[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] xen: Fix possible page fault in fifo events
sync_test_bit function require a long* read access to pointer. This is a problem if the you are using last entry in the page causing an access to next page. If this page is not readable you get a memory access failure (page fault). All other x64 bit functions access memory using 32 bit operations. For processors different than x64 long aligned operations are used. Signed-off-by: Frediano Ziglio <frediano.ziglio@xxxxxxxxxx> --- drivers/xen/events/events_fifo.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/drivers/xen/events/events_fifo.c b/drivers/xen/events/events_fifo.c index d302639..af4672d 100644 --- a/drivers/xen/events/events_fifo.c +++ b/drivers/xen/events/events_fifo.c @@ -168,6 +168,11 @@ static int evtchn_fifo_setup(struct irq_info *info) return ret; } +static __always_inline int test_fifo_bit(int nr, event_word_t *word) +{ + return (ACCESS_ONCE(*word) & (((event_word_t) 1) << nr)) != 0; +} + static void evtchn_fifo_bind_to_cpu(struct irq_info *info, unsigned cpu) { /* no-op */ @@ -188,7 +193,7 @@ static void evtchn_fifo_set_pending(unsigned port) static bool evtchn_fifo_is_pending(unsigned port) { event_word_t *word = event_word_from_port(port); - return sync_test_bit(EVTCHN_FIFO_BIT(PENDING, word), BM(word)); + return test_fifo_bit(EVTCHN_FIFO_PENDING, word); } static bool evtchn_fifo_test_and_set_mask(unsigned port) @@ -206,7 +211,7 @@ static void evtchn_fifo_mask(unsigned port) static bool evtchn_fifo_is_masked(unsigned port) { event_word_t *word = event_word_from_port(port); - return sync_test_bit(EVTCHN_FIFO_BIT(MASKED, word), BM(word)); + return test_fifo_bit(EVTCHN_FIFO_MASKED, word); } /* * Clear MASKED, spinning if BUSY is set. -- 1.9.1 _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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