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Add RTC clock conversions for BCD values, with non-panic validation.

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RTC clock hardware frequently uses BCD numbers.  Currently the low-level
bcd2bin() and bin2bcd() functions will KASSERT if given out-of-range BCD
values.  Every RTC driver must implement its own code for validating the
unreliable data coming from the hardware to avoid a potential kernel panic.

This change introduces two new functions, clock_bcd_to_ts() and
clock_ts_to_bcd().  The former validates its inputs and returns EINVAL if any
values are out of range. The latter guarantees the returned data will be
valid BCD in a known format (4-digit years, etc).

A new bcd_clocktime structure is used with the new functions.  It is similar
to the original clocktime structure, but defines the fields holding BCD
values as uint8_t (uint16_t for year), and adds a PM flag for handling hours
using AM/PM mode.

PR:		224813
Differential Revision:	https://reviews.freebsd.org/D13730 (no reviewers)
This commit is contained in:
ian 2018-01-14 17:01:37 +00:00
parent 0c2094e599
commit 9c7cac637a
2 changed files with 130 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

77
sys/kern/subr_clock.c
View File

@ -199,6 +199,55 @@ clock_ct_to_ts(struct clocktime *ct, struct timespec *ts)
return (0);
}
int
clock_bcd_to_ts(struct bcd_clocktime *bct, struct timespec *ts, bool ampm)
{
struct clocktime ct;
int bcent, byear;
/*
* Year may come in as 2-digit or 4-digit BCD. Split the value into
* separate BCD century and year values for validation and conversion.
*/
bcent = bct->year >> 8;
byear = bct->year & 0xff;
/*
* Ensure that all values are valid BCD numbers, to avoid assertions in
* the BCD-to-binary conversion routines. clock_ct_to_ts() will further
* validate the field ranges (such as 0 <= min <= 59) during conversion.
*/
if (!validbcd(bcent) || !validbcd(byear) || !validbcd(bct->mon) ||
!validbcd(bct->day) || !validbcd(bct->hour) ||
!validbcd(bct->min) || !validbcd(bct->sec)) {
if (ct_debug)
printf("clock_bcd_to_ts: bad BCD: "
"[%04x-%02x-%02x %02x:%02x:%02x]\n",
bct->year, bct->mon, bct->day,
bct->hour, bct->min, bct->sec);
return (EINVAL);
}
ct.year = FROMBCD(byear) + FROMBCD(bcent) * 100;
ct.mon = FROMBCD(bct->mon);
ct.day = FROMBCD(bct->day);
ct.hour = FROMBCD(bct->hour);
ct.min = FROMBCD(bct->min);
ct.sec = FROMBCD(bct->sec);
ct.dow = bct->dow;
ct.nsec = bct->nsec;
/* If asked to handle am/pm, convert from 12hr+pmflag to 24hr. */
if (ampm) {
if (ct.hour == 12)
ct.hour = 0;
if (bct->ispm)
ct.hour += 12;
}
return (clock_ct_to_ts(&ct, ts));
}
void
clock_ts_to_ct(struct timespec *ts, struct clocktime *ct)
{
@ -260,6 +309,34 @@ clock_ts_to_ct(struct timespec *ts, struct clocktime *ct)
("seconds %d not in 0-60", ct->sec));
}
void
clock_ts_to_bcd(struct timespec *ts, struct bcd_clocktime *bct, bool ampm)
{
struct clocktime ct;
clock_ts_to_ct(ts, &ct);
/* If asked to handle am/pm, convert from 24hr to 12hr+pmflag. */
bct->ispm = false;
if (ampm) {
if (ct.hour >= 12) {
ct.hour -= 12;
bct->ispm = true;
}
if (ct.hour == 0)
ct.hour = 12;
}
bct->year = TOBCD(ct.year % 100) | (TOBCD(ct.year / 100) << 8);
bct->mon = TOBCD(ct.mon);
bct->day = TOBCD(ct.day);
bct->hour = TOBCD(ct.hour);
bct->min = TOBCD(ct.min);
bct->sec = TOBCD(ct.sec);
bct->dow = ct.dow;
bct->nsec = ct.nsec;
}
int
utc_offset(void)
{

56
sys/sys/clock.h
View File

@ -60,9 +60,22 @@ extern int tz_dsttime;
int utc_offset(void);
/*
* Structure to hold the values typically reported by time-of-day clocks.
* This can be passed to the generic conversion functions to be converted
* to a struct timespec.
* Structure to hold the values typically reported by time-of-day clocks,
* expressed as binary integers (see below for a BCD version). This can be
* passed to the conversion functions to be converted to/from a struct timespec.
*
* On input, the year is interpreted as follows:
* 0 - 69 = 2000 - 2069
* 70 - 99 = 1970 - 1999
* 100 - 199 = 2000 - 2099 (Supports hardware "century bit".)
* 200 - 1969 = Invalid.
* 1970 - 9999 = Full 4-digit century+year.
*
* The dow field is ignored (not even validated) on input, but is always
* populated with day-of-week on output.
*
* clock_ct_to_ts() returns EINVAL if any values are out of range. The year
* field will always be 4-digit on output.
*/
struct clocktime {
int year; /* year (4 digit year) */
@ -78,6 +91,43 @@ struct clocktime {
int clock_ct_to_ts(struct clocktime *, struct timespec *);
void clock_ts_to_ct(struct timespec *, struct clocktime *);
/*
* Structure to hold the values typically reported by time-of-day clocks,
* expressed as BCD. This can be passed to the conversion functions to be
* converted to/from a struct timespec.
*
* The clock_bcd_to_ts() function interprets the values in the year through sec
* fields as BCD numbers, and returns EINVAL if any BCD values are out of range.
* After conversion to binary, the values are passed to clock_ct_to_ts() and
* undergo further validation as described above. Year may be 2 or 4-digit BCD,
* interpreted as described above. The nsec field is binary. If the ampm arg
* is true, the incoming hour and ispm values are interpreted as 12-hour am/pm
* representation of the hour, otherwise hour is interpreted as 24-hour and ispm
* is ignored.
*
* The clock_ts_to_bcd() function converts the timespec to BCD values stored
* into year through sec. The value in year will be 4-digit BCD (e.g.,
* 0x2017). The mon through sec values will be 2-digit BCD. The nsec field will
* be binary, and the range of dow makes its binary and BCD values identical.
* If the ampm arg is true, the hour and ispm fields are set to the 12-hour
* time plus a pm flag, otherwise the hour is set to 24-hour time and ispm is
* set to false.
*/
struct bcd_clocktime {
uint16_t year; /* year (2 or 4 digit year) */
uint8_t mon; /* month (1 - 12) */
uint8_t day; /* day (1 - 31) */
uint8_t hour; /* hour (0 - 23 or 1 - 12) */
uint8_t min; /* minute (0 - 59) */
uint8_t sec; /* second (0 - 59) */
uint8_t dow; /* day of week (0 - 6; 0 = Sunday) */
long nsec; /* nanoseconds */
bool ispm; /* true if hour represents pm time */
};
int clock_bcd_to_ts(struct bcd_clocktime *, struct timespec *, bool ampm);
void clock_ts_to_bcd(struct timespec *, struct bcd_clocktime *, bool ampm);
/*
* Time-of-day clock functions and flags. These functions might sleep.
*