Re: [PATCH] selftests/mm: remove the local PKEY_UNRESTRICTED fallback

[Hemanth Selam <hemanth.selam@gmail.com>]

On Tue, Aug 18, 2026 at 02:36:00PM +0000, Lorenzo Stoakes (ARM) wrote:
> But it might be worth checking in this case to see whether the problem here
> is in fact that we need PKEY_UNRESTRICTED defined over there?
>
> Hemanth - could you check please?

Checked.  It is already defined over there:

  tools/include/uapi/asm-generic/mman-common.h:88:#define PKEY_UNRESTRICTED	0x0

and it does reach the mm selftests without "make headers", through
TOOLS_INCLUDES.  The path is not obvious, so for the record:

  pkey-helpers.h
    -> <linux/mman.h>           tools/include/uapi/linux/mman.h
      -> <asm/mman.h>           /usr/include/asm/mman.h
                                (tools/include/uapi/asm/mman.h does not exist)
        -> <asm-generic/mman.h> tools/include/uapi/asm-generic/mman.h
                                (-isystem puts it ahead of the system one)
          -> <asm-generic/mman-common-tools.h>
            -> <asm-generic/mman-common.h>	PKEY_UNRESTRICTED

I built the pkey tests with KHDR_INCLUDES pointing at an empty directory,
that is, as if "make headers" had never run.  They build, and cpp -dD
says:

  defined in: tools/include/uapi/asm-generic/mman-common.h

Pointing TOOLS_INCLUDES at an empty directory as well is what breaks it:

  pkey-helpers.h:188:30: error: 'PKEY_UNRESTRICTED' undeclared

So that is where the definition comes from, and dropping the local
#ifndef does not depend on "make headers" being run.

The one thing worth being aware of is that the redirection into
tools/include/uapi only happens because the system <asm/mman.h> includes
<asm-generic/mman.h>.

I had a look at the history you pointed at, thanks, that was the part I
had wrong.  If I read it right this is exactly the mechanism from commit
e076eaca5906 ("selftests: break the dependency upon local header
files"), which added TOOLS_INCLUDES to the mm selftests so they build
without "make headers".  So for this particular macro the value comes
from the in-tree snapshot rather than from whatever the build host has
installed, which is why it does not vary per system here.

That said, if you would still rather keep the #ifndef as a matter of
course, I have no objection to dropping the patch, the guard costs
nothing.  I mainly wanted to answer the question with something
measured rather than assumed.

> This is incorrect. We explicitly do not have this requirement in mm selftests,
> and they're often built without having to do this step and tooling has been
> provided _explicitly_ to allow for that, which is why this kind of thing exists
> right now.

You are right, the commit message was wrong on that point.  v2 drops
that paragraph and describes the above instead.

On the powerpc header David mentioned, I would rather leave
tools/testing/selftests/powerpc/include/pkeys.h alone.  It is not the
same construct: it is an unconditional

  #undef PKEY_UNRESTRICTED
  #define PKEY_UNRESTRICTED	0x0

next to other powerpc specific overrides such as PKEY_DISABLE_EXECUTE
0x4, and that header only includes <sys/mman.h>, never <linux/mman.h>.
A probe including just <sys/mman.h> does not find PKEY_UNRESTRICTED,
with or without TOOLS_INCLUDES, so the definition there is load bearing
and removing it would break the build.

Thanks,
Hemanth