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