m68k: kernel: Add and use <asm/syscalls.h>

When building with W=1:

arch/m68k/kernel/sys_m68k.c:40:17: warning: no previous prototype for ‘sys_mmap2’ [-Wmissing-prototypes]
40 | asmlinkage long sys_mmap2(unsigned long addr, unsigned long len,
| ^~~~~~~~~
arch/m68k/kernel/sys_m68k.c:378:1: warning: no previous prototype for ‘sys_cacheflush’ [-Wmissing-prototypes]
378 | sys_cacheflush (unsigned long addr, int scope, int cache, unsigned long len)
| ^~~~~~~~~~~~~~
arch/m68k/kernel/sys_m68k.c:463:1: warning: no previous prototype for ‘sys_atomic_cmpxchg_32’ [-Wmissing-prototypes]
463 | sys_atomic_cmpxchg_32(unsigned long newval, int oldval, int d3, int d4, int d5,
| ^~~~~~~~~~~~~~~~~~~~~
arch/m68k/kernel/sys_m68k.c:564:16: warning: no previous prototype for ‘sys_getpagesize’ [-Wmissing-prototypes]
564 | asmlinkage int sys_getpagesize(void)
| ^~~~~~~~~~~~~~~
arch/m68k/kernel/sys_m68k.c:569:26: warning: no previous prototype for ‘sys_get_thread_area’ [-Wmissing-prototypes]
569 | asmlinkage unsigned long sys_get_thread_area(void)
| ^~~~~~~~~~~~~~~~~~~
arch/m68k/kernel/sys_m68k.c:574:16: warning: no previous prototype for ‘sys_set_thread_area’ [-Wmissing-prototypes]
574 | asmlinkage int sys_set_thread_area(unsigned long tp)
| ^~~~~~~~~~~~~~~~~~~
arch/m68k/kernel/sys_m68k.c:580:16: warning: no previous prototype for ‘sys_atomic_barrier’ [-Wmissing-prototypes]
580 | asmlinkage int sys_atomic_barrier(void)
| ^~~~~~~~~~~~~~~~~~

Fix this by introducing a new header file <asm/syscalls.h> for holding
the prototypes for m68k-specific syscalls, and including the generic
ones.

Signed-off-by: Geert Uytterhoeven <[e-mail]>
Acked-by: Arnd Bergmann <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

arch/m68k/include/asm/syscalls.h

···
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef _ASM_M68K_SYSCALLS_H
+#define _ASM_M68K_SYSCALLS_H
+
+#include <linux/compiler_types.h>
+#include <linux/linkage.h>
+
+asmlinkage int sys_cacheflush(unsigned long addr, int scope, int cache,
+			      unsigned long len);
+asmlinkage int sys_atomic_cmpxchg_32(unsigned long newval, int oldval, int d3,
+				     int d4, int d5, unsigned long __user *mem);
+asmlinkage int sys_getpagesize(void);
+asmlinkage unsigned long sys_get_thread_area(void);
+asmlinkage int sys_set_thread_area(unsigned long tp);
+asmlinkage int sys_atomic_barrier(void);
+
+#include <asm-generic/syscalls.h>
+
+#endif	/* _ASM_M68K_SYSCALLS_H */

arch/m68k/kernel/sys_m68k.c

···
 #include <asm/cachectl.h>
 #include <asm/traps.h>
 #include <asm/page.h>
+#include <asm/syscalls.h>
 #include <asm/unistd.h>
 #include <asm/cacheflush.h>