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authorKees Cook <keescook@chromium.org>2012-11-19 22:26:16 +0400
committerJohn Stultz <john.stultz@linaro.org>2013-01-16 06:16:02 +0400
commit1e817fb62cd185a2232ad4302579491805609489 (patch)
treed4155fb65a9fb32cd9236405a8b7534f39c293b9
parent9c3f9e281697d02889c3b08922f3b30be75f56c2 (diff)
downloadlinux-1e817fb62cd185a2232ad4302579491805609489.tar.xz
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: 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>
-rw-r--r--fs/pstore/ram.c10
-rw-r--r--include/linux/time.h1
-rw-r--r--kernel/time/timekeeping.c29
3 files changed, 32 insertions, 8 deletions
diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
index 1a4f6da58eab..dacfe78aee7e 100644
--- a/fs/pstore/ram.c
+++ b/fs/pstore/ram.c
@@ -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);
diff --git a/include/linux/time.h b/include/linux/time.h
index 4d358e9d10f1..0015aea4c4a7 100644
--- a/include/linux/time.h
+++ b/include/linux/time.h
@@ -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,
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 4c7de02eacdc..dfc7f87eb332 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -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);