arch/s390/kernel/runtime_instr.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright IBM Corp. 2012
   4  * Author(s): Jan Glauber <jang@linux.vnet.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 <linux/init.h>
  13 #include <linux/errno.h>
  14 #include <linux/kernel_stat.h>
  15 #include <linux/sched/task_stack.h>
  16
  17 #include <asm/runtime_instr.h>
  18 #include <asm/cpu_mf.h>
  19 #include <asm/irq.h>
  20
  21 /* empty control block to disable RI by loading it */
  22 struct runtime_instr_cb runtime_instr_empty_cb;
  23
  24 void runtime_instr_release(struct task_struct *tsk)
  25 {
  26         kfree(tsk->thread.ri_cb);
  27 }
  28
  29 static void disable_runtime_instr(void)
  30 {
  31         struct task_struct *task = current;
  32         struct pt_regs *regs;
  33
  34         if (!task->thread.ri_cb)
  35                 return;
  36         regs = task_pt_regs(task);
  37         preempt_disable();
  38         load_runtime_instr_cb(&runtime_instr_empty_cb);
  39         kfree(task->thread.ri_cb);
  40         task->thread.ri_cb = NULL;
  41         preempt_enable();
  42
  43         /*
  44          * Make sure the RI bit is deleted from the PSW. If the user did not
  45          * switch off RI before the system call the process will get a
  46          * specification exception otherwise.
  47          */
  48         regs->psw.mask &= ~PSW_MASK_RI;
  49 }
  50
  51 static void init_runtime_instr_cb(struct runtime_instr_cb *cb)
  52 {
  53         cb->rla = 0xfff;
  54         cb->s = 1;
  55         cb->k = 1;
  56         cb->ps = 1;
  57         cb->pc = 1;
  58         cb->key = PAGE_DEFAULT_KEY;
  59         cb->v = 1;
  60 }
  61
  62 SYSCALL_DEFINE1(s390_runtime_instr, int, command)
  63 {
  64         struct runtime_instr_cb *cb;
  65
  66         if (!test_facility(64))
  67                 return -EOPNOTSUPP;
  68
  69         if (command == S390_RUNTIME_INSTR_STOP) {
  70                 disable_runtime_instr();
  71                 return 0;
  72         }
  73
  74         if (command != S390_RUNTIME_INSTR_START)
  75                 return -EINVAL;
  76
  77         if (!current->thread.ri_cb) {
  78                 cb = kzalloc(sizeof(*cb), GFP_KERNEL);
  79                 if (!cb)
  80                         return -ENOMEM;
  81         } else {
  82                 cb = current->thread.ri_cb;
  83                 memset(cb, 0, sizeof(*cb));
  84         }
  85
  86         init_runtime_instr_cb(cb);
  87
  88         /* now load the control block to make it available */
  89         preempt_disable();
  90         current->thread.ri_cb = cb;
  91         load_runtime_instr_cb(cb);
  92         preempt_enable();
  93         return 0;
  94 }