| /* |
| * drivers/base/power/trace.c |
| * |
| * Copyright (C) 2006 Linus Torvalds |
| * |
| * Trace facility for suspend/resume problems, when none of the |
| * devices may be working. |
| */ |
| |
| #include <linux/resume-trace.h> |
| #include <linux/rtc.h> |
| |
| #include <asm/rtc.h> |
| |
| #include "power.h" |
| |
| /* |
| * Horrid, horrid, horrid. |
| * |
| * It turns out that the _only_ piece of hardware that actually |
| * keeps its value across a hard boot (and, more importantly, the |
| * POST init sequence) is literally the realtime clock. |
| * |
| * Never mind that an RTC chip has 114 bytes (and often a whole |
| * other bank of an additional 128 bytes) of nice SRAM that is |
| * _designed_ to keep data - the POST will clear it. So we literally |
| * can just use the few bytes of actual time data, which means that |
| * we're really limited. |
| * |
| * It means, for example, that we can't use the seconds at all |
| * (since the time between the hang and the boot might be more |
| * than a minute), and we'd better not depend on the low bits of |
| * the minutes either. |
| * |
| * There are the wday fields etc, but I wouldn't guarantee those |
| * are dependable either. And if the date isn't valid, either the |
| * hw or POST will do strange things. |
| * |
| * So we're left with: |
| * - year: 0-99 |
| * - month: 0-11 |
| * - day-of-month: 1-28 |
| * - hour: 0-23 |
| * - min: (0-30)*2 |
| * |
| * Giving us a total range of 0-16128000 (0xf61800), ie less |
| * than 24 bits of actual data we can save across reboots. |
| * |
| * And if your box can't boot in less than three minutes, |
| * you're screwed. |
| * |
| * Now, almost 24 bits of data is pitifully small, so we need |
| * to be pretty dense if we want to use it for anything nice. |
| * What we do is that instead of saving off nice readable info, |
| * we save off _hashes_ of information that we can hopefully |
| * regenerate after the reboot. |
| * |
| * In particular, this means that we might be unlucky, and hit |
| * a case where we have a hash collision, and we end up not |
| * being able to tell for certain exactly which case happened. |
| * But that's hopefully unlikely. |
| * |
| * What we do is to take the bits we can fit, and split them |
| * into three parts (16*997*1009 = 16095568), and use the values |
| * for: |
| * - 0-15: user-settable |
| * - 0-996: file + line number |
| * - 0-1008: device |
| */ |
| #define USERHASH (16) |
| #define FILEHASH (997) |
| #define DEVHASH (1009) |
| |
| #define DEVSEED (7919) |
| |
| static unsigned int dev_hash_value; |
| |
| static int set_magic_time(unsigned int user, unsigned int file, unsigned int device) |
| { |
| unsigned int n = user + USERHASH*(file + FILEHASH*device); |
| |
| // June 7th, 2006 |
| static struct rtc_time time = { |
| .tm_sec = 0, |
| .tm_min = 0, |
| .tm_hour = 0, |
| .tm_mday = 7, |
| .tm_mon = 5, // June - counting from zero |
| .tm_year = 106, |
| .tm_wday = 3, |
| .tm_yday = 160, |
| .tm_isdst = 1 |
| }; |
| |
| time.tm_year = (n % 100); |
| n /= 100; |
| time.tm_mon = (n % 12); |
| n /= 12; |
| time.tm_mday = (n % 28) + 1; |
| n /= 28; |
| time.tm_hour = (n % 24); |
| n /= 24; |
| time.tm_min = (n % 20) * 3; |
| n /= 20; |
| set_rtc_time(&time); |
| return n ? -1 : 0; |
| } |
| |
| static unsigned int read_magic_time(void) |
| { |
| struct rtc_time time; |
| unsigned int val; |
| |
| get_rtc_time(&time); |
| pr_info("Time: %2d:%02d:%02d Date: %02d/%02d/%02d\n", |
| time.tm_hour, time.tm_min, time.tm_sec, |
| time.tm_mon + 1, time.tm_mday, time.tm_year % 100); |
| val = time.tm_year; /* 100 years */ |
| if (val > 100) |
| val -= 100; |
| val += time.tm_mon * 100; /* 12 months */ |
| val += (time.tm_mday-1) * 100 * 12; /* 28 month-days */ |
| val += time.tm_hour * 100 * 12 * 28; /* 24 hours */ |
| val += (time.tm_min / 3) * 100 * 12 * 28 * 24; /* 20 3-minute intervals */ |
| return val; |
| } |
| |
| /* |
| * This is just the sdbm hash function with a user-supplied |
| * seed and final size parameter. |
| */ |
| static unsigned int hash_string(unsigned int seed, const char *data, unsigned int mod) |
| { |
| unsigned char c; |
| while ((c = *data++) != 0) { |
| seed = (seed << 16) + (seed << 6) - seed + c; |
| } |
| return seed % mod; |
| } |
| |
| void set_trace_device(struct device *dev) |
| { |
| dev_hash_value = hash_string(DEVSEED, dev_name(dev), DEVHASH); |
| } |
| EXPORT_SYMBOL(set_trace_device); |
| |
| /* |
| * We could just take the "tracedata" index into the .tracedata |
| * section instead. Generating a hash of the data gives us a |
| * chance to work across kernel versions, and perhaps more |
| * importantly it also gives us valid/invalid check (ie we will |
| * likely not give totally bogus reports - if the hash matches, |
| * it's not any guarantee, but it's a high _likelihood_ that |
| * the match is valid). |
| */ |
| void generate_resume_trace(const void *tracedata, unsigned int user) |
| { |
| unsigned short lineno = *(unsigned short *)tracedata; |
| const char *file = *(const char **)(tracedata + 2); |
| unsigned int user_hash_value, file_hash_value; |
| |
| user_hash_value = user % USERHASH; |
| file_hash_value = hash_string(lineno, file, FILEHASH); |
| set_magic_time(user_hash_value, file_hash_value, dev_hash_value); |
| } |
| EXPORT_SYMBOL(generate_resume_trace); |
| |
| extern char __tracedata_start, __tracedata_end; |
| static int show_file_hash(unsigned int value) |
| { |
| int match; |
| char *tracedata; |
| |
| match = 0; |
| for (tracedata = &__tracedata_start ; tracedata < &__tracedata_end ; |
| tracedata += 2 + sizeof(unsigned long)) { |
| unsigned short lineno = *(unsigned short *)tracedata; |
| const char *file = *(const char **)(tracedata + 2); |
| unsigned int hash = hash_string(lineno, file, FILEHASH); |
| if (hash != value) |
| continue; |
| pr_info(" hash matches %s:%u\n", file, lineno); |
| match++; |
| } |
| return match; |
| } |
| |
| static int show_dev_hash(unsigned int value) |
| { |
| int match = 0; |
| struct list_head *entry; |
| |
| device_pm_lock(); |
| entry = dpm_list.prev; |
| while (entry != &dpm_list) { |
| struct device * dev = to_device(entry); |
| unsigned int hash = hash_string(DEVSEED, dev_name(dev), DEVHASH); |
| if (hash == value) { |
| dev_info(dev, "hash matches\n"); |
| match++; |
| } |
| entry = entry->prev; |
| } |
| device_pm_unlock(); |
| return match; |
| } |
| |
| static unsigned int hash_value_early_read; |
| |
| int show_trace_dev_match(char *buf, size_t size) |
| { |
| unsigned int value = hash_value_early_read / (USERHASH * FILEHASH); |
| int ret = 0; |
| struct list_head *entry; |
| |
| /* |
| * It's possible that multiple devices will match the hash and we can't |
| * tell which is the culprit, so it's best to output them all. |
| */ |
| device_pm_lock(); |
| entry = dpm_list.prev; |
| while (size && entry != &dpm_list) { |
| struct device *dev = to_device(entry); |
| unsigned int hash = hash_string(DEVSEED, dev_name(dev), |
| DEVHASH); |
| if (hash == value) { |
| int len = snprintf(buf, size, "%s\n", |
| dev_driver_string(dev)); |
| if (len > size) |
| len = size; |
| buf += len; |
| ret += len; |
| size -= len; |
| } |
| entry = entry->prev; |
| } |
| device_pm_unlock(); |
| return ret; |
| } |
| |
| static int early_resume_init(void) |
| { |
| hash_value_early_read = read_magic_time(); |
| return 0; |
| } |
| |
| static int late_resume_init(void) |
| { |
| unsigned int val = hash_value_early_read; |
| unsigned int user, file, dev; |
| |
| user = val % USERHASH; |
| val = val / USERHASH; |
| file = val % FILEHASH; |
| val = val / FILEHASH; |
| dev = val /* % DEVHASH */; |
| |
| pr_info(" Magic number: %d:%d:%d\n", user, file, dev); |
| show_file_hash(file); |
| show_dev_hash(dev); |
| return 0; |
| } |
| |
| core_initcall(early_resume_init); |
| late_initcall(late_resume_init); |