time: add ADJ_OFFSET_SS_READ
Michael Kerrisk reported that a long standing bug in the adjtimex()
system call causes glibc's adjtime(3) function to deliver the wrong
results if 'delta' is NULL.
add the ADJ_OFFSET_SS_READ API detail, which will be used by glibc
to fix this API compatibility bug.
Also see: http://bugzilla.kernel.org/show_bug.cgi?id=6761
[ mingo@elte.hu: added patch description and made it backwards compatible ]
NOTE: the new flag is defined 0xa001 so that it returns -EINVAL on
older kernels - this way glibc can use it safely. Suggested by Ulrich
Drepper.
Acked-by: Ulrich Drepper <drepper@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/kernel/time/ntp.c b/kernel/time/ntp.c
index 14a2ecf..e64efaf 100644
--- a/kernel/time/ntp.c
+++ b/kernel/time/ntp.c
@@ -249,10 +249,12 @@
/* Now we validate the data before disabling interrupts */
- if ((txc->modes & ADJ_OFFSET_SINGLESHOT) == ADJ_OFFSET_SINGLESHOT)
+ if ((txc->modes & ADJ_OFFSET_SINGLESHOT) == ADJ_OFFSET_SINGLESHOT) {
/* singleshot must not be used with any other mode bits */
- if (txc->modes != ADJ_OFFSET_SINGLESHOT)
+ if (txc->modes != ADJ_OFFSET_SINGLESHOT &&
+ txc->modes != ADJ_OFFSET_SS_READ)
return -EINVAL;
+ }
if (txc->modes != ADJ_OFFSET_SINGLESHOT && (txc->modes & ADJ_OFFSET))
/* adjustment Offset limited to +- .512 seconds */
@@ -372,7 +374,8 @@
leave: if ((time_status & (STA_UNSYNC|STA_CLOCKERR)) != 0)
result = TIME_ERROR;
- if ((txc->modes & ADJ_OFFSET_SINGLESHOT) == ADJ_OFFSET_SINGLESHOT)
+ if ((txc->modes == ADJ_OFFSET_SINGLESHOT) ||
+ (txc->modes == ADJ_OFFSET_SS_READ))
txc->offset = save_adjust;
else
txc->offset = ((long)shift_right(time_offset, SHIFT_UPDATE)) *