| Quellcodebibliothek Statistik Leitseite products/sources/formale Sprachen/C/Linux/samples/livepatch/ (Open Source Betriebssystem Version 6.17.9©) Datei vom 24.10.2025 mit Größe 5 kB |
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Quelle livepatch-shadow-mod.c Sprache: C |
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// SPDX-License-Identifier: GPL-2.0-or-later
/* * Copyright (C) 2017 Joe Lawrence <joe.lawrence@redhat.com> */ /* * livepatch-shadow-mod.c - Shadow variables, buggy module demo * * Purpose * ------- * * As a demonstration of livepatch shadow variable API, this module * introduces memory leak behavior that livepatch modules * livepatch-shadow-fix1.ko and livepatch-shadow-fix2.ko correct and * enhance. * * WARNING - even though the livepatch-shadow-fix modules patch the * memory leak, please load these modules at your own risk -- some * amount of memory may leaked before the bug is patched. * * * Usage * ----- * * Step 1 - Load the buggy demonstration module: * * insmod samples/livepatch/livepatch-shadow-mod.ko * * Watch dmesg output for a few moments to see new dummy being allocated * and a periodic cleanup check. (Note: a small amount of memory is * being leaked.) * * * Step 2 - Load livepatch fix1: * * insmod samples/livepatch/livepatch-shadow-fix1.ko * * Continue watching dmesg and note that now livepatch_fix1_dummy_free() * and livepatch_fix1_dummy_alloc() are logging messages about leaked * memory and eventually leaks prevented. * * * Step 3 - Load livepatch fix2 (on top of fix1): * * insmod samples/livepatch/livepatch-shadow-fix2.ko * * This module extends functionality through shadow variables, as a new * "check" counter is added to the dummy structure. Periodic dmesg * messages will log these as dummies are cleaned up. * * * Step 4 - Cleanup * * Unwind the demonstration by disabling the livepatch fix modules, then * removing them and the demo module: * * echo 0 > /sys/kernel/livepatch/livepatch_shadow_fix2/enabled * echo 0 > /sys/kernel/livepatch/livepatch_shadow_fix1/enabled * rmmod livepatch-shadow-fix2 * rmmod livepatch-shadow-fix1 * rmmod livepatch-shadow-mod */ #include <linux/kernel.h> #include <linux/module.h> #include <linux/sched.h> #include <linux/slab.h> #include <linux/stat.h> #include <linux/workqueue.h> MODULE_LICENSE("GPL"); MODULE_AUTHOR("Joe Lawrence MODULE_DESCRIPTION("Buggy module for shadow variable demo"); /* Allocate new dummies every second */ #define ALLOC_PERIOD 1 /* Check for expired dummies after a few new ones have been allocated */ #define CLEANUP_PERIOD (3 * ALLOC_PERIOD) /* Dummies expire after a few cleanup instances */ #define EXPIRE_PERIOD (4 * CLEANUP_PERIOD) /* * Keep a list of all the dummies so we can clean up any residual ones * on module exit */ static LIST_HEAD(dummy_list); static DEFINE_MUTEX(dummy_list_mutex); struct dummy { struct list_head list; unsigned long jiffies_expire; }; static __used noinline struct dummy *dummy_alloc(void) { struct dummy *d; int *leak; d = kzalloc(sizeof(*d), GFP_KERNEL); if (!d) return NULL; d->jiffies_expire = jiffies + secs_to_jiffies(EXPIRE_PERIOD); /* Oops, forgot to save leak! */ leak = kzalloc(sizeof(*leak), GFP_KERNEL); if (!leak) { kfree(d); return NULL; } pr_info("%s: dummy @ %p, expires @ %lx\n", __func__, d, d->jiffies_expire); return d; } static __used noinline void dummy_free(struct dummy *d) { pr_info("%s: dummy @ %p, expired = %lx\n", __func__, d, d->jiffies_expire); kfree(d); } static __used noinline bool dummy_check(struct dummy *d, unsigned long jiffies) { return time_after(jiffies, d->jiffies_expire); } /* * alloc_work_func: allocates new dummy structures, allocates additional * memory, aptly named "leak", but doesn't keep * permanent record of it. */ static void alloc_work_func(struct work_struct *work); static DECLARE_DELAYED_WORK(alloc_dwork, alloc_work_func); static void alloc_work_func(struct work_struct *work) { struct dummy *d; d = dummy_alloc(); if (!d) return; mutex_lock(&dummy_list_mutex); list_add(&d->list, &dummy_list); mutex_unlock(&dummy_list_mutex); schedule_delayed_work(&alloc_dwork, secs_to_jiffies(ALLOC_PERIOD)); } /* * cleanup_work_func: frees dummy structures. Without knownledge of * "leak", it leaks the additional memory that * alloc_work_func created. */ static void cleanup_work_func(struct work_struct *work); static DECLARE_DELAYED_WORK(cleanup_dwork, cleanup_work_func); static void cleanup_work_func(struct work_struct *work) { struct dummy *d, *tmp; unsigned long j; j = jiffies; pr_info("%s: jiffies = %lx\n", __func__, j); mutex_lock(&dummy_list_mutex); list_for_each_entry_safe(d, tmp, &dummy_list, list) { /* Kick out and free any expired dummies */ if (dummy_check(d, j)) { list_del(&d->list); dummy_free(d); } } mutex_unlock(&dummy_list_mutex); schedule_delayed_work(&cleanup_dwork, secs_to_jiffies(CLEANUP_PERIOD)); } static int livepatch_shadow_mod_init(void) { schedule_delayed_work(&alloc_dwork, secs_to_jiffies(ALLOC_PERIOD)); schedule_delayed_work(&cleanup_dwork, secs_to_jiffies(CLEANUP_PERIOD)); return 0; } static void livepatch_shadow_mod_exit(void) { struct dummy *d, *tmp; /* Wait for any dummies at work */ cancel_delayed_work_sync(&alloc_dwork); cancel_delayed_work_sync(&cleanup_dwork); /* Cleanup residual dummies */ list_for_each_entry_safe(d, tmp, &dummy_list, list) { list_del(&d->list); dummy_free(d); } } module_init(livepatch_shadow_mod_init); module_exit(livepatch_shadow_mod_exit); ¤ Dauer der Verarbeitung: 0.13 Sekunden (vorverarbeitet) ¤*© Formatika GbR, Deutschland |
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2026-03-28