Re: [syslinux] Using memdisk with grub2 and a gzip-compressed ISO

[Andrei Borzenkov <arvidjaar@gmail.com>]

В Thu, 23 Apr 2015 20:30:09 -0700
"H. Peter Anvin" <hpa@zytor.com> пишет:

> On 04/23/2015 08:14 PM, Andrei Borzenkov wrote:
> > В Thu, 23 Apr 2015 15:17:02 -0700
> > "H. Peter Anvin" <hpa@zytor.com> пишет:
> > 
> >> On 04/23/2015 07:23 AM, David Shaw via Syslinux wrote:
> >>>
> >>> I'm not sure if this is related to the problem, but note the length
> >>> in the "Ramdisk" line from grub legacy is one byte shorter than the
> >>> length from grub2.  Also note that the length given in the "gzip
> >>> image" line is shifted one byte to the left in the grub legacy
> >>> version (i.e. it's exactly 0x100 times larger).
> >>>
> >>
> >> That would definitely break using a compressed ramdisk.
> > 
> > It does not break for kernel. What makes is so different in case of
> > syslinux?
> > 
> 
> Padding the image doesn't matter for the kernel, but memdisk relies on
> being able to see where the end of the compressed image is, because that
> is where the length is located.

CRC+length (in case of gzip) are located immediately after compressed
stream. After stream is decompressed you get location where it ends and
automatically where length is located.