cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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livepatch-callbacks-demo.c (5663B)


      1// SPDX-License-Identifier: GPL-2.0-or-later
      2/*
      3 * Copyright (C) 2017 Joe Lawrence <joe.lawrence@redhat.com>
      4 */
      5
      6/*
      7 * livepatch-callbacks-demo.c - (un)patching callbacks livepatch demo
      8 *
      9 *
     10 * Purpose
     11 * -------
     12 *
     13 * Demonstration of registering livepatch (un)patching callbacks.
     14 *
     15 *
     16 * Usage
     17 * -----
     18 *
     19 * Step 1 - load the simple module
     20 *
     21 *   insmod samples/livepatch/livepatch-callbacks-mod.ko
     22 *
     23 *
     24 * Step 2 - load the demonstration livepatch (with callbacks)
     25 *
     26 *   insmod samples/livepatch/livepatch-callbacks-demo.ko
     27 *
     28 *
     29 * Step 3 - cleanup
     30 *
     31 *   echo 0 > /sys/kernel/livepatch/livepatch_callbacks_demo/enabled
     32 *   rmmod livepatch_callbacks_demo
     33 *   rmmod livepatch_callbacks_mod
     34 *
     35 * Watch dmesg output to see livepatch enablement, callback execution
     36 * and patching operations for both vmlinux and module targets.
     37 *
     38 * NOTE: swap the insmod order of livepatch-callbacks-mod.ko and
     39 *       livepatch-callbacks-demo.ko to observe what happens when a
     40 *       target module is loaded after a livepatch with callbacks.
     41 *
     42 * NOTE: 'pre_patch_ret' is a module parameter that sets the pre-patch
     43 *       callback return status.  Try setting up a non-zero status
     44 *       such as -19 (-ENODEV):
     45 *
     46 *       # Load demo livepatch, vmlinux is patched
     47 *       insmod samples/livepatch/livepatch-callbacks-demo.ko
     48 *
     49 *       # Setup next pre-patch callback to return -ENODEV
     50 *       echo -19 > /sys/module/livepatch_callbacks_demo/parameters/pre_patch_ret
     51 *
     52 *       # Module loader refuses to load the target module
     53 *       insmod samples/livepatch/livepatch-callbacks-mod.ko
     54 *       insmod: ERROR: could not insert module samples/livepatch/livepatch-callbacks-mod.ko: No such device
     55 *
     56 * NOTE: There is a second target module,
     57 *       livepatch-callbacks-busymod.ko, available for experimenting
     58 *       with livepatch (un)patch callbacks.  This module contains
     59 *       a 'sleep_secs' parameter that parks the module on one of the
     60 *       functions that the livepatch demo module wants to patch.
     61 *       Modifying this value and tweaking the order of module loads can
     62 *       effectively demonstrate stalled patch transitions:
     63 *
     64 *       # Load a target module, let it park on 'busymod_work_func' for
     65 *       # thirty seconds
     66 *       insmod samples/livepatch/livepatch-callbacks-busymod.ko sleep_secs=30
     67 *
     68 *       # Meanwhile load the livepatch
     69 *       insmod samples/livepatch/livepatch-callbacks-demo.ko
     70 *
     71 *       # ... then load and unload another target module while the
     72 *       # transition is in progress
     73 *       insmod samples/livepatch/livepatch-callbacks-mod.ko
     74 *       rmmod samples/livepatch/livepatch-callbacks-mod.ko
     75 *
     76 *       # Finally cleanup
     77 *       echo 0 > /sys/kernel/livepatch/livepatch_callbacks_demo/enabled
     78 *       rmmod samples/livepatch/livepatch-callbacks-demo.ko
     79 */
     80
     81#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
     82
     83#include <linux/module.h>
     84#include <linux/kernel.h>
     85#include <linux/livepatch.h>
     86
     87static int pre_patch_ret;
     88module_param(pre_patch_ret, int, 0644);
     89MODULE_PARM_DESC(pre_patch_ret, "pre_patch_ret (default=0)");
     90
     91static const char *const module_state[] = {
     92	[MODULE_STATE_LIVE]	= "[MODULE_STATE_LIVE] Normal state",
     93	[MODULE_STATE_COMING]	= "[MODULE_STATE_COMING] Full formed, running module_init",
     94	[MODULE_STATE_GOING]	= "[MODULE_STATE_GOING] Going away",
     95	[MODULE_STATE_UNFORMED]	= "[MODULE_STATE_UNFORMED] Still setting it up",
     96};
     97
     98static void callback_info(const char *callback, struct klp_object *obj)
     99{
    100	if (obj->mod)
    101		pr_info("%s: %s -> %s\n", callback, obj->mod->name,
    102			module_state[obj->mod->state]);
    103	else
    104		pr_info("%s: vmlinux\n", callback);
    105}
    106
    107/* Executed on object patching (ie, patch enablement) */
    108static int pre_patch_callback(struct klp_object *obj)
    109{
    110	callback_info(__func__, obj);
    111	return pre_patch_ret;
    112}
    113
    114/* Executed on object unpatching (ie, patch disablement) */
    115static void post_patch_callback(struct klp_object *obj)
    116{
    117	callback_info(__func__, obj);
    118}
    119
    120/* Executed on object unpatching (ie, patch disablement) */
    121static void pre_unpatch_callback(struct klp_object *obj)
    122{
    123	callback_info(__func__, obj);
    124}
    125
    126/* Executed on object unpatching (ie, patch disablement) */
    127static void post_unpatch_callback(struct klp_object *obj)
    128{
    129	callback_info(__func__, obj);
    130}
    131
    132static void patched_work_func(struct work_struct *work)
    133{
    134	pr_info("%s\n", __func__);
    135}
    136
    137static struct klp_func no_funcs[] = {
    138	{ }
    139};
    140
    141static struct klp_func busymod_funcs[] = {
    142	{
    143		.old_name = "busymod_work_func",
    144		.new_func = patched_work_func,
    145	}, { }
    146};
    147
    148static struct klp_object objs[] = {
    149	{
    150		.name = NULL,	/* vmlinux */
    151		.funcs = no_funcs,
    152		.callbacks = {
    153			.pre_patch = pre_patch_callback,
    154			.post_patch = post_patch_callback,
    155			.pre_unpatch = pre_unpatch_callback,
    156			.post_unpatch = post_unpatch_callback,
    157		},
    158	},	{
    159		.name = "livepatch_callbacks_mod",
    160		.funcs = no_funcs,
    161		.callbacks = {
    162			.pre_patch = pre_patch_callback,
    163			.post_patch = post_patch_callback,
    164			.pre_unpatch = pre_unpatch_callback,
    165			.post_unpatch = post_unpatch_callback,
    166		},
    167	},	{
    168		.name = "livepatch_callbacks_busymod",
    169		.funcs = busymod_funcs,
    170		.callbacks = {
    171			.pre_patch = pre_patch_callback,
    172			.post_patch = post_patch_callback,
    173			.pre_unpatch = pre_unpatch_callback,
    174			.post_unpatch = post_unpatch_callback,
    175		},
    176	}, { }
    177};
    178
    179static struct klp_patch patch = {
    180	.mod = THIS_MODULE,
    181	.objs = objs,
    182};
    183
    184static int livepatch_callbacks_demo_init(void)
    185{
    186	return klp_enable_patch(&patch);
    187}
    188
    189static void livepatch_callbacks_demo_exit(void)
    190{
    191}
    192
    193module_init(livepatch_callbacks_demo_init);
    194module_exit(livepatch_callbacks_demo_exit);
    195MODULE_LICENSE("GPL");
    196MODULE_INFO(livepatch, "Y");