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| author |   Daniel Axtens <dja@axtens.net> | 2015-12-15 18:09:14 +1100 |
|---|---|---|
| committer |   Michael Ellerman <mpe@ellerman.id.au> | 2015-12-16 12:54:04 +1100 |
| commit | 00b912b0c88e690b1662067497182454357b18b0 (patch) | |
| tree | 1e6f6ab3201f4078645d5351c9a2721c4aedf54c /drivers/rtc | |
| parent | selftests/powerpc: Add test to check if VSRs are corrupted (diff) | |
| download | linux-dev-00b912b0c88e690b1662067497182454357b18b0.tar.xz linux-dev-00b912b0c88e690b1662067497182454357b18b0.zip | |
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.c | 2 |
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) |