1 // SPDX-License-Identifier: GPL-2.0-only
2 /* Pseudo NMI support on sparc64 systems.
3  *
4  * Copyright (C) 2009 David S. Miller <davem@davemloft.net>
5  *
6  * The NMI watchdog support and infrastructure is based almost
7  * entirely upon the x86 NMI support code.
8  */
9 #include <linux/kernel.h>
10 #include <linux/param.h>
11 #include <linux/init.h>
12 #include <linux/percpu.h>
13 #include <linux/nmi.h>
14 #include <linux/export.h>
15 #include <linux/kprobes.h>
16 #include <linux/kernel_stat.h>
17 #include <linux/reboot.h>
18 #include <linux/slab.h>
19 #include <linux/kdebug.h>
20 #include <linux/delay.h>
21 #include <linux/smp.h>
22 
23 #include <asm/perf_event.h>
24 #include <asm/ptrace.h>
25 #include <asm/pcr.h>
26 
27 #include "kstack.h"
28 
29 /* We don't have a real NMI on sparc64, but we can fake one
30  * up using profiling counter overflow interrupts and interrupt
31  * levels.
32  *
33  * The profile overflow interrupts at level 15, so we use
34  * level 14 as our IRQ off level.
35  */
36 
37 static int panic_on_timeout;
38 
39 /* nmi_active:
40  * >0: the NMI watchdog is active, but can be disabled
41  * <0: the NMI watchdog has not been set up, and cannot be enabled
42  *  0: the NMI watchdog is disabled, but can be enabled
43  */
44 atomic_t nmi_active = ATOMIC_INIT(0);		/* oprofile uses this */
45 EXPORT_SYMBOL(nmi_active);
46 static int nmi_init_done;
47 static unsigned int nmi_hz = HZ;
48 static DEFINE_PER_CPU(short, wd_enabled);
49 static int endflag __initdata;
50 
51 static DEFINE_PER_CPU(unsigned int, last_irq_sum);
52 static DEFINE_PER_CPU(long, alert_counter);
53 static DEFINE_PER_CPU(int, nmi_touch);
54 
arch_touch_nmi_watchdog(void)55 void arch_touch_nmi_watchdog(void)
56 {
57 	if (atomic_read(&nmi_active)) {
58 		int cpu;
59 
60 		for_each_present_cpu(cpu) {
61 			if (per_cpu(nmi_touch, cpu) != 1)
62 				per_cpu(nmi_touch, cpu) = 1;
63 		}
64 	}
65 }
66 EXPORT_SYMBOL(arch_touch_nmi_watchdog);
67 
die_nmi(const char * str,struct pt_regs * regs,int do_panic)68 static void die_nmi(const char *str, struct pt_regs *regs, int do_panic)
69 {
70 	int this_cpu = smp_processor_id();
71 
72 	if (notify_die(DIE_NMIWATCHDOG, str, regs, 0,
73 		       pt_regs_trap_type(regs), SIGINT) == NOTIFY_STOP)
74 		return;
75 
76 	if (do_panic || panic_on_oops)
77 		panic("Watchdog detected hard LOCKUP on cpu %d", this_cpu);
78 	else
79 		WARN(1, "Watchdog detected hard LOCKUP on cpu %d", this_cpu);
80 }
81 
perfctr_irq(int irq,struct pt_regs * regs)82 notrace __kprobes void perfctr_irq(int irq, struct pt_regs *regs)
83 {
84 	unsigned int sum, touched = 0;
85 	void *orig_sp;
86 
87 	clear_softint(1 << irq);
88 
89 	local_cpu_data().__nmi_count++;
90 
91 	nmi_enter();
92 
93 	orig_sp = set_hardirq_stack();
94 
95 	if (notify_die(DIE_NMI, "nmi", regs, 0,
96 		       pt_regs_trap_type(regs), SIGINT) == NOTIFY_STOP)
97 		touched = 1;
98 	else
99 		pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_disable);
100 
101 	sum = local_cpu_data().irq0_irqs;
102 	if (__this_cpu_read(nmi_touch)) {
103 		__this_cpu_write(nmi_touch, 0);
104 		touched = 1;
105 	}
106 	if (!touched && __this_cpu_read(last_irq_sum) == sum) {
107 		__this_cpu_inc(alert_counter);
108 		if (__this_cpu_read(alert_counter) == 30 * nmi_hz)
109 			die_nmi("BUG: NMI Watchdog detected LOCKUP",
110 				regs, panic_on_timeout);
111 	} else {
112 		__this_cpu_write(last_irq_sum, sum);
113 		__this_cpu_write(alert_counter, 0);
114 	}
115 	if (__this_cpu_read(wd_enabled)) {
116 		pcr_ops->write_pic(0, pcr_ops->nmi_picl_value(nmi_hz));
117 		pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_enable);
118 	}
119 
120 	restore_hardirq_stack(orig_sp);
121 
122 	nmi_exit();
123 }
124 
get_nmi_count(int cpu)125 static inline unsigned int get_nmi_count(int cpu)
126 {
127 	return cpu_data(cpu).__nmi_count;
128 }
129 
nmi_cpu_busy(void * data)130 static __init void nmi_cpu_busy(void *data)
131 {
132 	while (endflag == 0)
133 		mb();
134 }
135 
report_broken_nmi(int cpu,int * prev_nmi_count)136 static void report_broken_nmi(int cpu, int *prev_nmi_count)
137 {
138 	printk(KERN_CONT "\n");
139 
140 	printk(KERN_WARNING
141 		"WARNING: CPU#%d: NMI appears to be stuck (%d->%d)!\n",
142 			cpu, prev_nmi_count[cpu], get_nmi_count(cpu));
143 
144 	printk(KERN_WARNING
145 		"Please report this to bugzilla.kernel.org,\n");
146 	printk(KERN_WARNING
147 		"and attach the output of the 'dmesg' command.\n");
148 
149 	per_cpu(wd_enabled, cpu) = 0;
150 	atomic_dec(&nmi_active);
151 }
152 
stop_nmi_watchdog(void * unused)153 void stop_nmi_watchdog(void *unused)
154 {
155 	if (!__this_cpu_read(wd_enabled))
156 		return;
157 	pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_disable);
158 	__this_cpu_write(wd_enabled, 0);
159 	atomic_dec(&nmi_active);
160 }
161 
check_nmi_watchdog(void)162 static int __init check_nmi_watchdog(void)
163 {
164 	unsigned int *prev_nmi_count;
165 	int cpu, err;
166 
167 	if (!atomic_read(&nmi_active))
168 		return 0;
169 
170 	prev_nmi_count = kmalloc_array(nr_cpu_ids, sizeof(unsigned int),
171 				       GFP_KERNEL);
172 	if (!prev_nmi_count) {
173 		err = -ENOMEM;
174 		goto error;
175 	}
176 
177 	printk(KERN_INFO "Testing NMI watchdog ... ");
178 
179 	smp_call_function(nmi_cpu_busy, (void *)&endflag, 0);
180 
181 	for_each_possible_cpu(cpu)
182 		prev_nmi_count[cpu] = get_nmi_count(cpu);
183 	local_irq_enable();
184 	mdelay((20 * 1000) / nmi_hz); /* wait 20 ticks */
185 
186 	for_each_online_cpu(cpu) {
187 		if (!per_cpu(wd_enabled, cpu))
188 			continue;
189 		if (get_nmi_count(cpu) - prev_nmi_count[cpu] <= 5)
190 			report_broken_nmi(cpu, prev_nmi_count);
191 	}
192 	endflag = 1;
193 	if (!atomic_read(&nmi_active)) {
194 		kfree(prev_nmi_count);
195 		atomic_set(&nmi_active, -1);
196 		err = -ENODEV;
197 		goto error;
198 	}
199 	printk("OK.\n");
200 
201 	nmi_hz = 1;
202 
203 	kfree(prev_nmi_count);
204 	return 0;
205 error:
206 	on_each_cpu(stop_nmi_watchdog, NULL, 1);
207 	return err;
208 }
209 
start_nmi_watchdog(void * unused)210 void start_nmi_watchdog(void *unused)
211 {
212 	if (__this_cpu_read(wd_enabled))
213 		return;
214 
215 	__this_cpu_write(wd_enabled, 1);
216 	atomic_inc(&nmi_active);
217 
218 	pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_disable);
219 	pcr_ops->write_pic(0, pcr_ops->nmi_picl_value(nmi_hz));
220 
221 	pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_enable);
222 }
223 
nmi_adjust_hz_one(void * unused)224 static void nmi_adjust_hz_one(void *unused)
225 {
226 	if (!__this_cpu_read(wd_enabled))
227 		return;
228 
229 	pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_disable);
230 	pcr_ops->write_pic(0, pcr_ops->nmi_picl_value(nmi_hz));
231 
232 	pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_enable);
233 }
234 
nmi_adjust_hz(unsigned int new_hz)235 void nmi_adjust_hz(unsigned int new_hz)
236 {
237 	nmi_hz = new_hz;
238 	on_each_cpu(nmi_adjust_hz_one, NULL, 1);
239 }
240 EXPORT_SYMBOL_GPL(nmi_adjust_hz);
241 
nmi_shutdown(struct notifier_block * nb,unsigned long cmd,void * p)242 static int nmi_shutdown(struct notifier_block *nb, unsigned long cmd, void *p)
243 {
244 	on_each_cpu(stop_nmi_watchdog, NULL, 1);
245 	return 0;
246 }
247 
248 static struct notifier_block nmi_reboot_notifier = {
249 	.notifier_call = nmi_shutdown,
250 };
251 
nmi_init(void)252 int __init nmi_init(void)
253 {
254 	int err;
255 
256 	on_each_cpu(start_nmi_watchdog, NULL, 1);
257 
258 	err = check_nmi_watchdog();
259 	if (!err) {
260 		err = register_reboot_notifier(&nmi_reboot_notifier);
261 		if (err) {
262 			on_each_cpu(stop_nmi_watchdog, NULL, 1);
263 			atomic_set(&nmi_active, -1);
264 		}
265 	}
266 
267 	nmi_init_done = 1;
268 
269 	return err;
270 }
271 
setup_nmi_watchdog(char * str)272 static int __init setup_nmi_watchdog(char *str)
273 {
274 	if (!strncmp(str, "panic", 5))
275 		panic_on_timeout = 1;
276 
277 	return 0;
278 }
279 __setup("nmi_watchdog=", setup_nmi_watchdog);
280 
281 /*
282  * sparc specific NMI watchdog enable function.
283  * Enables watchdog if it is not enabled already.
284  */
watchdog_nmi_enable(unsigned int cpu)285 int watchdog_nmi_enable(unsigned int cpu)
286 {
287 	if (atomic_read(&nmi_active) == -1) {
288 		pr_warn("NMI watchdog cannot be enabled or disabled\n");
289 		return -1;
290 	}
291 
292 	/*
293 	 * watchdog thread could start even before nmi_init is called.
294 	 * Just Return in that case. Let nmi_init finish the init
295 	 * process first.
296 	 */
297 	if (!nmi_init_done)
298 		return 0;
299 
300 	smp_call_function_single(cpu, start_nmi_watchdog, NULL, 1);
301 
302 	return 0;
303 }
304 /*
305  * sparc specific NMI watchdog disable function.
306  * Disables watchdog if it is not disabled already.
307  */
watchdog_nmi_disable(unsigned int cpu)308 void watchdog_nmi_disable(unsigned int cpu)
309 {
310 	if (atomic_read(&nmi_active) == -1)
311 		pr_warn_once("NMI watchdog cannot be enabled or disabled\n");
312 	else
313 		smp_call_function_single(cpu, stop_nmi_watchdog, NULL, 1);
314 }
315