[RFC][PATCH v2 09/21] x86/pti: Function to clone page-table entries from a specified mm

Alexandre Chartre
2020-11-16T14:49:28Z

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@oracle.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