linux-hardening - [RFC PATCH 01/12] asm-generic/pgalloc: allow arch to override PMD alloc/free routines

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Date:   Wed, 26 Jan 2022 18:30:00 +0100
From:   Ard Biesheuvel <ardb@...nel.org>
To:     linux-arm-kernel@...ts.infradead.org
Cc:     kvmarm@...ts.cs.columbia.edu, linux-hardening@...r.kernel.org,
        Ard Biesheuvel <ardb@...nel.org>,
        Will Deacon <will@...nel.org>, Marc Zyngier <maz@...nel.org>,
        Fuad Tabba <tabba@...gle.com>,
        Quentin Perret <qperret@...gle.com>,
        Mark Rutland <mark.rutland@....com>,
        James Morse <james.morse@....com>,
        Catalin Marinas <catalin.marinas@....com>
Subject: [RFC PATCH 01/12] asm-generic/pgalloc: allow arch to override PMD alloc/free routines

Extend the existing CPP macro based hooks that allow architectures to
specialize the code that allocates and frees pages to be used as page
tables.

Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
---
 include/asm-generic/pgalloc.h | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/include/asm-generic/pgalloc.h b/include/asm-generic/pgalloc.h
index 977bea16cf1b..65f31f615d99 100644
--- a/include/asm-generic/pgalloc.h
+++ b/include/asm-generic/pgalloc.h
@@ -34,6 +34,7 @@ static inline pte_t *pte_alloc_one_kernel(struct mm_struct *mm)
 }
 #endif
 
+#ifndef __HAVE_ARCH_PTE_FREE_KERNEL
 /**
  * pte_free_kernel - free PTE-level kernel page table page
  * @mm: the mm_struct of the current context
@@ -43,6 +44,7 @@ static inline void pte_free_kernel(struct mm_struct *mm, pte_t *pte)
 {
 	free_page((unsigned long)pte);
 }
+#endif
 
 /**
  * __pte_alloc_one - allocate a page for PTE-level user page table
@@ -91,6 +93,7 @@ static inline pgtable_t pte_alloc_one(struct mm_struct *mm)
  * done with a reference count in struct page.
  */
 
+#ifndef __HAVE_ARCH_PTE_FREE
 /**
  * pte_free - free PTE-level user page table page
  * @mm: the mm_struct of the current context
@@ -101,11 +104,11 @@ static inline void pte_free(struct mm_struct *mm, struct page *pte_page)
 	pgtable_pte_page_dtor(pte_page);
 	__free_page(pte_page);
 }
+#endif
 
 
 #if CONFIG_PGTABLE_LEVELS > 2
 
-#ifndef __HAVE_ARCH_PMD_ALLOC_ONE
 /**
  * pmd_alloc_one - allocate a page for PMD-level page table
  * @mm: the mm_struct of the current context
@@ -116,7 +119,7 @@ static inline void pte_free(struct mm_struct *mm, struct page *pte_page)
  *
  * Return: pointer to the allocated memory or %NULL on error
  */
-static inline pmd_t *pmd_alloc_one(struct mm_struct *mm, unsigned long addr)
+static inline pmd_t *__pmd_alloc_one(struct mm_struct *mm, unsigned long addr)
 {
 	struct page *page;
 	gfp_t gfp = GFP_PGTABLE_USER;
@@ -132,6 +135,12 @@ static inline pmd_t *pmd_alloc_one(struct mm_struct *mm, unsigned long addr)
 	}
 	return (pmd_t *)page_address(page);
 }
+
+#ifndef __HAVE_ARCH_PMD_ALLOC_ONE
+static inline pmd_t *pmd_alloc_one(struct mm_struct *mm, unsigned long addr)
+{
+	return __pmd_alloc_one(mm, addr);
+}
 #endif
 
 #ifndef __HAVE_ARCH_PMD_FREE
-- 
2.30.2