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Commit 52bfb360 authored by John Stultz's avatar John Stultz Committed by Ingo Molnar
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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: default avatarUlrich Drepper <drepper@redhat.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 8232fd62

include/linux/timex.h

+1 −0
Original line number Diff line number Diff line
@@ -137,6 +137,7 @@ struct timex { 
#define ADJ_TIMECONST		0x0020	/* pll time constant */

#define ADJ_TICK		0x4000	/* tick value */

#define ADJ_OFFSET_SINGLESHOT	0x8001	/* old-fashioned adjtime */

#define ADJ_OFFSET_SS_READ	0xa001  /* read-only adjtime */



/* xntp 3.4 compatibility names */

#define MOD_OFFSET	ADJ_OFFSET

kernel/time/ntp.c

+6 −3
Original line number Diff line number Diff line
@@ -249,10 +249,12 @@ int do_adjtimex(struct timex *txc) 


	/* 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 @@ int do_adjtimex(struct timex *txc) 
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)) *