arm64: Add audit support

On AArch64, audit is supported through generic lib/audit.c and
compat_audit.c, and so this patch adds arch specific definitions required.

Acked-by Will Deacon <[e-mail]>
Acked-by: Richard Guy Briggs <[e-mail]>
Signed-off-by: AKASHI Takahiro <[e-mail]>
Signed-off-by: Catalin Marinas <[e-mail]>

arch/arm64/Kconfig

···
 	select ARM_AMBA
 	select ARM_ARCH_TIMER
 	select ARM_GIC
+	select AUDIT_ARCH_COMPAT_GENERIC
 	select BUILDTIME_EXTABLE_SORT
 	select CLONE_BACKWARDS
 	select COMMON_CLK
···
 	select GENERIC_STRNLEN_USER
 	select GENERIC_TIME_VSYSCALL
 	select HARDIRQS_SW_RESEND
+	select HAVE_ARCH_AUDITSYSCALL
 	select HAVE_ARCH_JUMP_LABEL
 	select HAVE_ARCH_KGDB
 	select HAVE_ARCH_TRACEHOOK

arch/arm64/include/asm/syscall.h

···
 #ifndef __ASM_SYSCALL_H
 #define __ASM_SYSCALL_H
 
+#include <uapi/linux/audit.h>
+#include <linux/compat.h>
 #include <linux/err.h>
 
 extern const void *sys_call_table[];
···
 	}
 
 	memcpy(&regs->regs[i], args, n * sizeof(args[0]));
+}
+
+/*
+ * We don't care about endianness (__AUDIT_ARCH_LE bit) here because
+ * AArch64 has the same system calls both on little- and big- endian.
+ */
+static inline int syscall_get_arch(void)
+{
+	if (is_compat_task())
+		return AUDIT_ARCH_ARM;
+
+	return AUDIT_ARCH_AARCH64;
 }
 
 #endif	/* __ASM_SYSCALL_H */

include/uapi/linux/audit.h

···
 #define __AUDIT_ARCH_64BIT 0x80000000
 #define __AUDIT_ARCH_LE	   0x40000000
 
+#define AUDIT_ARCH_AARCH64	(EM_AARCH64|__AUDIT_ARCH_64BIT|__AUDIT_ARCH_LE)
 #define AUDIT_ARCH_ALPHA	(EM_ALPHA|__AUDIT_ARCH_64BIT|__AUDIT_ARCH_LE)
 #define AUDIT_ARCH_ARM		(EM_ARM|__AUDIT_ARCH_LE)
 #define AUDIT_ARCH_ARMEB	(EM_ARM)