linux-kernel - [PATCH] arm64/mm: Simplify protection flag creation for kernel huge mappings

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Date:   Mon, 27 May 2019 09:28:15 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc:     Anshuman Khandual <anshuman.khandual@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Mark Rutland <mark.rutland@....com>
Subject: [PATCH] arm64/mm: Simplify protection flag creation for kernel huge mappings

Even though they have got the same value, PMD_TYPE_SECT and PUD_TYPE_SECT
get used for kernel huge mappings. But before that first the table bit gets
cleared using leaf level PTE_TABLE_BIT. Though functionally they are same,
we should use page table level specific macros to be consistent as per the
MMU specifications. Create page table level specific wrappers for kernel
huge mapping entries and just drop mk_sect_prot() which does not have any
other user.

Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
Cc: Catalin Marinas <catalin.marinas@....com>
Cc: Will Deacon <will.deacon@....com>
Cc: Mark Rutland <mark.rutland@....com>
---
 arch/arm64/include/asm/pgtable.h | 9 +++++++--
 arch/arm64/mm/mmu.c              | 8 ++------
 2 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index 2c41b04708fe..6478dd121228 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -335,9 +335,14 @@ static inline pmd_t pte_pmd(pte_t pte)
 	return __pmd(pte_val(pte));
 }
 
-static inline pgprot_t mk_sect_prot(pgprot_t prot)
+static inline pgprot_t mk_pud_sect_prot(pgprot_t prot)
 {
-	return __pgprot(pgprot_val(prot) & ~PTE_TABLE_BIT);
+	return __pgprot((pgprot_val(prot) & ~PUD_TABLE_BIT) | PUD_TYPE_SECT);
+}
+
+static inline pgprot_t mk_pmd_sect_prot(pgprot_t prot)
+{
+	return __pgprot((pgprot_val(prot) & ~PMD_TABLE_BIT) | PMD_TYPE_SECT);
 }
 
 #ifdef CONFIG_NUMA_BALANCING
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index a1bfc4413982..22c2e4f0768f 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -971,9 +971,7 @@ int __init arch_ioremap_pmd_supported(void)
 
 int pud_set_huge(pud_t *pudp, phys_addr_t phys, pgprot_t prot)
 {
-	pgprot_t sect_prot = __pgprot(PUD_TYPE_SECT |
-					pgprot_val(mk_sect_prot(prot)));
-	pud_t new_pud = pfn_pud(__phys_to_pfn(phys), sect_prot);
+	pud_t new_pud = pfn_pud(__phys_to_pfn(phys), mk_pud_sect_prot(prot));
 
 	/* Only allow permission changes for now */
 	if (!pgattr_change_is_safe(READ_ONCE(pud_val(*pudp)),
@@ -987,9 +985,7 @@ int pud_set_huge(pud_t *pudp, phys_addr_t phys, pgprot_t prot)
 
 int pmd_set_huge(pmd_t *pmdp, phys_addr_t phys, pgprot_t prot)
 {
-	pgprot_t sect_prot = __pgprot(PMD_TYPE_SECT |
-					pgprot_val(mk_sect_prot(prot)));
-	pmd_t new_pmd = pfn_pmd(__phys_to_pfn(phys), sect_prot);
+	pmd_t new_pmd = pfn_pmd(__phys_to_pfn(phys), mk_pmd_sect_prot(prot));
 
 	/* Only allow permission changes for now */
 	if (!pgattr_change_is_safe(READ_ONCE(pmd_val(*pmdp)),
-- 
2.20.1