tools/testing/selftests/livepatch/test_modules/test_klp_syscall.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (C) 2017-2023 SUSE
   4  * Authors: Libor Pechacek <[email protected]>
   5  *          Nicolai Stange <[email protected]>
   6  *          Marcos Paulo de Souza <[email protected]>
   7  */
   8
   9 #include <linux/module.h>
  10 #include <linux/kernel.h>
  11 #include <linux/sched.h>
  12 #include <linux/slab.h>
  13 #include <linux/livepatch.h>
  14
  15 #if defined(__x86_64__)
  16 #define FN_PREFIX __x64_
  17 #elif defined(__s390x__)
  18 #define FN_PREFIX __s390x_
  19 #elif defined(__aarch64__)
  20 #define FN_PREFIX __arm64_
  21 #else
  22 /* powerpc does not select ARCH_HAS_SYSCALL_WRAPPER */
  23 #define FN_PREFIX
  24 #endif
  25
  26 /* Protects klp_pids */
  27 static DEFINE_MUTEX(kpid_mutex);
  28
  29 static unsigned int npids, npids_pending;
  30 static int klp_pids[NR_CPUS];
  31 module_param_array(klp_pids, int, &npids_pending, 0);
  32 MODULE_PARM_DESC(klp_pids, "Array of pids to be transitioned to livepatched state.");
  33
  34 static ssize_t npids_show(struct kobject *kobj, struct kobj_attribute *attr,
  35                           char *buf)
  36 {
  37         return sprintf(buf, "%u\n", npids_pending);
  38 }
  39
  40 static struct kobj_attribute klp_attr = __ATTR_RO(npids);
  41 static struct kobject *klp_kobj;
  42
  43 static asmlinkage long lp_sys_getpid(void)
  44 {
  45         int i;
  46
  47         mutex_lock(&kpid_mutex);
  48         if (npids_pending > 0) {
  49                 for (i = 0; i < npids; i++) {
  50                         if (current->pid == klp_pids[i]) {
  51                                 klp_pids[i] = 0;
  52                                 npids_pending--;
  53                                 break;
  54                         }
  55                 }
  56         }
  57         mutex_unlock(&kpid_mutex);
  58
  59         return task_tgid_vnr(current);
  60 }
  61
  62 static struct klp_func vmlinux_funcs[] = {
  63         {
  64                 .old_name = __stringify(FN_PREFIX) "sys_getpid",
  65                 .new_func = lp_sys_getpid,
  66         }, {}
  67 };
  68
  69 static struct klp_object objs[] = {
  70         {
  71                 /* name being NULL means vmlinux */
  72                 .funcs = vmlinux_funcs,
  73         }, {}
  74 };
  75
  76 static struct klp_patch patch = {
  77         .mod = THIS_MODULE,
  78         .objs = objs,
  79 };
  80
  81 static int livepatch_init(void)
  82 {
  83         int ret;
  84
  85         klp_kobj = kobject_create_and_add("test_klp_syscall", kernel_kobj);
  86         if (!klp_kobj)
  87                 return -ENOMEM;
  88
  89         ret = sysfs_create_file(klp_kobj, &klp_attr.attr);
  90         if (ret) {
  91                 kobject_put(klp_kobj);
  92                 return ret;
  93         }
  94
  95         /*
  96          * Save the number pids to transition to livepatched state before the
  97          * number of pending pids is decremented.
  98          */
  99         npids = npids_pending;
 100
 101         return klp_enable_patch(&patch);
 102 }
 103
 104 static void livepatch_exit(void)
 105 {
 106         kobject_put(klp_kobj);
 107 }
 108
 109 module_init(livepatch_init);
 110 module_exit(livepatch_exit);
 111 MODULE_LICENSE("GPL");
 112 MODULE_INFO(livepatch, "Y");
 113 MODULE_AUTHOR("Libor Pechacek <[email protected]>");
 114 MODULE_AUTHOR("Nicolai Stange <[email protected]>");
 115 MODULE_AUTHOR("Marcos Paulo de Souza <[email protected]>");
 116 MODULE_DESCRIPTION("Livepatch test: syscall transition");