[PATCH v2 3/4] ARM: Reduce the number of #ifdef CONFIG_CPU_SW_DOMAIN_PAN

[Russell King (Oracle)]

On Tue, Mar 12, 2024 at 09:30:37AM +0100, Linus Walleij wrote:
> On Tue, Mar 12, 2024 at 9:22 AM Linus Walleij <linus.walleij at linaro.org> wrote:
> > On Mon, Mar 11, 2024 at 5:02 PM Russell King (Oracle)
> > <linux at armlinux.org.uk> wrote:
> > > On Wed, Feb 21, 2024 at 12:04:02AM +0100, Linus Walleij wrote:
> > > > @@ -24,9 +24,10 @@
> > > >   * perform such accesses (eg, via list poison values) which could then
> > > >   * be exploited for priviledge escalation.
> > > >   */
> > > > +#if defined(CONFIG_CPU_SW_DOMAIN_PAN)
> > > > +
> > > >  static __always_inline unsigned int uaccess_save_and_enable(void)
> > > >  {
> > > > -#ifdef CONFIG_CPU_SW_DOMAIN_PAN
> > >
> > > This is an interesting way to reduce the #ifdef count... why switch it
> > > from #ifdef to #if defined ?
> >
> > Hm that looks like a development artifact from a point where we
> > has if defined(A) && defined(B) and then one of them was removed.
> 
> Ah no, now I see it. In the next patch a pattern with
> 
> #elif defined(CONFIG_CPU_TTBR0_PAN)
> 
> is used, so in order to not look confusing the #elif defined() is paired
> with #if defined().

Looking closer, there is inconsistency in patch 2 and patch 3.

In patch 2, uaccess-asm.h, you move the #ifdef without changing it, and
in the other files it becomes #if defined.

In patch 3, you add #elif defined to all these files. So in
uaccess-asm.h, we end up with:

#ifdef
#elif defined

whereas others we have:

#if defined
#elif defined

So I think uaccess-asm.h needs to be changed as well. It probably would
make more sense in the patches if patch 2 if the #ifdef's were moved
without changing them, and in patch 3 which introduces the #elif
defined, to also then change the #ifdef to #if defined. Then the
commit messages don't need modification because it's obvious why the
change if #ifdef is happening.

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