cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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lib.c (5304B)


      1// SPDX-License-Identifier: GPL-2.0
      2/*
      3 * rtc and date/time utility functions
      4 *
      5 * Copyright (C) 2005-06 Tower Technologies
      6 * Author: Alessandro Zummo <a.zummo@towertech.it>
      7 *
      8 * based on arch/arm/common/rtctime.c and other bits
      9 *
     10 * Author: Cassio Neri <cassio.neri@gmail.com> (rtc_time64_to_tm)
     11 */
     12
     13#include <linux/export.h>
     14#include <linux/rtc.h>
     15
     16static const unsigned char rtc_days_in_month[] = {
     17	31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
     18};
     19
     20static const unsigned short rtc_ydays[2][13] = {
     21	/* Normal years */
     22	{ 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365 },
     23	/* Leap years */
     24	{ 0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335, 366 }
     25};
     26
     27/*
     28 * The number of days in the month.
     29 */
     30int rtc_month_days(unsigned int month, unsigned int year)
     31{
     32	return rtc_days_in_month[month] + (is_leap_year(year) && month == 1);
     33}
     34EXPORT_SYMBOL(rtc_month_days);
     35
     36/*
     37 * The number of days since January 1. (0 to 365)
     38 */
     39int rtc_year_days(unsigned int day, unsigned int month, unsigned int year)
     40{
     41	return rtc_ydays[is_leap_year(year)][month] + day - 1;
     42}
     43EXPORT_SYMBOL(rtc_year_days);
     44
     45/**
     46 * rtc_time64_to_tm - converts time64_t to rtc_time.
     47 *
     48 * @time:	The number of seconds since 01-01-1970 00:00:00.
     49 *		(Must be positive.)
     50 * @tm:		Pointer to the struct rtc_time.
     51 */
     52void rtc_time64_to_tm(time64_t time, struct rtc_time *tm)
     53{
     54	unsigned int secs;
     55	int days;
     56
     57	u64 u64tmp;
     58	u32 u32tmp, udays, century, day_of_century, year_of_century, year,
     59		day_of_year, month, day;
     60	bool is_Jan_or_Feb, is_leap_year;
     61
     62	/* time must be positive */
     63	days = div_s64_rem(time, 86400, &secs);
     64
     65	/* day of the week, 1970-01-01 was a Thursday */
     66	tm->tm_wday = (days + 4) % 7;
     67
     68	/*
     69	 * The following algorithm is, basically, Proposition 6.3 of Neri
     70	 * and Schneider [1]. In a few words: it works on the computational
     71	 * (fictitious) calendar where the year starts in March, month = 2
     72	 * (*), and finishes in February, month = 13. This calendar is
     73	 * mathematically convenient because the day of the year does not
     74	 * depend on whether the year is leap or not. For instance:
     75	 *
     76	 * March 1st		0-th day of the year;
     77	 * ...
     78	 * April 1st		31-st day of the year;
     79	 * ...
     80	 * January 1st		306-th day of the year; (Important!)
     81	 * ...
     82	 * February 28th	364-th day of the year;
     83	 * February 29th	365-th day of the year (if it exists).
     84	 *
     85	 * After having worked out the date in the computational calendar
     86	 * (using just arithmetics) it's easy to convert it to the
     87	 * corresponding date in the Gregorian calendar.
     88	 *
     89	 * [1] "Euclidean Affine Functions and Applications to Calendar
     90	 * Algorithms". https://arxiv.org/abs/2102.06959
     91	 *
     92	 * (*) The numbering of months follows rtc_time more closely and
     93	 * thus, is slightly different from [1].
     94	 */
     95
     96	udays		= ((u32) days) + 719468;
     97
     98	u32tmp		= 4 * udays + 3;
     99	century		= u32tmp / 146097;
    100	day_of_century	= u32tmp % 146097 / 4;
    101
    102	u32tmp		= 4 * day_of_century + 3;
    103	u64tmp		= 2939745ULL * u32tmp;
    104	year_of_century	= upper_32_bits(u64tmp);
    105	day_of_year	= lower_32_bits(u64tmp) / 2939745 / 4;
    106
    107	year		= 100 * century + year_of_century;
    108	is_leap_year	= year_of_century != 0 ?
    109		year_of_century % 4 == 0 : century % 4 == 0;
    110
    111	u32tmp		= 2141 * day_of_year + 132377;
    112	month		= u32tmp >> 16;
    113	day		= ((u16) u32tmp) / 2141;
    114
    115	/*
    116	 * Recall that January 01 is the 306-th day of the year in the
    117	 * computational (not Gregorian) calendar.
    118	 */
    119	is_Jan_or_Feb	= day_of_year >= 306;
    120
    121	/* Converts to the Gregorian calendar. */
    122	year		= year + is_Jan_or_Feb;
    123	month		= is_Jan_or_Feb ? month - 12 : month;
    124	day		= day + 1;
    125
    126	day_of_year	= is_Jan_or_Feb ?
    127		day_of_year - 306 : day_of_year + 31 + 28 + is_leap_year;
    128
    129	/* Converts to rtc_time's format. */
    130	tm->tm_year	= (int) (year - 1900);
    131	tm->tm_mon	= (int) month;
    132	tm->tm_mday	= (int) day;
    133	tm->tm_yday	= (int) day_of_year + 1;
    134
    135	tm->tm_hour = secs / 3600;
    136	secs -= tm->tm_hour * 3600;
    137	tm->tm_min = secs / 60;
    138	tm->tm_sec = secs - tm->tm_min * 60;
    139
    140	tm->tm_isdst = 0;
    141}
    142EXPORT_SYMBOL(rtc_time64_to_tm);
    143
    144/*
    145 * Does the rtc_time represent a valid date/time?
    146 */
    147int rtc_valid_tm(struct rtc_time *tm)
    148{
    149	if (tm->tm_year < 70 ||
    150	    tm->tm_year > (INT_MAX - 1900) ||
    151	    ((unsigned int)tm->tm_mon) >= 12 ||
    152	    tm->tm_mday < 1 ||
    153	    tm->tm_mday > rtc_month_days(tm->tm_mon,
    154					 ((unsigned int)tm->tm_year + 1900)) ||
    155	    ((unsigned int)tm->tm_hour) >= 24 ||
    156	    ((unsigned int)tm->tm_min) >= 60 ||
    157	    ((unsigned int)tm->tm_sec) >= 60)
    158		return -EINVAL;
    159
    160	return 0;
    161}
    162EXPORT_SYMBOL(rtc_valid_tm);
    163
    164/*
    165 * rtc_tm_to_time64 - Converts rtc_time to time64_t.
    166 * Convert Gregorian date to seconds since 01-01-1970 00:00:00.
    167 */
    168time64_t rtc_tm_to_time64(struct rtc_time *tm)
    169{
    170	return mktime64(((unsigned int)tm->tm_year + 1900), tm->tm_mon + 1,
    171			tm->tm_mday, tm->tm_hour, tm->tm_min, tm->tm_sec);
    172}
    173EXPORT_SYMBOL(rtc_tm_to_time64);
    174
    175/*
    176 * Convert rtc_time to ktime
    177 */
    178ktime_t rtc_tm_to_ktime(struct rtc_time tm)
    179{
    180	return ktime_set(rtc_tm_to_time64(&tm), 0);
    181}
    182EXPORT_SYMBOL_GPL(rtc_tm_to_ktime);
    183
    184/*
    185 * Convert ktime to rtc_time
    186 */
    187struct rtc_time rtc_ktime_to_tm(ktime_t kt)
    188{
    189	struct timespec64 ts;
    190	struct rtc_time ret;
    191
    192	ts = ktime_to_timespec64(kt);
    193	/* Round up any ns */
    194	if (ts.tv_nsec)
    195		ts.tv_sec++;
    196	rtc_time64_to_tm(ts.tv_sec, &ret);
    197	return ret;
    198}
    199EXPORT_SYMBOL_GPL(rtc_ktime_to_tm);