Re: [PATCH v9 44/44] kselftest/arm64: Check GCR_EL1 after context switch

[Marco Elver]

On Thu, 12 Nov 2020 at 16:59, Alexander Potapenko <glider@xxxxxxxxxx> wrote:
>
> On Tue, Nov 10, 2020 at 11:12 PM Andrey Konovalov <andreyknvl@xxxxxxxxxx> wrote:
> >
> > From: Vincenzo Frascino <vincenzo.frascino@xxxxxxx>
> >
> > This test is specific to MTE and verifies that the GCR_EL1 register
> > is context switched correctly.
> >
> > It spawn 1024 processes and each process spawns 5 threads. Each thread
>
> Nit: "spawns"
>
>
> > +       srand(time(NULL) ^ (pid << 16) ^ (tid << 16));
> > +
> > +       prctl_tag_mask = rand() % 0xffff;
>
> Nit: if you want values between 0 and 0xffff you probably want to use
> bitwise AND.

Another question would be, is the max here meant to be 0xffff or
0xffff-1. Because, as-is now, it's 0xffff-1. Only one of them has a
trivial conversion to bitwise AND ( x % 2^n == x & (2^n - 1) ).