[kernel-hardening] [PATCH v7 3/9] x86/mm: PUD VA support for physical mapping (x86_64)

[Kees Cook <keescook@chromium.org>]

From: Thomas Garnier <thgarnie@google.com>

Minor change that allows early boot physical mapping of PUD level virtual
addresses. The current implementation expects the virtual address to be
PUD aligned. For KASLR memory randomization, we need to be able to
randomize the offset used on the PUD table.

It has no impact on current usage.

Signed-off-by: Thomas Garnier <thgarnie@google.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 arch/x86/mm/init_64.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 6714712bd5da..7bf1ddb54537 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -465,7 +465,8 @@ phys_pmd_init(pmd_t *pmd_page, unsigned long paddr, unsigned long paddr_end,
 
 /*
  * Create PUD level page table mapping for physical addresses. The virtual
- * and physical address have to be aligned at this level.
+ * and physical address do not have to be aligned at this level. KASLR can
+ * randomize virtual addresses up to this level.
  * It returns the last physical address mapped.
  */
 static unsigned long __meminit
@@ -474,14 +475,18 @@ phys_pud_init(pud_t *pud_page, unsigned long paddr, unsigned long paddr_end,
 {
 	unsigned long pages = 0, paddr_next;
 	unsigned long paddr_last = paddr_end;
-	int i = pud_index(paddr);
+	unsigned long vaddr = (unsigned long)__va(paddr);
+	int i = pud_index(vaddr);
 
 	for (; i < PTRS_PER_PUD; i++, paddr = paddr_next) {
-		pud_t *pud = pud_page + pud_index(paddr);
+		pud_t *pud;
 		pmd_t *pmd;
 		pgprot_t prot = PAGE_KERNEL;
 
+		vaddr = (unsigned long)__va(paddr);
+		pud = pud_page + pud_index(vaddr);
 		paddr_next = (paddr & PUD_MASK) + PUD_SIZE;
+
 		if (paddr >= paddr_end) {
 			if (!after_bootmem &&
 			    !e820_any_mapped(paddr & PUD_MASK, paddr_next,
@@ -551,7 +556,7 @@ phys_pud_init(pud_t *pud_page, unsigned long paddr, unsigned long paddr_end,
 
 /*
  * Create page table mapping for the physical memory for specific physical
- * addresses. The virtual and physical addresses have to be aligned on PUD level
+ * addresses. The virtual and physical addresses have to be aligned on PMD level
  * down. It returns the last physical address mapped.
  */
 unsigned long __meminit
-- 
2.7.4