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Commit 1e817fb6 authored by Kees Cook's avatar Kees Cook Committed by John Stultz
Browse files

time: create __getnstimeofday for WARNless calls 



The pstore RAM backend can get called during resume, and must be defensive
against a suspended time source. Expose getnstimeofday logic that returns
an error instead of a WARN. This can be detected and the timestamp can
be zeroed out.

Reported-by: default avatarDoug Anderson <dianders@chromium.org>
Cc: John Stultz <johnstul@us.ibm.com>
Cc: Anton Vorontsov <anton.vorontsov@linaro.org>
Signed-off-by: default avatarKees Cook <keescook@chromium.org>
Signed-off-by: default avatarJohn Stultz <john.stultz@linaro.org>
parent 9c3f9e28

fs/pstore/ram.c

+7 −3
Original line number Diff line number Diff line
@@ -168,12 +168,16 @@ static ssize_t ramoops_pstore_read(u64 *id, enum pstore_type_id *type, 
static size_t ramoops_write_kmsg_hdr(struct persistent_ram_zone *prz)

{

	char *hdr;

	struct timeval timestamp;

	struct timespec timestamp;

	size_t len;



	do_gettimeofday(&timestamp);

	/* Report zeroed timestamp if called before timekeeping has resumed. */

	if (__getnstimeofday(&timestamp)) {

		timestamp.tv_sec = 0;

		timestamp.tv_nsec = 0;

	}

	hdr = kasprintf(GFP_ATOMIC, RAMOOPS_KERNMSG_HDR "%lu.%lu\n",

		(long)timestamp.tv_sec, (long)timestamp.tv_usec);

		(long)timestamp.tv_sec, (long)(timestamp.tv_nsec / 1000));

	WARN_ON_ONCE(!hdr);

	len = hdr ? strlen(hdr) : 0;

	persistent_ram_write(prz, hdr, len);

include/linux/time.h

+1 −0
Original line number Diff line number Diff line
@@ -158,6 +158,7 @@ extern int do_setitimer(int which, struct itimerval *value, 
			struct itimerval *ovalue);

extern unsigned int alarm_setitimer(unsigned int seconds);

extern int do_getitimer(int which, struct itimerval *value);

extern int __getnstimeofday(struct timespec *tv);

extern void getnstimeofday(struct timespec *tv);

extern void getrawmonotonic(struct timespec *ts);

extern void getnstime_raw_and_real(struct timespec *ts_raw,

kernel/time/timekeeping.c

+24 −5
Original line number Diff line number Diff line
@@ -214,19 +214,18 @@ static void timekeeping_forward_now(struct timekeeper *tk) 
}



/**

 * getnstimeofday - Returns the time of day in a timespec

 * __getnstimeofday - Returns the time of day in a timespec.

 * @ts:		pointer to the timespec to be set

 *

 * Returns the time of day in a timespec.

 * Updates the time of day in the timespec.

 * Returns 0 on success, or -ve when suspended (timespec will be undefined).

 */

void getnstimeofday(struct timespec *ts)

int __getnstimeofday(struct timespec *ts)

{

	struct timekeeper *tk = &timekeeper;

	unsigned long seq;

	s64 nsecs = 0;



	WARN_ON(timekeeping_suspended);



	do {

		seq = read_seqbegin(&tk->lock);
@@ -237,6 +236,26 @@ void getnstimeofday(struct timespec *ts) 


	ts->tv_nsec = 0;

	timespec_add_ns(ts, nsecs);



	/*

	 * Do not bail out early, in case there were callers still using

	 * the value, even in the face of the WARN_ON.

	 */

	if (unlikely(timekeeping_suspended))

		return -EAGAIN;

	return 0;

}

EXPORT_SYMBOL(__getnstimeofday);



/**

 * getnstimeofday - Returns the time of day in a timespec.

 * @ts:		pointer to the timespec to be set

 *

 * Returns the time of day in a timespec (WARN if suspended).

 */

void getnstimeofday(struct timespec *ts)

{

	WARN_ON(__getnstimeofday(ts));

}

EXPORT_SYMBOL(getnstimeofday);