[PATCH for-8.2 0/4] rtc devices: Avoid putting time_t in 32-bit variables

[Peter Maydell <peter.maydell@linaro.org>]

This patchset was prompted by a couple of Coverity warnings
(CID 1507157, 1517772) which note that in the m48t59 RTC device model
we keep an offset in a time_t variable but then truncate it by
passing it to qemu_get_timedate(), which currently uses an 'int'
argument for its offset parameter.

We can fix the Coverity complaint by making qemu_get_timedate()
take a time_t; we should also correspondingly make the
qemu_timedate_diff() function return a time_t. However this
will only push the issue out to callers of qemu_timedate_diff()
if they are putting the result in a 32-bit variable or doing
32-bit arithmetic on it.

Luckily there aren't that many callers of qemu_timedate_diff()
and most of them already use either time_t or int64_t for the
calculations they do on its return value. The first three
patches fix devices which weren't doing that; patch four then
fixes the rtc.c functions. If I missed any callsites in devices
then hopefully Coverity will point them out.

This patchset is a migration compat break for the aspeed boards,
because the offset field in aspeed_rtc is in its vmstate struct.
We could in theory make this a compatible migration change, but
I don't believe we care about migration compat for these boards.

I've only tested this with 'make check' and 'make check-avocado',
which probably do not exercise these RTC devices much.

I've tagged this as for-8.2 because the code has been like this
forever. We might as well give ourselves plenty of time to see
if there's any unforeseen consequences of widening the type.

thanks
-- PMM

Peter Maydell (4):
  hw/rtc/m48t59: Use 64-bit arithmetic in set_alarm()
  hw/rtc/twl92230: Use int64_t for sec_offset and alm_sec
  hw/rtc/aspeed_rtc: Use 64-bit offset for holding time_t difference
  rtc: Use time_t for passing and returning time offsets

 include/hw/rtc/aspeed_rtc.h | 2 +-
 include/sysemu/rtc.h        | 4 ++--
 hw/rtc/aspeed_rtc.c         | 5 ++---
 hw/rtc/m48t59.c             | 2 +-
 hw/rtc/twl92230.c           | 4 ++--
 softmmu/rtc.c               | 4 ++--
 6 files changed, 10 insertions(+), 11 deletions(-)

-- 
2.34.1