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 #include "entry.h"
22 
23 /* empty control block to disable RI by loading it */
24 struct runtime_instr_cb runtime_instr_empty_cb;
25 
runtime_instr_release(struct task_struct * tsk)26 void runtime_instr_release(struct task_struct *tsk)
27 {
28 	kfree(tsk->thread.ri_cb);
29 }
30 
disable_runtime_instr(void)31 static void disable_runtime_instr(void)
32 {
33 	struct task_struct *task = current;
34 	struct pt_regs *regs;
35 
36 	if (!task->thread.ri_cb)
37 		return;
38 	regs = task_pt_regs(task);
39 	preempt_disable();
40 	load_runtime_instr_cb(&runtime_instr_empty_cb);
41 	kfree(task->thread.ri_cb);
42 	task->thread.ri_cb = NULL;
43 	preempt_enable();
44 
45 	/*
46 	 * Make sure the RI bit is deleted from the PSW. If the user did not
47 	 * switch off RI before the system call the process will get a
48 	 * specification exception otherwise.
49 	 */
50 	regs->psw.mask &= ~PSW_MASK_RI;
51 }
52 
init_runtime_instr_cb(struct runtime_instr_cb * cb)53 static void init_runtime_instr_cb(struct runtime_instr_cb *cb)
54 {
55 	cb->rla = 0xfff;
56 	cb->s = 1;
57 	cb->k = 1;
58 	cb->ps = 1;
59 	cb->pc = 1;
60 	cb->key = PAGE_DEFAULT_KEY >> 4;
61 	cb->v = 1;
62 }
63 
64 /*
65  * The signum argument is unused. In older kernels it was used to
66  * specify a real-time signal. For backwards compatibility user space
67  * should pass a valid real-time signal number (the signum argument
68  * was checked in older kernels).
69  */
SYSCALL_DEFINE2(s390_runtime_instr,int,command,int,signum)70 SYSCALL_DEFINE2(s390_runtime_instr, int, command, int, signum)
71 {
72 	struct runtime_instr_cb *cb;
73 
74 	if (!test_facility(64))
75 		return -EOPNOTSUPP;
76 
77 	if (command == S390_RUNTIME_INSTR_STOP) {
78 		disable_runtime_instr();
79 		return 0;
80 	}
81 
82 	if (command != S390_RUNTIME_INSTR_START)
83 		return -EINVAL;
84 
85 	if (!current->thread.ri_cb) {
86 		cb = kzalloc(sizeof(*cb), GFP_KERNEL);
87 		if (!cb)
88 			return -ENOMEM;
89 	} else {
90 		cb = current->thread.ri_cb;
91 		memset(cb, 0, sizeof(*cb));
92 	}
93 
94 	init_runtime_instr_cb(cb);
95 
96 	/* now load the control block to make it available */
97 	preempt_disable();
98 	current->thread.ri_cb = cb;
99 	load_runtime_instr_cb(cb);
100 	preempt_enable();
101 	return 0;
102 }
103