score: add generic sys_call_table

This adds back a sys_call_table to the score architecture, which
got lost in the conversion to the generic unistd.h file.
It's rather worrying that the code got submitted without a
system call table, which evidently means that it got zero
testing.

Since the system call table has a different layout from the old
one (which was modeled after the mips-o32 one), I also try to
fix the entry.S path to use it. In the modified calling conventions,
all system call arguments are passed as registers r4 through r9,
instead of r4 through r7 plus stack for the fifth and sixth argument.

This matches what other architectures to when they normally pass
arguments on the stack.

Signed-off-by: Arnd Bergmann <[e-mail]>

arch/score/kernel/Makefile

···
 extra-y	:= head.o vmlinux.lds
 
 obj-y += entry.o init_task.o irq.o process.o ptrace.o \
-	setup.o signal.o sys_score.o time.o traps.o
+	setup.o signal.o sys_score.o time.o traps.o \
+	sys_call_table.o
 
 obj-$(CONFIG_MODULES) += module.o

arch/score/kernel/entry.S

···
 	sw	r4, [r0, PT_ORIG_R4]	#for restart syscall
 	sw	r7, [r0, PT_ORIG_R7]	#for restart syscall
 	sw	r27, [r0, PT_IS_SYSCALL] # it from syscall
+	sw	r8, [r0, 16]		# argument 5 from user r8
+	sw	r9, [r0, 20]		# argument 6 from user r9
 
 	lw	r9, [r0, PT_EPC]	# skip syscall on return
 	addi	r9, 4
···
 	cmpi.c	r27, __NR_syscalls 	# check syscall number
 	bgtu	illegal_syscall
 
-	slli	r8, r27, 3		# get syscall routine
+	slli	r8, r27, 2		# get syscall routine
 	la	r11, sys_call_table
 	add	r11, r11, r8
 	lw	r10, [r11]		# get syscall entry
-	lw	r11, [r11, 4]		# get number of args
 
 	cmpz.c	r10
 	beq	illegal_syscall
 
-	cmpi.c	r11, 4			# more than 4 arguments?
-	bgtu	stackargs
-
-stack_done:
 	lw	r8, [r28, TI_FLAGS]
 	li	r9, _TIF_SYSCALL_TRACE
 	and.c	r8, r8, r9
···
 					# restarting
 1:	sw	r4, [r0, PT_R2]		# result
 	j	syscall_exit
-
-stackargs:
-	lw	r8, [r0, PT_R0]
-	andri.c	r9, r8, 3		# test whether user sp is align a word
-	bne	bad_stack
-	subi	r11, 5
-	slli	r9, r11, 2
-	add.c	r9, r9, r8
-
-	bmi	bad_stack
-	la	r9, 3f			# calculate branch address
-	slli	r11, r11, 3
-	sub	r9, r9, r11
-	br	r9
-
-2:	lw	r9, [r8, 20]		# argument 6 from usp
-	sw	r9, [r0, 20]
-
-3:	lw	r9, [r8, 16]		# argument 5 from usp
-	sw	r9, [r0, 16]
-	j	stack_done
-
-	.section __ex_table,"a"
-	.word	2b, bad_stack
-	.word	3b, bad_stack
-	.previous
-
-	/*
-	 * The stackpointer for a call with more than 4 arguments is bad.
-	 * We probably should handle this case a bit more drastic.
-	 */
-bad_stack:
-	neg	r27, r27		# error
-	sw	r27, [r0, PT_ORIG_R4]
-	sw	r27, [r0, PT_R4]
-	ldi	r8, 1			# set error flag
-	sw	r8, [r0, PT_R7]
-	j	syscall_return
 
 illegal_syscall:
 	ldi	r4, -ENOSYS		# error

arch/score/kernel/sys_call_table.c

···
+#include <linux/syscalls.h>
+#include <linux/signal.h>
+#include <linux/unistd.h>
+
+#include <asm/syscalls.h>
+
+#undef __SYSCALL
+#define __SYSCALL(nr, call) [nr] = (call),
+
+void *sys_call_table[__NR_syscalls] = {
+#include <asm/unistd.h>
+};

arch/score/kernel/sys_score.c

···
 	if (!newsp)
 		newsp = regs->regs[0];
 	parent_tidptr = (int __user *)regs->regs[6];
-
-	child_tidptr = NULL;
-	if (clone_flags & (CLONE_CHILD_SETTID | CLONE_CHILD_CLEARTID)) {
-		int __user *__user *usp = (int __user *__user *)regs->regs[0];
-
-		if (get_user(child_tidptr, &usp[4]))
-			return -EFAULT;
-	}
+	child_tidptr = (int __user *)regs->regs[8];
 
 	return do_fork(clone_flags, newsp, regs, 0,
 			parent_tidptr, child_tidptr);