[syslinux] [PATCH] chain.c32: add menu support to grub loader

[Gert Hulselmans]

Paul Bolle wrote:
> Allow the grub loader to (optionally) support using a GRUB menu file.
> For example
>     chain fs grub=stage2,grub.conf
>
> will load GRUB's stage2 and pass the (absolute) path to the file
> "grub.conf" in the Syslinux filesystem to GRUB's stage2. The path is
> passed to stage2 in GRUB's device/partition syntax (eg, "(hd0,1)/foo").
> Note that we don't check whether the menu file actually exists in the
> Syslinux filesystem. GRUB will do the right thing if the file doesn't
> exist and will just fall back to its prompt.

> +	    if (path && opt.grubmenu) {
> +		char partition[5];	/* maximum is ",100" and up! */
> +		int len;
> +
> +		if (whichpart > 1)
> +		    sprintf(partition, ",%d", whichpart - 1);
> +		else
> +		    partition[0] = '\0';
> +		sprintf(path, "(%cd%d%s)/",
> +		        drive & 0x80 ? 'h': 'f',
> +		        (drive & 0x7),
> +			partition);
> +		len = strlen(path);
> +		strncpy (path + len, opt.grubmenu, 89 - len);
Why do you add (drivenumber,partition) to the config file name?

When the user adds the drivenumber and partition to its config filename
itself:
  chain.c32 hd0,3 grub=/boot/grub/stage2,(hd1,10)/anotherconf.lst

you get a "bad" configfilename: (hd0,2)/(hd1,10)/anotherconf.lst

In my patch, grub will search on the correct drive and partition
automatically, when you just use /anotherconf.lst.
GRUB just searches its config file on the drive (passed via DL) and
partition (install_partition). You don't need to add the right drive and
partition to the config filename yourself.

- Gert Hulselmans