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

[Philippe Mathieu-Daudé]

+Markus

On 20/7/23 17:58, Peter Maydell wrote:
> 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.

Do we need to change the type of the RTC_CHANGE event?

This is wrong, but to give an idea:

--- a/qapi/misc.json
+++ b/qapi/misc.json
@@ -553,47 +553,47 @@
 ##
 # @RTC_CHANGE:
 #
 # Emitted when the guest changes the RTC time.
 #
 # @offset: offset in seconds between base RTC clock (as specified by
 #     -rtc base), and new RTC clock value
 #
 # @qom-path: path to the RTC object in the QOM tree
 #
 # Note: This event is rate-limited.  It is not guaranteed that the RTC
 #     in the system implements this event, or even that the system has
 #     an RTC at all.
 #
 # Since: 0.13
 #
 # Example:
 #
 # <- { "event": "RTC_CHANGE",
 #      "data": { "offset": 78 },
 #      "timestamp": { "seconds": 1267020223, "microseconds": 435656 } }
 ##
 { 'event': 'RTC_CHANGE',
-  'data': { 'offset': 'int', 'qom-path': 'str' } }
+  'data': { 'offset': 'int64', 'qom-path': 'str' } }
---