linux-kernel - Re: [PATCH 1/2] vmlinux.lds.h: allow people to set a smaller rootfs alignment

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Date:	Wed, 09 Jun 2010 02:20:30 -0500
From:	Milton Miller <miltonm@....com>
To:	Mike Frysinger <vapier@...too.org>
Cc:	<linux-kernel@...r.kernel.org>, Tim Abbott <tabbott@...lice.com>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH 1/2] vmlinux.lds.h: allow people to set a smaller rootfs
	alignment


On Sat,  5 Jun 2010 at around 14:14:45 -0400, Mike Frysinger wrote:
> Add a new INIT_RAMFS() define to compliment the existing INIT_RAM_FS, but
> this one lets people control the alignment.
> 
> diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
> index 48c5299..9ca268f 100644
> --- a/include/asm-generic/vmlinux.lds.h
> +++ b/include/asm-generic/vmlinux.lds.h
> @@ -619,14 +619,15 @@ 
>  		VMLINUX_SYMBOL(__security_initcall_end) = .;
>  
>  #ifdef CONFIG_BLK_DEV_INITRD
> -#define INIT_RAM_FS							\
> -	. = ALIGN(PAGE_SIZE);						\
> +#define INIT_RAMFS(align)						\
> +	. = ALIGN(align);						\
>  	VMLINUX_SYMBOL(__initramfs_start) = .;				\
>  	*(.init.ramfs)							\
>  	VMLINUX_SYMBOL(__initramfs_end) = .;
>  #else
> -#define INIT_RAM_FS
> +#define INIT_RAMFS(align)
>  #endif
> +#define INIT_RAM_FS INIT_RAMFS(PAGE_SIZE)
>  

[ and patch 2/2 calls the new macro with align 4, for only blackfin ].

Mike,
As you identified, the alignment for the __initramfs is too large.

As can be seen by the grammer of the INIT_RAM_FS in [1], the section
itself always requires alignment of exactly 4 [2].

I realize it requires a bit more auditing and cordination, but we
should really just change the macro to align to 4.

[1] Documentation/early-userspace/buffer-format.txt,
[2] for the general case; as compressed fragments are aligin(1)

milton
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