// SPDX-License-Identifier: GPL-2.0-or-later /* * Copyright (C) 2017 Joe Lawrence <joe.lawrence@redhat.com> */ /* * livepatch-shadow-fix2.c - Shadow variables, livepatch demo * * Purpose * ------- * * Adds functionality to livepatch-shadow-mod's in-flight data * structures through a shadow variable. The livepatch patches a * routine that periodically inspects data structures, incrementing a * per-data-structure counter, creating the counter if needed. * * * Usage * ----- * * This module is not intended to be standalone. See the "Usage" * section of livepatch-shadow-mod.c. */ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt #include <linux/module.h> #include <linux/kernel.h> #include <linux/livepatch.h> #include <linux/slab.h> /* Shadow variable enums */ #define SV_LEAK 1 #define SV_COUNTER 2 struct dummy { struct list_head list; unsigned long jiffies_expire; }; static bool livepatch_fix2_dummy_check(struct dummy *d, unsigned long jiffies) { int *shadow_count; /* * Patch: handle in-flight dummy structures, if they do not * already have a SV_COUNTER shadow variable, then attach a * new one. */ shadow_count = klp_shadow_get_or_alloc(d, SV_COUNTER, sizeof(*shadow_count), GFP_NOWAIT, NULL, NULL); if (shadow_count) *shadow_count += 1; return time_after(jiffies, d->jiffies_expire); } static void livepatch_fix2_dummy_leak_dtor(void *obj, void *shadow_data) { void *d = obj; int **shadow_leak = shadow_data; kfree(*shadow_leak); pr_info("%s: dummy @ %p, prevented leak @ %p\n", __func__, d, *shadow_leak); } static void livepatch_fix2_dummy_free(struct dummy *d) { int **shadow_leak; int *shadow_count; /* Patch: copy the memory leak patch from the fix1 module. */ shadow_leak = klp_shadow_get(d, SV_LEAK); if (shadow_leak) klp_shadow_free(d, SV_LEAK, livepatch_fix2_dummy_leak_dtor); else pr_info("%s: dummy @ %p leaked!\n", __func__, d); /* * Patch: fetch the SV_COUNTER shadow variable and display * the final count. Detach the shadow variable. */ shadow_count = klp_shadow_get(d, SV_COUNTER); if (shadow_count) { pr_info("%s: dummy @ %p, check counter = %d\n", __func__, d, *shadow_count); klp_shadow_free(d, SV_COUNTER, NULL); } kfree(d); } static struct klp_func funcs[] = { { .old_name = "dummy_check", .new_func = livepatch_fix2_dummy_check, }, { .old_name = "dummy_free", .new_func = livepatch_fix2_dummy_free, }, { } }; static struct klp_object objs[] = { { .name = "livepatch_shadow_mod", .funcs = funcs, }, { } }; static struct klp_patch patch = { .mod = THIS_MODULE, .objs = objs, }; static int livepatch_shadow_fix2_init(void) { return klp_enable_patch(&patch); } static void livepatch_shadow_fix2_exit(void) { /* Cleanup any existing SV_COUNTER shadow variables */ klp_shadow_free_all(SV_COUNTER, NULL); } module_init(livepatch_shadow_fix2_init); module_exit(livepatch_shadow_fix2_exit); MODULE_LICENSE("GPL"); MODULE_INFO(livepatch, "Y");