1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 *
4 * Copyright (C) IBM Corporation, 2005
5 *               Jeff Muizelaar, 2006, 2007
6 *               Pekka Paalanen, 2008 <pq@iki.fi>
7 *
8 * Derived from the read-mod example from relay-examples by Tom Zanussi.
9 */
10
11#define pr_fmt(fmt) "mmiotrace: " fmt
12
13#include <linux/moduleparam.h>
14#include <linux/debugfs.h>
15#include <linux/slab.h>
16#include <linux/uaccess.h>
17#include <linux/io.h>
18#include <linux/mmiotrace.h>
19#include <linux/pgtable.h>
20#include <asm/e820/api.h> /* for ISA_START_ADDRESS */
21#include <linux/atomic.h>
22#include <linux/percpu.h>
23#include <linux/cpu.h>
24
25#include "pf_in.h"
26
27struct trap_reason {
28	unsigned long addr;
29	unsigned long ip;
30	enum reason_type type;
31	int active_traces;
32};
33
34struct remap_trace {
35	struct list_head list;
36	struct kmmio_probe probe;
37	resource_size_t phys;
38	unsigned long id;
39};
40
41/* Accessed per-cpu. */
42static DEFINE_PER_CPU(struct trap_reason, pf_reason);
43static DEFINE_PER_CPU(struct mmiotrace_rw, cpu_trace);
44
45static DEFINE_MUTEX(mmiotrace_mutex);
46static DEFINE_SPINLOCK(trace_lock);
47static atomic_t mmiotrace_enabled;
48static LIST_HEAD(trace_list);		/* struct remap_trace */
49
50/*
51 * Locking in this file:
52 * - mmiotrace_mutex enforces enable/disable_mmiotrace() critical sections.
53 * - mmiotrace_enabled may be modified only when holding mmiotrace_mutex
54 *   and trace_lock.
55 * - Routines depending on is_enabled() must take trace_lock.
56 * - trace_list users must hold trace_lock.
57 * - is_enabled() guarantees that mmio_trace_{rw,mapping} are allowed.
58 * - pre/post callbacks assume the effect of is_enabled() being true.
59 */
60
61/* module parameters */
62static unsigned long	filter_offset;
63static bool		nommiotrace;
64static bool		trace_pc;
65
66module_param(filter_offset, ulong, 0);
67module_param(nommiotrace, bool, 0);
68module_param(trace_pc, bool, 0);
69
70MODULE_PARM_DESC(filter_offset, "Start address of traced mappings.");
71MODULE_PARM_DESC(nommiotrace, "Disable actual MMIO tracing.");
72MODULE_PARM_DESC(trace_pc, "Record address of faulting instructions.");
73
74static bool is_enabled(void)
75{
76	return atomic_read(&mmiotrace_enabled);
77}
78
79static void print_pte(unsigned long address)
80{
81	unsigned int level;
82	pte_t *pte = lookup_address(address, &level);
83
84	if (!pte) {
85		pr_err("Error in %s: no pte for page 0x%08lx\n",
86		       __func__, address);
87		return;
88	}
89
90	if (level == PG_LEVEL_2M) {
91		pr_emerg("4MB pages are not currently supported: 0x%08lx\n",
92			 address);
93		BUG();
94	}
95	pr_info("pte for 0x%lx: 0x%llx 0x%llx\n",
96		address,
97		(unsigned long long)pte_val(*pte),
98		(unsigned long long)pte_val(*pte) & _PAGE_PRESENT);
99}
100
101/*
102 * For some reason the pre/post pairs have been called in an
103 * unmatched order. Report and die.
104 */
105static void die_kmmio_nesting_error(struct pt_regs *regs, unsigned long addr)
106{
107	const struct trap_reason *my_reason = &get_cpu_var(pf_reason);
108	pr_emerg("unexpected fault for address: 0x%08lx, last fault for address: 0x%08lx\n",
109		 addr, my_reason->addr);
110	print_pte(addr);
111	pr_emerg("faulting IP is at %pS\n", (void *)regs->ip);
112	pr_emerg("last faulting IP was at %pS\n", (void *)my_reason->ip);
113#ifdef __i386__
114	pr_emerg("eax: %08lx   ebx: %08lx   ecx: %08lx   edx: %08lx\n",
115		 regs->ax, regs->bx, regs->cx, regs->dx);
116	pr_emerg("esi: %08lx   edi: %08lx   ebp: %08lx   esp: %08lx\n",
117		 regs->si, regs->di, regs->bp, regs->sp);
118#else
119	pr_emerg("rax: %016lx   rcx: %016lx   rdx: %016lx\n",
120		 regs->ax, regs->cx, regs->dx);
121	pr_emerg("rsi: %016lx   rdi: %016lx   rbp: %016lx   rsp: %016lx\n",
122		 regs->si, regs->di, regs->bp, regs->sp);
123#endif
124	put_cpu_var(pf_reason);
125	BUG();
126}
127
128static void pre(struct kmmio_probe *p, struct pt_regs *regs,
129						unsigned long addr)
130{
131	struct trap_reason *my_reason = &get_cpu_var(pf_reason);
132	struct mmiotrace_rw *my_trace = &get_cpu_var(cpu_trace);
133	const unsigned long instptr = instruction_pointer(regs);
134	const enum reason_type type = get_ins_type(instptr);
135	struct remap_trace *trace = p->private;
136
137	/* it doesn't make sense to have more than one active trace per cpu */
138	if (my_reason->active_traces)
139		die_kmmio_nesting_error(regs, addr);
140	else
141		my_reason->active_traces++;
142
143	my_reason->type = type;
144	my_reason->addr = addr;
145	my_reason->ip = instptr;
146
147	my_trace->phys = addr - trace->probe.addr + trace->phys;
148	my_trace->map_id = trace->id;
149
150	/*
151	 * Only record the program counter when requested.
152	 * It may taint clean-room reverse engineering.
153	 */
154	if (trace_pc)
155		my_trace->pc = instptr;
156	else
157		my_trace->pc = 0;
158
159	/*
160	 * XXX: the timestamp recorded will be *after* the tracing has been
161	 * done, not at the time we hit the instruction. SMP implications
162	 * on event ordering?
163	 */
164
165	switch (type) {
166	case REG_READ:
167		my_trace->opcode = MMIO_READ;
168		my_trace->width = get_ins_mem_width(instptr);
169		break;
170	case REG_WRITE:
171		my_trace->opcode = MMIO_WRITE;
172		my_trace->width = get_ins_mem_width(instptr);
173		my_trace->value = get_ins_reg_val(instptr, regs);
174		break;
175	case IMM_WRITE:
176		my_trace->opcode = MMIO_WRITE;
177		my_trace->width = get_ins_mem_width(instptr);
178		my_trace->value = get_ins_imm_val(instptr);
179		break;
180	default:
181		{
182			unsigned char *ip = (unsigned char *)instptr;
183			my_trace->opcode = MMIO_UNKNOWN_OP;
184			my_trace->width = 0;
185			my_trace->value = (*ip) << 16 | *(ip + 1) << 8 |
186								*(ip + 2);
187		}
188	}
189	put_cpu_var(cpu_trace);
190	put_cpu_var(pf_reason);
191}
192
193static void post(struct kmmio_probe *p, unsigned long condition,
194							struct pt_regs *regs)
195{
196	struct trap_reason *my_reason = &get_cpu_var(pf_reason);
197	struct mmiotrace_rw *my_trace = &get_cpu_var(cpu_trace);
198
199	/* this should always return the active_trace count to 0 */
200	my_reason->active_traces--;
201	if (my_reason->active_traces) {
202		pr_emerg("unexpected post handler");
203		BUG();
204	}
205
206	switch (my_reason->type) {
207	case REG_READ:
208		my_trace->value = get_ins_reg_val(my_reason->ip, regs);
209		break;
210	default:
211		break;
212	}
213
214	mmio_trace_rw(my_trace);
215	put_cpu_var(cpu_trace);
216	put_cpu_var(pf_reason);
217}
218
219static void ioremap_trace_core(resource_size_t offset, unsigned long size,
220							void __iomem *addr)
221{
222	static atomic_t next_id;
223	struct remap_trace *trace = kmalloc(sizeof(*trace), GFP_KERNEL);
224	/* These are page-unaligned. */
225	struct mmiotrace_map map = {
226		.phys = offset,
227		.virt = (unsigned long)addr,
228		.len = size,
229		.opcode = MMIO_PROBE
230	};
231
232	if (!trace) {
233		pr_err("kmalloc failed in ioremap\n");
234		return;
235	}
236
237	*trace = (struct remap_trace) {
238		.probe = {
239			.addr = (unsigned long)addr,
240			.len = size,
241			.pre_handler = pre,
242			.post_handler = post,
243			.private = trace
244		},
245		.phys = offset,
246		.id = atomic_inc_return(&next_id)
247	};
248	map.map_id = trace->id;
249
250	spin_lock_irq(&trace_lock);
251	if (!is_enabled()) {
252		kfree(trace);
253		goto not_enabled;
254	}
255
256	mmio_trace_mapping(&map);
257	list_add_tail(&trace->list, &trace_list);
258	if (!nommiotrace)
259		register_kmmio_probe(&trace->probe);
260
261not_enabled:
262	spin_unlock_irq(&trace_lock);
263}
264
265void mmiotrace_ioremap(resource_size_t offset, unsigned long size,
266						void __iomem *addr)
267{
268	if (!is_enabled()) /* recheck and proper locking in *_core() */
269		return;
270
271	pr_debug("ioremap_*(0x%llx, 0x%lx) = %p\n",
272		 (unsigned long long)offset, size, addr);
273	if ((filter_offset) && (offset != filter_offset))
274		return;
275	ioremap_trace_core(offset, size, addr);
276}
277
278static void iounmap_trace_core(volatile void __iomem *addr)
279{
280	struct mmiotrace_map map = {
281		.phys = 0,
282		.virt = (unsigned long)addr,
283		.len = 0,
284		.opcode = MMIO_UNPROBE
285	};
286	struct remap_trace *trace;
287	struct remap_trace *tmp;
288	struct remap_trace *found_trace = NULL;
289
290	pr_debug("Unmapping %p.\n", addr);
291
292	spin_lock_irq(&trace_lock);
293	if (!is_enabled())
294		goto not_enabled;
295
296	list_for_each_entry_safe(trace, tmp, &trace_list, list) {
297		if ((unsigned long)addr == trace->probe.addr) {
298			if (!nommiotrace)
299				unregister_kmmio_probe(&trace->probe);
300			list_del(&trace->list);
301			found_trace = trace;
302			break;
303		}
304	}
305	map.map_id = (found_trace) ? found_trace->id : -1;
306	mmio_trace_mapping(&map);
307
308not_enabled:
309	spin_unlock_irq(&trace_lock);
310	if (found_trace) {
311		synchronize_rcu(); /* unregister_kmmio_probe() requirement */
312		kfree(found_trace);
313	}
314}
315
316void mmiotrace_iounmap(volatile void __iomem *addr)
317{
318	might_sleep();
319	if (is_enabled()) /* recheck and proper locking in *_core() */
320		iounmap_trace_core(addr);
321}
322
323int mmiotrace_printk(const char *fmt, ...)
324{
325	int ret = 0;
326	va_list args;
327	unsigned long flags;
328	va_start(args, fmt);
329
330	spin_lock_irqsave(&trace_lock, flags);
331	if (is_enabled())
332		ret = mmio_trace_printk(fmt, args);
333	spin_unlock_irqrestore(&trace_lock, flags);
334
335	va_end(args);
336	return ret;
337}
338EXPORT_SYMBOL(mmiotrace_printk);
339
340static void clear_trace_list(void)
341{
342	struct remap_trace *trace;
343	struct remap_trace *tmp;
344
345	/*
346	 * No locking required, because the caller ensures we are in a
347	 * critical section via mutex, and is_enabled() is false,
348	 * i.e. nothing can traverse or modify this list.
349	 * Caller also ensures is_enabled() cannot change.
350	 */
351	list_for_each_entry(trace, &trace_list, list) {
352		pr_notice("purging non-iounmapped trace @0x%08lx, size 0x%lx.\n",
353			  trace->probe.addr, trace->probe.len);
354		if (!nommiotrace)
355			unregister_kmmio_probe(&trace->probe);
356	}
357	synchronize_rcu(); /* unregister_kmmio_probe() requirement */
358
359	list_for_each_entry_safe(trace, tmp, &trace_list, list) {
360		list_del(&trace->list);
361		kfree(trace);
362	}
363}
364
365#ifdef CONFIG_HOTPLUG_CPU
366static cpumask_var_t downed_cpus;
367
368static void enter_uniprocessor(void)
369{
370	int cpu;
371	int err;
372
373	if (!cpumask_available(downed_cpus) &&
374	    !alloc_cpumask_var(&downed_cpus, GFP_KERNEL)) {
375		pr_notice("Failed to allocate mask\n");
376		goto out;
377	}
378
379	cpus_read_lock();
380	cpumask_copy(downed_cpus, cpu_online_mask);
381	cpumask_clear_cpu(cpumask_first(cpu_online_mask), downed_cpus);
382	if (num_online_cpus() > 1)
383		pr_notice("Disabling non-boot CPUs...\n");
384	cpus_read_unlock();
385
386	for_each_cpu(cpu, downed_cpus) {
387		err = remove_cpu(cpu);
388		if (!err)
389			pr_info("CPU%d is down.\n", cpu);
390		else
391			pr_err("Error taking CPU%d down: %d\n", cpu, err);
392	}
393out:
394	if (num_online_cpus() > 1)
395		pr_warn("multiple CPUs still online, may miss events.\n");
396}
397
398static void leave_uniprocessor(void)
399{
400	int cpu;
401	int err;
402
403	if (!cpumask_available(downed_cpus) || cpumask_empty(downed_cpus))
404		return;
405	pr_notice("Re-enabling CPUs...\n");
406	for_each_cpu(cpu, downed_cpus) {
407		err = add_cpu(cpu);
408		if (!err)
409			pr_info("enabled CPU%d.\n", cpu);
410		else
411			pr_err("cannot re-enable CPU%d: %d\n", cpu, err);
412	}
413}
414
415#else /* !CONFIG_HOTPLUG_CPU */
416static void enter_uniprocessor(void)
417{
418	if (num_online_cpus() > 1)
419		pr_warn("multiple CPUs are online, may miss events. "
420			"Suggest booting with maxcpus=1 kernel argument.\n");
421}
422
423static void leave_uniprocessor(void)
424{
425}
426#endif
427
428void enable_mmiotrace(void)
429{
430	mutex_lock(&mmiotrace_mutex);
431	if (is_enabled())
432		goto out;
433
434	if (nommiotrace)
435		pr_info("MMIO tracing disabled.\n");
436	kmmio_init();
437	enter_uniprocessor();
438	spin_lock_irq(&trace_lock);
439	atomic_inc(&mmiotrace_enabled);
440	spin_unlock_irq(&trace_lock);
441	pr_info("enabled.\n");
442out:
443	mutex_unlock(&mmiotrace_mutex);
444}
445
446void disable_mmiotrace(void)
447{
448	mutex_lock(&mmiotrace_mutex);
449	if (!is_enabled())
450		goto out;
451
452	spin_lock_irq(&trace_lock);
453	atomic_dec(&mmiotrace_enabled);
454	BUG_ON(is_enabled());
455	spin_unlock_irq(&trace_lock);
456
457	clear_trace_list(); /* guarantees: no more kmmio callbacks */
458	leave_uniprocessor();
459	kmmio_cleanup();
460	pr_info("disabled.\n");
461out:
462	mutex_unlock(&mmiotrace_mutex);
463}
464