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>

2 files changed, 527 insertions, 1 deletions

diff --git a/arch/sh/kernel/cpu/sh3/Makefile b/arch/sh/kernel/cpu/sh3/Makefile
index 58d3815695f..83905e4e438 100644
--- a/arch/sh/kernel/cpu/sh3/Makefile
+++ b/arch/sh/kernel/cpu/sh3/Makefile
@@ -2,7 +2,7 @@
 # Makefile for the Linux/SuperH SH-3 backends.
 #
 
-obj-y	:= ex.o probe.o
+obj-y	:= ex.o probe.o entry.o
 
 # CPU subtype setup
 obj-$(CONFIG_CPU_SUBTYPE_SH7705)	+= setup-sh7705.o
diff --git a/arch/sh/kernel/cpu/sh3/entry.S b/arch/sh/kernel/cpu/sh3/entry.S
new file mode 100644
index 00000000000..8bcd63f9f35
--- /dev/null
+++ b/arch/sh/kernel/cpu/sh3/entry.S
@@ -0,0 +1,526 @@
+/*
+ * arch/sh/kernel/entry.S
+ *
+ *  Copyright (C) 1999, 2000, 2002  Niibe Yutaka
+ *  Copyright (C) 2003 - 2006  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.
+ */
+#include <linux/sys.h>
+#include <linux/errno.h>
+#include <linux/linkage.h>
+#include <asm/asm-offsets.h>
+#include <asm/thread_info.h>
+#include <asm/cpu/mmu_context.h>
+#include <asm/unistd.h>
+
+! 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_KGDB_NMI)
+NMI_VEC = 0x1c0			! Must catch early for debounce
+#endif
+
+/* Offsets to the stack */
+OFF_R0  =  0		/* Return value. New ABI also arg4 */
+OFF_R1  =  4     	/* New ABI: arg5 */
+OFF_R2  =  8     	/* New ABI: arg6 */
+OFF_R3  =  12     	/* New ABI: syscall_nr */
+OFF_R4  =  16     	/* New ABI: arg0 */
+OFF_R5  =  20     	/* New ABI: arg1 */
+OFF_R6  =  24     	/* New ABI: arg2 */
+OFF_R7  =  28     	/* New ABI: arg3 */
+OFF_SP	=  (15*4)
+OFF_PC  =  (16*4)
+OFF_SR	=  (16*4+8)
+OFF_TRA	=  (16*4+6*4)
+
+
+#define k0	r0
+#define k1	r1
+#define k2	r2
+#define k3	r3
+#define k4	r4
+
+#define g_imask		r6	/* r6_bank1 */
+#define k_g_imask	r6_bank	/* r6_bank1 */
+#define current		r7	/* r7_bank1 */
+
+#include <asm/entry-macros.S>
+	
+/*
+ * Kernel mode register usage:
+ *	k0	scratch
+ *	k1	scratch
+ *	k2	scratch (Exception code)
+ *	k3	scratch (Return address)
+ *	k4	scratch
+ *	k5	reserved
+ *	k6	Global Interrupt Mask (0--15 << 4)
+ *	k7	CURRENT_THREAD_INFO (pointer to current thread info)
+ */
+
+!
+! TLB Miss / Initial Page write exception handling
+!			_and_
+! TLB hits, but the access violate the protection.
+! It can be valid access, such as stack grow and/or C-O-W.
+!
+!
+! Find the pmd/pte entry and loadtlb
+! If it's not found, cause address error (SEGV)
+!
+! Although this could be written in assembly language (and it'd be faster),
+! this first version depends *much* on C implementation.
+!
+
+#if defined(CONFIG_MMU)
+	.align	2
+ENTRY(tlb_miss_load)
+	bra	call_dpf
+	 mov	#0, r5
+
+	.align	2
+ENTRY(tlb_miss_store)
+	bra	call_dpf
+	 mov	#1, r5
+
+	.align	2
+ENTRY(initial_page_write)
+	bra	call_dpf
+	 mov	#1, r5
+
+	.align	2
+ENTRY(tlb_protection_violation_load)
+	bra	call_dpf
+	 mov	#0, r5
+
+	.align	2
+ENTRY(tlb_protection_violation_store)
+	bra	call_dpf
+	 mov	#1, r5
+
+call_dpf:
+	mov.l	1f, r0
+	mov	r5, r8
+	mov.l	@r0, r6
+	mov	r6, r9
+	mov.l	2f, r0
+	sts	pr, r10
+	jsr	@r0
+	 mov	r15, r4
+	!
+	tst	r0, r0
+	bf/s	0f
+	 lds	r10, pr
+	rts
+	 nop
+0:	sti
+	mov.l	3f, r0
+	mov	r9, r6
+	mov	r8, r5
+	jmp	@r0
+	 mov	r15, r4
+
+	.align 2
+1:	.long	MMU_TEA
+2:	.long	__do_page_fault
+3:	.long	do_page_fault
+
+	.align	2
+ENTRY(address_error_load)
+	bra	call_dae
+	 mov	#0,r5		! writeaccess = 0
+
+	.align	2
+ENTRY(address_error_store)
+	bra	call_dae
+	 mov	#1,r5		! writeaccess = 1
+
+	.align	2
+call_dae:
+	mov.l	1f, r0
+	mov.l	@r0, r6		! address
+	mov.l	2f, r0
+	jmp	@r0
+	 mov	r15, r4		! regs
+
+	.align 2
+1:	.long	MMU_TEA
+2:	.long   do_address_error
+#endif /* CONFIG_MMU */
+
+#if defined(CONFIG_SH_STANDARD_BIOS)
+	/* Unwind the stack and jmp to the debug entry */
+debug_kernel_fw:
+	mov.l	@r15+, r0
+	mov.l	@r15+, r1
+	mov.l	@r15+, r2
+	mov.l	@r15+, r3
+	mov.l	@r15+, r4
+	mov.l	@r15+, r5
+	mov.l	@r15+, r6
+	mov.l	@r15+, r7
+	stc	sr, r8
+	mov.l	1f, r9			! BL =1, RB=1, IMASK=0x0F
+	or	r9, r8
+	ldc	r8, sr			! here, change the register bank
+	mov.l	@r15+, r8
+	mov.l	@r15+, r9
+	mov.l	@r15+, r10
+	mov.l	@r15+, r11
+	mov.l	@r15+, r12
+	mov.l	@r15+, r13
+	mov.l	@r15+, r14
+	mov.l	@r15+, k0
+	ldc.l	@r15+, spc
+	lds.l	@r15+, pr
+	mov.l	@r15+, k1
+	ldc.l	@r15+, gbr
+	lds.l	@r15+, mach
+	lds.l	@r15+, macl
+	mov	k0, r15
+	!
+	mov.l	2f, k0
+	mov.l	@k0, k0
+	jmp	@k0
+	 ldc	k1, ssr
+	.align	2
+1:	.long	0x300000f0
+2:	.long	gdb_vbr_vector
+#endif /* CONFIG_SH_STANDARD_BIOS */
+
+restore_all:
+	mov.l	@r15+, r0
+	mov.l	@r15+, r1
+	mov.l	@r15+, r2
+	mov.l	@r15+, r3
+	mov.l	@r15+, r4
+	mov.l	@r15+, r5
+	mov.l	@r15+, r6
+	mov.l	@r15+, r7
+	!
+	stc	sr, r8
+	mov.l	7f, r9
+	or	r9, r8			! BL =1, RB=1
+	ldc	r8, sr			! here, change the register bank
+	!
+	mov.l	@r15+, r8
+	mov.l	@r15+, r9
+	mov.l	@r15+, r10
+	mov.l	@r15+, r11
+	mov.l	@r15+, r12
+	mov.l	@r15+, r13
+	mov.l	@r15+, r14
+	mov.l	@r15+, k4		! original stack pointer
+	ldc.l	@r15+, spc
+	lds.l	@r15+, pr
+	mov.l	@r15+, k3		! original SR
+	ldc.l	@r15+, gbr
+	lds.l	@r15+, mach
+	lds.l	@r15+, macl
+	add	#4, r15			! Skip syscall number
+	!
+#ifdef CONFIG_SH_DSP
+	mov.l	@r15+, k0		! DSP mode marker
+	mov.l	5f, k1
+	cmp/eq	k0, k1			! Do we have a DSP stack frame?
+	bf	skip_restore
+
+	stc	sr, k0			! Enable CPU DSP mode
+	or	k1, k0			! (within kernel it may be disabled)
+	ldc	k0, sr
+	mov	r2, k0			! Backup r2
+
+	! Restore DSP registers from stack
+	mov	r15, r2
+	movs.l	@r2+, a1
+	movs.l	@r2+, a0g
+	movs.l	@r2+, a1g
+	movs.l	@r2+, m0
+	movs.l	@r2+, m1
+	mov	r2, r15
+
+	lds.l	@r15+, a0
+	lds.l	@r15+, x0
+	lds.l	@r15+, x1
+	lds.l	@r15+, y0
+	lds.l	@r15+, y1
+	lds.l	@r15+, dsr
+	ldc.l	@r15+, rs
+	ldc.l	@r15+, re
+	ldc.l	@r15+, mod
+
+	mov	k0, r2			! Restore r2
+skip_restore:
+#endif
+	!
+	! Calculate new SR value
+	mov	k3, k2			! original SR value
+	mov	#0xf0, k1
+	extu.b	k1, k1
+	not	k1, k1
+	and	k1, k2			! Mask orignal SR value
+	!
+	mov	k3, k0			! Calculate IMASK-bits
+	shlr2	k0
+	and	#0x3c, k0
+	cmp/eq	#0x3c, k0
+	bt/s	6f
+	 shll2	k0
+	mov	g_imask, k0
+	!
+6:	or	k0, k2			! Set the IMASK-bits
+	ldc	k2, ssr
+	!
+#if defined(CONFIG_KGDB_NMI)
+	! Clear in_nmi
+	mov.l	6f, k0
+	mov	#0, k1
+	mov.b	k1, @k0
+#endif
+	mov.l	@r15+, k2		! restore EXPEVT
+	mov	k4, r15
+	rte
+	 nop
+
+	.align	2
+5:	.long	0x00001000	! DSP
+7:	.long	0x30000000
+
+! common exception handler
+#include "../../entry.S"
+	
+! Exception Vector Base
+!
+!	Should be aligned page boundary.
+!
+	.balign 	4096,0,4096
+ENTRY(vbr_base)
+	.long	0
+!
+	.balign 	256,0,256
+general_exception:
+	mov.l	1f, k2
+	mov.l	2f, k3
+	bra	handle_exception
+	 mov.l	@k2, k2
+	.align	2
+1:	.long	EXPEVT
+2:	.long	ret_from_exception
+!
+!
+	.balign 	1024,0,1024
+tlb_miss:
+	mov.l	1f, k2
+	mov.l	4f, k3
+	bra	handle_exception
+	 mov.l	@k2, k2
+!
+	.balign 	512,0,512
+interrupt:
+	mov.l	2f, k2
+	mov.l	3f, k3
+#if defined(CONFIG_KGDB_NMI)
+	! Debounce (filter nested NMI)
+	mov.l	@k2, k0
+	mov.l	5f, k1
+	cmp/eq	k1, k0
+	bf	0f
+	mov.l	6f, k1
+	tas.b	@k1
+	bt	0f
+	rte
+	 nop
+	.align	2
+5:	.long	NMI_VEC
+6:	.long	in_nmi
+0:
+#endif /* defined(CONFIG_KGDB_NMI) */
+	bra	handle_exception
+	 mov	#-1, k2		! interrupt exception marker
+
+	.align	2
+1:	.long	EXPEVT
+2:	.long	INTEVT
+3:	.long	ret_from_irq
+4:	.long	ret_from_exception
+
+!
+!
+	.align	2
+ENTRY(handle_exception)
+	! Using k0, k1 for scratch registers (r0_bank1, r1_bank),
+	! save all registers onto stack.
+	!
+	stc	ssr, k0		! Is it from kernel space?
+	shll	k0		! Check MD bit (bit30) by shifting it into...
+	shll	k0		!       ...the T bit
+	bt/s	1f		! It's a kernel to kernel transition.
+	 mov	r15, k0		! save original stack to k0
+	/* User space to kernel */
+	mov	#(THREAD_SIZE >> 8), k1
+	shll8	k1		! k1 := THREAD_SIZE
+	add	current, k1
+	mov	k1, r15		! change to kernel stack
+	!
+1:	mov.l	2f, k1
+	!
+#ifdef CONFIG_SH_DSP
+	mov.l	r2, @-r15		! Save r2, we need another reg
+	stc	sr, k4
+	mov.l	1f, r2
+	tst	r2, k4			! Check if in DSP mode
+	mov.l	@r15+, r2		! Restore r2 now
+	bt/s	skip_save
+	 mov	#0, k4			! Set marker for no stack frame
+
+	mov	r2, k4			! Backup r2 (in k4) for later
+
+	! Save DSP registers on stack
+	stc.l	mod, @-r15
+	stc.l	re, @-r15
+	stc.l	rs, @-r15
+	sts.l	dsr, @-r15
+	sts.l	y1, @-r15
+	sts.l	y0, @-r15
+	sts.l	x1, @-r15
+	sts.l	x0, @-r15
+	sts.l	a0, @-r15
+
+	! GAS is broken, does not generate correct "movs.l Ds,@-As" instr.
+
+	! FIXME: Make sure that this is still the case with newer toolchains,
+	! as we're not at all interested in supporting ancient toolchains at
+	! this point. -- PFM.
+
+	mov	r15, r2
+	.word	0xf653			! movs.l	a1, @-r2
+	.word	0xf6f3			! movs.l	a0g, @-r2
+	.word	0xf6d3			! movs.l	a1g, @-r2
+	.word	0xf6c3			! movs.l	m0, @-r2
+	.word	0xf6e3			! movs.l	m1, @-r2
+	mov	r2, r15
+
+	mov	k4, r2			! Restore r2
+	mov.l	1f, k4			! Force DSP stack frame
+skip_save:
+	mov.l	k4, @-r15		! Push DSP mode marker onto stack
+#endif
+	! Save the user registers on the stack.
+	mov.l	k2, @-r15	! EXPEVT
+
+	mov	#-1, k4
+	mov.l	k4, @-r15	! set TRA (default: -1)
+	!
+	sts.l	macl, @-r15
+	sts.l	mach, @-r15
+	stc.l	gbr, @-r15
+	stc.l	ssr, @-r15
+	sts.l	pr, @-r15
+	stc.l	spc, @-r15
+	!
+	lds	k3, pr		! Set the return address to pr
+	!
+	mov.l	k0, @-r15	! save orignal stack
+	mov.l	r14, @-r15
+	mov.l	r13, @-r15
+	mov.l	r12, @-r15
+	mov.l	r11, @-r15
+	mov.l	r10, @-r15
+	mov.l	r9, @-r15
+	mov.l	r8, @-r15
+	!
+	stc	sr, r8		! Back to normal register bank, and
+	or	k1, r8		! Block all interrupts
+	mov.l	3f, k1
+	and	k1, r8		! ...
+	ldc	r8, sr		! ...changed here.
+	!
+	mov.l	r7, @-r15
+	mov.l	r6, @-r15
+	mov.l	r5, @-r15
+	mov.l	r4, @-r15
+	mov.l	r3, @-r15
+	mov.l	r2, @-r15
+	mov.l	r1, @-r15
+	mov.l	r0, @-r15
+
+	/*
+	 * This gets a bit tricky.. in the INTEVT case we don't want to use
+	 * the VBR offset as a destination in the jump call table, since all
+	 * of the destinations are the same. In this case, (interrupt) sets
+	 * a marker in r2 (now r2_bank since SR.RB changed), which we check
+	 * to determine the exception type. For all other exceptions, we
+	 * forcibly read EXPEVT from memory and fix up the jump address, in
+	 * the interrupt exception case we jump to do_IRQ() and defer the
+	 * INTEVT read until there. As a bonus, we can also clean up the SR.RB
+	 * checks that do_IRQ() was doing..
+	 */
+	stc	r2_bank, r8
+	cmp/pz	r8
+	bf	interrupt_exception
+	shlr2	r8
+	shlr	r8
+	mov.l	4f, r9
+	add	r8, r9
+	mov.l	@r9, r9
+	jmp	@r9
+	 nop
+	rts
+	 nop
+
+	.align	2
+1:	.long	0x00001000	! DSP=1
+2:	.long	0x000080f0	! FD=1, IMASK=15
+3:	.long	0xcfffffff	! RB=0, BL=0
+4:	.long	exception_handling_table
+
+interrupt_exception:
+	mov.l	1f, r9
+	jmp	@r9
+	 nop
+	rts
+	 nop
+
+	.align 2
+1:	.long	do_IRQ
+
+	.align	2
+ENTRY(exception_none)
+	rts
+	 nop