Linus Torvalds | eb71c87 | 2006-06-24 14:27:42 -0700 | [diff] [blame] | 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); |
| 115 | printk("Time: %2d:%02d:%02d Date: %02d/%02d/%02d\n", |
| 116 | time.tm_hour, time.tm_min, time.tm_sec, |
Rafael J. Wysocki | f059bca | 2007-10-18 03:04:48 -0700 | [diff] [blame] | 117 | time.tm_mon + 1, time.tm_mday, time.tm_year % 100); |
Linus Torvalds | eb71c87 | 2006-06-24 14:27:42 -0700 | [diff] [blame] | 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 | { |
Kay Sievers | 1e0b2cf | 2008-10-30 01:36:48 +0100 | [diff] [blame] | 143 | dev_hash_value = hash_string(DEVSEED, dev_name(dev), DEVHASH); |
Linus Torvalds | eb71c87 | 2006-06-24 14:27:42 -0700 | [diff] [blame] | 144 | } |
Nigel Cunningham | 44bf4ce | 2007-07-21 17:10:41 +0200 | [diff] [blame] | 145 | EXPORT_SYMBOL(set_trace_device); |
Linus Torvalds | eb71c87 | 2006-06-24 14:27:42 -0700 | [diff] [blame] | 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 | */ |
Jan Beulich | 63687a5 | 2008-05-12 15:44:41 +0200 | [diff] [blame] | 156 | void generate_resume_trace(const void *tracedata, unsigned int user) |
Linus Torvalds | eb71c87 | 2006-06-24 14:27:42 -0700 | [diff] [blame] | 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 | } |
Nigel Cunningham | 44bf4ce | 2007-07-21 17:10:41 +0200 | [diff] [blame] | 166 | EXPORT_SYMBOL(generate_resume_trace); |
Linus Torvalds | eb71c87 | 2006-06-24 14:27:42 -0700 | [diff] [blame] | 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; |
Nigel Cunningham | 44bf4ce | 2007-07-21 17:10:41 +0200 | [diff] [blame] | 175 | for (tracedata = &__tracedata_start ; tracedata < &__tracedata_end ; |
| 176 | tracedata += 2 + sizeof(unsigned long)) { |
Linus Torvalds | eb71c87 | 2006-06-24 14:27:42 -0700 | [diff] [blame] | 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; |
| 182 | printk(" hash matches %s:%u\n", file, lineno); |
| 183 | match++; |
| 184 | } |
| 185 | return match; |
| 186 | } |
| 187 | |
| 188 | static int show_dev_hash(unsigned int value) |
| 189 | { |
| 190 | int match = 0; |
James Hogan | 2ac21c6 | 2010-10-11 23:59:58 +0200 | [diff] [blame^] | 191 | struct list_head *entry; |
Linus Torvalds | eb71c87 | 2006-06-24 14:27:42 -0700 | [diff] [blame] | 192 | |
James Hogan | 2ac21c6 | 2010-10-11 23:59:58 +0200 | [diff] [blame^] | 193 | device_pm_lock(); |
| 194 | entry = dpm_list.prev; |
Rafael J. Wysocki | 1eede07 | 2008-05-20 23:00:01 +0200 | [diff] [blame] | 195 | while (entry != &dpm_list) { |
Linus Torvalds | eb71c87 | 2006-06-24 14:27:42 -0700 | [diff] [blame] | 196 | struct device * dev = to_device(entry); |
Kay Sievers | 1e0b2cf | 2008-10-30 01:36:48 +0100 | [diff] [blame] | 197 | unsigned int hash = hash_string(DEVSEED, dev_name(dev), DEVHASH); |
Linus Torvalds | eb71c87 | 2006-06-24 14:27:42 -0700 | [diff] [blame] | 198 | if (hash == value) { |
Greg Kroah-Hartman | fc3a882 | 2008-05-02 06:02:41 +0200 | [diff] [blame] | 199 | dev_info(dev, "hash matches\n"); |
Linus Torvalds | eb71c87 | 2006-06-24 14:27:42 -0700 | [diff] [blame] | 200 | match++; |
| 201 | } |
| 202 | entry = entry->prev; |
| 203 | } |
James Hogan | 2ac21c6 | 2010-10-11 23:59:58 +0200 | [diff] [blame^] | 204 | device_pm_unlock(); |
Linus Torvalds | eb71c87 | 2006-06-24 14:27:42 -0700 | [diff] [blame] | 205 | return match; |
| 206 | } |
| 207 | |
| 208 | static unsigned int hash_value_early_read; |
| 209 | |
| 210 | static int early_resume_init(void) |
| 211 | { |
| 212 | hash_value_early_read = read_magic_time(); |
| 213 | return 0; |
| 214 | } |
| 215 | |
| 216 | static int late_resume_init(void) |
| 217 | { |
| 218 | unsigned int val = hash_value_early_read; |
| 219 | unsigned int user, file, dev; |
| 220 | |
| 221 | user = val % USERHASH; |
| 222 | val = val / USERHASH; |
| 223 | file = val % FILEHASH; |
| 224 | val = val / FILEHASH; |
| 225 | dev = val /* % DEVHASH */; |
| 226 | |
| 227 | printk(" Magic number: %d:%d:%d\n", user, file, dev); |
| 228 | show_file_hash(file); |
| 229 | show_dev_hash(dev); |
| 230 | return 0; |
| 231 | } |
| 232 | |
| 233 | core_initcall(early_resume_init); |
| 234 | late_initcall(late_resume_init); |