On 28 September 2016 at 02:16, P J P <ppan...@redhat.com> wrote:
> From: Prasad J Pandit <p...@fedoraproject.org>
>
> ARM A9MP processor has a peripheral timer with an auto-increment
> register, which holds an increment step value. A user could set
> this value to zero, when auto-increment control bit is enabled.
> This leads to an infinite loop in 'a9_gtimer_update' while
> updating comparator value. Remove the loop incrementing the
> comparator value; Add check to avoid value zero.
>
> Reported-by: Li Qiang <liqiang...@360.cn>
> Signed-off-by: Prasad J Pandit <p...@fedoraproject.org>
> ---
> hw/timer/a9gtimer.c | 22 ++++++++++------------
> 1 file changed, 10 insertions(+), 12 deletions(-)
>
> Update per
> -> https://lists.gnu.org/archive/html/qemu-devel/2016-09/msg05682.html
>
> diff --git a/hw/timer/a9gtimer.c b/hw/timer/a9gtimer.c
> index 772f85f..021ae59 100644
> --- a/hw/timer/a9gtimer.c
> +++ b/hw/timer/a9gtimer.c
> @@ -72,7 +72,7 @@ static void a9_gtimer_update(A9GTimerState *s, bool sync)
> {
>
> A9GTimerUpdate update = a9_gtimer_get_update(s);
> - int i;
> + uint32_t i, inc;
Why have you changed the type of i when you haven't changed
any of the code that works with it?
Since the gtb->compare field is 64 bit your inc variable should
probably be uint64_t.
> int64_t next_cdiff = 0;
>
> for (i = 0; i < s->num_cpu; ++i) {
> @@ -82,16 +82,14 @@ static void a9_gtimer_update(A9GTimerState *s, bool sync)
> if ((s->control & R_CONTROL_TIMER_ENABLE) &&
> (gtb->control & R_CONTROL_COMP_ENABLE)) {
> /* R2p0+, where the compare function is >= */
> - while (gtb->compare < update.new) {
> - DB_PRINT("Compare event happened for CPU %d\n", i);
> - gtb->status = 1;
> - if (gtb->control & R_CONTROL_AUTO_INCREMENT) {
> - DB_PRINT("Auto incrementing timer compare by %" PRId32
> "\n",
> - gtb->inc);
> - gtb->compare += gtb->inc;
> - } else {
> - break;
> - }
> + DB_PRINT("Compare event happened for CPU %d\n", i);
This is wrong -- this debug print should only happen when the
comparator matches (ie when gtb->compare is less than update.new),
not every time.
> + gtb->status = 1;
Similarly the status flag should only be set when the comparator
matches.
> + if (gtb->control & R_CONTROL_AUTO_INCREMENT
> + && gtb->compare < update.new) {
> + inc = ((update.new - gtb->compare - 1) / gtb->inc) *
> gtb->inc;
I suggest using either QEMU_ALIGN_UP or QEMU_ALIGN_DOWN here,
depending on which way round you're trying for.
Also this will divide by zero if gtb->inc is 0 (as for instance
it will be on reset).
> + DB_PRINT("Auto incrementing timer compare by %"
> + PRId32 "\n",
> inc);
> + gtb->compare += inc;
> }
> cdiff = (int64_t)gtb->compare - (int64_t)update.new + 1;
> if (cdiff > 0 && (cdiff < next_cdiff || !next_cdiff)) {
> @@ -210,7 +208,7 @@ static void a9_gtimer_write(void *opaque, hwaddr addr,
> uint64_t value,
> gtb->compare = deposit64(gtb->compare, shift, 32, value);
> break;
> case R_AUTO_INCREMENT:
> - gtb->inc = value;
> + gtb->inc = value ? value : 1;
Where has this change come from ??
> return;
> default:
> return;
> --
> 2.5.5
>
thanks
-- PMM
