[PATCH v3 4/7] selftests/nolibc: add XARCH and ARCH mapping support

[Zhangjin Wu]

Hi, Willy, Thomas

Beside the extra config stuff, here is the left one need your last confirm.

Let's summarize it, without 'override', we are able to use such styles (I added
a $(error ARCH=$(ARCH) XARCH=$(XARCH)) line for tmp test):

    $ make ARCH=powerpc
    Makefile:29: *** ARCH=powerpc, XARCH=ppc.  Stop.
    
    $ make ARCH=powerpc XARCH=ppc
    Makefile:29: *** ARCH=powerpc, XARCH=ppc.  Stop.
    $ make ARCH=powerpc XARCH=ppc64
    Makefile:29: *** ARCH=powerpc, XARCH=ppc64.  Stop.
    $ make ARCH=powerpc XARCH=ppc66le
    Makefile:29: *** ARCH=powerpc, XARCH=ppc66le.  Stop.

    $ make XARCH=ppc
    Makefile:29: *** ARCH=powerpc, XARCH=ppc.  Stop.
    $ make XARCH=ppc64
    Makefile:29: *** ARCH=powerpc, XARCH=ppc64.  Stop.
    $ make XARCH=ppc64le
    Makefile:29: *** ARCH=powerpc, XARCH=ppc64le.  Stop.

with 'override', we are further able to use:

    $ make ARCH=powerpc
    Makefile:29: *** ARCH=powerpc, XARCH=ppc.  Stop.
    $ make ARCH=ppc
    Makefile:29: *** ARCH=powerpc, XARCH=ppc.  Stop.
    $ make ARCH=ppc64
    Makefile:29: *** ARCH=powerpc, XARCH=ppc64.  Stop.
    $ make ARCH=ppc64le
    Makefile:29: *** ARCH=powerpc, XARCH=ppc64le.  Stop.

So, with 'override', users will be able to directly use the famous ARCH, it is
able to accept powerpc, ppc, ppc64, ppc64le and users can simply ignore XARCH
and we are able to only use XARCH as an internal variable to temply save input
ARCH and then convert it to an internal ARCH.

Without 'override', we must carefully document its usage, it may be:

    # XARCH and ARCH mapping
    #
    # Usage:
    #      $ make ARCH=<kernel-supported-ARCH> XARCH=<nolibc-test-supported-variants> ...
    #
    #      e.g. make ARCH=powerpc XARCH=[ppc|ppc64|ppc64le]

    # XARCH is used to save user-input ARCH variant
    # configure default variants for target kernel supported architectures

For the help page, if we only use '\$$XARCH or \$$ARCH', it may mislead users:

	@echo "  run-user               runs the executable under QEMU (uses \$$ARCH or \\$XARCH, \$$TEST)"

That's why I at last add the 'override' keyword to make sure even if users
wrongly and only use ARCH as the argument, it must not fail, or we forcely ask
user pass ARCH and XARCH together.

	@echo "  run-user               runs the executable under QEMU (uses \$$ARCH and \\$XARCH, \$$TEST)"

Or we simply only and always ask users to use XARCH (as the first version does)
for nolibc-test and let ARCH as the default one from a previous build kernel:

	@echo "  run-user               runs the executable under QEMU (uses \$$XARCH, \$$TEST)"

That means, the ugly 'override' does help us to save lots of teach work ;-)

I'm ok with 'override' or not, welcome your confirm, which direction do you
prefer?

Thanks,
Zhangjin

> Most of the CPU architectures have different variants, but kernel
> usually only accepts parts of them via the ARCH variable, the others
> should be customized via kernel config files.
> 
> To simplify testing, the external ARCH variable is extended to accept
> more CPU variants from user's input, a new internal XARCH variable is
> added to save users' ARCH input and used to customize variant specific
> variables, at last XARCH is converted to the internal ARCH variable
> acceptable by kernel:
> 
>   e.g. make run ARCH=<one of the supported variants>
>                /
>               v
>   external ARCH from cmdline -> internal XARCH -> internal ARCH for kernel
>                                           |
>                                           `--> variant specific variables
> 
> XARCH and ARCH are carefully mapped to allow users to pass architecture
> variants via external ARCH (or XARCH) from cmdline:
> 
> - From developers' perspective
> 
>   - XARCH records the architecture variant from user's ARCH input, after
>     'override ARCH', ARCH is overridden and mapped from XARCH to the one
>     supported by kernel
> 
>   - Map from XARCH to the kernel supported ARCH: 'ARCH_<XARCH> = <ARCH>'
> 
>   - Configure a default variant for kernel supported ARCH: 'XARCH_<ARCH> = <XARCH>'
> 
> - From users' perspective
> 
>   - ARCH (or XARCH) are architecture variants of a target architecture
> 
>   - the variants are XARCH names from the "ARCH_<XARCH> = <ARCH>" mapping list
> 
> PowerPC is the first user and also a very good reference architecture of
> this mapping, it has variants with different combinations of
> 32-bit/64-bit and bit endian/little endian.
> 
> To use this mapping, the other architectures can refer to PowerPC, If
> the target architecture only has one variant, XARCH is simply an alias
> of ARCH, no additional mapping required.
> 
> Suggested-by: Willy Tarreau <w@xxxxxx>
> Link: https://lore.kernel.org/lkml/20230702171715.GD16233@xxxxxx/
> Reviewed-by: Thomas Weißschuh <linux@xxxxxxxxxxxxxx>
> Signed-off-by: Zhangjin Wu <falcon@xxxxxxxxxxx>
> ---
>  tools/testing/selftests/nolibc/Makefile | 25 +++++++++++++++++--------
>  1 file changed, 17 insertions(+), 8 deletions(-)
> 
> diff --git a/tools/testing/selftests/nolibc/Makefile b/tools/testing/selftests/nolibc/Makefile
> index 9576f1a0a98d..5afb3e7d7723 100644
> --- a/tools/testing/selftests/nolibc/Makefile
> +++ b/tools/testing/selftests/nolibc/Makefile
> @@ -14,6 +14,14 @@ include $(srctree)/scripts/subarch.include
>  ARCH = $(SUBARCH)
>  endif
>  
> +# XARCH is used to save user-input ARCH variant
> +# configure default variants for target kernel supported architectures
> +XARCH           := $(or $(XARCH_$(ARCH)),$(ARCH))
> +
> +# ARCH is supported by kernel
> +# map from user input variants to their kernel supported architectures
> +override ARCH   := $(or $(ARCH_$(XARCH)),$(XARCH))
> +
>  # kernel image names by architecture
>  IMAGE_i386       = arch/x86/boot/bzImage
>  IMAGE_x86_64     = arch/x86/boot/bzImage
> @@ -24,7 +32,7 @@ IMAGE_mips       = vmlinuz
>  IMAGE_riscv      = arch/riscv/boot/Image
>  IMAGE_s390       = arch/s390/boot/bzImage
>  IMAGE_loongarch  = arch/loongarch/boot/vmlinuz.efi
> -IMAGE            = $(IMAGE_$(ARCH))
> +IMAGE            = $(IMAGE_$(XARCH))
>  IMAGE_NAME       = $(notdir $(IMAGE))
>  
>  # default kernel configurations that appear to be usable
> @@ -37,10 +45,10 @@ DEFCONFIG_mips       = malta_defconfig
>  DEFCONFIG_riscv      = defconfig
>  DEFCONFIG_s390       = defconfig
>  DEFCONFIG_loongarch  = defconfig
> -DEFCONFIG            = $(DEFCONFIG_$(ARCH))
> +DEFCONFIG            = $(DEFCONFIG_$(XARCH))
>  
>  # extra kernel config files under configs/, include common + architecture specific
> -EXTCONFIG            = common.config $(ARCH).config
> +EXTCONFIG            = common.config $(XARCH).config
>  
>  # optional tests to run (default = all)
>  TEST =
> @@ -55,7 +63,7 @@ QEMU_ARCH_mips       = mipsel  # works with malta_defconfig
>  QEMU_ARCH_riscv      = riscv64
>  QEMU_ARCH_s390       = s390x
>  QEMU_ARCH_loongarch  = loongarch64
> -QEMU_ARCH            = $(QEMU_ARCH_$(ARCH))
> +QEMU_ARCH            = $(QEMU_ARCH_$(XARCH))
>  
>  # QEMU_ARGS : some arch-specific args to pass to qemu
>  QEMU_ARGS_i386       = -M pc -append "console=ttyS0,9600 i8042.noaux panic=-1 $(TEST:%=NOLIBC_TEST=%)"
> @@ -67,7 +75,7 @@ QEMU_ARGS_mips       = -M malta -append "panic=-1 $(TEST:%=NOLIBC_TEST=%)"
>  QEMU_ARGS_riscv      = -M virt -append "console=ttyS0 panic=-1 $(TEST:%=NOLIBC_TEST=%)"
>  QEMU_ARGS_s390       = -M s390-ccw-virtio -m 1G -append "console=ttyS0 panic=-1 $(TEST:%=NOLIBC_TEST=%)"
>  QEMU_ARGS_loongarch  = -M virt -append "console=ttyS0,115200 panic=-1 $(TEST:%=NOLIBC_TEST=%)"
> -QEMU_ARGS            = $(QEMU_ARGS_$(ARCH)) $(QEMU_ARGS_EXTRA)
> +QEMU_ARGS            = $(QEMU_ARGS_$(XARCH)) $(QEMU_ARGS_EXTRA)
>  
>  # OUTPUT is only set when run from the main makefile, otherwise
>  # it defaults to this nolibc directory.
> @@ -84,7 +92,7 @@ CFLAGS_mips = -EL
>  CFLAGS_STACKPROTECTOR ?= $(call cc-option,-mstack-protector-guard=global $(call cc-option,-fstack-protector-all))
>  CFLAGS  ?= -Os -fno-ident -fno-asynchronous-unwind-tables -std=c89 \
>  		$(call cc-option,-fno-stack-protector) \
> -		$(CFLAGS_$(ARCH)) $(CFLAGS_STACKPROTECTOR)
> +		$(CFLAGS_$(XARCH)) $(CFLAGS_STACKPROTECTOR)
>  LDFLAGS := -s
>  
>  REPORT  ?= awk '/\[OK\][\r]*$$/{p++} /\[FAIL\][\r]*$$/{if (!f) printf("\n"); f++; print;} /\[SKIPPED\][\r]*$$/{s++} \
> @@ -111,12 +119,13 @@ help:
>  	@echo ""
>  	@echo "Currently using the following variables:"
>  	@echo "  ARCH          = $(ARCH)"
> +	@echo "  XARCH         = $(XARCH)"
>  	@echo "  CROSS_COMPILE = $(CROSS_COMPILE)"
>  	@echo "  CC            = $(CC)"
>  	@echo "  OUTPUT        = $(OUTPUT)"
>  	@echo "  TEST          = $(TEST)"
> -	@echo "  QEMU_ARCH     = $(if $(QEMU_ARCH),$(QEMU_ARCH),UNKNOWN_ARCH) [determined from \$$ARCH]"
> -	@echo "  IMAGE_NAME    = $(if $(IMAGE_NAME),$(IMAGE_NAME),UNKNOWN_ARCH) [determined from \$$ARCH]"
> +	@echo "  QEMU_ARCH     = $(if $(QEMU_ARCH),$(QEMU_ARCH),UNKNOWN_ARCH) [determined from \$$XARCH]"
> +	@echo "  IMAGE_NAME    = $(if $(IMAGE_NAME),$(IMAGE_NAME),UNKNOWN_ARCH) [determined from \$$XARCH]"
>  	@echo ""
>  
>  all: run
> -- 
> 2.25.1