arch/s390/kernel/runtime_instr.c

   1 /*
   2  * Copyright IBM Corp. 2012
   3  * Author(s): Jan Glauber <jang@linux.vnet.ibm.com>
   4  */
   5
   6 #include <linux/kernel.h>
   7 #include <linux/syscalls.h>
   8 #include <linux/signal.h>
   9 #include <linux/mm.h>
  10 #include <linux/slab.h>
  11 #include <linux/init.h>
  12 #include <linux/errno.h>
  13 #include <linux/kernel_stat.h>
  14 #include <linux/sched/task_stack.h>
  15
  16 #include <asm/runtime_instr.h>
  17 #include <asm/cpu_mf.h>
  18 #include <asm/irq.h>
  19
  20 /* empty control block to disable RI by loading it */
  21 struct runtime_instr_cb runtime_instr_empty_cb;
  22
  23 static void disable_runtime_instr(void)
  24 {
  25         struct pt_regs *regs = task_pt_regs(current);
  26
  27         load_runtime_instr_cb(&runtime_instr_empty_cb);
  28
  29         /*
  30          * Make sure the RI bit is deleted from the PSW. If the user did not
  31          * switch off RI before the system call the process will get a
  32          * specification exception otherwise.
  33          */
  34         regs->psw.mask &= ~PSW_MASK_RI;
  35 }
  36
  37 static void init_runtime_instr_cb(struct runtime_instr_cb *cb)
  38 {
  39         cb->buf_limit = 0xfff;
  40         cb->pstate = 1;
  41         cb->pstate_set_buf = 1;
  42         cb->pstate_sample = 1;
  43         cb->pstate_collect = 1;
  44         cb->key = PAGE_DEFAULT_KEY;
  45         cb->valid = 1;
  46 }
  47
  48 void exit_thread_runtime_instr(void)
  49 {
  50         struct task_struct *task = current;
  51
  52         if (!task->thread.ri_cb)
  53                 return;
  54         disable_runtime_instr();
  55         kfree(task->thread.ri_cb);
  56         task->thread.ri_cb = NULL;
  57 }
  58
  59 SYSCALL_DEFINE1(s390_runtime_instr, int, command)
  60 {
  61         struct runtime_instr_cb *cb;
  62
  63         if (!test_facility(64))
  64                 return -EOPNOTSUPP;
  65
  66         if (command == S390_RUNTIME_INSTR_STOP) {
  67                 preempt_disable();
  68                 exit_thread_runtime_instr();
  69                 preempt_enable();
  70                 return 0;
  71         }
  72
  73         if (command != S390_RUNTIME_INSTR_START)
  74                 return -EINVAL;
  75
  76         if (!current->thread.ri_cb) {
  77                 cb = kzalloc(sizeof(*cb), GFP_KERNEL);
  78                 if (!cb)
  79                         return -ENOMEM;
  80         } else {
  81                 cb = current->thread.ri_cb;
  82                 memset(cb, 0, sizeof(*cb));
  83         }
  84
  85         init_runtime_instr_cb(cb);
  86
  87         /* now load the control block to make it available */
  88         preempt_disable();
  89         current->thread.ri_cb = cb;
  90         load_runtime_instr_cb(cb);
  91         preempt_enable();
  92         return 0;
  93 }