Re: [PATCH] Fix initramfs size calculation

Sam Ravnborg
2010-08-25T18:06:08Z

On Wed, Aug 25, 2010 at 05:57:12PM +0200, Michael Holzheu wrote:
> The size of a built-in initramfs is calculated in init/initramfs.c by
> "__initramfs_end - __initramfs_start". Those symbols are defined in the
> linker script include/asm-generic/vmlinux.lds.h:
>
> #define INIT_RAM_FS \
> . = ALIGN(PAGE_SIZE); \
> VMLINUX_SYMBOL(__initramfs_start) = .; \
> *(.init.ramfs) \
> VMLINUX_SYMBOL(__initramfs_end) = .;
>
> If the initramfs file has an odd number of bytes, the "__initramfs_end"
> symbol points to an odd address, for example, the symbols in the System.map
> might look like:
>
> 0000000000572000 T __initramfs_start
> 00000000005bcd05 T __initramfs_end <-- odd address
>
> At least on s390 this is a problem:

Another way to fix this could be to align . to an even
address like this:
> #define INIT_RAM_FS \
> . = ALIGN(PAGE_SIZE); \
> VMLINUX_SYMBOL(__initramfs_start) = .; \
> *(.init.ramfs) \
. = ALIGN(32); \
> VMLINUX_SYMBOL(__initramfs_end) = .;
>

32 was selected as this is what we will introduce as the default
alignment in linker scripts anyway.

This I guess is a problem we have had some time and a minimal fix is
easier to have backported by the stable team.

> The patch also restructures the "usr/initramfs_data.xxx.S" files to use a
> common macro that includes the (compressed) initramfs file and calculates
> the __initramfs_size.
I like this anyway. Could you do this as a separate patch?

Sam