On 03.01.19 11:07, Janosch Frank wrote:
> When doing an IPL normal the memory will not be zeroed and hence the
> BSS section can have any value. We need to clear it by ourselves.
>
> Signed-off-by: Janosch Frank <frankja@xxxxxxxxxxxxx>
> Reviewed-by: Thomas Huth <thuth@xxxxxxxxxx>
> ---
> s390x/cstart64.S | 22 ++++++++++++++++++++--
> s390x/flat.lds | 2 ++
> 2 files changed, 22 insertions(+), 2 deletions(-)
>
> diff --git a/s390x/cstart64.S b/s390x/cstart64.S
> index 6622633..dedfe80 100644
> --- a/s390x/cstart64.S
> +++ b/s390x/cstart64.S
> @@ -39,7 +39,22 @@ start:
> /* setup initial PSW mask + control registers*/
> larl %r1, initial_psw
> lpswe 0(%r1)
> -init_psw_cont:
> +clear_bss_start:
> + larl %r2, __bss_start
> + larl %r3, __bss_end
> + slgr %r3, %r2 # Get sizeof bss
> + aghi %r3,-1
> + srlg %r4,%r3,8 # Calc number of 256 byte chunks
> + ltgr %r4,%r4
> + lgr %r1,%r2
> + jz clear_bss_remainder # If none, clear remaining bytes
> +clear_bss_loop:
> + xc 0(256,%r1), 0(%r1) # Clear 256 byte chunks via xor
> + la %r1, 256(%r1)
> + brctg %r4, clear_bss_loop
> +clear_bss_remainder:
> + larl %r2, memsetxc
> + ex %r3, 0(%r2)
> /* setup pgm interrupt handler */
> larl %r1, pgm_int_psw
> mvc GEN_LC_PGM_NEW_PSW(16), 0(%r1)
> @@ -71,6 +86,9 @@ init_psw_cont:
> /* call exit() */
> j exit
>
> +memsetxc:
> + xc 0(1,%r1),0(%r1)
> +
> .macro SAVE_REGS
> /* save grs 0-15 */
> stmg %r0, %r15, GEN_LC_SW_INT_GRS
> @@ -159,7 +177,7 @@ svc_int:
>
> .align 8
> initial_psw:
> - .quad 0x0000000180000000, init_psw_cont
> + .quad 0x0000000180000000, clear_bss_start
> pgm_int_psw:
> .quad 0x0000000180000000, pgm_int
> ext_int_psw:
> diff --git a/s390x/flat.lds b/s390x/flat.lds
> index 977af7c..403d967 100644
> --- a/s390x/flat.lds
> +++ b/s390x/flat.lds
> @@ -40,7 +40,9 @@ SECTIONS
> . = ALIGN(16);
> .rodata : { *(.rodata) *(.rodata.*) }
> . = ALIGN(16);
> + __bss_start = .;
> .bss : { *(.bss) }
> + __bss_end = .;
> . = ALIGN(64K);
> edata = .;
> . += 64K;
>
Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
--
Thanks,
David / dhildenb
