From e2dde67c3f46f5bbe7deb90e52b61977df30a52c Mon Sep 17 00:00:00 2001 From: Vladimir 'φ-coder/phcoder' Serbinenko Date: Sat, 9 Nov 2013 18:52:21 +0100 Subject: 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. --- xen/time.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) (limited to 'xen') 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) { -- cgit v1.2.3