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authorDaniel Axtens <dja@axtens.net>2015-12-15 18:09:14 +1100
committerMichael Ellerman <mpe@ellerman.id.au>2015-12-16 12:54:04 +1100
commit00b912b0c88e690b1662067497182454357b18b0 (patch)
tree1e6f6ab3201f4078645d5351c9a2721c4aedf54c /drivers/rtc
parent5f337e3e5b04b32793fd51adab438d46df99c933 (diff)
downloadlinux-00b912b0c88e690b1662067497182454357b18b0.tar.bz2
powerpc: Remove broken GregorianDay()
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>
Diffstat (limited to 'drivers/rtc')
-rw-r--r--drivers/rtc/rtc-opal.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/rtc/rtc-opal.c b/drivers/rtc/rtc-opal.c
index df39ce02a99d..9c18d6fd8107 100644
--- a/drivers/rtc/rtc-opal.c
+++ b/drivers/rtc/rtc-opal.c
@@ -40,7 +40,7 @@ static void opal_to_tm(u32 y_m_d, u64 h_m_s_ms, struct rtc_time *tm)
tm->tm_min = bcd2bin((h_m_s_ms >> 48) & 0xff);
tm->tm_sec = bcd2bin((h_m_s_ms >> 40) & 0xff);
- GregorianDay(tm);
+ tm->tm_wday = -1;
}
static void tm_to_opal(struct rtc_time *tm, u32 *y_m_d, u64 *h_m_s_ms)