arm64: avoid prototype warnings for syscalls

With W=1 warnings enabled, there are lots of complaints about
missing prototypes for system calls, plus a few other related
ones:

arch/arm64/kernel/sys_compat.c:68:6: error: no previous prototype for 'compat_arm_syscall' [-Werror=missing-prototypes]
arch/arm64/include/asm/syscall_wrapper.h:76:32: error: no previous prototype for '__arm64_sys_io_setup' [-Werror=missing-prototypes]
arch/arm64/include/asm/syscall_wrapper.h:41:32: error: no previous prototype for '__arm64_compat_sys_io_setup' [-Werror=missing-prototypes]
arch/arm64/include/asm/syscall_wrapper.h:76:32: error: no previous prototype for '__arm64_sys_io_destroy' [-Werror=missing-prototypes]
arch/arm64/include/asm/syscall_wrapper.h:76:32: error: no previous prototype for '__arm64_sys_io_submit' [-Werror=missing-prototypes]

Add declarations to the syscall macros to avoid all of these, plus
one for the compat syscall entry.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20230516160642.523862-4-arnd@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

Author: arndb

arch/arm64/include/asm/compat.h

@@ -96,6 +96,8 @@ static inline int is_compat_thread(struct thread_info *thread)
 	return test_ti_thread_flag(thread, TIF_32BIT);
 }
 
+long compat_arm_syscall(struct pt_regs *regs, int scno);
+
 #else /* !CONFIG_COMPAT */
 
 static inline int is_compat_thread(struct thread_info *thread)

arch/arm64/include/asm/syscall_wrapper.h

@@ -38,6 +38,7 @@
 	asmlinkage long __arm64_compat_sys_##sname(const struct pt_regs *__unused)
 
 #define COND_SYSCALL_COMPAT(name) 							\
+	asmlinkage long __arm64_compat_sys_##name(const struct pt_regs *regs);		\
 	asmlinkage long __weak __arm64_compat_sys_##name(const struct pt_regs *regs)	\
 	{										\
 		return sys_ni_syscall();						\
@@ -53,6 +54,7 @@
 	ALLOW_ERROR_INJECTION(__arm64_sys##name, ERRNO);			\
 	static long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__));		\
 	static inline long __do_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__));	\
+	asmlinkage long __arm64_sys##name(const struct pt_regs *regs);		\
 	asmlinkage long __arm64_sys##name(const struct pt_regs *regs)		\
 	{									\
 		return __se_sys##name(SC_ARM64_REGS_TO_ARGS(x,__VA_ARGS__));	\
@@ -73,11 +75,13 @@
 	asmlinkage long __arm64_sys_##sname(const struct pt_regs *__unused)
 
 #define COND_SYSCALL(name)							\
+	asmlinkage long __arm64_sys_##name(const struct pt_regs *regs);		\
 	asmlinkage long __weak __arm64_sys_##name(const struct pt_regs *regs)	\
 	{									\
 		return sys_ni_syscall();					\
 	}
 
+asmlinkage long __arm64_sys_ni_syscall(const struct pt_regs *__unused);
 #define SYS_NI(name) SYSCALL_ALIAS(__arm64_sys_##name, sys_ni_posix_timers);
 
 #endif /* __ASM_SYSCALL_WRAPPER_H */