[PATCHv3 09/11] arm64: Add page size to the kernel image header
mark.rutland at arm.com
Wed Oct 14 10:27:56 PDT 2015
On Wed, Oct 14, 2015 at 12:20:32PM +0100, Suzuki K. Poulose wrote:
> From: Ard Biesheuvel <ard.biesheuvel at linaro.org>
> 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 at linaro.org>
> Signed-off-by: Suzuki K. Poulose <suzuki.poulose at arm.com>
> Acked-by: Catalin Marinas <catalin.marinas at arm.com>
> Reviewed-by: Christoffer Dall <christoffer.dall at linaro.org>
> Documentation/arm64/booting.txt | 7 ++++++-
> arch/arm64/kernel/image.h | 5 ++++-
> 2 files changed, 10 insertions(+), 2 deletions(-)
> diff --git a/Documentation/arm64/booting.txt b/Documentation/arm64/booting.txt
> index 7d9d3c2..aaf6d77 100644
> --- 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 6eb8fee..e45759e 100644
> --- a/arch/arm64/kernel/image.h
> +++ b/arch/arm64/kernel/image.h
> @@ -47,7 +47,10 @@
> #define __HEAD_FLAG_BE 0
> -#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)
I'd prefer that we also had brackets around the whole of the
__HEAD_FLAGS value, so we don't get caught out later on by some
unexpected expansion (though we are safe currently).
Acked-by: Mark Rutland <mark.rutland at arm.com>
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