[RFC PATCH v9 05/13] mm: add a user_virt_to_phys symbol

[Khalid Aziz <khalid.aziz@oracle.com>]

From: Tycho Andersen <tycho@tycho.ws>

We need someting like this for testing XPFO. Since it's architecture
specific, putting it in the test code is slightly awkward, so let's make it
an arch-specific symbol and export it for use in LKDTM.

CC: linux-arm-kernel@lists.infradead.org
CC: x86@kernel.org
Signed-off-by: Tycho Andersen <tycho@tycho.ws>
Tested-by: Marco Benatto <marco.antonio.780@gmail.com>
Signed-off-by: Khalid Aziz <khalid.aziz@oracle.com>
Cc: Khalid Aziz <khalid@gonehiking.org>
---
v7: * make user_virt_to_phys a GPL symbol

v6: * add a definition of user_virt_to_phys in the !CONFIG_XPFO case

 arch/x86/mm/xpfo.c   | 57 ++++++++++++++++++++++++++++++++++++++++++++
 include/linux/xpfo.h |  4 ++++
 2 files changed, 61 insertions(+)

diff --git a/arch/x86/mm/xpfo.c b/arch/x86/mm/xpfo.c
index 3045bb7e4659..b42513347865 100644
--- a/arch/x86/mm/xpfo.c
+++ b/arch/x86/mm/xpfo.c
@@ -121,3 +121,60 @@ inline void xpfo_flush_kernel_tlb(struct page *page, int order)
 	flush_tlb_kernel_range(kaddr, kaddr + (1 << order) * size);
 }
 EXPORT_SYMBOL_GPL(xpfo_flush_kernel_tlb);
+
+/* Convert a user space virtual address to a physical address.
+ * Shamelessly copied from slow_virt_to_phys() and lookup_address() in
+ * arch/x86/mm/pageattr.c
+ */
+phys_addr_t user_virt_to_phys(unsigned long addr)
+{
+	phys_addr_t phys_addr;
+	unsigned long offset;
+	pgd_t *pgd;
+	p4d_t *p4d;
+	pud_t *pud;
+	pmd_t *pmd;
+	pte_t *pte;
+
+	pgd = pgd_offset(current->mm, addr);
+	if (pgd_none(*pgd))
+		return 0;
+
+	p4d = p4d_offset(pgd, addr);
+	if (p4d_none(*p4d))
+		return 0;
+
+	if (p4d_large(*p4d) || !p4d_present(*p4d)) {
+		phys_addr = (unsigned long)p4d_pfn(*p4d) << PAGE_SHIFT;
+		offset = addr & ~P4D_MASK;
+		goto out;
+	}
+
+	pud = pud_offset(p4d, addr);
+	if (pud_none(*pud))
+		return 0;
+
+	if (pud_large(*pud) || !pud_present(*pud)) {
+		phys_addr = (unsigned long)pud_pfn(*pud) << PAGE_SHIFT;
+		offset = addr & ~PUD_MASK;
+		goto out;
+	}
+
+	pmd = pmd_offset(pud, addr);
+	if (pmd_none(*pmd))
+		return 0;
+
+	if (pmd_large(*pmd) || !pmd_present(*pmd)) {
+		phys_addr = (unsigned long)pmd_pfn(*pmd) << PAGE_SHIFT;
+		offset = addr & ~PMD_MASK;
+		goto out;
+	}
+
+	pte =  pte_offset_kernel(pmd, addr);
+	phys_addr = (phys_addr_t)pte_pfn(*pte) << PAGE_SHIFT;
+	offset = addr & ~PAGE_MASK;
+
+out:
+	return (phys_addr_t)(phys_addr | offset);
+}
+EXPORT_SYMBOL_GPL(user_virt_to_phys);
diff --git a/include/linux/xpfo.h b/include/linux/xpfo.h
index c1d232da7ee0..5d8d06e4b796 100644
--- a/include/linux/xpfo.h
+++ b/include/linux/xpfo.h
@@ -89,6 +89,8 @@ static inline void xpfo_kunmap(void *kaddr, struct page *page)
 void xpfo_alloc_pages(struct page *page, int order, gfp_t gfp, bool will_map);
 void xpfo_free_pages(struct page *page, int order);
 
+phys_addr_t user_virt_to_phys(unsigned long addr);
+
 #else /* !CONFIG_XPFO */
 
 static inline void xpfo_init_single_page(struct page *page) { }
@@ -102,6 +104,8 @@ static inline void xpfo_free_pages(struct page *page, int order) { }
 static inline void set_kpte(void *kaddr, struct page *page, pgprot_t prot) { }
 static inline void xpfo_flush_kernel_tlb(struct page *page, int order) { }
 
+static inline phys_addr_t user_virt_to_phys(unsigned long addr) { return 0; }
+
 #endif /* CONFIG_XPFO */
 
 #if (!defined(CONFIG_HIGHMEM)) && (!defined(ARCH_HAS_KMAP))
-- 
2.17.1