sh: Exception vector rework and SH-2/SH-2A support.

This splits out common bits from the existing exception handler for
use between SH-2/SH-2A and SH-3/4, and adds support for the SH-2/2A
exceptions.

Signed-off-by: Yoshinori Sato <ysato@users.sourceforge.jp>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>

1 files changed, 372 insertions, 0 deletions

diff --git a/arch/sh/kernel/entry-common.S b/arch/sh/kernel/entry-common.S
new file mode 100644
index 00000000000..5bc7fa91d09
--- /dev/null
+++ b/arch/sh/kernel/entry-common.S
@@ -0,0 +1,372 @@
+/* $Id: entry.S,v 1.37 2004/06/11 13:02:46 doyu Exp $
+ *
+ *  linux/arch/sh/entry.S
+ *
+ *  Copyright (C) 1999, 2000, 2002  Niibe Yutaka
+ *  Copyright (C) 2003  Paul Mundt
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ */
+
+! NOTE:
+! GNU as (as of 2.9.1) changes bf/s into bt/s and bra, when the address
+! to be jumped is too far, but it causes illegal slot exception.
+
+/*	
+ * entry.S contains the system-call and fault low-level handling routines.
+ * This also contains the timer-interrupt handler, as well as all interrupts
+ * and faults that can result in a task-switch.
+ *
+ * NOTE: This code handles signal-recognition, which happens every time
+ * after a timer-interrupt and after each system call.
+ *
+ * NOTE: This code uses a convention that instructions in the delay slot
+ * of a transfer-control instruction are indented by an extra space, thus:
+ *
+ *    jmp	@k0	    ! control-transfer instruction
+ *     ldc	k1, ssr     ! delay slot
+ *
+ * Stack layout in 'ret_from_syscall':
+ * 	ptrace needs to have all regs on the stack.
+ *	if the order here is changed, it needs to be
+ *	updated in ptrace.c and ptrace.h
+ *
+ *	r0
+ *      ...
+ *	r15 = stack pointer
+ *	spc
+ *	pr
+ *	ssr
+ *	gbr
+ *	mach
+ *	macl
+ *	syscall #
+ *
+ */
+
+#if defined(CONFIG_PREEMPT)
+#  define preempt_stop()	cli
+#else
+#  define preempt_stop()
+#  define resume_kernel		__restore_all
+#endif
+
+#if defined(CONFIG_SH_STANDARD_BIOS) || defined(CONFIG_SH_KGDB)
+! Handle kernel debug if either kgdb (SW) or gdb-stub (FW) is present.
+! If both are configured, handle the debug traps (breakpoints) in SW,
+! but still allow BIOS traps to FW.
+
+	.align	2
+debug_kernel:
+#if defined(CONFIG_SH_STANDARD_BIOS) && defined(CONFIG_SH_KGDB)
+	/* Force BIOS call to FW (debug_trap put TRA in r8) */
+	mov	r8,r0
+	shlr2	r0
+	cmp/eq	#0x3f,r0
+	bt	debug_kernel_fw
+#endif /* CONFIG_SH_STANDARD_BIOS && CONFIG_SH_KGDB */
+
+debug_enter:		
+#if defined(CONFIG_SH_KGDB)
+	/* Jump to kgdb, pass stacked regs as arg */
+debug_kernel_sw:
+	mov.l	3f, r0
+	jmp	@r0
+	 mov	r15, r4
+	.align	2
+3:	.long	kgdb_handle_exception
+#endif /* CONFIG_SH_KGDB */
+
+#endif /* CONFIG_SH_STANDARD_BIOS || CONFIG_SH_KGDB */
+
+
+	.align	2
+debug_trap:	
+#if defined(CONFIG_SH_STANDARD_BIOS) || defined(CONFIG_SH_KGDB)
+	mov	#OFF_SR, r0
+	mov.l	@(r0,r15), r0		! get status register
+	shll	r0
+	shll	r0			! kernel space?
+	bt/s	debug_kernel
+#endif
+	 mov.l	@r15, r0		! Restore R0 value
+	mov.l	1f, r8
+	jmp	@r8
+	 nop
+
+	.align	2
+ENTRY(exception_error)
+	!
+	sti
+	mov.l	2f, r0
+	jmp	@r0
+	 nop
+
+!
+	.align	2
+1:	.long	break_point_trap_software
+2:	.long	do_exception_error
+
+	.align	2
+ret_from_exception:
+	preempt_stop()
+ENTRY(ret_from_irq)
+	!
+	mov	#OFF_SR, r0
+	mov.l	@(r0,r15), r0	! get status register
+	shll	r0
+	shll	r0		! kernel space?
+	get_current_thread_info r8, r0
+	bt	resume_kernel	! Yes, it's from kernel, go back soon
+
+#ifdef CONFIG_PREEMPT
+	bra	resume_userspace
+	 nop
+ENTRY(resume_kernel)
+	mov.l	@(TI_PRE_COUNT,r8), r0	! current_thread_info->preempt_count
+	tst	r0, r0
+	bf	noresched
+need_resched:
+	mov.l	@(TI_FLAGS,r8), r0	! current_thread_info->flags
+	tst	#_TIF_NEED_RESCHED, r0	! need_resched set?
+	bt	noresched
+
+	mov	#OFF_SR, r0
+	mov.l	@(r0,r15), r0		! get status register
+	and	#0xf0, r0		! interrupts off (exception path)?
+	cmp/eq	#0xf0, r0
+	bt	noresched
+
+	mov.l	1f, r0
+	mov.l	r0, @(TI_PRE_COUNT,r8)
+
+	sti
+	mov.l	2f, r0
+	jsr	@r0
+	 nop
+	mov	#0, r0
+	mov.l	r0, @(TI_PRE_COUNT,r8)
+	cli
+
+	bra	need_resched
+	 nop
+noresched:
+	bra	__restore_all
+	 nop
+
+	.align 2
+1:	.long	PREEMPT_ACTIVE
+2:	.long	schedule
+#endif
+
+ENTRY(resume_userspace)
+	! r8: current_thread_info
+	cli
+	mov.l	@(TI_FLAGS,r8), r0		! current_thread_info->flags
+	tst	#_TIF_WORK_MASK, r0
+	bt/s	__restore_all
+	 tst	#_TIF_NEED_RESCHED, r0
+
+	.align	2
+work_pending:
+	! r0: current_thread_info->flags
+	! r8: current_thread_info
+	! t:  result of "tst	#_TIF_NEED_RESCHED, r0"
+	bf/s	work_resched
+	 tst	#(_TIF_SIGPENDING | _TIF_RESTORE_SIGMASK), r0
+work_notifysig:
+	bt/s	__restore_all
+	 mov	r15, r4
+	mov	r12, r5		! set arg1(save_r0)
+	mov	r0, r6
+	mov.l	2f, r1
+	mov.l	3f, r0
+	jmp	@r1
+	 lds	r0, pr
+work_resched:
+#ifndef CONFIG_PREEMPT
+	! gUSA handling
+	mov.l	@(OFF_SP,r15), r0	! get user space stack pointer
+	mov	r0, r1
+	shll	r0
+	bf/s	1f
+	 shll	r0
+	bf/s	1f
+	 mov	#OFF_PC, r0
+	! 				  SP >= 0xc0000000 : gUSA mark
+	mov.l	@(r0,r15), r2		! get user space PC (program counter)
+	mov.l	@(OFF_R0,r15), r3	! end point
+	cmp/hs	r3, r2			! r2 >= r3? 
+	bt	1f
+	add	r3, r1			! rewind point #2
+	mov.l	r1, @(r0,r15)		! reset PC to rewind point #2
+	!
+1:
+#endif
+	mov.l	1f, r1
+	jsr	@r1				! schedule
+	 nop
+	cli
+	!
+	mov.l	@(TI_FLAGS,r8), r0		! current_thread_info->flags
+	tst	#_TIF_WORK_MASK, r0
+	bt	__restore_all
+	bra	work_pending
+	 tst	#_TIF_NEED_RESCHED, r0
+
+	.align	2
+1:	.long	schedule
+2:	.long	do_notify_resume
+3:	.long	restore_all
+
+	.align	2
+syscall_exit_work:
+	! r0: current_thread_info->flags
+	! r8: current_thread_info
+	tst	#_TIF_SYSCALL_TRACE, r0
+	bt/s	work_pending
+	 tst	#_TIF_NEED_RESCHED, r0
+	sti
+	! XXX setup arguments...
+	mov.l	4f, r0			! do_syscall_trace
+	jsr	@r0
+	 nop
+	bra	resume_userspace
+	 nop
+
+	.align	2
+syscall_trace_entry:
+	!                     	Yes it is traced.
+	! XXX setup arguments...
+	mov.l	4f, r11		! Call do_syscall_trace which notifies
+	jsr	@r11	    	! superior (will chomp R[0-7])
+	 nop
+	!			Reload R0-R4 from kernel stack, where the
+	!   	    	    	parent may have modified them using
+	!   	    	    	ptrace(POKEUSR).  (Note that R0-R2 are
+	!   	    	    	used by the system call handler directly
+	!   	    	    	from the kernel stack anyway, so don't need
+	!   	    	    	to be reloaded here.)  This allows the parent
+	!   	    	    	to rewrite system calls and args on the fly.
+	mov.l	@(OFF_R4,r15), r4   ! arg0
+	mov.l	@(OFF_R5,r15), r5
+	mov.l	@(OFF_R6,r15), r6
+	mov.l	@(OFF_R7,r15), r7   ! arg3
+	mov.l	@(OFF_R3,r15), r3   ! syscall_nr
+	!   	    	    Arrange for do_syscall_trace to be called
+	!   	    	    again as the system call returns.
+	mov.l	2f, r10			! Number of syscalls
+	cmp/hs	r10, r3
+	bf	syscall_call
+	mov	#-ENOSYS, r0
+	bra	syscall_exit
+	 mov.l	r0, @(OFF_R0,r15)	! Return value
+
+__restore_all:
+	mov.l	1f,r0
+	jmp	@r0
+	 nop
+
+	.align	2
+1:	.long	restore_all
+
+/*
+ * Syscall interface:
+ *
+ *	Syscall #: R3
+ *	Arguments #0 to #3: R4--R7
+ *	Arguments #4 to #6: R0, R1, R2
+ *	TRA: (number of arguments + 0x10) x 4
+ *
+ * This code also handles delegating other traps to the BIOS/gdb stub
+ * according to:
+ *
+ * Trap number
+ * (TRA>>2) 	    Purpose
+ * -------- 	    -------
+ * 0x0-0xf  	    old syscall ABI
+ * 0x10-0x1f  	    new syscall ABI
+ * 0x20-0xff  	    delegated through debug_trap to BIOS/gdb stub.
+ *
+ * Note: When we're first called, the TRA value must be shifted
+ * right 2 bits in order to get the value that was used as the "trapa"
+ * argument.
+ */
+
+	.align	2
+	.globl	ret_from_fork
+ret_from_fork:
+	mov.l	1f, r8
+	jsr	@r8
+	 mov	r0, r4
+	bra	syscall_exit
+	 nop
+	.align	2
+1:	.long	schedule_tail
+	!
+ENTRY(system_call)
+#if !defined(CONFIG_CPU_SH2)
+	mov.l	1f, r9
+	mov.l	@r9, r8		! Read from TRA (Trap Address) Register
+#endif
+	!
+	! Is the trap argument >= 0x20? (TRA will be >= 0x80)
+	mov	#0x7f, r9
+	cmp/hi	r9, r8
+	bt/s	0f
+	 mov	#OFF_TRA, r9
+	add	r15, r9
+	!
+	mov.l	r8, @r9			! set TRA value to tra
+	sti
+	!   	    	    Call the system call handler through the table.
+	!   	    	    First check for bad syscall number
+	mov	r3, r9
+	mov.l	2f, r8			! Number of syscalls
+	cmp/hs	r8, r9
+	get_current_thread_info r8, r10
+	bf	good_system_call
+syscall_badsys:			! Bad syscall number
+	mov	#-ENOSYS, r0
+	bra	resume_userspace
+	 mov.l	r0, @(OFF_R0,r15)	! Return value
+	!
+0:
+	bra	debug_trap
+	 nop
+	!
+good_system_call:		! Good syscall number
+	mov.l	@(TI_FLAGS,r8), r8
+	mov	#_TIF_SYSCALL_TRACE, r10
+	tst	r10, r8
+	bf	syscall_trace_entry
+	!
+syscall_call:
+	shll2	r9		! x4
+	mov.l	3f, r8		! Load the address of sys_call_table
+	add	r8, r9
+	mov.l	@r9, r8
+	jsr	@r8	    	! jump to specific syscall handler
+	 nop
+	mov.l	@(OFF_R0,r15), r12		! save r0
+	mov.l	r0, @(OFF_R0,r15)		! save the return value
+	!
+syscall_exit:
+	cli
+	!
+	get_current_thread_info r8, r0
+	mov.l	@(TI_FLAGS,r8), r0		! current_thread_info->flags
+	tst	#_TIF_ALLWORK_MASK, r0
+	bf	syscall_exit_work
+	bra	__restore_all
+	 nop
+	.align	2
+#if !defined(CONFIG_CPU_SH2)
+1:	.long	TRA
+#endif
+2:	.long	NR_syscalls
+3:	.long	sys_call_table
+4:	.long	do_syscall_trace