Thread (5 messages) 5 messages, 3 authors, 2021-09-29

Re: [PATCH][next] rtc: msc313: Fix unintentional sign extension issue on left shift of a u16

From: Daniel Palmer <hidden>
Date: 2021-09-29 12:54:37
Also in: kernel-janitors, linux-rtc, lkml

Hi Romain,

On Tue, 28 Sept 2021 at 22:55, Romain Perier [off-list ref] wrote:
Hi,

Le mar. 28 sept. 2021 à 15:31, Daniel Palmer [off-list ref] a écrit :
The crazy stuff being, I ran rtctest from selftests and rtc-range (1)
that tests a variety
of dates including 2038 and 2106 for example. Both tests passed :) (probably
because *this case* specifically did not happen while running the test)
I suspect it works because for reading the time because seconds is a
u32 not unsigned long like the other functions.
So if the high word of the register is read, is promoted to a wider
type and sign extended it doesn't actually matter because it gets
truncated to 32 bits so the sign extended part is gone.

Cheers,

Daniel

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