Re: [PATCH] linux-user: Don't assume 0 is not a valid host timer_t value

[Jon Alduan]

Hello Peter,

I can say so far, your patch solved the issue! Great thanks for that!

Regarding the libc version:

From my WSL2 Ubuntu 21.04 x86_64:

$ ls -l /lib32/libc*
-rwxr-xr-x 1 root root 2042632 Mar 31  2021 /lib32/libc-2.33.so

My gcc version 10 does use the same libc version.

As already mentioned, I can also reproduce this on a VM with Ubuntu 20.04 and libc-2.31.

In addition, originally, this issue was first reproduced with an own buildroot RootFS and containing libc-2.28.

As you see, the libcs are not that old. What about the virtual environment? I could not check this hypothesis, but I hope to do so soon.

Thank you again and best regards

Jon

El lun, 25 jul 2022 a las 14:45, Peter Maydell (<peter.maydell@linaro.org>) escribió:

On Mon, 25 Jul 2022 at 12:13, Daniel P. Berrangé <berrange@redhat.com> wrote:
>
> On Mon, Jul 25, 2022 at 12:00:35PM +0100, Peter Maydell wrote:
> > For handling guest POSIX timers, we currently use an array
> > g_posix_timers[], whose entries are a host timer_t value, or 0 for
> > "this slot is unused".  When the guest calls the timer_create syscall
> > we look through the array for a slot containing 0, and use that for
> > the new timer.
> >
> > This scheme assumes that host timer_t values can never be zero.  This
> > is unfortunately not a valid assumption -- for some host libc
> > versions, timer_t values are simply indexes starting at 0.  When
> > using this kind of host libc, the effect is that the first and second
> > timers end up sharing a slot, and so when the guest tries to operate
> > on the first timer it changes the second timer instead.
>
> For sake of historical record, could you mention here which specific
> libc impl / version highlights the problem.

Jon, which host libc are you seeing this with?

thanks
-- PMM

--

j.A