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(I'm so sorry!) Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel os linux
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123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199200201202203204205206207208209210211212213214215216217218219220221222223224225226227228229230231232233234235236237238239240241242243244245246247248249250251252253254255256257258259260261262263264265266267268269270271272273274275276277278279280281282283284285286287288289290291292293294295296297298299300301302303304305306// SPDX-License-Identifier: GPL-2.0/* * drivers/base/power/trace.c * * Copyright (C) 2006 Linus Torvalds * * Trace facility for suspend/resume problems, when none of the * devices may be working. */#define pr_fmt(fmt) "PM: " fmt
#include <linux/pm-trace.h>#include <linux/export.h>#include <linux/rtc.h>#include <linux/suspend.h>#include <linux/init.h>
#include <linux/mc146818rtc.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)
bool pm_trace_rtc_abused __read_mostly;EXPORT_SYMBOL_GPL(pm_trace_rtc_abused);
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; mc146818_set_time(&time); pm_trace_rtc_abused = true; return n ? -1 : 0;}
static unsigned int read_magic_time(void){ struct rtc_time time; unsigned int val;
if (mc146818_get_time(&time, 1000) < 0) { pr_err("Unable to read current time from RTC\n"); return 0; }
pr_info("RTC time: %ptRt, date: %ptRd\n", &time, &time); 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_pm_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;
if (!x86_platform.legacy.rtc) return;
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_pm_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 = scnprintf(buf, size, "%s\n", dev_driver_string(dev)); buf += len; ret += len; size -= len; } entry = entry->prev; } device_pm_unlock(); return ret;}
static intpm_trace_notify(struct notifier_block *nb, unsigned long mode, void *_unused){ switch (mode) { case PM_POST_HIBERNATION: case PM_POST_SUSPEND: if (pm_trace_rtc_abused) { pm_trace_rtc_abused = false; pr_warn("Possible incorrect RTC due to pm_trace, please use 'ntpdate' or 'rdate' to reset it.\n"); } break; default: break; } return 0;}
static struct notifier_block pm_trace_nb = { .notifier_call = pm_trace_notify,};
static int __init early_resume_init(void){ if (!x86_platform.legacy.rtc) return 0;
hash_value_early_read = read_magic_time(); register_pm_notifier(&pm_trace_nb); return 0;}
static int __init late_resume_init(void){ unsigned int val = hash_value_early_read; unsigned int user, file, dev;
if (!x86_platform.legacy.rtc) return 0;
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);