tools/nolibc: Add m68k support

Add nolibc support for m68k. Should be helpful for nommu where
linking libc can bloat even hello world to the point where you get
an OOM just trying to load it.

Signed-off-by: Daniel Palmer <daniel@thingy.jp>
Link: https://lore.kernel.org/r/20250426224738.284874-1-daniel@0x0f.com
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>

4 files changed, 153 insertions, 0 deletions

diff --git a/tools/include/nolibc/arch-m68k.h b/tools/include/nolibc/arch-m68k.h
new file mode 100644
index 000000000000..6dac1845f298
--- /dev/null
+++ b/tools/include/nolibc/arch-m68k.h
@@ -0,0 +1,141 @@
+/* SPDX-License-Identifier: LGPL-2.1 OR MIT */
+/*
+ * m68k specific definitions for NOLIBC
+ * Copyright (C) 2025 Daniel Palmer<daniel@thingy.jp>
+ *
+ * Roughly based on one or more of the other arch files.
+ *
+ */
+
+#ifndef _NOLIBC_ARCH_M68K_H
+#define _NOLIBC_ARCH_M68K_H
+
+#include "compiler.h"
+#include "crt.h"
+
+#define _NOLIBC_SYSCALL_CLOBBERLIST "memory"
+
+#define my_syscall0(num)                                                      \
+({                                                                            \
+	register long _num __asm__ ("d0") = (num);                            \
+									      \
+	__asm__ volatile (                                                    \
+		"trap #0\n"                                                   \
+		: "+r"(_num)                                                  \
+		: "r"(_num)                                                   \
+		: _NOLIBC_SYSCALL_CLOBBERLIST                                 \
+	);                                                                    \
+	_num;                                                                 \
+})
+
+#define my_syscall1(num, arg1)                                                \
+({                                                                            \
+	register long _num __asm__ ("d0") = (num);                            \
+	register long _arg1 __asm__ ("d1") = (long)(arg1);                    \
+									      \
+	__asm__ volatile (                                                    \
+		"trap #0\n"                                                   \
+		: "+r"(_num)                                                  \
+		: "r"(_arg1)                                                  \
+		: _NOLIBC_SYSCALL_CLOBBERLIST                                 \
+	);                                                                    \
+	_num;                                                                 \
+})
+
+#define my_syscall2(num, arg1, arg2)                                          \
+({                                                                            \
+	register long _num __asm__ ("d0") = (num);                            \
+	register long _arg1 __asm__ ("d1") = (long)(arg1);                    \
+	register long _arg2 __asm__ ("d2") = (long)(arg2);                    \
+									      \
+	__asm__ volatile (                                                    \
+		"trap #0\n"                                                   \
+		: "+r"(_num)                                                  \
+		: "r"(_arg1), "r"(_arg2)                                      \
+		: _NOLIBC_SYSCALL_CLOBBERLIST                                 \
+	);                                                                    \
+	_num;                                                                 \
+})
+
+#define my_syscall3(num, arg1, arg2, arg3)                                    \
+({                                                                            \
+	register long _num __asm__ ("d0")  = (num);                           \
+	register long _arg1 __asm__ ("d1") = (long)(arg1);                    \
+	register long _arg2 __asm__ ("d2") = (long)(arg2);                    \
+	register long _arg3 __asm__ ("d3") = (long)(arg3);                    \
+									      \
+	__asm__ volatile (                                                    \
+		"trap #0\n"                                                   \
+		: "+r"(_num)                                                  \
+		: "r"(_arg1), "r"(_arg2), "r"(_arg3)                          \
+		: _NOLIBC_SYSCALL_CLOBBERLIST                                 \
+	);                                                                    \
+	_num;                                                                 \
+})
+
+#define my_syscall4(num, arg1, arg2, arg3, arg4)                              \
+({                                                                            \
+	register long _num __asm__ ("d0") = (num);                            \
+	register long _arg1 __asm__ ("d1") = (long)(arg1);                    \
+	register long _arg2 __asm__ ("d2") = (long)(arg2);                    \
+	register long _arg3 __asm__ ("d3") = (long)(arg3);                    \
+	register long _arg4 __asm__ ("d4") = (long)(arg4);                    \
+									      \
+	__asm__ volatile (                                                    \
+		"trap #0\n"                                                   \
+		: "+r" (_num)                                                 \
+		: "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4)              \
+		: _NOLIBC_SYSCALL_CLOBBERLIST                                 \
+	);                                                                    \
+	_num;                                                                 \
+})
+
+#define my_syscall5(num, arg1, arg2, arg3, arg4, arg5)                        \
+({                                                                            \
+	register long _num __asm__ ("d0") = (num);                            \
+	register long _arg1 __asm__ ("d1") = (long)(arg1);                    \
+	register long _arg2 __asm__ ("d2") = (long)(arg2);                    \
+	register long _arg3 __asm__ ("d3") = (long)(arg3);                    \
+	register long _arg4 __asm__ ("d4") = (long)(arg4);                    \
+	register long _arg5 __asm__ ("d5") = (long)(arg5);                    \
+									      \
+	__asm__ volatile (                                                    \
+		"trap #0\n"                                                   \
+		: "+r" (_num)                                                 \
+		: "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5)  \
+		: _NOLIBC_SYSCALL_CLOBBERLIST                                 \
+	);                                                                    \
+	_num;                                                                 \
+})
+
+#define my_syscall6(num, arg1, arg2, arg3, arg4, arg5, arg6)                  \
+({                                                                            \
+	register long _num __asm__ ("d0")  = (num);                           \
+	register long _arg1 __asm__ ("d1") = (long)(arg1);                    \
+	register long _arg2 __asm__ ("d2") = (long)(arg2);                    \
+	register long _arg3 __asm__ ("d3") = (long)(arg3);                    \
+	register long _arg4 __asm__ ("d4") = (long)(arg4);                    \
+	register long _arg5 __asm__ ("d5") = (long)(arg5);                    \
+	register long _arg6 __asm__ ("a0") = (long)(arg6);                    \
+									      \
+	__asm__ volatile (                                                    \
+		"trap #0\n"                                                   \
+		: "+r" (_num)                                                 \
+		: "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5), \
+		  "r"(_arg6)                                                  \
+		: _NOLIBC_SYSCALL_CLOBBERLIST                                 \
+	);                                                                    \
+	_num;                                                                 \
+})
+
+void _start(void);
+void __attribute__((weak, noreturn)) __nolibc_entrypoint __no_stack_protector _start(void)
+{
+	__asm__ volatile (
+		"movel %sp, %sp@-\n"
+		"jsr _start_c\n"
+	);
+	__nolibc_entrypoint_epilogue();
+}
+
+#endif /* _NOLIBC_ARCH_M68K_H */
diff --git a/tools/include/nolibc/arch.h b/tools/include/nolibc/arch.h
index b8c1da9a88d1..d20b2304aac2 100644
--- a/tools/include/nolibc/arch.h
+++ b/tools/include/nolibc/arch.h
@@ -35,6 +35,8 @@
 #include "arch-loongarch.h"
 #elif defined(__sparc__)
 #include "arch-sparc.h"
+#elif defined(__m68k__)
+#include "arch-m68k.h"
 #else
 #error Unsupported Architecture
 #endif
diff --git a/tools/testing/selftests/nolibc/Makefile b/tools/testing/selftests/nolibc/Makefile
index d17750761d9f..2671383045db 100644
--- a/tools/testing/selftests/nolibc/Makefile
+++ b/tools/testing/selftests/nolibc/Makefile
@@ -80,6 +80,7 @@ IMAGE_s390       = arch/s390/boot/bzImage
 IMAGE_loongarch  = arch/loongarch/boot/vmlinuz.efi
 IMAGE_sparc32    = arch/sparc/boot/image
 IMAGE_sparc64    = arch/sparc/boot/image
+IMAGE_m68k       = vmlinux
 IMAGE            = $(objtree)/$(IMAGE_$(XARCH))
 IMAGE_NAME       = $(notdir $(IMAGE))
 
@@ -103,8 +104,10 @@ DEFCONFIG_s390       = defconfig compat.config
 DEFCONFIG_loongarch  = defconfig
 DEFCONFIG_sparc32    = sparc32_defconfig
 DEFCONFIG_sparc64    = sparc64_defconfig
+DEFCONFIG_m68k       = virt_defconfig
 DEFCONFIG            = $(DEFCONFIG_$(XARCH))
 
+EXTRACONFIG_m68k      = -e CONFIG_BLK_DEV_INITRD
 EXTRACONFIG           = $(EXTRACONFIG_$(XARCH))
 
 # optional tests to run (default = all)
@@ -130,6 +133,7 @@ QEMU_ARCH_s390       = s390x
 QEMU_ARCH_loongarch  = loongarch64
 QEMU_ARCH_sparc32    = sparc
 QEMU_ARCH_sparc64    = sparc64
+QEMU_ARCH_m68k       = m68k
 QEMU_ARCH            = $(QEMU_ARCH_$(XARCH))
 
 QEMU_ARCH_USER_ppc64le = ppc64le
@@ -162,6 +166,7 @@ QEMU_ARGS_s390       = -M s390-ccw-virtio -append "console=ttyS0 panic=-1 $(TEST
 QEMU_ARGS_loongarch  = -M virt -append "console=ttyS0,115200 panic=-1 $(TEST:%=NOLIBC_TEST=%)"
 QEMU_ARGS_sparc32    = -M SS-5 -m 256M -append "console=ttyS0,115200 panic=-1 $(TEST:%=NOLIBC_TEST=%)"
 QEMU_ARGS_sparc64    = -M sun4u -append "console=ttyS0,115200 panic=-1 $(TEST:%=NOLIBC_TEST=%)"
+QEMU_ARGS_m68k       = -M virt -append "console=ttyGF0,115200 panic=-1 $(TEST:%=NOLIBC_TEST=%)"
 QEMU_ARGS            = -m 1G $(QEMU_ARGS_$(XARCH)) $(QEMU_ARGS_BIOS) $(QEMU_ARGS_EXTRA)
 
 # OUTPUT is only set when run from the main makefile, otherwise
diff --git a/tools/testing/selftests/nolibc/run-tests.sh b/tools/testing/selftests/nolibc/run-tests.sh
index 040956a9f5b8..8277599e6441 100755
--- a/tools/testing/selftests/nolibc/run-tests.sh
+++ b/tools/testing/selftests/nolibc/run-tests.sh
@@ -26,6 +26,7 @@ all_archs=(
 	s390x s390
 	loongarch
 	sparc32 sparc64
+	m68k
 )
 archs="${all_archs[@]}"
 
@@ -186,6 +187,10 @@ test_arch() {
 		echo "Unsupported configuration"
 		return
 	fi
+	if [ "$arch" = "m68k" ] && [ "$llvm" = "1" ]; then
+		echo "Unsupported configuration"
+		return
+	fi
 
 	mkdir -p "$build_dir"
 	swallow_output "${MAKE[@]}" defconfig