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

[Thomas Huth]

On 18/03/2024 06.14, Kautuk Consul wrote:
> Hi,
>>
>> On 2024-02-22 01:10:46, 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..e680847 100644
>>> --- a/slof/fs/packages/disk-label.fs
>>> +++ b/slof/fs/packages/disk-label.fs
>>> @@ -139,6 +139,13 @@ CONSTANT /gpt-part-entry
>>>      block block-size read drop    \ read sector
>>>   ;
>>>
>>> +\ read sector to array "block" and return actual bytes read
>>> +: read-sector-ret ( sector-number -- actual)

Please add a space between "actual" and ")". I'd maybe also rather say 
"actual-bytes" so that nobody expects "actual-sectors" here.

>>> +   \ block-size is 0x200 on disks, 0x800 on cdrom drives
>>> +   block-size * 0 seek drop      \ seek to sector
>>> +   block block-size read    \ read sector
>>> +;

Could we please avoid duplicating code here? "read-sector" could now simply 
be implemented via read-sector-ret instead:

\ 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       \ read sector
;

: read-sector ( sector-number -- )
     read-sector-ret drop
;

>>>   : (.part-entry) ( part-entry )
>>>      cr ." part-entry>active:        " dup part-entry>active c@ .d
>>>      cr ." part-entry>start-head:    " dup part-entry>start-head c@ .d
>>> @@ -204,7 +211,8 @@ CONSTANT /gpt-part-entry
>>>            part-entry>sector-offset l at -le    ( current sector )
>>>            dup to part-start to lpart-start  ( current )
>>>            BEGIN
>>> -            part-start read-sector          \ read EBR
>>> +            part-start read-sector-ret          \ read EBR
>>> +            block-size < IF UNLOOP 0 EXIT THEN
>>>               1 partition>start-sector IF
>>>                  \ ." Logical Partition found at " part-start .d cr
>>>                  1+
>>> @@ -279,6 +287,7 @@ 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 +361,7 @@ 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
>>>
>>>      debug-disk-label? IF
>>>         ." Found " dos-logical-partitions .d ." logical partitions" cr
>>> -- 
>>> 2.31.1
>>>
> 
> So how does the patch look ? Any comments from anyone ?

Sorry, your original patch somehow didn't make it to my Inbox (though it's 
visible on http://patchwork.ozlabs.org/project/slof/list/ so the problem is 
certainly on my receiving side), so I just learnt about this patch today.

Anyway, apart from the code duplication, it looks fine to me, so if you 
could fix that in a v2, that would be great!

  Thomas