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eb71c87a LT |
1 | /* |
2 | * drivers/base/power/trace.c | |
3 | * | |
4 | * Copyright (C) 2006 Linus Torvalds | |
5 | * | |
6 | * Trace facility for suspend/resume problems, when none of the | |
7 | * devices may be working. | |
8 | */ | |
9 | ||
10 | #include <linux/resume-trace.h> | |
11 | #include <linux/rtc.h> | |
12 | ||
13 | #include <asm/rtc.h> | |
14 | ||
15 | #include "power.h" | |
16 | ||
17 | /* | |
18 | * Horrid, horrid, horrid. | |
19 | * | |
20 | * It turns out that the _only_ piece of hardware that actually | |
21 | * keeps its value across a hard boot (and, more importantly, the | |
22 | * POST init sequence) is literally the realtime clock. | |
23 | * | |
24 | * Never mind that an RTC chip has 114 bytes (and often a whole | |
25 | * other bank of an additional 128 bytes) of nice SRAM that is | |
26 | * _designed_ to keep data - the POST will clear it. So we literally | |
27 | * can just use the few bytes of actual time data, which means that | |
28 | * we're really limited. | |
29 | * | |
30 | * It means, for example, that we can't use the seconds at all | |
31 | * (since the time between the hang and the boot might be more | |
32 | * than a minute), and we'd better not depend on the low bits of | |
33 | * the minutes either. | |
34 | * | |
35 | * There are the wday fields etc, but I wouldn't guarantee those | |
36 | * are dependable either. And if the date isn't valid, either the | |
37 | * hw or POST will do strange things. | |
38 | * | |
39 | * So we're left with: | |
40 | * - year: 0-99 | |
41 | * - month: 0-11 | |
42 | * - day-of-month: 1-28 | |
43 | * - hour: 0-23 | |
44 | * - min: (0-30)*2 | |
45 | * | |
46 | * Giving us a total range of 0-16128000 (0xf61800), ie less | |
47 | * than 24 bits of actual data we can save across reboots. | |
48 | * | |
49 | * And if your box can't boot in less than three minutes, | |
50 | * you're screwed. | |
51 | * | |
52 | * Now, almost 24 bits of data is pitifully small, so we need | |
53 | * to be pretty dense if we want to use it for anything nice. | |
54 | * What we do is that instead of saving off nice readable info, | |
55 | * we save off _hashes_ of information that we can hopefully | |
56 | * regenerate after the reboot. | |
57 | * | |
58 | * In particular, this means that we might be unlucky, and hit | |
59 | * a case where we have a hash collision, and we end up not | |
60 | * being able to tell for certain exactly which case happened. | |
61 | * But that's hopefully unlikely. | |
62 | * | |
63 | * What we do is to take the bits we can fit, and split them | |
64 | * into three parts (16*997*1009 = 16095568), and use the values | |
65 | * for: | |
66 | * - 0-15: user-settable | |
67 | * - 0-996: file + line number | |
68 | * - 0-1008: device | |
69 | */ | |
70 | #define USERHASH (16) | |
71 | #define FILEHASH (997) | |
72 | #define DEVHASH (1009) | |
73 | ||
74 | #define DEVSEED (7919) | |
75 | ||
76 | static unsigned int dev_hash_value; | |
77 | ||
78 | static int set_magic_time(unsigned int user, unsigned int file, unsigned int device) | |
79 | { | |
80 | unsigned int n = user + USERHASH*(file + FILEHASH*device); | |
81 | ||
82 | // June 7th, 2006 | |
83 | static struct rtc_time time = { | |
84 | .tm_sec = 0, | |
85 | .tm_min = 0, | |
86 | .tm_hour = 0, | |
87 | .tm_mday = 7, | |
88 | .tm_mon = 5, // June - counting from zero | |
89 | .tm_year = 106, | |
90 | .tm_wday = 3, | |
91 | .tm_yday = 160, | |
92 | .tm_isdst = 1 | |
93 | }; | |
94 | ||
95 | time.tm_year = (n % 100); | |
96 | n /= 100; | |
97 | time.tm_mon = (n % 12); | |
98 | n /= 12; | |
99 | time.tm_mday = (n % 28) + 1; | |
100 | n /= 28; | |
101 | time.tm_hour = (n % 24); | |
102 | n /= 24; | |
103 | time.tm_min = (n % 20) * 3; | |
104 | n /= 20; | |
105 | set_rtc_time(&time); | |
106 | return n ? -1 : 0; | |
107 | } | |
108 | ||
109 | static unsigned int read_magic_time(void) | |
110 | { | |
111 | struct rtc_time time; | |
112 | unsigned int val; | |
113 | ||
114 | get_rtc_time(&time); | |
0295a34d | 115 | pr_info("Time: %2d:%02d:%02d Date: %02d/%02d/%02d\n", |
eb71c87a | 116 | time.tm_hour, time.tm_min, time.tm_sec, |
f059bca1 | 117 | time.tm_mon + 1, time.tm_mday, time.tm_year % 100); |
eb71c87a LT |
118 | val = time.tm_year; /* 100 years */ |
119 | if (val > 100) | |
120 | val -= 100; | |
121 | val += time.tm_mon * 100; /* 12 months */ | |
122 | val += (time.tm_mday-1) * 100 * 12; /* 28 month-days */ | |
123 | val += time.tm_hour * 100 * 12 * 28; /* 24 hours */ | |
124 | val += (time.tm_min / 3) * 100 * 12 * 28 * 24; /* 20 3-minute intervals */ | |
125 | return val; | |
126 | } | |
127 | ||
128 | /* | |
129 | * This is just the sdbm hash function with a user-supplied | |
130 | * seed and final size parameter. | |
131 | */ | |
132 | static unsigned int hash_string(unsigned int seed, const char *data, unsigned int mod) | |
133 | { | |
134 | unsigned char c; | |
135 | while ((c = *data++) != 0) { | |
136 | seed = (seed << 16) + (seed << 6) - seed + c; | |
137 | } | |
138 | return seed % mod; | |
139 | } | |
140 | ||
141 | void set_trace_device(struct device *dev) | |
142 | { | |
1e0b2cf9 | 143 | dev_hash_value = hash_string(DEVSEED, dev_name(dev), DEVHASH); |
eb71c87a | 144 | } |
44bf4cea | 145 | EXPORT_SYMBOL(set_trace_device); |
eb71c87a LT |
146 | |
147 | /* | |
148 | * We could just take the "tracedata" index into the .tracedata | |
149 | * section instead. Generating a hash of the data gives us a | |
150 | * chance to work across kernel versions, and perhaps more | |
151 | * importantly it also gives us valid/invalid check (ie we will | |
152 | * likely not give totally bogus reports - if the hash matches, | |
153 | * it's not any guarantee, but it's a high _likelihood_ that | |
154 | * the match is valid). | |
155 | */ | |
63687a52 | 156 | void generate_resume_trace(const void *tracedata, unsigned int user) |
eb71c87a LT |
157 | { |
158 | unsigned short lineno = *(unsigned short *)tracedata; | |
159 | const char *file = *(const char **)(tracedata + 2); | |
160 | unsigned int user_hash_value, file_hash_value; | |
161 | ||
162 | user_hash_value = user % USERHASH; | |
163 | file_hash_value = hash_string(lineno, file, FILEHASH); | |
164 | set_magic_time(user_hash_value, file_hash_value, dev_hash_value); | |
165 | } | |
44bf4cea | 166 | EXPORT_SYMBOL(generate_resume_trace); |
eb71c87a LT |
167 | |
168 | extern char __tracedata_start, __tracedata_end; | |
169 | static int show_file_hash(unsigned int value) | |
170 | { | |
171 | int match; | |
172 | char *tracedata; | |
173 | ||
174 | match = 0; | |
44bf4cea NC |
175 | for (tracedata = &__tracedata_start ; tracedata < &__tracedata_end ; |
176 | tracedata += 2 + sizeof(unsigned long)) { | |
eb71c87a LT |
177 | unsigned short lineno = *(unsigned short *)tracedata; |
178 | const char *file = *(const char **)(tracedata + 2); | |
179 | unsigned int hash = hash_string(lineno, file, FILEHASH); | |
180 | if (hash != value) | |
181 | continue; | |
0295a34d | 182 | pr_info(" hash matches %s:%u\n", file, lineno); |
eb71c87a LT |
183 | match++; |
184 | } | |
185 | return match; | |
186 | } | |
187 | ||
188 | static int show_dev_hash(unsigned int value) | |
189 | { | |
190 | int match = 0; | |
2ac21c6b | 191 | struct list_head *entry; |
eb71c87a | 192 | |
2ac21c6b JH |
193 | device_pm_lock(); |
194 | entry = dpm_list.prev; | |
1eede070 | 195 | while (entry != &dpm_list) { |
eb71c87a | 196 | struct device * dev = to_device(entry); |
1e0b2cf9 | 197 | unsigned int hash = hash_string(DEVSEED, dev_name(dev), DEVHASH); |
eb71c87a | 198 | if (hash == value) { |
fc3a8828 | 199 | dev_info(dev, "hash matches\n"); |
eb71c87a LT |
200 | match++; |
201 | } | |
202 | entry = entry->prev; | |
203 | } | |
2ac21c6b | 204 | device_pm_unlock(); |
eb71c87a LT |
205 | return match; |
206 | } | |
207 | ||
208 | static unsigned int hash_value_early_read; | |
209 | ||
d33ac60b JH |
210 | int show_trace_dev_match(char *buf, size_t size) |
211 | { | |
212 | unsigned int value = hash_value_early_read / (USERHASH * FILEHASH); | |
213 | int ret = 0; | |
214 | struct list_head *entry; | |
215 | ||
216 | /* | |
217 | * It's possible that multiple devices will match the hash and we can't | |
218 | * tell which is the culprit, so it's best to output them all. | |
219 | */ | |
220 | device_pm_lock(); | |
221 | entry = dpm_list.prev; | |
222 | while (size && entry != &dpm_list) { | |
223 | struct device *dev = to_device(entry); | |
224 | unsigned int hash = hash_string(DEVSEED, dev_name(dev), | |
225 | DEVHASH); | |
226 | if (hash == value) { | |
227 | int len = snprintf(buf, size, "%s\n", | |
228 | dev_driver_string(dev)); | |
229 | if (len > size) | |
230 | len = size; | |
231 | buf += len; | |
232 | ret += len; | |
233 | size -= len; | |
234 | } | |
235 | entry = entry->prev; | |
236 | } | |
237 | device_pm_unlock(); | |
238 | return ret; | |
239 | } | |
240 | ||
eb71c87a LT |
241 | static int early_resume_init(void) |
242 | { | |
243 | hash_value_early_read = read_magic_time(); | |
244 | return 0; | |
245 | } | |
246 | ||
247 | static int late_resume_init(void) | |
248 | { | |
249 | unsigned int val = hash_value_early_read; | |
250 | unsigned int user, file, dev; | |
251 | ||
252 | user = val % USERHASH; | |
253 | val = val / USERHASH; | |
254 | file = val % FILEHASH; | |
255 | val = val / FILEHASH; | |
256 | dev = val /* % DEVHASH */; | |
257 | ||
0295a34d | 258 | pr_info(" Magic number: %d:%d:%d\n", user, file, dev); |
eb71c87a LT |
259 | show_file_hash(file); |
260 | show_dev_hash(dev); | |
261 | return 0; | |
262 | } | |
263 | ||
264 | core_initcall(early_resume_init); | |
265 | late_initcall(late_resume_init); |