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| author | Ard Biesheuvel <ard.biesheuvel@linaro.org> | 2015-06-09 12:15:35 +0300 |
|---|---|---|
| committer | Alexandre Belloni <alexandre.belloni@free-electrons.com> | 2015-06-25 02:13:44 +0300 |
| commit | b2bd2370a25b78a7090ac701836d414cdb731bea (patch) | |
| tree | c8add915914b5d963912ba61d065624d3f5ebcfa /drivers/rtc/rtc-efi.c | |
| parent | c86a6c28957a9e8e9a71582a32e96971ad411ffe (diff) | |
| download | linux-b2bd2370a25b78a7090ac701836d414cdb731bea.tar.xz | |
rtc: efi: use correct EFI 'epoch'
The rtc-efi driver declares that the EFI 'epoch' is 1/1/1998, but
the UEFI spec does not define it at all. It does define a range of
[1900, 9999] for the 'Year' member of the EFI_TIME struct, so let's
use 1900 as the minimum year and not 1998.
Also, move the validation of the year to the convert_from_efi_time()
routine where all other EFI_TIME fields are validated as well.
This prevents rtc_read_time() failures when the RTC that backs the
EFI time services is set to a date before 1998, e.g., when it has
lost power.
This also optimizes the compute_wday() routine, by replacing the for
loop with a simple arithmetic expression, and by reusing the yearday
value that we need to compute anyway when populating the
rtc_time::tm_yday field.
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Cc: rtc-linux@googlegroups.com
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Diffstat (limited to 'drivers/rtc/rtc-efi.c')
| -rw-r--r-- | drivers/rtc/rtc-efi.c | 39 |
1 files changed, 14 insertions, 25 deletions
diff --git a/drivers/rtc/rtc-efi.c b/drivers/rtc/rtc-efi.c index c5fbabb1e0fc..3806961b4348 100644 --- a/drivers/rtc/rtc-efi.c +++ b/drivers/rtc/rtc-efi.c @@ -24,10 +24,6 @@ #include <linux/efi.h> #define EFI_ISDST (EFI_TIME_ADJUST_DAYLIGHT|EFI_TIME_IN_DAYLIGHT) -/* - * EFI Epoch is 1/1/1998 - */ -#define EFI_RTC_EPOCH 1998 /* * returns day of the year [0-365] @@ -38,31 +34,24 @@ compute_yday(efi_time_t *eft) /* efi_time_t.month is in the [1-12] so, we need -1 */ return rtc_year_days(eft->day, eft->month - 1, eft->year); } + /* * returns day of the week [0-6] 0=Sunday - * - * Don't try to provide a year that's before 1998, please ! */ static int -compute_wday(efi_time_t *eft) +compute_wday(efi_time_t *eft, int yday) { - int y; - int ndays = 0; - - if (eft->year < EFI_RTC_EPOCH) { - pr_err("EFI year < " __stringify(EFI_RTC_EPOCH) ", invalid date\n"); - return -1; - } - - for (y = EFI_RTC_EPOCH; y < eft->year; y++) - ndays += 365 + (is_leap_year(y) ? 1 : 0); - - ndays += compute_yday(eft); + int ndays = eft->year * (365 % 7) + + (eft->year - 1) / 4 + - (eft->year - 1) / 100 + + (eft->year - 1) / 400 + + yday; /* - * 4=1/1/1998 was a Thursday + * 1/1/0000 may or may not have been a Sunday (if it ever existed at + * all) but assuming it was makes this calculation work correctly. */ - return (ndays + 4) % 7; + return ndays % 7; } static void @@ -103,16 +92,16 @@ convert_from_efi_time(efi_time_t *eft, struct rtc_time *wtime) if (!eft->month || eft->month > 12) return false; wtime->tm_mon = eft->month - 1; - wtime->tm_year = eft->year - 1900; - /* day of the week [0-6], Sunday=0 */ - wtime->tm_wday = compute_wday(eft); - if (wtime->tm_wday < 0) + if (eft->year < 1900 || eft->year > 9999) return false; + wtime->tm_year = eft->year - 1900; /* day in the year [1-365]*/ wtime->tm_yday = compute_yday(eft); + /* day of the week [0-6], Sunday=0 */ + wtime->tm_wday = compute_wday(eft, wtime->tm_yday); switch (eft->daylight & EFI_ISDST) { case EFI_ISDST: |