Contributors: 20
| Author |
Tokens |
Token Proportion |
Commits |
Commit Proportion |
| Linus Torvalds |
794 |
72.05% |
1 |
4.00% |
| James Hogan |
89 |
8.08% |
2 |
8.00% |
| Chen Yu |
86 |
7.80% |
1 |
4.00% |
| Juergen Gross |
37 |
3.36% |
1 |
4.00% |
| Tom Rini |
20 |
1.81% |
3 |
12.00% |
| Nigel Cunningham |
16 |
1.45% |
1 |
4.00% |
| Mateusz Jończyk |
14 |
1.27% |
1 |
4.00% |
| Kay Sievers |
9 |
0.82% |
1 |
4.00% |
| Joe Perches |
7 |
0.64% |
1 |
4.00% |
| Rafael J. Wysocki |
4 |
0.36% |
1 |
4.00% |
| Greg Kroah-Hartman |
4 |
0.36% |
2 |
8.00% |
| Paul Gortmaker |
3 |
0.27% |
1 |
4.00% |
| Andy Shevchenko |
3 |
0.27% |
1 |
4.00% |
| Mandeep Singh Baines |
3 |
0.27% |
1 |
4.00% |
| Fu Zhonghui |
3 |
0.27% |
1 |
4.00% |
| Arnd Bergmann |
3 |
0.27% |
1 |
4.00% |
| Mario Limonciello |
2 |
0.18% |
2 |
8.00% |
| Christophe Jaillet |
2 |
0.18% |
1 |
4.00% |
| Eric Biggers |
2 |
0.18% |
1 |
4.00% |
| Jan Beulich |
1 |
0.09% |
1 |
4.00% |
| Total |
1102 |
|
25 |
|
// 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 = 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
pm_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);