[PATCHv3 09/11] arm64: Add page size to the kernel image header
Suzuki K. Poulose
Suzuki.Poulose at arm.com
Thu Oct 15 02:19:13 PDT 2015
On 14/10/15 18:27, Mark Rutland wrote:
> 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).
Sure, will add that.
> With that:
> Acked-by: Mark Rutland <mark.rutland at arm.com>
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