[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 ?