00b912b0c8
GregorianDay() is supposed to calculate the day of the week (tm->tm_wday) for a given day/month/year. In that calcuation it indexed into an array called MonthOffset using tm->tm_mon-1. However tm_mon is zero-based, not one-based, so this is off-by-one. It also means that every January, GregoiranDay() will access element -1 of the MonthOffset array. It also doesn't appear to be a correct algorithm either: see in contrast kernel/time/timeconv.c's time_to_tm function. It's been broken forever, which suggests no-one in userland uses this. It looks like no-one in the kernel uses tm->tm_wday either (see e.g. drivers/rtc/rtc-ds1305.c:319). tm->tm_wday is conventionally set to -1 when not available in hardware so we can simply set it to -1 and drop the function. (There are over a dozen other drivers in drivers/rtc that do this.) Found using UBSAN. Cc: Andrey Ryabinin <aryabinin@virtuozzo.com> Cc: Andrew Morton <akpm@linux-foundation.org> # as an example of what UBSan finds. Cc: Alessandro Zummo <a.zummo@towertech.it> Cc: Alexandre Belloni <alexandre.belloni@free-electrons.com> Cc: rtc-linux@googlegroups.com Signed-off-by: Daniel Axtens <dja@axtens.net> Acked-by: Alexandre Belloni <alexandre.belloni@free-electrons.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
87 lines
2.1 KiB
C
87 lines
2.1 KiB
C
/*
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* PowerNV Real Time Clock.
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*
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* Copyright 2011 IBM Corp.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#include <linux/kernel.h>
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#include <linux/time.h>
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#include <linux/bcd.h>
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#include <linux/rtc.h>
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#include <linux/delay.h>
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#include <linux/platform_device.h>
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#include <linux/of_platform.h>
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#include <asm/opal.h>
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#include <asm/firmware.h>
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#include <asm/machdep.h>
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static void opal_to_tm(u32 y_m_d, u64 h_m_s_ms, struct rtc_time *tm)
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{
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tm->tm_year = ((bcd2bin(y_m_d >> 24) * 100) +
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bcd2bin((y_m_d >> 16) & 0xff)) - 1900;
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tm->tm_mon = bcd2bin((y_m_d >> 8) & 0xff) - 1;
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tm->tm_mday = bcd2bin(y_m_d & 0xff);
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tm->tm_hour = bcd2bin((h_m_s_ms >> 56) & 0xff);
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tm->tm_min = bcd2bin((h_m_s_ms >> 48) & 0xff);
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tm->tm_sec = bcd2bin((h_m_s_ms >> 40) & 0xff);
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tm->tm_wday = -1;
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}
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unsigned long __init opal_get_boot_time(void)
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{
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struct rtc_time tm;
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u32 y_m_d;
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u64 h_m_s_ms;
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__be32 __y_m_d;
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__be64 __h_m_s_ms;
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long rc = OPAL_BUSY;
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if (!opal_check_token(OPAL_RTC_READ))
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return 0;
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while (rc == OPAL_BUSY || rc == OPAL_BUSY_EVENT) {
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rc = opal_rtc_read(&__y_m_d, &__h_m_s_ms);
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if (rc == OPAL_BUSY_EVENT)
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opal_poll_events(NULL);
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else
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mdelay(10);
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}
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if (rc != OPAL_SUCCESS)
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return 0;
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y_m_d = be32_to_cpu(__y_m_d);
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h_m_s_ms = be64_to_cpu(__h_m_s_ms);
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opal_to_tm(y_m_d, h_m_s_ms, &tm);
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return mktime(tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday,
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tm.tm_hour, tm.tm_min, tm.tm_sec);
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}
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static __init int opal_time_init(void)
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{
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struct platform_device *pdev;
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struct device_node *rtc;
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rtc = of_find_node_by_path("/ibm,opal/rtc");
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if (rtc) {
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pdev = of_platform_device_create(rtc, "opal-rtc", NULL);
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of_node_put(rtc);
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} else {
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if (opal_check_token(OPAL_RTC_READ) ||
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opal_check_token(OPAL_READ_TPO))
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pdev = platform_device_register_simple("opal-rtc", -1,
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NULL, 0);
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else
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return -ENODEV;
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}
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return PTR_ERR_OR_ZERO(pdev);
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}
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machine_subsys_initcall(powernv, opal_time_init);
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