On 2019-01-10 16:41, Janosch Frank wrote:
> Currently tests are run with the --kernel option of Qemu, which will
> load the ELF file and jump to the start address. When booting from
> disk, we need to specify a start address. This is done by setting the
> initial short PSW at 0x0.
>
> .text was moved to 0x11000 because the bootloader can write from
> 0x10480 until 0x11000 if it has a lot to write. 0x10480 to 0x10600 was
> not enough safe space.
>
> Signed-off-by: Janosch Frank <frankja@xxxxxxxxxxxxx>
> Reviewed-by: Thomas Huth <thuth@xxxxxxxxxx>
> Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
> ---
> s390x/cstart64.S | 8 +++++++-
> s390x/flat.lds | 13 ++++++++++++-
> 2 files changed, 19 insertions(+), 2 deletions(-)
>
> diff --git a/s390x/cstart64.S b/s390x/cstart64.S
> index dc7ddd6..385915e 100644
> --- a/s390x/cstart64.S
> +++ b/s390x/cstart64.S
> @@ -14,7 +14,13 @@
>
> .section .init
>
> -/* entry point - for KVM + TCG we directly start in 64 bit mode */
> +/*
> + * Short init between 0x10000 and 0x10480 and then jump to 0x11000.
> + * 0x10480 - 0x11000 are written to by bootloader.
> + *
> + * For KVM and TCG kernel boot we are in 64 bit z/Arch mode.
> + * When booting from disk the initial short psw is in 31 bit mode.
> + */
> .globl start
> start:
> /* setup stack */
> diff --git a/s390x/flat.lds b/s390x/flat.lds
> index b6e2172..977af7c 100644
> --- a/s390x/flat.lds
> +++ b/s390x/flat.lds
> @@ -1,10 +1,21 @@
> SECTIONS
> {
> + /*
> + * Initial short psw for disk boot, with 31 bit addressing for
> + * non z/Arch environment compatibility and the instruction
> + * address 0x10000 (cstart64.S .init).
> + */
> + .lowcore : {
> + . = 0;
> + LONG(0x00080000)
> + LONG(0x80010000)
> + }
> + . = 0x10000;
In case you respin: I think we could/should remove the "-Ttext=0x10000"
from the s390x/Makefile now.
Thomas
