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time: create __getnstimeofday for WARNless calls

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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: Doug Anderson <dianders@chromium.org>
Cc: John Stultz <johnstul@us.ibm.com>
Cc: Anton Vorontsov <anton.vorontsov@linaro.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: John Stultz <john.stultz@linaro.org>
This commit is contained in:
Kees Cook 2012-11-19 10:26:16 -08:00 committed by John Stultz
parent 9c3f9e2816
commit 1e817fb62c
3 changed files with 32 additions and 8 deletions
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10
fs/pstore/ram.c
View File

@ -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);

1
include/linux/time.h
View File

@ -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,

29
kernel/time/timekeeping.c
View File

@ -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);