Package: manpages-dev
Version: 2.67-1
Severity: minor
File: /usr/share/man/man2/settimeofday.2.gz
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Architecture: i386 (i686)
Kernel: Linux 2.6.18-4-486
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`man settimeofday' says:
The use of the timezone structure is obsolete; the tz argument
should normally be specified as NULL.
But, on linux kernel, the FAT filesystem driver uses tz->tz_minuteswest
parameter for timestamp conversion. `tz' argument is still alive, not
retired.
Here is the detail in kernel:
linux-2.6.17.1/kernel/time.c handles settimeofday(2) syscall and stores
tz parameter into sys_tz global variable.
//////////
struct timezone sys_tz;
EXPORT_SYMBOL(sys_tz);
...(snip)...
int do_sys_settimeofday(struct timespec *tv, struct timezone *tz)
{
static int firsttime = 1;
int error = 0;
if (tv && !timespec_valid(tv))
return -EINVAL;
error = security_settime(tv, tz);
if (error)
return error;
if (tz) {
/* SMP safe, global irq locking makes it work. */
sys_tz = *tz;
if (firsttime) {
firsttime = 0;
if (!tv)
warp_clock();
}
}
if (tv)
{
/* SMP safe, again the code in arch/foo/time.c should
* globally block out interrupts when it runs.
*/
return do_settimeofday(tv);
}
return 0;
}
//////////
linux-2.6.17.1/fs/fat/misc.c uses the `sys_tz' variable for timestamp
conversion. FAT filesystem has only yy-mm-dd-hh-mm-ss format
timestamp, no timezone infomation. So linux kernel handles the
timestamp as localtime with using tz->tz_minuteswest parameter.
//////////
extern struct timezone sys_tz;
...(snip)...
/* Convert a MS-DOS time/date pair to a UNIX date (seconds since 1 1 70). */
int date_dos2unix(unsigned short time, unsigned short date)
{
int month, year, secs;
/*
* first subtract and mask after that... Otherwise, if
* date == 0, bad things happen
*/
month = ((date >> 5) - 1) & 15;
year = date >> 9;
secs = (time & 31)*2+60*((time >> 5) & 63)+(time >> 11)*3600+86400*
((date & 31)-1+day_n[month]+(year/4)+year*365-((year & 3) ==
0 &&
month < 2 ? 1 : 0)+3653);
/* days since 1.1.70 plus 80's leap day */
secs += sys_tz.tz_minuteswest*60;
return secs;
}
//////////
Thanks.
----
Kunihiko IMAI
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