Re: [PATCH] pc-bios/s390x: Pack ResetInfo struct

[Cornelia Huck <cohuck@redhat.com>]

On Wed,  5 Feb 2020 13:21:26 -0500
"Jason J. Herne" <jjherne@linux.ibm.com> wrote:

> This fixes vfio-ccw when booting non-Linux operating systems. Without this
> struct being packed, a few extra bytes of low core memory get overwritten when
> we  assign a value to memory address 0 in jump_to_IPL_2. This is enough to
> cause some non-Linux OSes of fail when booting.

s/of/to/

> 
> The problem was introduced by:
> 5c6f0d5f46a77d77 "pc-bios/s390x: Fix reset psw mask".

So, what introduced the problem was turning two 32 bit values into a 64
bit value?

> 
> The fix is to pack the struct thereby removing the 4 bytes of padding that get
> added at the end, likely to allow an array of these structs to naturally align
> on an 8-byte boundary.
> 
> Fixes: 5c6f0d5f46a7 ("pc-bios/s390x: Fix reset psw mask")
> CC: Janosch Frank <frankja@linux.ibm.com>
> Signed-off-by: Jason J. Herne <jjherne@linux.ibm.com>
> ---
>  pc-bios/s390-ccw/jump2ipl.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/pc-bios/s390-ccw/jump2ipl.c b/pc-bios/s390-ccw/jump2ipl.c
> index da13c43cc0..1e9eaa037f 100644
> --- a/pc-bios/s390-ccw/jump2ipl.c
> +++ b/pc-bios/s390-ccw/jump2ipl.c
> @@ -18,7 +18,7 @@
>  typedef struct ResetInfo {
>      uint64_t ipl_psw;
>      uint32_t ipl_continue;
> -} ResetInfo;
> +} __attribute__((packed)) ResetInfo;
>  
>  static ResetInfo save;
>  

I'm wondering if we have more stuff like that lurking in the bios.