[OpenBIOS] [PATCH] ppc: add Apple copyright hack to Adler-32

[Mark Cave-Ayland]

On 10/06/15 00:21, Cormac O'Brien wrote:

> This patch modifies the adler32 word to set an Apple copyright string in the
> device tree in order to allow Mac OS 9 to boot.

I think it's worth mentioning something here along the lines of "Since
OS 9 checks the copyright string on boot and the OS 9 bootloader is one
of the only users of adler32, use this word as a convenient injection
point for a fake copyright message which is enough to fool OS 9 into
booting". It's really just nit-picking on clarifying the message in the
source below.

> Signed-off-by: Cormac O'Brien <i.am.cormac.obrien at gmail.com>
> 
> ---
>  arch/ppc/qemu/init.c  |  2 +-
>  arch/ppc/qemu/qemu.fs | 28 ++++++++++++++++++++++++++++
>  2 files changed, 29 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/ppc/qemu/init.c b/arch/ppc/qemu/init.c
> index d31b8ba..a5073a3 100644
> --- a/arch/ppc/qemu/init.c
> +++ b/arch/ppc/qemu/init.c
> @@ -1003,7 +1003,7 @@ arch_of_init(void)
>      /* Implementation of filll word (required by BootX) */
>      bind_func("filll", ffilll);
>  
> -    bind_func("adler32", adler32);
> +    bind_func("(adler32)", adler32);
>      
>      bind_func("platform-boot", boot);
>      bind_func("(go)", go);
> diff --git a/arch/ppc/qemu/qemu.fs b/arch/ppc/qemu/qemu.fs
> index 458af1b..939985a 100644
> --- a/arch/ppc/qemu/qemu.fs
> +++ b/arch/ppc/qemu/qemu.fs
> @@ -93,3 +93,31 @@ variable keyboard-phandle 0 keyboard-phandle !
>  :noname
>    set-defaults
>  ; PREPOST-initializer
> +
> +\ -------------------------------------------------------------------------
> +\ Adler-32 wrapper
> +\ -------------------------------------------------------------------------
> +
> +: adler32 ( adler buf len -- checksum )
> +  \ Since Mac OS 9 is the only system using this word, we take this
> +  \ opportunity to inject a copyright message that is necessary for the
> +  \ system to boot.
> +  " /" find-package if
> +    " set-property" $find if
> +      ( adler buf len phandle xt )
> +      >r >r
> +      " Copyright 1983-2001 Apple Computer, Inc. THIS MESSAGE FOR COMPATIBILITY ONLY"
> +      encode-string " copyright"
> +      r> r> execute

You should be able to get away with not using the R stack here - have a
look at using 2swap instead.

> +    else
> +      ." Can't find " type cr

Whilst it's nice to have error checking, I could probably live without
this particular else clause, since if the / node in the device tree is
missing then the adler32 word is likely to be the very least of our
problems...

> +    then
> +  then
> +
> +  " (adler32)" $find if
> +    execute
> +  else
> +    3drop 0
> +    ." Can't find" type cr

Maybe add (adler32) here so we know what can't be found?

> +  then
> +;

Other than that, I think the patch looks good.


ATB,

Mark.