avr32: wire up preadv2 and pwritev2 syscalls

This patch wires up the new preadv2 and pwritev2 syscall on AVR32.

On AVR32, all parameters beyond the 5th are passed on the stack. System
calls don't use the stack -- they borrow a callee-saved register
instead. This means that syscalls that take 6 parameters must be called
through a stub that pushes the last parameter on the stack.
Signed-off-by: Hans-Christian Noren Egtvedt <egtvedt@samfundet.no>

arch/avr32/include/uapi/asm/unistd.h

@@ -338,5 +338,7 @@
 #define __NR_membarrier		323
 #define __NR_mlock2		324
 #define __NR_copy_file_range    325
+#define __NR_preadv2            326
+#define __NR_pwritev2           327
 
 #endif /* _UAPI__ASM_AVR32_UNISTD_H */

arch/avr32/kernel/syscall-stubs.S

@@ -133,3 +133,21 @@ __sys_copy_file_range:
 	call	sys_copy_file_range
 	sub	sp, -4
 	popm	pc
+
+	.global __sys_preadv2
+	.type	__sys_preadv2,@function
+__sys_preadv2:
+	pushm	lr
+	st.w	--sp, ARG6
+	call	sys_preadv2
+	sub	sp, -4
+	popm	pc
+
+	.global __sys_pwritev2
+	.type	__sys_pwritev2,@function
+__sys_pwritev2:
+	pushm	lr
+	st.w	--sp, ARG6
+	call	sys_pwritev2
+	sub	sp, -4
+	popm	pc

arch/avr32/kernel/syscall_table.S

@@ -339,4 +339,6 @@ sys_call_table:
 	.long	sys_membarrier
 	.long	sys_mlock2
 	.long   __sys_copy_file_range   /* 325 */
+	.long   __sys_preadv2
+	.long   __sys_pwritev2
 	.long	sys_ni_syscall		/* r8 is saturated at nr_syscalls */