Re: [kvm-unit-tests PATCH] s390x/snippets: Define all things that are needed to link the libc

[Janosch Frank <frankja@linux.ibm.com>]

On 10/8/21 11:26, Thomas Huth wrote:
> In the long run, we want to use parts of the libc like memset() etc.,
> too. However, to be able to link it correctly, we have to provide
> some stub functions like puts() and exit() to avoid that too much
> other stuff from the lib folder gets pulled into the binaries, which
> we cannot provide in the snippets (like the sclp support).
> 
> Signed-off-by: Thomas Huth <thuth@redhat.com>

Reviewed-by: Janosch Frank <frankja@linux.ibm.com>
Thanks, picked!

> ---
>   s390x/Makefile            |  2 +-
>   s390x/snippets/c/cstart.S | 11 +++++++++++
>   2 files changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/s390x/Makefile b/s390x/Makefile
> index ef8041a..b2a7c1f 100644
> --- a/s390x/Makefile
> +++ b/s390x/Makefile
> @@ -80,7 +80,7 @@ asmlib = $(TEST_DIR)/cstart64.o $(TEST_DIR)/cpu.o
>   FLATLIBS = $(libcflat)
>   
>   SNIPPET_DIR = $(TEST_DIR)/snippets
> -snippet_asmlib = $(SNIPPET_DIR)/c/cstart.o
> +snippet_asmlib = $(SNIPPET_DIR)/c/cstart.o lib/auxinfo.o
>   
>   # perquisites (=guests) for the snippet hosts.
>   # $(TEST_DIR)/<snippet-host>.elf: snippets = $(SNIPPET_DIR)/<c/asm>/<snippet>.gbin
> diff --git a/s390x/snippets/c/cstart.S b/s390x/snippets/c/cstart.S
> index a175480..1862703 100644
> --- a/s390x/snippets/c/cstart.S
> +++ b/s390x/snippets/c/cstart.S
> @@ -20,6 +20,17 @@ start:
>   	lghi	%r15, 0x4000 - 160
>   	sam64
>   	brasl	%r14, main
> +	/*
> +	 * If main() returns, we stop the CPU with the code below. We also
> +	 * route some functions that are required by the libc (but not usable
> +	 * from snippets) to the CPU stop code below, so that snippets can
> +	 * still be linked against the libc code (to use non-related functions
> +	 * like memset() etc.)
> +	 */
> +.global puts
> +.global exit
> +puts:
> +exit:
>   	/* For now let's only use cpu 0 in snippets so this will always work. */
>   	xgr	%r0, %r0
>   	sigp    %r2, %r0, SIGP_STOP
>