[PATCH 1/3] ARM: Split KERNEL_OFFSET from PAGE_OFFSET

[Linus Walleij]

We want to be able to compile the kernel into an address different
from PAGE_OFFSET (start of lowmem) + TEXT_OFFSET, so start to pry
apart the address of where the kernel is located from the address
where the lowmem is located by defining and using KERNEL_OFFSET in
a few key places.

Signed-off-by: Linus Walleij <linus.walleij at linaro.org>
---
 arch/arm/include/asm/memory.h | 8 +++++++-
 arch/arm/kernel/head.S        | 3 +--
 arch/arm/kernel/vmlinux.lds.S | 2 +-
 3 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/arch/arm/include/asm/memory.h b/arch/arm/include/asm/memory.h
index a711322d9f40..a5f1d1826a98 100644
--- a/arch/arm/include/asm/memory.h
+++ b/arch/arm/include/asm/memory.h
@@ -20,8 +20,14 @@
 #endif
 #include <asm/kasan_def.h>
 
-/* PAGE_OFFSET - the virtual address of the start of the kernel image */
+/*
+ * PAGE_OFFSET: the virtual address of the start of lowmem, memory above
+ *   the virtual address range for userspace.
+ * KERNEL_OFFSET: the virtual address of the start of the kernel image.
+ *   we may further offset this with TEXT_OFFSET in practice.
+ */
 #define PAGE_OFFSET		UL(CONFIG_PAGE_OFFSET)
+#define KERNEL_OFFSET		(PAGE_OFFSET)
 
 #ifdef CONFIG_MMU
 
diff --git a/arch/arm/kernel/head.S b/arch/arm/kernel/head.S
index 7f62c5eccdf3..4e2daaa7636a 100644
--- a/arch/arm/kernel/head.S
+++ b/arch/arm/kernel/head.S
@@ -23,7 +23,6 @@
 #if defined(CONFIG_DEBUG_LL) && !defined(CONFIG_DEBUG_SEMIHOSTING)
 #include CONFIG_DEBUG_LL_INCLUDE
 #endif
-
 /*
  * swapper_pg_dir is the virtual address of the initial page table.
  * We place the page tables 16K below KERNEL_RAM_VADDR.  Therefore, we must
@@ -31,7 +30,7 @@
  * the least significant 16 bits to be 0x8000, but we could probably
  * relax this restriction to KERNEL_RAM_VADDR >= PAGE_OFFSET + 0x4000.
  */
-#define KERNEL_RAM_VADDR	(PAGE_OFFSET + TEXT_OFFSET)
+#define KERNEL_RAM_VADDR	(KERNEL_OFFSET + TEXT_OFFSET)
 #if (KERNEL_RAM_VADDR & 0xffff) != 0x8000
 #error KERNEL_RAM_VADDR must start at 0xXXXX8000
 #endif
diff --git a/arch/arm/kernel/vmlinux.lds.S b/arch/arm/kernel/vmlinux.lds.S
index f7f4620d59c3..20c4f6d20c7a 100644
--- a/arch/arm/kernel/vmlinux.lds.S
+++ b/arch/arm/kernel/vmlinux.lds.S
@@ -47,7 +47,7 @@ SECTIONS
 #endif
 	}
 
-	. = PAGE_OFFSET + TEXT_OFFSET;
+	. = KERNEL_OFFSET + TEXT_OFFSET;
 	.head.text : {
 		_text = .;
 		HEAD_TEXT
-- 
2.31.1