Re: [PATCH 1/3] s390x: snippets: Add gitignore as well as linker script and start assembly

[Thomas Huth <thuth@redhat.com>]

On 24/06/2021 14.01, Janosch Frank wrote:
> Snippets are small guests That can be run under a unit test as the
> hypervisor. They can be written in C or assembly. The C code needs a
> linker script and a start assembly file that jumps to main to work
> properly. So let's add that as well as a gitignore entry for the new
> files.
> 
> Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
> ---
>   .gitignore                |  1 +
>   s390x/snippets/c/cstart.S | 15 ++++++++++++
>   s390x/snippets/c/flat.lds | 51 +++++++++++++++++++++++++++++++++++++++
>   3 files changed, 67 insertions(+)
>   create mode 100644 s390x/snippets/c/cstart.S
>   create mode 100644 s390x/snippets/c/flat.lds
> 
> diff --git a/.gitignore b/.gitignore
> index 8534fb7..b3cf2cb 100644
> --- a/.gitignore
> +++ b/.gitignore
> @@ -23,3 +23,4 @@ cscope.*
>   /api/dirty-log
>   /api/dirty-log-perf
>   /s390x/*.bin
> +/s390x/snippets/*/*.gbin
> diff --git a/s390x/snippets/c/cstart.S b/s390x/snippets/c/cstart.S
> new file mode 100644
> index 0000000..d7f6525
> --- /dev/null
> +++ b/s390x/snippets/c/cstart.S
> @@ -0,0 +1,15 @@
> +#include <asm/sigp.h>
> +
> +.section .init
> +	.globl start
> +start:
> +	/* XOR all registers with themselves to clear them fully. */
> +	.irp i, 0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15
> +	xgr \i,\i
> +	.endr
> +	/* 0x3000 is the stack page for now */
> +	lghi	%r15, 0x4000 - 160
> +	brasl	%r14, main
> +	/* For now let's only use cpu 0 in snippets so this will always work. */
> +	xgr	%r0, %r0
> +	sigp    %r2, %r0, SIGP_STOP
> diff --git a/s390x/snippets/c/flat.lds b/s390x/snippets/c/flat.lds
> new file mode 100644
> index 0000000..5e70732
> --- /dev/null
> +++ b/s390x/snippets/c/flat.lds
> @@ -0,0 +1,51 @@
> +SECTIONS
> +{
> +	.lowcore : {
> +		/*
> +		 * Initial short psw for disk boot, with 31 bit addressing for
> +		 * non z/Arch environment compatibility and the instruction
> +		 * address 0x10000 (cstart64.S .init).

I think this comment needs some adjustments (0x10000 => 0x4000 and do not 
talk about cstart64.S)?

Also, what about switching to 64-bit mode in the snippets?

  Thomas


> +		 */
> +		. = 0;
> +		 LONG(0x00080000)
> +		 LONG(0x80004000)
> +		 /* Restart new PSW for booting via PSW restart. */
> +		 . = 0x1a0;
> +		 QUAD(0x0000000180000000)
> +		 QUAD(0x0000000000004000)
> +	}
> +	. = 0x4000;
> +	.text : {
> +		*(.init)
> +		*(.text)
> +		*(.text.*)
> +	}
> +	. = ALIGN(64K);
> +	etext = .;
> +	.opd : { *(.opd) }
> +	. = ALIGN(16);
> +	.dynamic : {
> +		dynamic_start = .;
> +		*(.dynamic)
> +	}
> +	.dynsym : {
> +		dynsym_start = .;
> +		*(.dynsym)
> +	}
> +	.rela.dyn : { *(.rela*) }
> +	. = ALIGN(16);
> +	.data : {
> +		*(.data)
> +		*(.data.rel*)
> +	}
> +	. = ALIGN(16);
> +	.rodata : { *(.rodata) *(.rodata.*) }
> +	. = ALIGN(16);
> +	__bss_start = .;
> +	.bss : { *(.bss) }
> +	__bss_end = .;
> +	. = ALIGN(64K);
> +	edata = .;
> +	. += 64K;
> +	. = ALIGN(64K);
> +}
>