seccomp: Get compat syscalls from asm-generic header

Move retrieval of compat syscall numbers into inline function defined in
asm-generic header so that arches may override it.

[ralf@linux-mips.org: Resolve merge conflict.]
Suggested-by: Paul Burton <paul.burton@imgtec.com>
Signed-off-by: Matt Redfearn <matt.redfearn@imgtec.com>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: IMG-MIPSLinuxKerneldevelopers@imgtec.com
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Will Drewry <wad@chromium.org>
Cc: linux-arch@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/12978/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

include/asm-generic/seccomp.h

@@ -29,4 +29,18 @@
 #define __NR_seccomp_sigreturn		__NR_rt_sigreturn
 #endif
 
+#ifdef CONFIG_COMPAT
+#ifndef get_compat_mode1_syscalls
+static inline const int *get_compat_mode1_syscalls(void)
+{
+	static const int mode1_syscalls_32[] = {
+		__NR_seccomp_read_32, __NR_seccomp_write_32,
+		__NR_seccomp_exit_32, __NR_seccomp_sigreturn_32,
+		0, /* null terminated */
+	};
+	return mode1_syscalls_32;
+}
+#endif
+#endif /* CONFIG_COMPAT */
+
 #endif /* _ASM_GENERIC_SECCOMP_H */

kernel/seccomp.c

@@ -518,19 +518,12 @@ static int mode1_syscalls[] = {
 	0, /* null terminated */
 };
 
-#ifdef CONFIG_COMPAT
-static int mode1_syscalls_32[] = {
-	__NR_seccomp_read_32, __NR_seccomp_write_32, __NR_seccomp_exit_32, __NR_seccomp_sigreturn_32,
-	0, /* null terminated */
-};
-#endif
-
 static void __secure_computing_strict(int this_syscall)
 {
 	int *syscall_whitelist = mode1_syscalls;
 #ifdef CONFIG_COMPAT
 	if (in_compat_syscall())
-		syscall_whitelist = mode1_syscalls_32;
+		syscall_whitelist = get_compat_mode1_syscalls();
 #endif
 	do {
 		if (*syscall_whitelist == this_syscall)