bug#64937: boot time on Linux

[Po Lu via GNU coreutils Bug Reports <bug-coreutils@gnu.org>]

Bruno Haible <bruno@clisp.org> writes:

> I wrote:
>> > No, it isn't. The attached file, when compiled and run under Termux (which
>> > doesn't have particular permissions), prints e.g.:
>> >
>> > from clock  : 1691616762.476870660 = 2023-08-09 21:32:42.476870660
>> > from sysinfo: 1691616762.329261637 = 2023-08-09 21:32:42.329261637
>> >
>> > Note that this uses the kernel's uptime counter, so it will not work well
>> > when the user changes the current time manually. But this is rare on Android.
>
> It works well enough, that I'm adding it to Gnulib, through the attached patch.
>
> Po Lu wrote:
>> This uses the uptime counter (which also results in an SELinux denial
>> for me, but different Android distributions have SELinux policies of
>> varying strictness)
>
> How did you run the program, and which of the two calls (clock_gettime, sysinfo)
> failed for you? Maybe it depends not only on the Android version and device,
> but also on the permissions required by the app?

Both clock_gettime (CLOCK_BOOTIME, ... sysinfo fail with AVC denial
errors and errno set to EACCESS.

I think it is a bit of a stretch to ascribe this to an app's requested
permissions, though, since none of the listed permissions available to
user programs seems pertinent.