linux-kernel - [PATCH 2/5] add get_pte(): helper function: fetching pte for va

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Date:	Mon, 20 Apr 2009 04:36:03 +0300
From:	Izik Eidus <ieidus@...hat.com>
To:	akpm@...ux-foundation.org
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	kvm@...r.kernel.org, avi@...hat.com, aarcange@...hat.com,
	chrisw@...hat.com, mtosatti@...hat.com, hugh@...itas.com,
	Izik Eidus <ieidus@...hat.com>
Subject: [PATCH 2/5] add get_pte(): helper function: fetching pte for va

get_pte() receive mm_struct of a task, and a virtual address and return
the pte corresponding to it.

this function return NULL in case it couldnt fetch the pte.

Signed-off-by: Izik Eidus <ieidus@...hat.com>
---
 include/linux/mm.h |   24 ++++++++++++++++++++++++
 1 files changed, 24 insertions(+), 0 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index bff1f0d..9a34109 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -894,6 +894,30 @@ int vma_wants_writenotify(struct vm_area_struct *vma);
 
 extern pte_t *get_locked_pte(struct mm_struct *mm, unsigned long addr, spinlock_t **ptl);
 
+static inline pte_t *get_pte(struct mm_struct *mm, unsigned long addr)
+{
+	pgd_t *pgd;
+	pud_t *pud;
+	pmd_t *pmd;
+	pte_t *ptep = NULL;
+
+	pgd = pgd_offset(mm, addr);
+	if (!pgd_present(*pgd))
+		goto out;
+
+	pud = pud_offset(pgd, addr);
+	if (!pud_present(*pud))
+		goto out;
+
+	pmd = pmd_offset(pud, addr);
+	if (!pmd_present(*pmd))
+		goto out;
+
+	ptep = pte_offset_map(pmd, addr);
+out:
+	return ptep;
+}
+
 #ifdef __PAGETABLE_PUD_FOLDED
 static inline int __pud_alloc(struct mm_struct *mm, pgd_t *pgd,
 						unsigned long address)
-- 
1.5.6.5

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