
         }
     }
 }
 
 int klp_module_coming(struct module *mod)
 {
     int ret;
     struct klp_patch *patch;
     struct klp_object *obj;
 
     if (WARN_ON(mod->state != MODULE_STATE_COMING))
         return -EINVAL;
 
     if (!strcmp(mod->name, "vmlinux")) {
         pr_err("vmlinux.ko: invalid module name");
         return -EINVAL;
     }
 
     mutex_lock(&klp_mutex);
     /*
      * Each module has to know that klp_module_coming()
      * has been called. We never know what module will
      * get patched by a new patch.
      */
     mod->klp_alive = true;
 
     klp_for_each_patch(patch) {
         klp_for_each_object(patch, obj) {
             if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
                 continue;
 
             obj->mod = mod;
 
             ret = klp_init_object_loaded(patch, obj);
             if (ret) {
                 pr_warn("failed to initialize patch '%s' for module '%s' (%d)\n",
                     patch->mod->name, obj->mod->name, ret);
                 goto err;
             }
 
             pr_notice("applying patch '%s' to loading module '%s'\n",
                   patch->mod->name, obj->mod->name);
 
             ret = klp_pre_patch_callback(obj);
             if (ret) {
                 pr_warn("pre-patch callback failed for object '%s'\n",
                     obj->name);
                 goto err;
             }
 
             ret = klp_patch_object(obj);
             if (ret) {
                 pr_warn("failed to apply patch '%s' to module '%s' (%d)\n",
                     patch->mod->name, obj->mod->name, ret);
 
                 klp_post_unpatch_callback(obj);
                 goto err;
             }
 
             if (patch != klp_transition_patch)
                 klp_post_patch_callback(obj);
 
             break;
         }
     }
 
     mutex_unlock(&klp_mutex);
 
     return 0;
 
 err:
     /*
      * If a patch is unsuccessfully applied, return
      * error to the module loader.
      */
     pr_warn("patch '%s' failed for module '%s', refusing to load module '%s'\n",
         patch->mod->name, obj->mod->name, obj->mod->name);
     mod->klp_alive = false;
     obj->mod = NULL;
     klp_cleanup_module_patches_limited(mod, patch);
     mutex_unlock(&klp_mutex);
 
     return ret;
 }
 
 void klp_module_going(struct module *mod)
 {
     if (WARN_ON(mod->state != MODULE_STATE_GOING &&
             mod->state != MODULE_STATE_COMING))
         return;
 
     mutex_lock(&klp_mutex);
     /*
      * Each module has to know that klp_module_going()
      * has been called. We never know what module will
      * get patched by a new patch.
      */
     mod->klp_alive = false;
 
     klp_cleanup_module_patches_limited(mod, NULL);
 
     mutex_unlock(&klp_mutex);
 }
 
 static int __init klp_init(void)
 {
     klp_root_kobj = kobject_create_and_add("livepatch", kernel_kobj);
     if (!klp_root_kobj)
         return -ENOMEM;
 
     return 0;
 }
 
 module_init(klp_init);

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