arch/s390/kernel/guarded_storage.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright IBM Corp. 2016
   4  * Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>
   5  */
   6
   7 #include <linux/kernel.h>
   8 #include <linux/syscalls.h>
   9 #include <linux/signal.h>
  10 #include <linux/mm.h>
  11 #include <linux/slab.h>
  12 #include <asm/guarded_storage.h>
  13 #include "entry.h"
  14
  15 void exit_thread_gs(void)
  16 {
  17         preempt_disable();
  18         kfree(current->thread.gs_cb);
  19         kfree(current->thread.gs_bc_cb);
  20         current->thread.gs_cb = current->thread.gs_bc_cb = NULL;
  21         preempt_enable();
  22 }
  23
  24 static int gs_enable(void)
  25 {
  26         struct gs_cb *gs_cb;
  27
  28         if (!current->thread.gs_cb) {
  29                 gs_cb = kzalloc(sizeof(*gs_cb), GFP_KERNEL);
  30                 if (!gs_cb)
  31                         return -ENOMEM;
  32                 gs_cb->gsd = 25;
  33                 preempt_disable();
  34                 __ctl_set_bit(2, 4);
  35                 load_gs_cb(gs_cb);
  36                 current->thread.gs_cb = gs_cb;
  37                 preempt_enable();
  38         }
  39         return 0;
  40 }
  41
  42 static int gs_disable(void)
  43 {
  44         if (current->thread.gs_cb) {
  45                 preempt_disable();
  46                 kfree(current->thread.gs_cb);
  47                 current->thread.gs_cb = NULL;
  48                 __ctl_clear_bit(2, 4);
  49                 preempt_enable();
  50         }
  51         return 0;
  52 }
  53
  54 static int gs_set_bc_cb(struct gs_cb __user *u_gs_cb)
  55 {
  56         struct gs_cb *gs_cb;
  57
  58         gs_cb = current->thread.gs_bc_cb;
  59         if (!gs_cb) {
  60                 gs_cb = kzalloc(sizeof(*gs_cb), GFP_KERNEL);
  61                 if (!gs_cb)
  62                         return -ENOMEM;
  63                 current->thread.gs_bc_cb = gs_cb;
  64         }
  65         if (copy_from_user(gs_cb, u_gs_cb, sizeof(*gs_cb)))
  66                 return -EFAULT;
  67         return 0;
  68 }
  69
  70 static int gs_clear_bc_cb(void)
  71 {
  72         struct gs_cb *gs_cb;
  73
  74         gs_cb = current->thread.gs_bc_cb;
  75         current->thread.gs_bc_cb = NULL;
  76         kfree(gs_cb);
  77         return 0;
  78 }
  79
  80 void gs_load_bc_cb(struct pt_regs *regs)
  81 {
  82         struct gs_cb *gs_cb;
  83
  84         preempt_disable();
  85         clear_thread_flag(TIF_GUARDED_STORAGE);
  86         gs_cb = current->thread.gs_bc_cb;
  87         if (gs_cb) {
  88                 kfree(current->thread.gs_cb);
  89                 current->thread.gs_bc_cb = NULL;
  90                 __ctl_set_bit(2, 4);
  91                 load_gs_cb(gs_cb);
  92                 current->thread.gs_cb = gs_cb;
  93         }
  94         preempt_enable();
  95 }
  96
  97 static int gs_broadcast(void)
  98 {
  99         struct task_struct *sibling;
 100
 101         read_lock(&tasklist_lock);
 102         for_each_thread(current, sibling) {
 103                 if (!sibling->thread.gs_bc_cb)
 104                         continue;
 105                 if (test_and_set_tsk_thread_flag(sibling, TIF_GUARDED_STORAGE))
 106                         kick_process(sibling);
 107         }
 108         read_unlock(&tasklist_lock);
 109         return 0;
 110 }
 111
 112 SYSCALL_DEFINE2(s390_guarded_storage, int, command,
 113                 struct gs_cb __user *, gs_cb)
 114 {
 115         if (!MACHINE_HAS_GS)
 116                 return -EOPNOTSUPP;
 117         switch (command) {
 118         case GS_ENABLE:
 119                 return gs_enable();
 120         case GS_DISABLE:
 121                 return gs_disable();
 122         case GS_SET_BC_CB:
 123                 return gs_set_bc_cb(gs_cb);
 124         case GS_CLEAR_BC_CB:
 125                 return gs_clear_bc_cb();
 126         case GS_BROADCAST:
 127                 return gs_broadcast();
 128         default:
 129                 return -EINVAL;
 130         }
 131 }