linux-kernel - [PATCH] mm: debug_vm_pgtable: Don't use _

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Date:   Wed, 22 Sep 2021 04:18:15 +0800
From:   guoren@...nel.org
To:     guoren@...nel.org, akpm@...ux-foundation.org
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Guo Ren <guoren@...ux.alibaba.com>
Subject: [PATCH] mm: debug_vm_pgtable: Don't use __P000 directly

From: Guo Ren <guoren@...ux.alibaba.com>

The __Pxxx/__Sxxx macros are only for init protection_map[]. All
usage of them in linux should come from protection_map array.

Becasue a lot of architectures would re-initilize protection_map[]
array, eg: x86-mem_encrypt, m68k-motorola, mips, arm, sparc.

Using __P000 maybe won't cause bug because hw would deny access
with PROT_NONE permission, but it's not rigorous.

Signed-off-by: Guo Ren <guoren@...ux.alibaba.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
---
 mm/debug_vm_pgtable.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
index 1403639302e4..a6ebbf6e53dd 100644
--- a/mm/debug_vm_pgtable.c
+++ b/mm/debug_vm_pgtable.c
@@ -1104,13 +1104,13 @@ static int __init init_args(struct pgtable_debug_args *args)
 	/*
 	 * Initialize the debugging data.
 	 *
-	 * __P000 (or even __S000) will help create page table entries with
+	 * __P000 (protection_map[0]) will help create page table entries with
 	 * PROT_NONE permission as required for pxx_protnone_tests().
 	 */
 	memset(args, 0, sizeof(*args));
 	args->vaddr              = get_random_vaddr();
 	args->page_prot          = vm_get_page_prot(VMFLAGS);
-	args->page_prot_none     = __P000;
+	args->page_prot_none     = protection_map[0];
 	args->is_contiguous_page = false;
 	args->pud_pfn            = ULONG_MAX;
 	args->pmd_pfn            = ULONG_MAX;
-- 
2.25.1