[PATCH 2/3] arm64: remove __calc_phys_offset

[Ard Biesheuvel]

This removes the function __calc_phys_offset and all open coded
virtual to physical address translations using the offset kept
in x28.

Instead, just use absolute or PC-relative symbol references as
appropriate when referring to virtual or physical addresses,
respectively.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel at linaro.org>
---
 arch/arm64/kernel/head.S | 49 ++++++++++++------------------------------------
 1 file changed, 12 insertions(+), 37 deletions(-)

diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index fb912314d5e1..1651c0fd50e6 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -36,8 +36,6 @@
 #include <asm/page.h>
 #include <asm/virt.h>
 
-#define KERNEL_RAM_VADDR	(PAGE_OFFSET + TEXT_OFFSET)
-
 #if (TEXT_OFFSET & 0xfff) != 0
 #error TEXT_OFFSET must be at least 4KB aligned
 #elif (PAGE_OFFSET & 0x1fffff) != 0
@@ -46,13 +44,6 @@
 #error TEXT_OFFSET must be less than 2MB
 #endif
 
-	.macro	pgtbl, ttb0, ttb1, virt_to_phys
-	ldr	\ttb1, =swapper_pg_dir
-	ldr	\ttb0, =idmap_pg_dir
-	add	\ttb1, \ttb1, \virt_to_phys
-	add	\ttb0, \ttb0, \virt_to_phys
-	.endm
-
 #ifdef CONFIG_ARM64_64K_PAGES
 #define BLOCK_SHIFT	PAGE_SHIFT
 #define BLOCK_SIZE	PAGE_SIZE
@@ -63,7 +54,7 @@
 #define TABLE_SHIFT	PUD_SHIFT
 #endif
 
-#define KERNEL_START	KERNEL_RAM_VADDR
+#define KERNEL_START	_text
 #define KERNEL_END	_end
 
 /*
@@ -242,7 +233,7 @@ section_table:
 ENTRY(stext)
 	mov	x21, x0				// x21=FDT
 	bl	el2_setup			// Drop to EL1, w20=cpu_boot_mode
-	bl	__calc_phys_offset		// x24=PHYS_OFFSET, x28=PHYS_OFFSET-PAGE_OFFSET
+	adrp	x24, KERNEL_START - TEXT_OFFSET	// x24=PHYS_OFFSET
 	bl	set_cpu_boot_mode_flag
 
 	bl	__vet_fdt
@@ -343,7 +334,8 @@ ENDPROC(__vet_fdt)
  *   - pgd entry for fixed mappings (TTBR1)
  */
 __create_page_tables:
-	pgtbl	x25, x26, x28			// idmap_pg_dir and swapper_pg_dir addresses
+	adrp    x25, idmap_pg_dir
+	adrp    x26, swapper_pg_dir
 	mov	x27, lr
 
 	/*
@@ -372,12 +364,10 @@ __create_page_tables:
 	 * Create the identity mapping.
 	 */
 	mov	x0, x25				// idmap_pg_dir
-	ldr	x3, =KERNEL_START
-	add	x3, x3, x28			// __pa(KERNEL_START)
+	adrp	x3, KERNEL_START		// __pa(KERNEL_START)
 	create_pgd_entry x0, x3, x5, x6
-	ldr	x6, =KERNEL_END
 	mov	x5, x3				// __pa(KERNEL_START)
-	add	x6, x6, x28			// __pa(KERNEL_END)
+	adr_l	x6, KERNEL_END			// __pa(KERNEL_END)
 	create_block_map x0, x7, x3, x5, x6
 
 	/*
@@ -386,7 +376,7 @@ __create_page_tables:
 	mov	x0, x26				// swapper_pg_dir
 	mov	x5, #PAGE_OFFSET
 	create_pgd_entry x0, x5, x3, x6
-	ldr	x6, =KERNEL_END
+	ldr	x6, =KERNEL_END			// __va(KERNEL_END)
 	mov	x3, x24				// phys offset
 	create_block_map x0, x7, x3, x5, x6
 
@@ -538,8 +528,7 @@ ENDPROC(el2_setup)
  * in x20. See arch/arm64/include/asm/virt.h for more info.
  */
 ENTRY(set_cpu_boot_mode_flag)
-	ldr	x1, =__boot_cpu_mode		// Compute __boot_cpu_mode
-	add	x1, x1, x28
+	adr_l	x1, __boot_cpu_mode
 	cmp	w20, #BOOT_CPU_MODE_EL2
 	b.ne	1f
 	add	x1, x1, #4
@@ -570,7 +559,7 @@ ENTRY(__boot_cpu_mode)
 	 */
 ENTRY(secondary_holding_pen)
 	bl	el2_setup			// Drop to EL1, w20=cpu_boot_mode
-	bl	__calc_phys_offset		// x24=PHYS_OFFSET, x28=PHYS_OFFSET-PAGE_OFFSET
+	adrp	x24, KERNEL_START - TEXT_OFFSET	// x24=PHYS_OFFSET
 	bl	set_cpu_boot_mode_flag
 	mrs	x0, mpidr_el1
 	ldr     x1, =MPIDR_HWID_BITMASK
@@ -589,7 +578,7 @@ ENDPROC(secondary_holding_pen)
 	 */
 ENTRY(secondary_entry)
 	bl	el2_setup			// Drop to EL1
-	bl	__calc_phys_offset		// x24=PHYS_OFFSET, x28=PHYS_OFFSET-PAGE_OFFSET
+	adrp	x24, KERNEL_START - TEXT_OFFSET	// x24=PHYS_OFFSET
 	bl	set_cpu_boot_mode_flag
 	b	secondary_startup
 ENDPROC(secondary_entry)
@@ -598,7 +587,8 @@ ENTRY(secondary_startup)
 	/*
 	 * Common entry point for secondary CPUs.
 	 */
-	pgtbl	x25, x26, x28			// x25=TTBR0, x26=TTBR1
+	adrp    x25, idmap_pg_dir
+	adrp    x26, swapper_pg_dir
 	bl	__cpu_setup			// initialise processor
 
 	ldr	x21, =secondary_data
@@ -636,18 +626,3 @@ __enable_mmu:
 	isb
 	br	x27
 ENDPROC(__enable_mmu)
-
-/*
- * Calculate the start of physical memory.
- */
-__calc_phys_offset:
-	adr	x0, 1f
-	ldp	x1, x2, [x0]
-	sub	x28, x0, x1			// x28 = PHYS_OFFSET - PAGE_OFFSET
-	add	x24, x2, x28			// x24 = PHYS_OFFSET
-	ret
-ENDPROC(__calc_phys_offset)
-
-	.align 3
-1:	.quad	.
-	.quad	PAGE_OFFSET
-- 
1.8.3.2