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1 : : // SPDX-License-Identifier: GPL-2.0
2 : : /*
3 : : * drivers/base/power/trace.c
4 : : *
5 : : * Copyright (C) 2006 Linus Torvalds
6 : : *
7 : : * Trace facility for suspend/resume problems, when none of the
8 : : * devices may be working.
9 : : */
10 : : #define pr_fmt(fmt) "PM: " fmt
11 : :
12 : : #include <linux/pm-trace.h>
13 : : #include <linux/export.h>
14 : : #include <linux/rtc.h>
15 : : #include <linux/suspend.h>
16 : :
17 : : #include <linux/mc146818rtc.h>
18 : :
19 : : #include "power.h"
20 : :
21 : : /*
22 : : * Horrid, horrid, horrid.
23 : : *
24 : : * It turns out that the _only_ piece of hardware that actually
25 : : * keeps its value across a hard boot (and, more importantly, the
26 : : * POST init sequence) is literally the realtime clock.
27 : : *
28 : : * Never mind that an RTC chip has 114 bytes (and often a whole
29 : : * other bank of an additional 128 bytes) of nice SRAM that is
30 : : * _designed_ to keep data - the POST will clear it. So we literally
31 : : * can just use the few bytes of actual time data, which means that
32 : : * we're really limited.
33 : : *
34 : : * It means, for example, that we can't use the seconds at all
35 : : * (since the time between the hang and the boot might be more
36 : : * than a minute), and we'd better not depend on the low bits of
37 : : * the minutes either.
38 : : *
39 : : * There are the wday fields etc, but I wouldn't guarantee those
40 : : * are dependable either. And if the date isn't valid, either the
41 : : * hw or POST will do strange things.
42 : : *
43 : : * So we're left with:
44 : : * - year: 0-99
45 : : * - month: 0-11
46 : : * - day-of-month: 1-28
47 : : * - hour: 0-23
48 : : * - min: (0-30)*2
49 : : *
50 : : * Giving us a total range of 0-16128000 (0xf61800), ie less
51 : : * than 24 bits of actual data we can save across reboots.
52 : : *
53 : : * And if your box can't boot in less than three minutes,
54 : : * you're screwed.
55 : : *
56 : : * Now, almost 24 bits of data is pitifully small, so we need
57 : : * to be pretty dense if we want to use it for anything nice.
58 : : * What we do is that instead of saving off nice readable info,
59 : : * we save off _hashes_ of information that we can hopefully
60 : : * regenerate after the reboot.
61 : : *
62 : : * In particular, this means that we might be unlucky, and hit
63 : : * a case where we have a hash collision, and we end up not
64 : : * being able to tell for certain exactly which case happened.
65 : : * But that's hopefully unlikely.
66 : : *
67 : : * What we do is to take the bits we can fit, and split them
68 : : * into three parts (16*997*1009 = 16095568), and use the values
69 : : * for:
70 : : * - 0-15: user-settable
71 : : * - 0-996: file + line number
72 : : * - 0-1008: device
73 : : */
74 : : #define USERHASH (16)
75 : : #define FILEHASH (997)
76 : : #define DEVHASH (1009)
77 : :
78 : : #define DEVSEED (7919)
79 : :
80 : : bool pm_trace_rtc_abused __read_mostly;
81 : : EXPORT_SYMBOL_GPL(pm_trace_rtc_abused);
82 : :
83 : : static unsigned int dev_hash_value;
84 : :
85 : 0 : static int set_magic_time(unsigned int user, unsigned int file, unsigned int device)
86 : : {
87 : 0 : unsigned int n = user + USERHASH*(file + FILEHASH*device);
88 : :
89 : : // June 7th, 2006
90 : 0 : static struct rtc_time time = {
91 : : .tm_sec = 0,
92 : : .tm_min = 0,
93 : : .tm_hour = 0,
94 : : .tm_mday = 7,
95 : : .tm_mon = 5, // June - counting from zero
96 : : .tm_year = 106,
97 : : .tm_wday = 3,
98 : : .tm_yday = 160,
99 : : .tm_isdst = 1
100 : : };
101 : :
102 : 0 : time.tm_year = (n % 100);
103 : 0 : n /= 100;
104 : 0 : time.tm_mon = (n % 12);
105 : 0 : n /= 12;
106 : 0 : time.tm_mday = (n % 28) + 1;
107 : 0 : n /= 28;
108 : 0 : time.tm_hour = (n % 24);
109 : 0 : n /= 24;
110 : 0 : time.tm_min = (n % 20) * 3;
111 : 0 : n /= 20;
112 : 0 : mc146818_set_time(&time);
113 : 0 : pm_trace_rtc_abused = true;
114 [ # # ]: 0 : return n ? -1 : 0;
115 : : }
116 : :
117 : 3 : static unsigned int read_magic_time(void)
118 : : {
119 : 3 : struct rtc_time time;
120 : 3 : unsigned int val;
121 : :
122 : 3 : mc146818_get_time(&time);
123 : 3 : pr_info("RTC time: %ptRt, date: %ptRd\n", &time, &time);
124 : 3 : val = time.tm_year; /* 100 years */
125 [ + - ]: 3 : if (val > 100)
126 : 3 : val -= 100;
127 : 3 : val += time.tm_mon * 100; /* 12 months */
128 : 3 : val += (time.tm_mday-1) * 100 * 12; /* 28 month-days */
129 : 3 : val += time.tm_hour * 100 * 12 * 28; /* 24 hours */
130 : 3 : val += (time.tm_min / 3) * 100 * 12 * 28 * 24; /* 20 3-minute intervals */
131 : 3 : return val;
132 : : }
133 : :
134 : : /*
135 : : * This is just the sdbm hash function with a user-supplied
136 : : * seed and final size parameter.
137 : : */
138 : 36 : static unsigned int hash_string(unsigned int seed, const char *data, unsigned int mod)
139 : : {
140 : 36 : unsigned char c;
141 [ - - + + : 7300 : while ((c = *data++) != 0) {
+ + - - -
- ]
142 : 6457 : seed = (seed << 16) + (seed << 6) - seed + c;
143 : : }
144 : 843 : return seed % mod;
145 : : }
146 : :
147 : 0 : void set_trace_device(struct device *dev)
148 : : {
149 [ # # ]: 0 : dev_hash_value = hash_string(DEVSEED, dev_name(dev), DEVHASH);
150 : 0 : }
151 : : EXPORT_SYMBOL(set_trace_device);
152 : :
153 : : /*
154 : : * We could just take the "tracedata" index into the .tracedata
155 : : * section instead. Generating a hash of the data gives us a
156 : : * chance to work across kernel versions, and perhaps more
157 : : * importantly it also gives us valid/invalid check (ie we will
158 : : * likely not give totally bogus reports - if the hash matches,
159 : : * it's not any guarantee, but it's a high _likelihood_ that
160 : : * the match is valid).
161 : : */
162 : 0 : void generate_pm_trace(const void *tracedata, unsigned int user)
163 : : {
164 : 0 : unsigned short lineno = *(unsigned short *)tracedata;
165 : 0 : const char *file = *(const char **)(tracedata + 2);
166 : 0 : unsigned int user_hash_value, file_hash_value;
167 : :
168 : 0 : user_hash_value = user % USERHASH;
169 : 0 : file_hash_value = hash_string(lineno, file, FILEHASH);
170 : 0 : set_magic_time(user_hash_value, file_hash_value, dev_hash_value);
171 : 0 : }
172 : : EXPORT_SYMBOL(generate_pm_trace);
173 : :
174 : : extern char __tracedata_start[], __tracedata_end[];
175 : 3 : static int show_file_hash(unsigned int value)
176 : : {
177 : 3 : int match;
178 : 3 : char *tracedata;
179 : :
180 : 3 : match = 0;
181 [ + + ]: 39 : for (tracedata = __tracedata_start ; tracedata < __tracedata_end ;
182 : 36 : tracedata += 2 + sizeof(unsigned long)) {
183 : 36 : unsigned short lineno = *(unsigned short *)tracedata;
184 : 36 : const char *file = *(const char **)(tracedata + 2);
185 : 36 : unsigned int hash = hash_string(lineno, file, FILEHASH);
186 [ + - ]: 36 : if (hash != value)
187 : 36 : continue;
188 : 0 : pr_info(" hash matches %s:%u\n", file, lineno);
189 : 0 : match++;
190 : : }
191 : 3 : return match;
192 : : }
193 : :
194 : 3 : static int show_dev_hash(unsigned int value)
195 : : {
196 : 3 : int match = 0;
197 : 3 : struct list_head *entry;
198 : :
199 : 3 : device_pm_lock();
200 : 3 : entry = dpm_list.prev;
201 [ + + ]: 810 : while (entry != &dpm_list) {
202 [ + - ]: 807 : struct device * dev = to_device(entry);
203 [ + - ]: 807 : unsigned int hash = hash_string(DEVSEED, dev_name(dev), DEVHASH);
204 [ - + ]: 807 : if (hash == value) {
205 : 0 : dev_info(dev, "hash matches\n");
206 : 0 : match++;
207 : : }
208 : 807 : entry = entry->prev;
209 : : }
210 : 3 : device_pm_unlock();
211 : 3 : return match;
212 : : }
213 : :
214 : : static unsigned int hash_value_early_read;
215 : :
216 : 0 : int show_trace_dev_match(char *buf, size_t size)
217 : : {
218 : 0 : unsigned int value = hash_value_early_read / (USERHASH * FILEHASH);
219 : 0 : int ret = 0;
220 : 0 : struct list_head *entry;
221 : :
222 : : /*
223 : : * It's possible that multiple devices will match the hash and we can't
224 : : * tell which is the culprit, so it's best to output them all.
225 : : */
226 : 0 : device_pm_lock();
227 : 0 : entry = dpm_list.prev;
228 [ # # # # ]: 0 : while (size && entry != &dpm_list) {
229 [ # # ]: 0 : struct device *dev = to_device(entry);
230 [ # # ]: 0 : unsigned int hash = hash_string(DEVSEED, dev_name(dev),
231 : : DEVHASH);
232 [ # # ]: 0 : if (hash == value) {
233 : 0 : int len = snprintf(buf, size, "%s\n",
234 : : dev_driver_string(dev));
235 [ # # ]: 0 : if (len > size)
236 : 0 : len = size;
237 : 0 : buf += len;
238 : 0 : ret += len;
239 : 0 : size -= len;
240 : : }
241 : 0 : entry = entry->prev;
242 : : }
243 : 0 : device_pm_unlock();
244 : 0 : return ret;
245 : : }
246 : :
247 : : static int
248 : 0 : pm_trace_notify(struct notifier_block *nb, unsigned long mode, void *_unused)
249 : : {
250 [ # # ]: 0 : switch (mode) {
251 : 0 : case PM_POST_HIBERNATION:
252 : : case PM_POST_SUSPEND:
253 [ # # ]: 0 : if (pm_trace_rtc_abused) {
254 : 0 : pm_trace_rtc_abused = false;
255 : 0 : pr_warn("Possible incorrect RTC due to pm_trace, please use 'ntpdate' or 'rdate' to reset it.\n");
256 : : }
257 : : break;
258 : : default:
259 : : break;
260 : : }
261 : 0 : return 0;
262 : : }
263 : :
264 : : static struct notifier_block pm_trace_nb = {
265 : : .notifier_call = pm_trace_notify,
266 : : };
267 : :
268 : 3 : static int early_resume_init(void)
269 : : {
270 : 3 : hash_value_early_read = read_magic_time();
271 : 3 : register_pm_notifier(&pm_trace_nb);
272 : 3 : return 0;
273 : : }
274 : :
275 : 3 : static int late_resume_init(void)
276 : : {
277 : 3 : unsigned int val = hash_value_early_read;
278 : 3 : unsigned int user, file, dev;
279 : :
280 : 3 : user = val % USERHASH;
281 : 3 : val = val / USERHASH;
282 : 3 : file = val % FILEHASH;
283 : 3 : val = val / FILEHASH;
284 : 3 : dev = val /* % DEVHASH */;
285 : :
286 : 3 : pr_info(" Magic number: %d:%d:%d\n", user, file, dev);
287 : 3 : show_file_hash(file);
288 : 3 : show_dev_hash(dev);
289 : 3 : return 0;
290 : : }
291 : :
292 : : core_initcall(early_resume_init);
293 : : late_initcall(late_resume_init);
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