xtensa: add audit support

All bits needed for syscall audit are present on xtensa. Add
audit_syscall_entry and audit_syscall_exit calls and select
HAVE_ARCH_AUDITSYSCALL in Kconfig.
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

arch/xtensa/Kconfig

@@ -21,6 +21,7 @@ config XTENSA
 	select GENERIC_PCI_IOMAP
 	select GENERIC_SCHED_CLOCK
 	select GENERIC_STRNCPY_FROM_USER if KASAN
+	select HAVE_ARCH_AUDITSYSCALL
 	select HAVE_ARCH_JUMP_LABEL if !XIP_KERNEL
 	select HAVE_ARCH_KASAN if MMU && !XIP_KERNEL
 	select HAVE_ARCH_TRACEHOOK

arch/xtensa/include/asm/thread_info.h

@@ -111,15 +111,17 @@ static inline struct thread_info *current_thread_info(void)
 #define TIF_RESTORE_SIGMASK	6	/* restore signal mask in do_signal() */
 #define TIF_NOTIFY_RESUME	7	/* callback before returning to user */
 #define TIF_DB_DISABLED		8	/* debug trap disabled for syscall */
+#define TIF_SYSCALL_AUDIT	9	/* syscall auditing active */
 
 #define _TIF_SYSCALL_TRACE	(1<<TIF_SYSCALL_TRACE)
 #define _TIF_SIGPENDING		(1<<TIF_SIGPENDING)
 #define _TIF_NEED_RESCHED	(1<<TIF_NEED_RESCHED)
 #define _TIF_SINGLESTEP		(1<<TIF_SINGLESTEP)
 #define _TIF_SYSCALL_TRACEPOINT	(1<<TIF_SYSCALL_TRACEPOINT)
+#define _TIF_SYSCALL_AUDIT	(1<<TIF_SYSCALL_AUDIT)
 
 #define _TIF_WORK_MASK		(_TIF_SYSCALL_TRACE | _TIF_SINGLESTEP | \
-				 _TIF_SYSCALL_TRACEPOINT)
+				 _TIF_SYSCALL_TRACEPOINT | _TIF_SYSCALL_AUDIT)
 
 #define THREAD_SIZE KERNEL_STACK_SIZE
 #define THREAD_SIZE_ORDER (KERNEL_STACK_SHIFT - PAGE_SHIFT)

arch/xtensa/kernel/ptrace.c

@@ -12,6 +12,7 @@
  * Marc Gauthier<marc@tensilica.com> <marc@alumni.uwaterloo.ca>
  */
 
+#include <linux/audit.h>
 #include <linux/errno.h>
 #include <linux/hw_breakpoint.h>
 #include <linux/kernel.h>
@@ -562,6 +563,9 @@ int do_syscall_trace_enter(struct pt_regs *regs)
 	if (test_thread_flag(TIF_SYSCALL_TRACEPOINT))
 		trace_sys_enter(regs, syscall_get_nr(current, regs));
 
+	audit_syscall_entry(regs->syscall, regs->areg[6],
+			    regs->areg[3], regs->areg[4],
+			    regs->areg[5]);
 	return 1;
 }
 
@@ -569,6 +573,8 @@ void do_syscall_trace_leave(struct pt_regs *regs)
 {
 	int step;
 
+	audit_syscall_exit(regs);
+
 	if (test_thread_flag(TIF_SYSCALL_TRACEPOINT))
 		trace_sys_exit(regs, regs_return_value(regs));