Re: [PATCH v3 3/4] xen/arm: switch ARM to use generic implementation of bug.h

[Julien Grall <julien@xxxxxxx>]

Hi Oleksii,

On 28/02/2023 15:09, Oleksii wrote:
> On Sat, 2023-02-25 at 16:49 +0000, Julien Grall wrote:
> > Hi Oleksii,
> >
> > On 24/02/2023 11:31, Oleksii Kurochko wrote:
> > > The following changes were made:
> > > * make GENERIC_BUG_FRAME mandatory for ARM
> > I have asked in patch #1 but will ask it again because I think this
> > should be recorded in the commit message. Can you outline why it is
> > not
> > possible to completely switch to the generic version?
> I haven't tried to switch ARM too because of comment regarding 'i' in
> <asm/bug.h>:
> /*
>   * GCC will not allow to use "i"  when PIE is enabled (Xen doesn't set
> the
>   * flag but instead rely on the default value from the compiler). So
> the
>   * easiest way to implement run_in_exception_handler() is to pass the
> to
>   * be called function in a fixed register.
>   */
I would expect this comment to be valid for any arch. So if there is a 
need to deal with PIE, then we would not be able to use "i" in the BUG 
frame.
Note that we are now explicitly compiling Xen without PIE (see Config.mk).

Cheers,

--
Julien Grall