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

[Kautuk Consul]

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 in the following interminable loop:
> > <SNIP>
> > Trying to load:  from: /pci at 800000020000000/scsi at 3 ... virtioblk_transfer: Access beyond end of device!
> > virtioblk_transfer: Access beyond end of device!
> > virtioblk_transfer: Access beyond end of device!
> > virtioblk_transfer: Access beyond end of device!
> > virtioblk_transfer: Access beyond end of device!
> > virtioblk_transfer: Access beyond end of device!
> > virtioblk_transfer: Access beyond end of device!
> > virtioblk_transfer: Access beyond end of device!
> > virtioblk_transfer: Access beyond end of device!
> > virtioblk_transfer: Access beyond end of device!
> > virtioblk_transfer: Access beyond end of device!
> > virtioblk_transfer: Access beyond end of device!
> > virtioblk_transfer: Access beyond end of device!
> > virtioblk_transfer: Access beyond end of device!
> > virtioblk_transfer: Access beyond end of device!
> > virtioblk_transfer: Access beyond end of device!
> > virtioblk_transfer: Access beyond end of device!
> > </SNIP>
> > 
> > Change the count-dos-logical-partitions Forth subroutine and the Forth
> > subroutines calling count-dos-logical-partitions to check for this access
> > beyond end of device error.
> > 
> > After making the above changes, it fails properly with the correct error
> > message as follows:
> > <SNIP>
> > Trying to load:  from: /pci at 800000020000000/scsi at 3 ... virtioblk_transfer: Access beyond end of device!
> > virtioblk_transfer: Access beyond end of device!
> > virtioblk_transfer: Access beyond end of device!
> > virtioblk_transfer: Access beyond end of device!
> > virtioblk_transfer: Access beyond end of device!
> > virtioblk_transfer: Access beyond end of device!
> > virtioblk_transfer: Access beyond end of device!
> > virtioblk_transfer: Access beyond end of device!
> > virtioblk_transfer: Access beyond end of device!
> > virtioblk_transfer: Access beyond end of device!
> > 
> > E3404: Not a bootable device!
> > 
> > E3407: Load failed
> > 
> >   Type 'boot' and press return to continue booting the system.
> >   Type 'reset-all' and press return to reboot the system.
> > 
> > Ready!
> > 0 >
> > </SNIP>
> > 
> > Signed-off-by: Kautuk Consul <kconsul at linux.vnet.ibm.com>
> > ---
> >  slof/fs/packages/disk-label.fs | 12 +++++++++++-
> >  1 file changed, 11 insertions(+), 1 deletion(-)
> > 
> > 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)
> > +   \ block-size is 0x200 on disks, 0x800 on cdrom drives
> > +   block-size * 0 seek drop      \ seek to sector
> > +   block block-size read    \ read sector
> > +;
> > +
> >  : (.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 ?