[PATCH 2/6] arm64/mm: add create_pgd_mapping() to create private page tables

[Ard Biesheuvel]

For UEFI, we need to install the memory mappings used for Runtime Services
in a dedicated set of page tables. Add create_pgd_mapping(), which allows
us to allocate and install those page table entries early.
This also adds a 'map_xn' option, that creates regions with the PXN and
UXN bits set.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel at linaro.org>
---
 arch/arm64/include/asm/mmu.h |  3 +++
 arch/arm64/mm/mmu.c          | 28 ++++++++++++++++++++--------
 2 files changed, 23 insertions(+), 8 deletions(-)

diff --git a/arch/arm64/include/asm/mmu.h b/arch/arm64/include/asm/mmu.h
index c2f006c48bdb..bcf166043a8b 100644
--- a/arch/arm64/include/asm/mmu.h
+++ b/arch/arm64/include/asm/mmu.h
@@ -33,5 +33,8 @@ extern void __iomem *early_io_map(phys_addr_t phys, unsigned long virt);
 extern void init_mem_pgprot(void);
 /* create an identity mapping for memory (or io if map_io is true) */
 extern void create_id_mapping(phys_addr_t addr, phys_addr_t size, int map_io);
+extern void create_pgd_mapping(struct mm_struct *mm, phys_addr_t phys,
+			       unsigned long virt, phys_addr_t size,
+			       int map_io, int map_xn);
 
 #endif
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 7eaa6a8c8467..f7d17a5a1f56 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -157,7 +157,7 @@ static void __init alloc_init_pte(pmd_t *pmd, unsigned long addr,
 
 static void __init alloc_init_pmd(struct mm_struct *mm, pud_t *pud,
 				  unsigned long addr, unsigned long end,
-				  phys_addr_t phys, int map_io)
+				  phys_addr_t phys, int map_io, int map_xn)
 {
 	pmd_t *pmd;
 	unsigned long next;
@@ -167,6 +167,9 @@ static void __init alloc_init_pmd(struct mm_struct *mm, pud_t *pud,
 	if (map_io) {
 		prot_sect = PROT_SECT_DEVICE_nGnRE;
 		prot_pte = __pgprot(PROT_DEVICE_nGnRE);
+	} else if (map_xn) {
+		prot_sect = PROT_SECT_NORMAL;
+		prot_pte = PAGE_KERNEL;
 	} else {
 		prot_sect = PROT_SECT_NORMAL_EXEC;
 		prot_pte = PAGE_KERNEL_EXEC;
@@ -203,7 +206,7 @@ static void __init alloc_init_pmd(struct mm_struct *mm, pud_t *pud,
 
 static void __init alloc_init_pud(struct mm_struct *mm, pgd_t *pgd,
 				  unsigned long addr, unsigned long end,
-				  unsigned long phys, int map_io)
+				  unsigned long phys, int map_io, int map_xn)
 {
 	pud_t *pud;
 	unsigned long next;
@@ -221,7 +224,7 @@ static void __init alloc_init_pud(struct mm_struct *mm, pgd_t *pgd,
 		/*
 		 * For 4K granule only, attempt to put down a 1GB block
 		 */
-		if (!map_io && (PAGE_SHIFT == 12) &&
+		if (!map_io && !map_xn && (PAGE_SHIFT == 12) &&
 		    ((addr | next | phys) & ~PUD_MASK) == 0) {
 			pud_t old_pud = *pud;
 			set_pud(pud, __pud(phys | PROT_SECT_NORMAL_EXEC));
@@ -239,7 +242,8 @@ static void __init alloc_init_pud(struct mm_struct *mm, pgd_t *pgd,
 				flush_tlb_all();
 			}
 		} else {
-			alloc_init_pmd(mm, pud, addr, next, phys, map_io);
+			alloc_init_pmd(mm, pud, addr, next, phys, map_io,
+				       map_xn);
 		}
 		phys += next - addr;
 	} while (pud++, addr = next, addr != end);
@@ -251,7 +255,7 @@ static void __init alloc_init_pud(struct mm_struct *mm, pgd_t *pgd,
  */
 static void __init __create_mapping(struct mm_struct *mm, pgd_t *pgd,
 				    phys_addr_t phys, unsigned long virt,
-				    phys_addr_t size, int map_io)
+				    phys_addr_t size, int map_io, int map_xn)
 {
 	unsigned long addr, length, end, next;
 
@@ -261,7 +265,7 @@ static void __init __create_mapping(struct mm_struct *mm, pgd_t *pgd,
 	end = addr + length;
 	do {
 		next = pgd_addr_end(addr, end);
-		alloc_init_pud(mm, pgd, addr, next, phys, map_io);
+		alloc_init_pud(mm, pgd, addr, next, phys, map_io, map_xn);
 		phys += next - addr;
 	} while (pgd++, addr = next, addr != end);
 }
@@ -275,7 +279,7 @@ static void __init create_mapping(phys_addr_t phys, unsigned long virt,
 		return;
 	}
 	__create_mapping(&init_mm, pgd_offset_k(virt & PAGE_MASK), phys, virt,
-			 size, 0);
+			 size, 0, 0);
 }
 
 void __init create_id_mapping(phys_addr_t addr, phys_addr_t size, int map_io)
@@ -285,7 +289,15 @@ void __init create_id_mapping(phys_addr_t addr, phys_addr_t size, int map_io)
 		return;
 	}
 	__create_mapping(&init_mm, &idmap_pg_dir[pgd_index(addr)],
-			 addr, addr, size, map_io);
+			 addr, addr, size, map_io, 0);
+}
+
+void __init create_pgd_mapping(struct mm_struct *mm, phys_addr_t phys,
+			       unsigned long virt, phys_addr_t size,
+			       int map_io, int map_xn)
+{
+	__create_mapping(mm, pgd_offset(mm, virt), phys, virt, size, map_io,
+			 map_xn);
 }
 
 static void __init map_mem(void)
-- 
1.8.3.2