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