[syslinux] Using memdisk with grub2 and a compressed iso

[David Shaw]

Hello,

I'm having a problem booting a compressed ISO image using memdisk via grub2 (version 2.02).  The entry in my grub.cfg looks like:

menuentry 'boot ISO image' {
    linux16 /memdisk iso
    initrd16 /my-image.iso.gz
  }

When selected, this starts to boot and then fails with:

   Ramdisk at 0x37979000, length 0x0033b298
   gzip image: decompressed addr 0x7f7f7000, len 0x00008f58: failed
   Decompression error: output buffer overrun

FWIW, my-image.iso.gz is 3388055 bytes long compressed, and 9394176 bytes long uncompressed.  The box in question has 8GiB of RAM.

1) I have tried this with memdisk from syslinux 4.02, 4.05, and 6.03.  Same failure each time.
2) Changing the level of compression (i.e. gzip -1 instead of gzip -9) does not make it work.
3) Doing the same thing with grub1 (version 0.97), but using the same image and same version of memdisk, *does* work.
4) Uncompressing the ISO *does* make it work.

Any suggestions on where to look next?

David