arm64: Add page size to the kernel image header

This patch adds the page size to the arm64 kernel image header
so that one can infer the PAGESIZE used by the kernel. This will
be helpful to diagnose failures to boot the kernel with page size
not supported by the CPU.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Suzuki K. Poulose <suzuki.poulose@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

diff --git a/Documentation/arm64/booting.txt b/Documentation/arm64/booting.txt
index 7d9d3c2286b282d96f03cd1545be5780e998002e..aaf6d77e4148d63b6ffa514334f9dfd8f0a9c4ac 100644 (file)
--- a/Documentation/arm64/booting.txt
+++ b/Documentation/arm64/booting.txt
@@ -104,7 +104,12 @@ Header notes:
 - The flags field (introduced in v3.17) is a little-endian 64-bit field
   composed as follows:
   Bit 0:       Kernel endianness.  1 if BE, 0 if LE.
-  Bits 1-63:   Reserved.
+  Bit 1-2:     Kernel Page size.
+                       0 - Unspecified.
+                       1 - 4K
+                       2 - 16K
+                       3 - 64K
+  Bits 3-63:   Reserved.
 
 - When image_size is zero, a bootloader should attempt to keep as much
   memory as possible free for use by the kernel immediately after the

diff --git a/arch/arm64/kernel/image.h b/arch/arm64/kernel/image.h
index 6eb8fee93321ae3fa43a33e6612771b1fa27aba8..bc2abb8b1599576ae2dec02bce0c46c48fc707dd 100644 (file)
--- a/arch/arm64/kernel/image.h
+++ b/arch/arm64/kernel/image.h
@@ -47,7 +47,10 @@
 #define __HEAD_FLAG_BE 0
 #endif
 
-#define __HEAD_FLAGS   (__HEAD_FLAG_BE << 0)
+#define __HEAD_FLAG_PAGE_SIZE ((PAGE_SHIFT - 10) / 2)
+
+#define __HEAD_FLAGS   ((__HEAD_FLAG_BE << 0) |        \
+                        (__HEAD_FLAG_PAGE_SIZE << 1))
 
 /*
  * These will output as part of the Image header, which should be little-endian