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[PATCHv3 09/11] arm64: Add page size to the kernel image header

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  [PATCHv3 09/11] arm64: Add page size to the kernel image header "Suzuki K. Poulose" <suzuki.poulose@arm.com> - 2015-10-14 13:30 +0200
    Re: [PATCHv3 09/11] arm64: Add page size to the kernel image header Mark Rutland <mark.rutland@arm.com> - 2015-10-14 19:30 +0200
      Re: [PATCHv3 09/11] arm64: Add page size to the kernel image header "Suzuki K. Poulose" <Suzuki.Poulose@arm.com> - 2015-10-15 11:20 +0200

#1246545 — [PATCHv3 09/11] arm64: Add page size to the kernel image header

From: Ard Biesheuvel <ard.biesheuvel@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@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>
---
 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
 #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
-- 
1.7.9.5

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#1247019

On Wed, Oct 14, 2015 at 12:20:32PM +0100, Suzuki K. Poulose wrote:
> From: Ard Biesheuvel <ard.biesheuvel@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@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>
> ---
>  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
>  #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)

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).

With that:

Acked-by: Mark Rutland <mark.rutland@arm.com>

Thanks,
Mark.
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#1247601

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@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@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>
>> ---
>>   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
>>   #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)
>
> 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@arm.com>

Thanks
Suzuki

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