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authorVladimir 'φ-coder/phcoder' Serbinenko <phcoder@gmail.com>2013-11-09 18:52:21 +0100
committerSamuel Thibault <samuel.thibault@ens-lyon.org>2013-11-09 18:52:21 +0100
commite2dde67c3f46f5bbe7deb90e52b61977df30a52c (patch)
treea4090bea6ecedb4cfe7b78aef465311a04740503
parent24d8170fa18e3bad9ef2fa1e100e34e93a6c1126 (diff)
Fix overflow in Xen clock computation
* xen/time.c (hyp_get_stime): Split `delta` into `delta_high` and `delta_low`, as it may overflow 4 second timing nowadays.
-rw-r--r--xen/time.c6
1 files changed, 5 insertions, 1 deletions
diff --git a/xen/time.c b/xen/time.c
index a11e7eb..93d87d4 100644
--- a/xen/time.c
+++ b/xen/time.c
@@ -34,6 +34,7 @@ static unsigned64_t lastnsec;
static unsigned64_t hyp_get_stime(void) {
unsigned32_t version;
unsigned64_t cpu_clock, last_cpu_clock, delta, system_time;
+ unsigned64_t delta_high, delta_low;
unsigned32_t mul;
signed8_t shift;
volatile struct vcpu_time_info *time = &hyp_shared_info.vcpu_info[0].time;
@@ -54,7 +55,10 @@ static unsigned64_t hyp_get_stime(void) {
delta >>= -shift;
else
delta <<= shift;
- return system_time + ((delta * (unsigned64_t) mul) >> 32);
+ delta_high = delta >> 32;
+ delta_low = (unsigned32_t) delta;
+ return system_time + ((delta_low * (unsigned64_t) mul) >> 32)
+ + (delta_high * (unsigned64_t) mul);
}
unsigned64_t hyp_get_time(void) {