[PATCH 1/4] arm64: use tagged pointers to distinguish kernel text from the linear mapping

[ard.biesheuvel@linaro.org (Ard Biesheuvel)]

This enables tagged pointers for kernel addresses, and uses it to
tag statically allocated kernel objects. This allows us to use a
separate translation regime for kernel text in the next patch.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
 arch/arm64/include/asm/memory.h        | 20 +++++++++++++++++++-
 arch/arm64/include/asm/pgtable-hwdef.h |  1 +
 arch/arm64/kernel/vmlinux.lds.S        |  4 ++--
 arch/arm64/mm/mmu.c                    |  4 ++--
 arch/arm64/mm/proc.S                   |  3 ++-
 5 files changed, 26 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
index f800d45ea226..7dfe1b0c9c01 100644
--- a/arch/arm64/include/asm/memory.h
+++ b/arch/arm64/include/asm/memory.h
@@ -107,6 +107,10 @@
 #define MT_S2_NORMAL		0xf
 #define MT_S2_DEVICE_nGnRE	0x1
 
+#define __TEXT(x)	((x) & ~(UL(1) << 56))
+#define __VIRT(x)	((x) | (UL(1) << 56))
+#define __IS_TEXT(x)	(!((x) & (UL(1) << 56)))
+
 #ifndef __ASSEMBLY__
 
 extern phys_addr_t		memstart_addr;
@@ -141,9 +145,23 @@ static inline void *phys_to_virt(phys_addr_t x)
 }
 
 /*
+ * Return the physical address of a statically allocated object that
+ * is covered by the kernel Image mapping. We use tagged pointers to
+ * distinguish between the virtual linear and the virtual kimage range.
+ */
+static inline phys_addr_t __text_to_phys(unsigned long x)
+{
+	return __virt_to_phys(__VIRT(x));
+}
+
+/*
  * Drivers should NOT use these either.
  */
-#define __pa(x)			__virt_to_phys((unsigned long)(x))
+#define __pa(x)	({					\
+	unsigned long __x = (unsigned long)(x);		\
+	__IS_TEXT(__x) ? __text_to_phys(__x) :		\
+			 __virt_to_phys(__x); })
+
 #define __va(x)			((void *)__phys_to_virt((phys_addr_t)(x)))
 #define pfn_to_kaddr(pfn)	__va((pfn) << PAGE_SHIFT)
 #define virt_to_pfn(x)      __phys_to_pfn(__virt_to_phys(x))
diff --git a/arch/arm64/include/asm/pgtable-hwdef.h b/arch/arm64/include/asm/pgtable-hwdef.h
index 5f930cc9ea83..8bcec4e626b4 100644
--- a/arch/arm64/include/asm/pgtable-hwdef.h
+++ b/arch/arm64/include/asm/pgtable-hwdef.h
@@ -163,5 +163,6 @@
 #define TCR_TG1_64K		(UL(3) << 30)
 #define TCR_ASID16		(UL(1) << 36)
 #define TCR_TBI0		(UL(1) << 37)
+#define TCR_TBI1		(UL(1) << 38)
 
 #endif
diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S
index 5d9d2dca530d..434ef407ef0f 100644
--- a/arch/arm64/kernel/vmlinux.lds.S
+++ b/arch/arm64/kernel/vmlinux.lds.S
@@ -74,7 +74,7 @@ SECTIONS
 		*(.discard.*)
 	}
 
-	. = PAGE_OFFSET + TEXT_OFFSET;
+	. = __TEXT(PAGE_OFFSET) + TEXT_OFFSET;
 
 	.head.text : {
 		_text = .;
@@ -171,4 +171,4 @@ ASSERT(((__hyp_idmap_text_start + PAGE_SIZE) > __hyp_idmap_text_end),
 /*
  * If padding is applied before .head.text, virt<->phys conversions will fail.
  */
-ASSERT(_text == (PAGE_OFFSET + TEXT_OFFSET), "HEAD is misaligned")
+ASSERT(_text == (__TEXT(PAGE_OFFSET) + TEXT_OFFSET), "HEAD is misaligned")
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index c9267acb699c..43496748e3d9 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -267,7 +267,7 @@ static void *late_alloc(unsigned long size)
 static void __ref create_mapping(phys_addr_t phys, unsigned long virt,
 				  phys_addr_t size, pgprot_t prot)
 {
-	if (virt < VMALLOC_START) {
+	if (__VIRT(virt) < VMALLOC_START) {
 		pr_warn("BUG: not creating mapping for %pa at 0x%016lx - outside kernel range\n",
 			&phys, virt);
 		return;
@@ -287,7 +287,7 @@ void __init create_pgd_mapping(struct mm_struct *mm, phys_addr_t phys,
 static void create_mapping_late(phys_addr_t phys, unsigned long virt,
 				  phys_addr_t size, pgprot_t prot)
 {
-	if (virt < VMALLOC_START) {
+	if (__VIRT(virt) < VMALLOC_START) {
 		pr_warn("BUG: not creating mapping for %pa@0x%016lx - outside kernel range\n",
 			&phys, virt);
 		return;
diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S
index 28eebfb6af76..7f2d7f73bc93 100644
--- a/arch/arm64/mm/proc.S
+++ b/arch/arm64/mm/proc.S
@@ -232,7 +232,8 @@ ENTRY(__cpu_setup)
 	 * both user and kernel.
 	 */
 	ldr	x10, =TCR_TxSZ(VA_BITS) | TCR_CACHE_FLAGS | TCR_SMP_FLAGS | \
-			TCR_TG_FLAGS | TCR_ASID16 | TCR_TBI0
+			TCR_TG_FLAGS | TCR_ASID16 | TCR_TBI0 | TCR_TBI1
+
 	/*
 	 * Read the PARange bits from ID_AA64MMFR0_EL1 and set the IPS bits in
 	 * TCR_EL1.
-- 
1.8.3.2