Re: [PATCH 2/3] s390x: snippets: Add snippet compilation

[Thomas Huth <thuth@redhat.com>]

On 24/06/2021 14.01, Janosch Frank wrote:
> From: Steffen Eiden <seiden@linux.ibm.com>
> 
> This patch provides the necessary make targets to properly compile
> snippets and link them into their associated host.
> 
> To define the guest-host definition, we use the make-feature
> `SECONDEXPANSION` in combination with `Target specific Variable
> Values`. The variable `snippets` has different values depending on the
> current target. This enables us to define which snippets (=guests)
> belong to which hosts. Furthermore, using the second-expansion, we can
> use `snippets` in the perquisites of the host's `%.elf` rule, which
> otherwise would be not set.
> 
> Signed-off-by: Steffen Eiden <seiden@linux.ibm.com>
> ---
>   s390x/Makefile | 27 +++++++++++++++++++++------
>   1 file changed, 21 insertions(+), 6 deletions(-)
> 
> diff --git a/s390x/Makefile b/s390x/Makefile
> index 8820e99..ba32f4c 100644
> --- a/s390x/Makefile
> +++ b/s390x/Makefile
> @@ -76,11 +76,26 @@ OBJDIRS += lib/s390x
>   asmlib = $(TEST_DIR)/cstart64.o $(TEST_DIR)/cpu.o
>   
>   FLATLIBS = $(libcflat)
> -%.elf: %.o $(FLATLIBS) $(SRCDIR)/s390x/flat.lds $(asmlib)
> -	$(CC) $(CFLAGS) -c -o $(@:.elf=.aux.o) \
> -		$(SRCDIR)/lib/auxinfo.c -DPROGNAME=\"$@\"
> -	$(CC) $(LDFLAGS) -o $@ -T $(SRCDIR)/s390x/flat.lds \
> -		$(filter %.o, $^) $(FLATLIBS) $(@:.elf=.aux.o)
> +
> +SNIPPET_DIR = $(TEST_DIR)/snippets
> +snippet_asmlib = $(SNIPPET_DIR)/c/cstart.o
> +
> +# perquisites (=guests) for the snippet hosts.
> +# $(TEST_DIR)/<snippet-host>.elf: snippets = $(SNIPPET_DIR)/<c/asm>/<snippet>.gbin
> +
> +$(SNIPPET_DIR)/asm/%.gbin: $(SNIPPET_DIR)/asm/%.o $(FLATLIBS)
> +	$(OBJCOPY) -O binary $(patsubst %.gbin,%.o,$@) $@
> +	$(OBJCOPY) -I binary -O elf64-s390 -B "s390:64-bit" $@ $@
> +
> +$(SNIPPET_DIR)/c/%.gbin: $(SNIPPET_DIR)/c/%.o $(snippet_asmlib) $(FLATLIBS)
> +	$(CC) $(LDFLAGS) -o $@ -T $(SNIPPET_DIR)/c/flat.lds $(patsubst %.gbin,%.o,$@) $(snippet_asmlib) $(FLATLIBS)
> +	$(OBJCOPY) -O binary $@ $@
> +	$(OBJCOPY) -I binary -O elf64-s390 -B "s390:64-bit" $@ $@
> +
> +.SECONDEXPANSION:
> +%.elf: $$(snippets) %.o $(FLATLIBS) $(SRCDIR)/s390x/flat.lds $(asmlib)
> +	$(CC) $(CFLAGS) -c -o $(@:.elf=.aux.o) $(SRCDIR)/lib/auxinfo.c -DPROGNAME=\"$@\"
> +	$(CC) $(LDFLAGS) -o $@ -T $(SRCDIR)/s390x/flat.lds $(filter %.o, $^) $(FLATLIBS) $(snippets) $(@:.elf=.aux.o)

Wow, weird Makefile magic, never seend that before ... but it sounds 
reasonable, so:

Acked-by: Thomas Huth <thuth@redhat.com>