[PATCH v3 3/3] selftests/nolibc: riscv: customize makefile for rv32

[Zhangjin Wu]

Both riscv64 and riscv32 have:

* the same ARCH value, it is riscv
* the same arch/riscv source code tree

The only differences are:

* riscv64 uses defconfig, riscv32 uses rv32_defconfig
* riscv64 uses qemu-system-riscv64, riscv32 uses qemu-system-riscv32
* riscv32 has different compiler options (-march= and -mabi=)

So, riscv32 can share most of the settings with riscv64, there is no
need to add it as a whole new architecture but just need a flag to
record and reflect the difference.

The 32bit mips and loongarch may be able to use the same method, so,
let's use a meaningful flag: CONFIG_32BIT. If required in the future,
this flag can also be automatically loaded from
include/config/auto.conf.

With this patch, it is able to run nolibc test for rv32 like this:

    $ make run ARCH=riscv32 CROSS_COMPILE=riscv64-linux-gnu- ...

Signed-off-by: Zhangjin Wu <falcon at tinylab.org>
---
 tools/testing/selftests/nolibc/Makefile | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/nolibc/Makefile b/tools/testing/selftests/nolibc/Makefile
index 44088535682e..ea434a0acdc1 100644
--- a/tools/testing/selftests/nolibc/Makefile
+++ b/tools/testing/selftests/nolibc/Makefile
@@ -14,6 +14,12 @@ include $(srctree)/scripts/subarch.include
 ARCH = $(SUBARCH)
 endif
 
+# Allow pass ARCH=riscv|riscv32|riscv64, riscv implies riscv64
+ifneq ($(findstring xriscv,x$(ARCH)),)
+  CONFIG_32BIT := $(if $(findstring 32x,$(ARCH)x),1)
+  override ARCH := riscv
+endif
+
 # kernel image names by architecture
 IMAGE_i386       = arch/x86/boot/bzImage
 IMAGE_x86_64     = arch/x86/boot/bzImage
@@ -34,7 +40,7 @@ DEFCONFIG_x86        = defconfig
 DEFCONFIG_arm64      = defconfig
 DEFCONFIG_arm        = multi_v7_defconfig
 DEFCONFIG_mips       = malta_defconfig
-DEFCONFIG_riscv      = defconfig
+DEFCONFIG_riscv      = $(if $(CONFIG_32BIT),rv32_defconfig,defconfig)
 DEFCONFIG_s390       = defconfig
 DEFCONFIG_loongarch  = defconfig
 DEFCONFIG            = $(DEFCONFIG_$(ARCH))
@@ -49,7 +55,7 @@ QEMU_ARCH_x86        = x86_64
 QEMU_ARCH_arm64      = aarch64
 QEMU_ARCH_arm        = arm
 QEMU_ARCH_mips       = mipsel  # works with malta_defconfig
-QEMU_ARCH_riscv      = riscv64
+QEMU_ARCH_riscv      = $(if $(CONFIG_32BIT),riscv32,riscv64)
 QEMU_ARCH_s390       = s390x
 QEMU_ARCH_loongarch  = loongarch64
 QEMU_ARCH            = $(QEMU_ARCH_$(ARCH))
@@ -76,6 +82,7 @@ else
 Q=@
 endif
 
+CFLAGS_riscv = $(if $(CONFIG_32BIT),-march=rv32i -mabi=ilp32)
 CFLAGS_s390 = -m64
 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 \
-- 
2.25.1