/* * transition.c - Kernel Live Patching transition functions * * Copyright (C) 2015-2016 Josh Poimboeuf <jpoimboe@redhat.com> * * 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/>. */ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt #include <linux/cpu.h>#include <linux/stacktrace.h>#include "core.h"#include "patch.h"#include "transition.h"#include "../sched/sched.h" #define MAX_STACK_ENTRIES 100#define STACK_ERR_BUF_SIZE 128 struct klp_patch *klp_transition_patch; static int klp_target_state = KLP_UNDEFINED; /* * This work can be performed periodically to finish patching or unpatching any * "straggler" tasks which failed to transition in the first attempt. */static void klp_transition_work_fn(struct work_struct *work){ mutex_lock(&klp_mutex); if (klp_transition_patch) klp_try_complete_transition(); mutex_unlock(&klp_mutex);}static DECLARE_DELAYED_WORK(klp_transition_work, klp_transition_work_fn); /* * This function is just a stub to implement a hard force * of synchronize_sched(). This requires synchronizing * tasks even in userspace and idle. */static void klp_sync(struct work_struct *work){} /* * We allow to patch also functions where RCU is not watching, * e.g. before user_exit(). We can not rely on the RCU infrastructure * to do the synchronization. Instead hard force the sched synchronization. * * This approach allows to use RCU functions for manipulating func_stack * safely. */static void klp_synchronize_transition(void){ schedule_on_each_cpu(klp_sync);} /* * The transition to the target patch state is complete. Clean up the data * structures. */static void klp_complete_transition(void){ struct klp_object *obj; struct klp_func *func; struct task_struct *g, *task; unsigned int cpu; bool immediate_func = false; pr_debug("'%s': completing %s transition\n", klp_transition_patch->mod->name, klp_target_state == KLP_PATCHED ? "patching" : "unpatching"); if (klp_target_state == KLP_UNPATCHED) { /* * All tasks have transitioned to KLP_UNPATCHED so we can now * remove the new functions from the func_stack. */ klp_unpatch_objects(klp_transition_patch); /* * Make sure klp_ftrace_handler() can no longer see functions * from this patch on the ops->func_stack. Otherwise, after * func->transition gets cleared, the handler may choose a * removed function. */ klp_synchronize_transition(); } if (klp_transition_patch->immediate) goto done; klp_for_each_object(klp_transition_patch, obj) { klp_for_each_func(obj, func) { func->transition = false; if (func->immediate) immediate_func = true; } } /* Prevent klp_ftrace_handler() from seeing KLP_UNDEFINED state */ if (klp_target_state == KLP_PATCHED) klp_synchronize_transition(); read_lock(&tasklist_lock); for_each_process_thread(g, task) { WARN_ON_ONCE(test_tsk_thread_flag(task, TIF_PATCH_PENDING)); task->patch_state = KLP_UNDEFINED; } read_unlock(&tasklist_lock); for_each_possible_cpu(cpu) { task = idle_task(cpu); WARN_ON_ONCE(test_tsk_thread_flag(task, TIF_PATCH_PENDING)); task->patch_state = KLP_UNDEFINED; } done: klp_for_each_object(klp_transition_patch, obj) { if (!klp_is_object_loaded(obj)) continue; if (klp_target_state == KLP_PATCHED) klp_post_patch_callback(obj); else if (klp_target_state == KLP_UNPATCHED) klp_post_unpatch_callback(obj); } pr_notice("'%s': %s complete\n", klp_transition_patch->mod->name, klp_target_state == KLP_PATCHED ? "patching" : "unpatching"); /* * See complementary comment in __klp_enable_patch() for why we * keep the module reference for immediate patches. */ if (!klp_transition_patch->immediate && !immediate_func && klp_target_state == KLP_UNPATCHED) { module_put(klp_transition_patch->mod); } klp_target_state = KLP_UNDEFINED; klp_transition_patch = NULL;} /* * This is called in the error path, to cancel a transition before it has * started, i.e. klp_init_transition() has been called but * klp_start_transition() hasn't. If the transition *has* been started, * klp_reverse_transition() should be used instead. */void klp_cancel_transition(void){ if (WARN_ON_ONCE(klp_target_state != KLP_PATCHED)) return; pr_debug("'%s': canceling patching transition, going to unpatch\n", klp_transition_patch->mod->name); klp_target_state = KLP_UNPATCHED; klp_complete_transition();} /* * Switch the patched state of the task to the set of functions in the target * patch state. * * NOTE: If task is not 'current', the caller must ensure the task is inactive. * Otherwise klp_ftrace_handler() might read the wrong 'patch_state' value. */void klp_update_patch_state(struct task_struct *task){ /* * A variant of synchronize_sched() is used to allow patching functions * where RCU is not watching, see klp_synchronize_transition(). */ preempt_disable_notrace(); /* * This test_and_clear_tsk_thread_flag() call also serves as a read * barrier (smp_rmb) for two cases: * * 1) Enforce the order of the TIF_PATCH_PENDING read and the * klp_target_state read. The corresponding write barrier is in * klp_init_transition(). * * 2) Enforce the order of the TIF_PATCH_PENDING read and a future read * of func->transition, if klp_ftrace_handler() is called later on * the same CPU. See __klp_disable_patch(). */ if (test_and_clear_tsk_thread_flag(task, TIF_PATCH_PENDING)) task->patch_state = READ_ONCE(klp_target_state); preempt_enable_notrace();} /* * Determine whether the given stack trace includes any references to a * to-be-patched or to-be-unpatched function. */static int klp_check_stack_func(struct klp_func *func, struct stack_trace *trace){ unsigned long func_addr, func_size, address; struct klp_ops *ops; int i; if (func->immediate) return 0; for (i = 0; i < trace->nr_entries; i++) { address = trace->entries[i]; if (klp_target_state == KLP_UNPATCHED) { /* * Check for the to-be-unpatched function * (the func itself). */ func_addr = (unsigned long)func->new_func; func_size = func->new_size; } else { /* * Check for the to-be-patched function * (the previous func). */ ops = klp_find_ops(func->old_addr); if (list_is_singular(&ops->func_stack)) { /* original function */ func_addr = func->old_addr; func_size = func->old_size; } else { /* previously patched function */ struct klp_func *prev; prev = list_next_entry(func, stack_node); func_addr = (unsigned long)prev->new_func; func_size = prev->new_size; } } if (address >= func_addr && address < func_addr + func_size) return -EAGAIN; } return 0;} /* * Determine whether it's safe to transition the task to the target patch state * by looking for any to-be-patched or to-be-unpatched functions on its stack. */static int klp_check_stack(struct task_struct *task, char *err_buf){ static unsigned long entries[MAX_STACK_ENTRIES]; struct stack_trace trace; struct klp_object *obj; struct klp_func *func; int ret; trace.skip = 0; trace.nr_entries = 0; trace.max_entries = MAX_STACK_ENTRIES; trace.entries = entries; ret = save_stack_trace_tsk_reliable(task, &trace); WARN_ON_ONCE(ret == -ENOSYS); if (ret) { snprintf(err_buf, STACK_ERR_BUF_SIZE, "%s: %s:%d has an unreliable stack\n", __func__, task->comm, task->pid); return ret; } klp_for_each_object(klp_transition_patch, obj) { if (!obj->patched) continue; klp_for_each_func(obj, func) { ret = klp_check_stack_func(func, &trace); if (ret) { snprintf(err_buf, STACK_ERR_BUF_SIZE, "%s: %s:%d is sleeping on function %s\n", __func__, task->comm, task->pid, func->old_name); return ret; } } } return 0;} /* * Try to safely switch a task to the target patch state. If it's currently * running, or it's sleeping on a to-be-patched or to-be-unpatched function, or * if the stack is unreliable, return false. */static bool klp_try_switch_task(struct task_struct *task){ struct rq *rq; struct rq_flags flags; int ret; bool success = false; char err_buf[STACK_ERR_BUF_SIZE]; err_buf[0] = '\0'; /* check if this task has already switched over */ if (task->patch_state == klp_target_state) return true; /* * For arches which don't have reliable stack traces, we have to rely * on other methods (e.g., switching tasks at kernel exit). */ if (!klp_have_reliable_stack()) return false; /* * Now try to check the stack for any to-be-patched or to-be-unpatched * functions. If all goes well, switch the task to the target patch * state. */ rq = task_rq_lock(task, &flags); if (task_running(rq, task) && task != current) { snprintf(err_buf, STACK_ERR_BUF_SIZE, "%s: %s:%d is running\n", __func__, task->comm, task->pid); goto done; } ret = klp_check_stack(task, err_buf); if (ret) goto done; success = true; clear_tsk_thread_flag(task, TIF_PATCH_PENDING); task->patch_state = klp_target_state; done: task_rq_unlock(rq, task, &flags); /* * Due to console deadlock issues, pr_debug() can't be used while * holding the task rq lock. Instead we have to use a temporary buffer * and print the debug message after releasing the lock. */ if (err_buf[0] != '\0') pr_debug("%s", err_buf); return success; } /* * Try to switch all remaining tasks to the target patch state by walking the * stacks of sleeping tasks and looking for any to-be-patched or * to-be-unpatched functions. If such functions are found, the task can't be * switched yet. * * If any tasks are still stuck in the initial patch state, schedule a retry. */void klp_try_complete_transition(void){ unsigned int cpu; struct task_struct *g, *task; bool complete = true; WARN_ON_ONCE(klp_target_state == KLP_UNDEFINED); /* * If the patch can be applied or reverted immediately, skip the * per-task transitions. */ if (klp_transition_patch->immediate) goto success; /* * Try to switch the tasks to the target patch state by walking their * stacks and looking for any to-be-patched or to-be-unpatched * functions. If such functions are found on a stack, or if the stack * is deemed unreliable, the task can't be switched yet. * * Usually this will transition most (or all) of the tasks on a system * unless the patch includes changes to a very common function. */ read_lock(&tasklist_lock); for_each_process_thread(g, task) if (!klp_try_switch_task(task)) complete = false; read_unlock(&tasklist_lock); /* * Ditto for the idle "swapper" tasks. */ get_online_cpus(); for_each_possible_cpu(cpu) { task = idle_task(cpu); if (cpu_online(cpu)) { if (!klp_try_switch_task(task)) complete = false; } else if (task->patch_state != klp_target_state) { /* offline idle tasks can be switched immediately */ clear_tsk_thread_flag(task, TIF_PATCH_PENDING); task->patch_state = klp_target_state; } } put_online_cpus(); if (!complete) { /* * Some tasks weren't able to be switched over. Try again * later and/or wait for other methods like kernel exit * switching. */ schedule_delayed_work(&klp_transition_work, round_jiffies_relative(HZ)); return; } success: /* we're done, now cleanup the data structures */ klp_complete_transition();} /* * Start the transition to the specified target patch state so tasks can begin * switching to it. */void klp_start_transition(void){ struct task_struct *g, *task; unsigned int cpu; WARN_ON_ONCE(klp_target_state == KLP_UNDEFINED); pr_notice("'%s': starting %s transition\n", klp_transition_patch->mod->name, klp_target_state == KLP_PATCHED ? "patching" : "unpatching"); /* * If the patch can be applied or reverted immediately, skip the * per-task transitions. */ if (klp_transition_patch->immediate) return; /* * Mark all normal tasks as needing a patch state update. They'll * switch either in klp_try_complete_transition() or as they exit the * kernel. */ read_lock(&tasklist_lock); for_each_process_thread(g, task) if (task->patch_state != klp_target_state) set_tsk_thread_flag(task, TIF_PATCH_PENDING); read_unlock(&tasklist_lock); /* * Mark all idle tasks as needing a patch state update. They'll switch * either in klp_try_complete_transition() or at the idle loop switch * point. */ for_each_possible_cpu(cpu) { task = idle_task(cpu); if (task->patch_state != klp_target_state) set_tsk_thread_flag(task, TIF_PATCH_PENDING); }} /* * Initialize the global target patch state and all tasks to the initial patch * state, and initialize all function transition states to true in preparation * for patching or unpatching. */void klp_init_transition(struct klp_patch *patch, int state){ struct task_struct *g, *task; unsigned int cpu; struct klp_object *obj; struct klp_func *func; int initial_state = !state; WARN_ON_ONCE(klp_target_state != KLP_UNDEFINED); klp_transition_patch = patch;Lines 1–500 of 610. Load more
/* * transition.c - Kernel Live Patching transition functions * * Copyright (C) 2015-2016 Josh Poimboeuf <jpoimboe@redhat.com> * * 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/>. */ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt #include <linux/cpu.h> #include <linux/stacktrace.h> #include "core.h" #include "patch.h" #include "transition.h" #include "../sched/sched.h" #define MAX_STACK_ENTRIES 100 #define STACK_ERR_BUF_SIZE 128 struct klp_patch *klp_transition_patch; static int klp_target_state = KLP_UNDEFINED; /* * This work can be performed periodically to finish patching or unpatching any * "straggler" tasks which failed to transition in the first attempt. */ static void klp_transition_work_fn(struct work_struct *work) { mutex_lock(&klp_mutex); if (klp_transition_patch) klp_try_complete_transition(); mutex_unlock(&klp_mutex); } static DECLARE_DELAYED_WORK(klp_transition_work, klp_transition_work_fn); /* * This function is just a stub to implement a hard force * of synchronize_sched(). This requires synchronizing * tasks even in userspace and idle. */ static void klp_sync(struct work_struct *work) { } /* * We allow to patch also functions where RCU is not watching, * e.g. before user_exit(). We can not rely on the RCU infrastructure * to do the synchronization. Instead hard force the sched synchronization. * * This approach allows to use RCU functions for manipulating func_stack * safely. */ static void klp_synchronize_transition(void) { schedule_on_each_cpu(klp_sync); } /* * The transition to the target patch state is complete. Clean up the data * structures. */ static void klp_complete_transition(void) { struct klp_object *obj; struct klp_func *func; struct task_struct *g, *task; unsigned int cpu; bool immediate_func = false; pr_debug("'%s': completing %s transition\n", klp_transition_patch->mod->name, klp_target_state == KLP_PATCHED ? "patching" : "unpatching"); if (klp_target_state == KLP_UNPATCHED) { /* * All tasks have transitioned to KLP_UNPATCHED so we can now * remove the new functions from the func_stack. */ klp_unpatch_objects(klp_transition_patch); /* * Make sure klp_ftrace_handler() can no longer see functions * from this patch on the ops->func_stack. Otherwise, after * func->transition gets cleared, the handler may choose a * removed function. */ klp_synchronize_transition(); } if (klp_transition_patch->immediate) goto done; klp_for_each_object(klp_transition_patch, obj) { klp_for_each_func(obj, func) { func->transition = false; if (func->immediate) immediate_func = true; } } /* Prevent klp_ftrace_handler() from seeing KLP_UNDEFINED state */ if (klp_target_state == KLP_PATCHED) klp_synchronize_transition(); read_lock(&tasklist_lock); for_each_process_thread(g, task) { WARN_ON_ONCE(test_tsk_thread_flag(task, TIF_PATCH_PENDING)); task->patch_state = KLP_UNDEFINED; } read_unlock(&tasklist_lock); for_each_possible_cpu(cpu) { task = idle_task(cpu); WARN_ON_ONCE(test_tsk_thread_flag(task, TIF_PATCH_PENDING)); task->patch_state = KLP_UNDEFINED; } done: klp_for_each_object(klp_transition_patch, obj) { if (!klp_is_object_loaded(obj)) continue; if (klp_target_state == KLP_PATCHED) klp_post_patch_callback(obj); else if (klp_target_state == KLP_UNPATCHED) klp_post_unpatch_callback(obj); } pr_notice("'%s': %s complete\n", klp_transition_patch->mod->name, klp_target_state == KLP_PATCHED ? "patching" : "unpatching"); /* * See complementary comment in __klp_enable_patch() for why we * keep the module reference for immediate patches. */ if (!klp_transition_patch->immediate && !immediate_func && klp_target_state == KLP_UNPATCHED) { module_put(klp_transition_patch->mod); } klp_target_state = KLP_UNDEFINED; klp_transition_patch = NULL; } /* * This is called in the error path, to cancel a transition before it has * started, i.e. klp_init_transition() has been called but * klp_start_transition() hasn't. If the transition *has* been started, * klp_reverse_transition() should be used instead. */ void klp_cancel_transition(void) { if (WARN_ON_ONCE(klp_target_state != KLP_PATCHED)) return; pr_debug("'%s': canceling patching transition, going to unpatch\n", klp_transition_patch->mod->name); klp_target_state = KLP_UNPATCHED; klp_complete_transition(); } /* * Switch the patched state of the task to the set of functions in the target * patch state. * * NOTE: If task is not 'current', the caller must ensure the task is inactive. * Otherwise klp_ftrace_handler() might read the wrong 'patch_state' value. */ void klp_update_patch_state(struct task_struct *task) { /* * A variant of synchronize_sched() is used to allow patching functions * where RCU is not watching, see klp_synchronize_transition(). */ preempt_disable_notrace(); /* * This test_and_clear_tsk_thread_flag() call also serves as a read * barrier (smp_rmb) for two cases: * * 1) Enforce the order of the TIF_PATCH_PENDING read and the * klp_target_state read. The corresponding write barrier is in * klp_init_transition(). * * 2) Enforce the order of the TIF_PATCH_PENDING read and a future read * of func->transition, if klp_ftrace_handler() is called later on * the same CPU. See __klp_disable_patch(). */ if (test_and_clear_tsk_thread_flag(task, TIF_PATCH_PENDING)) task->patch_state = READ_ONCE(klp_target_state); preempt_enable_notrace(); } /* * Determine whether the given stack trace includes any references to a * to-be-patched or to-be-unpatched function. */ static int klp_check_stack_func(struct klp_func *func, struct stack_trace *trace) { unsigned long func_addr, func_size, address; struct klp_ops *ops; int i; if (func->immediate) return 0; for (i = 0; i < trace->nr_entries; i++) { address = trace->entries[i]; if (klp_target_state == KLP_UNPATCHED) { /* * Check for the to-be-unpatched function * (the func itself). */ func_addr = (unsigned long)func->new_func; func_size = func->new_size; } else { /* * Check for the to-be-patched function * (the previous func). */ ops = klp_find_ops(func->old_addr); if (list_is_singular(&ops->func_stack)) { /* original function */ func_addr = func->old_addr; func_size = func->old_size; } else { /* previously patched function */ struct klp_func *prev; prev = list_next_entry(func, stack_node); func_addr = (unsigned long)prev->new_func; func_size = prev->new_size; } } if (address >= func_addr && address < func_addr + func_size) return -EAGAIN; } return 0; } /* * Determine whether it's safe to transition the task to the target patch state * by looking for any to-be-patched or to-be-unpatched functions on its stack. */ static int klp_check_stack(struct task_struct *task, char *err_buf) { static unsigned long entries[MAX_STACK_ENTRIES]; struct stack_trace trace; struct klp_object *obj; struct klp_func *func; int ret; trace.skip = 0; trace.nr_entries = 0; trace.max_entries = MAX_STACK_ENTRIES; trace.entries = entries; ret = save_stack_trace_tsk_reliable(task, &trace); WARN_ON_ONCE(ret == -ENOSYS); if (ret) { snprintf(err_buf, STACK_ERR_BUF_SIZE, "%s: %s:%d has an unreliable stack\n", __func__, task->comm, task->pid); return ret; } klp_for_each_object(klp_transition_patch, obj) { if (!obj->patched) continue; klp_for_each_func(obj, func) { ret = klp_check_stack_func(func, &trace); if (ret) { snprintf(err_buf, STACK_ERR_BUF_SIZE, "%s: %s:%d is sleeping on function %s\n", __func__, task->comm, task->pid, func->old_name); return ret; } } } return 0; } /* * Try to safely switch a task to the target patch state. If it's currently * running, or it's sleeping on a to-be-patched or to-be-unpatched function, or * if the stack is unreliable, return false. */ static bool klp_try_switch_task(struct task_struct *task) { struct rq *rq; struct rq_flags flags; int ret; bool success = false; char err_buf[STACK_ERR_BUF_SIZE]; err_buf[0] = '\0'; /* check if this task has already switched over */ if (task->patch_state == klp_target_state) return true; /* * For arches which don't have reliable stack traces, we have to rely * on other methods (e.g., switching tasks at kernel exit). */ if (!klp_have_reliable_stack()) return false; /* * Now try to check the stack for any to-be-patched or to-be-unpatched * functions. If all goes well, switch the task to the target patch * state. */ rq = task_rq_lock(task, &flags); if (task_running(rq, task) && task != current) { snprintf(err_buf, STACK_ERR_BUF_SIZE, "%s: %s:%d is running\n", __func__, task->comm, task->pid); goto done; } ret = klp_check_stack(task, err_buf); if (ret) goto done; success = true; clear_tsk_thread_flag(task, TIF_PATCH_PENDING); task->patch_state = klp_target_state; done: task_rq_unlock(rq, task, &flags); /* * Due to console deadlock issues, pr_debug() can't be used while * holding the task rq lock. Instead we have to use a temporary buffer * and print the debug message after releasing the lock. */ if (err_buf[0] != '\0') pr_debug("%s", err_buf); return success; } /* * Try to switch all remaining tasks to the target patch state by walking the * stacks of sleeping tasks and looking for any to-be-patched or * to-be-unpatched functions. If such functions are found, the task can't be * switched yet. * * If any tasks are still stuck in the initial patch state, schedule a retry. */ void klp_try_complete_transition(void) { unsigned int cpu; struct task_struct *g, *task; bool complete = true; WARN_ON_ONCE(klp_target_state == KLP_UNDEFINED); /* * If the patch can be applied or reverted immediately, skip the * per-task transitions. */ if (klp_transition_patch->immediate) goto success; /* * Try to switch the tasks to the target patch state by walking their * stacks and looking for any to-be-patched or to-be-unpatched * functions. If such functions are found on a stack, or if the stack * is deemed unreliable, the task can't be switched yet. * * Usually this will transition most (or all) of the tasks on a system * unless the patch includes changes to a very common function. */ read_lock(&tasklist_lock); for_each_process_thread(g, task) if (!klp_try_switch_task(task)) complete = false; read_unlock(&tasklist_lock); /* * Ditto for the idle "swapper" tasks. */ get_online_cpus(); for_each_possible_cpu(cpu) { task = idle_task(cpu); if (cpu_online(cpu)) { if (!klp_try_switch_task(task)) complete = false; } else if (task->patch_state != klp_target_state) { /* offline idle tasks can be switched immediately */ clear_tsk_thread_flag(task, TIF_PATCH_PENDING); task->patch_state = klp_target_state; } } put_online_cpus(); if (!complete) { /* * Some tasks weren't able to be switched over. Try again * later and/or wait for other methods like kernel exit * switching. */ schedule_delayed_work(&klp_transition_work, round_jiffies_relative(HZ)); return; } success: /* we're done, now cleanup the data structures */ klp_complete_transition(); } /* * Start the transition to the specified target patch state so tasks can begin * switching to it. */ void klp_start_transition(void) { struct task_struct *g, *task; unsigned int cpu; WARN_ON_ONCE(klp_target_state == KLP_UNDEFINED); pr_notice("'%s': starting %s transition\n", klp_transition_patch->mod->name, klp_target_state == KLP_PATCHED ? "patching" : "unpatching"); /* * If the patch can be applied or reverted immediately, skip the * per-task transitions. */ if (klp_transition_patch->immediate) return; /* * Mark all normal tasks as needing a patch state update. They'll * switch either in klp_try_complete_transition() or as they exit the * kernel. */ read_lock(&tasklist_lock); for_each_process_thread(g, task) if (task->patch_state != klp_target_state) set_tsk_thread_flag(task, TIF_PATCH_PENDING); read_unlock(&tasklist_lock); /* * Mark all idle tasks as needing a patch state update. They'll switch * either in klp_try_complete_transition() or at the idle loop switch * point. */ for_each_possible_cpu(cpu) { task = idle_task(cpu); if (task->patch_state != klp_target_state) set_tsk_thread_flag(task, TIF_PATCH_PENDING); } } /* * Initialize the global target patch state and all tasks to the initial patch * state, and initialize all function transition states to true in preparation * for patching or unpatching. */ void klp_init_transition(struct klp_patch *patch, int state) { struct task_struct *g, *task; unsigned int cpu; struct klp_object *obj; struct klp_func *func; int initial_state = !state; WARN_ON_ONCE(klp_target_state != KLP_UNDEFINED); klp_transition_patch = patch;