| Message ID | 20160620200040.2813298-1-arnd@arndb.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Arnd Bergmann <arnd@arndb.de> writes: > Jeff Moyer looked up the blktrace source to see if an overflow might > happen. The situation is as follows: > > - The time stamp is not used by the program itself, only for > printing human-readable output. > - We normally don't print the timestamp at all, except when an > undocumented format option is given to blkparse. > - The assumption is that no other program besides blktrace > even looks at this data, but of course cannot be sure. > - On 64-bit systems, the time gets read from the unsigned > 32-bit kernel structure into a timespec in a way that will > work correctly until 2106, so there is no 2038 problem. > - On 32-bit systems that have a new (future) libc build with > a 64-bit time_t type, it will work the same way. > - On current 32-bit systems, the time is passed into localtime(), > at which point the overflow happens, but those systems are > already broken. > > In short, it's good enough for now, so update the comment. > > Signed-off-by: Arnd Bergmann <arnd@arndb.de> > Fixes: 59a37f8baeb2 ("blktrace: avoid using timespec") > Cc: Jeff Moyer <jmoyer@redhat.com> Acked-by: Jeff Moyer <jmoyer@redhat.com> > --- > kernel/trace/blktrace.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c > index b0816e4a61a5..4a3666779589 100644 > --- a/kernel/trace/blktrace.c > +++ b/kernel/trace/blktrace.c > @@ -131,7 +131,8 @@ static void trace_note_time(struct blk_trace *bt) > unsigned long flags; > u32 words[2]; > > - /* need to check user space to see if this breaks in y2038 or y2106 */ > + /* blktrace converts this to a time_t and will overflow in > + 2106, not in 2038 */ > ktime_get_real_ts64(&now); > words[0] = (u32)now.tv_sec; > words[1] = now.tv_nsec; -- To unsubscribe from this list: send the line "unsubscribe linux-block" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c index b0816e4a61a5..4a3666779589 100644 --- a/kernel/trace/blktrace.c +++ b/kernel/trace/blktrace.c @@ -131,7 +131,8 @@ static void trace_note_time(struct blk_trace *bt) unsigned long flags; u32 words[2]; - /* need to check user space to see if this breaks in y2038 or y2106 */ + /* blktrace converts this to a time_t and will overflow in + 2106, not in 2038 */ ktime_get_real_ts64(&now); words[0] = (u32)now.tv_sec; words[1] = now.tv_nsec;
Jeff Moyer looked up the blktrace source to see if an overflow might happen. The situation is as follows: - The time stamp is not used by the program itself, only for printing human-readable output. - We normally don't print the timestamp at all, except when an undocumented format option is given to blkparse. - The assumption is that no other program besides blktrace even looks at this data, but of course cannot be sure. - On 64-bit systems, the time gets read from the unsigned 32-bit kernel structure into a timespec in a way that will work correctly until 2106, so there is no 2038 problem. - On 32-bit systems that have a new (future) libc build with a 64-bit time_t type, it will work the same way. - On current 32-bit systems, the time is passed into localtime(), at which point the overflow happens, but those systems are already broken. In short, it's good enough for now, so update the comment. Signed-off-by: Arnd Bergmann <arnd@arndb.de> Fixes: 59a37f8baeb2 ("blktrace: avoid using timespec") Cc: Jeff Moyer <jmoyer@redhat.com> --- kernel/trace/blktrace.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)