[RFC PATCH 1/3] arm64: head.S: replace early literals with constant immediates

[Ard Biesheuvel]

In preparation of making the kernel relocatable, replace literal
symbol references with immediate constants. This is necessary, as
the literals will not be populated with meaningful values until
after the relocation code has executed.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel at linaro.org>
---
 arch/arm64/kernel/efi-entry.S |  2 +-
 arch/arm64/kernel/head.S      | 36 +++++++++++++++---------------------
 2 files changed, 16 insertions(+), 22 deletions(-)

diff --git a/arch/arm64/kernel/efi-entry.S b/arch/arm64/kernel/efi-entry.S
index 8ce9b0577442..f78e6a1de825 100644
--- a/arch/arm64/kernel/efi-entry.S
+++ b/arch/arm64/kernel/efi-entry.S
@@ -61,7 +61,7 @@ ENTRY(efi_stub_entry)
 	 */
 	mov	x20, x0		// DTB address
 	ldr	x0, [sp, #16]	// relocated _text address
-	ldr	x21, =stext_offset
+	movz	x21, #:abs_g0:stext_offset
 	add	x21, x0, x21
 
 	/*
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 9c856f2aa7a5..1ea3cd2aba34 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -46,11 +46,9 @@
 #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
+	.macro	pgtbl, ttb0, ttb1
+	adrp	\ttb1, swapper_pg_dir
+	adrp	\ttb0, idmap_pg_dir
 	.endm
 
 #ifdef CONFIG_ARM64_64K_PAGES
@@ -63,7 +61,7 @@
 #define TABLE_SHIFT	PUD_SHIFT
 #endif
 
-#define KERNEL_START	KERNEL_RAM_VADDR
+#define KERNEL_START	_text
 #define KERNEL_END	_end
 
 /*
@@ -322,7 +320,7 @@ ENDPROC(stext)
  *     been enabled
  */
 __create_page_tables:
-	pgtbl	x25, x26, x28			// idmap_pg_dir and swapper_pg_dir addresses
+	pgtbl	x25, x26			// idmap_pg_dir and swapper_pg_dir addresses
 	mov	x27, lr
 
 	/*
@@ -351,8 +349,7 @@ __create_page_tables:
 	 * Create the identity mapping.
 	 */
 	mov	x0, x25				// idmap_pg_dir
-	ldr	x3, =KERNEL_START
-	add	x3, x3, x28			// __pa(KERNEL_START)
+	adr_l	x3, KERNEL_START		// __pa(KERNEL_START)
 
 #ifndef CONFIG_ARM64_VA_BITS_48
 #define EXTRA_SHIFT	(PGDIR_SHIFT + PAGE_SHIFT - 3)
@@ -391,9 +388,8 @@ __create_page_tables:
 #endif
 
 	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
 
 	/*
@@ -402,8 +398,10 @@ __create_page_tables:
 	mov	x0, x26				// swapper_pg_dir
 	mov	x5, #PAGE_OFFSET
 	create_pgd_entry x0, x5, x3, x6
-	ldr	x6, =KERNEL_END
+	adr_l	x6, KERNEL_END
 	mov	x3, x24				// phys offset
+	sub	x6, x6, x3			// kernel memsize
+	add	x6, x6, x5			// __va(KERNEL_END)
 	create_block_map x0, x7, x3, x5, x6
 
 	/*
@@ -538,8 +536,7 @@ 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		// Compute __boot_cpu_mode
 	cmp	w20, #BOOT_CPU_MODE_EL2
 	b.ne	1f
 	add	x1, x1, #4
@@ -598,7 +595,7 @@ ENTRY(secondary_startup)
 	/*
 	 * Common entry point for secondary CPUs.
 	 */
-	pgtbl	x25, x26, x28			// x25=TTBR0, x26=TTBR1
+	pgtbl	x25, x26			// x25=TTBR0, x26=TTBR1
 	bl	__cpu_setup			// initialise processor
 
 	ldr	x21, =secondary_data
@@ -655,17 +652,14 @@ ENDPROC(__turn_mmu_on)
  * Calculate the start of physical memory.
  */
 __calc_phys_offset:
-	adr	x0, 1f
-	ldp	x1, x2, [x0]
+	adrp	x0, KERNEL_START		// __pa(KERNEL_START)
+	ldr	x1, =KERNEL_RAM_VADDR		// __va(KERNEL_START)
+	mov	x2, PAGE_OFFSET
 	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
-
 /*
  * Exception handling. Something went wrong and we can't proceed. We ought to
  * tell the user, but since we don't have any guarantee that we're even
-- 
1.8.3.2