linux-kernel - [RFC][PATCH 11/24] x86/pti: Function to clone page-table entries from a specified mm

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Message-Id: <20201109112319.264511-12-alexandre.chartre@oracle.com>
Date:   Mon,  9 Nov 2020 12:23:06 +0100
From:   Alexandre Chartre <alexandre.chartre@...cle.com>
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Subject: [RFC][PATCH 11/24] x86/pti: Function to clone page-table entries from a specified mm

PTI has a function to clone page-table entries but only from the
init_mm page-table. Provide a new function to clone page-table
entries from a specified mm page-table.

Signed-off-by: Alexandre Chartre <alexandre.chartre@...cle.com>
---
 arch/x86/include/asm/pti.h | 10 ++++++++++
 arch/x86/mm/pti.c          | 32 ++++++++++++++++----------------
 2 files changed, 26 insertions(+), 16 deletions(-)

diff --git a/arch/x86/include/asm/pti.h b/arch/x86/include/asm/pti.h
index 07375b476c4f..5484e69ff8d3 100644
--- a/arch/x86/include/asm/pti.h
+++ b/arch/x86/include/asm/pti.h
@@ -4,9 +4,19 @@
 #ifndef __ASSEMBLY__
 
 #ifdef CONFIG_PAGE_TABLE_ISOLATION
+
+enum pti_clone_level {
+	PTI_CLONE_PMD,
+	PTI_CLONE_PTE,
+};
+
+struct mm_struct;
+
 extern void pti_init(void);
 extern void pti_check_boottime_disable(void);
 extern void pti_finalize(void);
+extern void pti_clone_pgtable(struct mm_struct *mm, unsigned long start,
+			      unsigned long end, enum pti_clone_level level);
 #else
 static inline void pti_check_boottime_disable(void) { }
 #endif
diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c
index 1aab92930569..ebc8cd2f1cd8 100644
--- a/arch/x86/mm/pti.c
+++ b/arch/x86/mm/pti.c
@@ -294,14 +294,8 @@ static void __init pti_setup_vsyscall(void)
 static void __init pti_setup_vsyscall(void) { }
 #endif
 
-enum pti_clone_level {
-	PTI_CLONE_PMD,
-	PTI_CLONE_PTE,
-};
-
-static void
-pti_clone_pgtable(unsigned long start, unsigned long end,
-		  enum pti_clone_level level)
+void pti_clone_pgtable(struct mm_struct *mm, unsigned long start,
+		       unsigned long end, enum pti_clone_level level)
 {
 	unsigned long addr;
 
@@ -320,7 +314,7 @@ pti_clone_pgtable(unsigned long start, unsigned long end,
 		if (addr < start)
 			break;
 
-		pgd = pgd_offset_k(addr);
+		pgd = pgd_offset(mm, addr);
 		if (WARN_ON(pgd_none(*pgd)))
 			return;
 		p4d = p4d_offset(pgd, addr);
@@ -409,6 +403,12 @@ pti_clone_pgtable(unsigned long start, unsigned long end,
 	}
 }
 
+static void pti_clone_init_pgtable(unsigned long start, unsigned long end,
+				   enum pti_clone_level level)
+{
+	pti_clone_pgtable(&init_mm, start, end, level);
+}
+
 #ifdef CONFIG_X86_64
 /*
  * Clone a single p4d (i.e. a top-level entry on 4-level systems and a
@@ -476,7 +476,7 @@ static void __init pti_clone_user_shared(void)
 	start = CPU_ENTRY_AREA_BASE;
 	end   = start + (PAGE_SIZE * CPU_ENTRY_AREA_PAGES);
 
-	pti_clone_pgtable(start, end, PTI_CLONE_PMD);
+	pti_clone_init_pgtable(start, end, PTI_CLONE_PMD);
 }
 #endif /* CONFIG_X86_64 */
 
@@ -495,9 +495,9 @@ static void __init pti_setup_espfix64(void)
  */
 static void pti_clone_entry_text(void)
 {
-	pti_clone_pgtable((unsigned long) __entry_text_start,
-			  (unsigned long) __entry_text_end,
-			  PTI_CLONE_PMD);
+	pti_clone_init_pgtable((unsigned long) __entry_text_start,
+			       (unsigned long) __entry_text_end,
+			       PTI_CLONE_PMD);
 }
 
 /*
@@ -572,11 +572,11 @@ static void pti_clone_kernel_text(void)
 	 * pti_set_kernel_image_nonglobal() did to clear the
 	 * global bit.
 	 */
-	pti_clone_pgtable(start, end_clone, PTI_LEVEL_KERNEL_IMAGE);
+	pti_clone_init_pgtable(start, end_clone, PTI_LEVEL_KERNEL_IMAGE);
 
 	/*
-	 * pti_clone_pgtable() will set the global bit in any PMDs
-	 * that it clones, but we also need to get any PTEs in
+	 * pti_clone_init_pgtable() will set the global bit in any
+	 * PMDs that it clones, but we also need to get any PTEs in
 	 * the last level for areas that are not huge-page-aligned.
 	 */
 
-- 
2.18.4