[PATCH v2] selftests/mm: remove the local PKEY_UNRESTRICTED fallback

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

pkey-helpers.h defines PKEY_UNRESTRICTED itself when the macro is not
already known, a stopgap from when the generic definition was still
under review.  It has been merged since, commit 6d61527d931b ("mm/pkey:
Add PKEY_UNRESTRICTED macro"), so the guard is never taken and the FIXME
can be honoured.

The definition comes from tools/include/uapi/asm-generic/mman-common.h
via TOOLS_INCLUDES, which commit e076eaca5906 ("selftests: break the
dependency upon local header files") added so that the mm selftests
build without "make headers".  It is reached through the
<asm-generic/mman.h> that the system <asm/mman.h> includes.  Building
the pkey tests with KHDR_INCLUDES pointing at an empty directory
confirms that; emptying TOOLS_INCLUDES as well is what makes the macro
go missing.

No functional change intended.

Signed-off-by: Hemanth Selam <hemanth.selam@gmail.com>
---
Changes in v2:
 - Drop the incorrect claim that the mm selftests are built against the
   headers of the kernel source and would fail without "make headers".
   They are not, as Lorenzo pointed out; describe where the definition
   really comes from instead.
 - Leave tools/testing/selftests/powerpc/include/pkeys.h alone, as
   discussed with David on v1.  Unlike the mm one it is an unconditional
   #undef/#define next to other powerpc specific overrides, and that
   header only includes <sys/mman.h>, which does not provide
   PKEY_UNRESTRICTED with or without TOOLS_INCLUDES, so its definition
   is load bearing.

The full include path, for reference:

  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
          -> <asm-generic/mman-common-tools.h>
            -> <asm-generic/mman-common.h>      PKEY_UNRESTRICTED

With KHDR_INCLUDES pointing at an empty directory the tests still build,
and cpp -dD reports the macro coming from
tools/include/uapi/asm-generic/mman-common.h.  Emptying TOOLS_INCLUDES
as well gives:

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

pkey_sighandler_tests and mseal_test are byte identical before and
after; protection_keys differs only in the __LINE__ values that
pkey-helpers.h embeds into its debug output.

v1: https://lore.kernel.org/all/20260818114945.1312987-1-hemanth.selam@gmail.com/
 tools/testing/selftests/mm/pkey-helpers.h | 7 -------
 1 file changed, 7 deletions(-)

diff --git a/tools/testing/selftests/mm/pkey-helpers.h b/tools/testing/selftests/mm/pkey-helpers.h
index 2c377f4e9df1..626c2e1655dc 100644
--- a/tools/testing/selftests/mm/pkey-helpers.h
+++ b/tools/testing/selftests/mm/pkey-helpers.h
@@ -112,13 +112,6 @@ void record_pkey_malloc(void *ptr, long size, int prot);
 #define PKEY_MASK	(PKEY_DISABLE_ACCESS | PKEY_DISABLE_WRITE)
 #endif
 
-/*
- * FIXME: Remove once the generic PKEY_UNRESTRICTED definition is merged.
- */
-#ifndef PKEY_UNRESTRICTED
-#define PKEY_UNRESTRICTED 0x0
-#endif
-
 #ifndef set_pkey_bits
 static inline u64 set_pkey_bits(u64 reg, int pkey, u64 flags)
 {
-- 
2.43.7