[SLOF] [PATCH v2] slof/fs/packages/disk-label.fs: improve checking for DOS boot partitions

[Thomas Huth]

On 18/03/2024 11.30, Kautuk Consul wrote:
> While testing with a qcow2 with a DOS boot partition it was found that
> when we set the logical_block_size in the guest XML to >512 then the
> boot would fail 
...
> diff --git a/slof/fs/packages/disk-label.fs b/slof/fs/packages/disk-label.fs
> index 661c6b0..2630701 100644
> --- a/slof/fs/packages/disk-label.fs
> +++ b/slof/fs/packages/disk-label.fs
> @@ -132,11 +132,16 @@ CONSTANT /gpt-part-entry
>      debug-disk-label? IF dup ." actual=" .d cr THEN
>   ;
>   
> -\ read sector to array "block"
> -: read-sector ( sector-number -- )
> +\ read sector to array "block" and return actual bytes read
> +: read-sector-ret ( sector-number -- actual-bytes )
>      \ block-size is 0x200 on disks, 0x800 on cdrom drives
>      block-size * 0 seek drop      \ seek to sector
> -   block block-size read drop    \ read sector
> +   block block-size read    \ read sector
> +;
> +
> +\ read sector to array "block"
> +: read-sector ( sector-number -- )
> +   read-sector-ret drop
>   ;
>   
>   : (.part-entry) ( part-entry )
> @@ -204,7 +209,8 @@ CONSTANT /gpt-part-entry
>            part-entry>sector-offset l at -le    ( current sector )
>            dup to part-start to lpart-start  ( current )

I just noticed that according to the stack comment above, there is a 
"current" item on the stack...

>            BEGIN
> -            part-start read-sector          \ read EBR
> +            part-start read-sector-ret          \ read EBR
> +            block-size < IF UNLOOP 0 EXIT THEN

... which doesn't get dropped here before the EXIT ? Is the stack still 
right after this function exited early?

>               1 partition>start-sector IF
>                  \ ." Logical Partition found at " part-start .d cr
>                  1+
> @@ -279,6 +285,7 @@ CONSTANT /gpt-part-entry
>      THEN
>   
>      count-dos-logical-partitions TO dos-logical-partitions
> +   dos-logical-partitions 0= IF false EXIT THEN
>   
>      debug-disk-label? IF
>         ." Found " dos-logical-partitions .d ." logical partitions" cr
> @@ -352,6 +359,7 @@ CONSTANT /gpt-part-entry
>      no-mbr? IF drop FALSE EXIT THEN  \ read MBR and check for DOS disk-label magic
>   
>      count-dos-logical-partitions TO dos-logical-partitions
> +   dos-logical-partitions 0= IF 0 EXIT THEN

Similar question here, what about the "addr" stack item? Shouldn't it be 
dropped first?

  Thomas


PS: I'm still having trouble receiving your mail, I just discovered v2 on 
patchwork and downloaded it from there...