// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *  Written 1992,1993 by Werner Almesberger
 *  22/11/2000 - Fixed fat_date_unix2dos for dates earlier than 01/01/1980
 *               and date_dos2unix for date==0 by Igor Zhbanov(bsg@uniyar.ac.ru)
 * Copyright (C) 2012-2013 Samsung Electronics Co., Ltd.
 */

#include <linux/time.h>
#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/buffer_head.h>

#include "exfat_raw.h"
#include "exfat_fs.h"

/*
 * exfat_fs_error reports a file system problem that might indicate fa data
 * corruption/inconsistency. Depending on 'errors' mount option the
 * panic() is called, or error message is printed FAT and nothing is done,
 * or filesystem is remounted read-only (default behavior).
 * In case the file system is remounted read-only, it can be made writable
 * again by remounting it.
 */
void __exfat_fs_error(struct super_block *sb, int report, const char *fmt, ...)
{
        struct exfat_mount_options *opts = &EXFAT_SB(sb)->options;
        va_list args;
        struct va_format vaf;

        if (report) {
                va_start(args, fmt);
                vaf.fmt = fmt;
                vaf.va = &args;
                exfat_msg(sb, KERN_ERR, "error, %pV\n", &vaf);
                va_end(args);
        }

        if (opts->errors == EXFAT_ERRORS_PANIC) {
                panic("exFAT-fs (%s): fs panic from previous error\n",
                        sb->s_id);
        } else if (opts->errors == EXFAT_ERRORS_RO && !sb_rdonly(sb)) {
                sb->s_flags |= SB_RDONLY;
                exfat_msg(sb, KERN_ERR, "Filesystem has been set read-only");
        }
}

/*
 * exfat_msg() - print preformated EXFAT specific messages.
 * All logs except what uses exfat_fs_error() should be written by exfat_msg()
 */
void exfat_msg(struct super_block *sb, const char *level, const char *fmt, ...)
{
        struct va_format vaf;
        va_list args;

        va_start(args, fmt);
        vaf.fmt = fmt;
        vaf.va = &args;
        /* level means KERN_ pacility level */
        printk("%sexFAT-fs (%s): %pV\n", level, sb->s_id, &vaf);
        va_end(args);
}

#define SECS_PER_MIN    (60)
#define TIMEZONE_SEC(x) ((x) * 15 * SECS_PER_MIN)

static void exfat_adjust_tz(struct timespec64 *ts, u8 tz_off)
{
        if (tz_off <= 0x3F)
                ts->tv_sec -= TIMEZONE_SEC(tz_off);
        else /* 0x40 <= (tz_off & 0x7F) <=0x7F */
                ts->tv_sec += TIMEZONE_SEC(0x80 - tz_off);
}

/* Convert a EXFAT time/date pair to a UNIX date (seconds since 1 1 70). */
void exfat_get_entry_time(struct exfat_sb_info *sbi, struct timespec64 *ts,
                u8 tz, __le16 time, __le16 date, u8 time_ms)
{
        u16 t = le16_to_cpu(time);
        u16 d = le16_to_cpu(date);

        ts->tv_sec = mktime64(1980 + (d >> 9), d >> 5 & 0x000F, d & 0x001F,
                              t >> 11, (t >> 5) & 0x003F, (t & 0x001F) << 1);


        /* time_ms field represent 0 ~ 199(1990 ms) */
        if (time_ms) {
                ts->tv_sec += time_ms / 100;
                ts->tv_nsec = (time_ms % 100) * 10 * NSEC_PER_MSEC;
        } else
                ts->tv_nsec = 0;

        if (tz & EXFAT_TZ_VALID)
                /* Adjust timezone to UTC0. */
                exfat_adjust_tz(ts, tz & ~EXFAT_TZ_VALID);
        else
                /* Convert from local time to UTC using time_offset. */
                ts->tv_sec -= sbi->options.time_offset * SECS_PER_MIN;
}

/* Convert linear UNIX date to a EXFAT time/date pair. */
void exfat_set_entry_time(struct exfat_sb_info *sbi, struct timespec64 *ts,
                u8 *tz, __le16 *time, __le16 *date, u8 *time_ms)
{
        struct tm tm;
        u16 t, d;

        time64_to_tm(ts->tv_sec, 0, &tm);
        t = (tm.tm_hour << 11) | (tm.tm_min << 5) | (tm.tm_sec >> 1);
        d = ((tm.tm_year - 80) <<  9) | ((tm.tm_mon + 1) << 5) | tm.tm_mday;

        *time = cpu_to_le16(t);
        *date = cpu_to_le16(d);

        /* time_ms field represent 0 ~ 199(1990 ms) */
        if (time_ms)
                *time_ms = (tm.tm_sec & 1) * 100 +
                        ts->tv_nsec / (10 * NSEC_PER_MSEC);

        /*
         * Record 00h value for OffsetFromUtc field and 1 value for OffsetValid
         * to indicate that local time and UTC are the same.
         */
        *tz = EXFAT_TZ_VALID;
}

/*
 * The timestamp for access_time has double seconds granularity.
 * (There is no 10msIncrement field for access_time unlike create/modify_time)
 * atime also has only a 2-second resolution.
 */
void exfat_truncate_atime(struct timespec64 *ts)
{
        ts->tv_sec = round_down(ts->tv_sec, 2);
        ts->tv_nsec = 0;
}

unsigned short exfat_calc_chksum_2byte(void *data, int len,
                unsigned short chksum, int type)
{
        int i;
        unsigned char *c = (unsigned char *)data;

        for (i = 0; i < len; i++, c++) {
                if (((i == 2) || (i == 3)) && (type == CS_DIR_ENTRY))
                        continue;
                chksum = (((chksum & 1) << 15) | ((chksum & 0xFFFE) >> 1)) +
                        (unsigned short)*c;
        }
        return chksum;
}

void exfat_update_bh(struct super_block *sb, struct buffer_head *bh, int sync)
{
        set_bit(EXFAT_SB_DIRTY, &EXFAT_SB(sb)->s_state);
        set_buffer_uptodate(bh);
        mark_buffer_dirty(bh);

        if (sync)
                sync_dirty_buffer(bh);
}

void exfat_chain_set(struct exfat_chain *ec, unsigned int dir,
                unsigned int size, unsigned char flags)
{
        ec->dir = dir;
        ec->size = size;
        ec->flags = flags;
}

void exfat_chain_dup(struct exfat_chain *dup, struct exfat_chain *ec)
{
        return exfat_chain_set(dup, ec->dir, ec->size, ec->flags);
}