ARM: ARMv7-M: Add support for exception handling

This patch implements the exception handling for the ARMv7-M
architecture (pretty different from the A or R profiles).

It bases on work done earlier by Catalin for 2.6.33 but was nearly
completely rewritten to use a pt_regs layout compatible to the A
profile.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Jonathan Austin <jonathan.austin@arm.com>
Tested-by: Jonathan Austin <jonathan.austin@arm.com>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>

1 files changed, 143 insertions, 0 deletions

diff --git a/arch/arm/kernel/entry-v7m.S b/arch/arm/kernel/entry-v7m.S
new file mode 100644
index 000000000000..e00621f1403f
--- /dev/null
+++ b/arch/arm/kernel/entry-v7m.S
@@ -0,0 +1,143 @@
+/*
+ * linux/arch/arm/kernel/entry-v7m.S
+ *
+ * Copyright (C) 2008 ARM Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * Low-level vector interface routines for the ARMv7-M architecture
+ */
+#include <asm/memory.h>
+#include <asm/glue.h>
+#include <asm/thread_notify.h>
+#include <asm/v7m.h>
+
+#include <mach/entry-macro.S>
+
+#include "entry-header.S"
+
+#ifdef CONFIG_TRACE_IRQFLAGS
+#error "CONFIG_TRACE_IRQFLAGS not supported on the current ARMv7M implementation"
+#endif
+
+__invalid_entry:
+	v7m_exception_entry
+	adr	r0, strerr
+	mrs	r1, ipsr
+	mov	r2, lr
+	bl	printk
+	mov	r0, sp
+	bl	show_regs
+1:	b	1b
+ENDPROC(__invalid_entry)
+
+strerr:	.asciz	"\nUnhandled exception: IPSR = %08lx LR = %08lx\n"
+
+	.align	2
+__irq_entry:
+	v7m_exception_entry
+
+	@
+	@ Invoke the IRQ handler
+	@
+	mrs	r0, ipsr
+	ldr	r1, =V7M_xPSR_EXCEPTIONNO
+	and	r0, r1
+	sub	r0, #16
+	mov	r1, sp
+	stmdb	sp!, {lr}
+	@ routine called with r0 = irq number, r1 = struct pt_regs *
+	bl	nvic_do_IRQ
+
+	pop	{lr}
+	@
+	@ Check for any pending work if returning to user
+	@
+	ldr	r1, =BASEADDR_V7M_SCB
+	ldr	r0, [r1, V7M_SCB_ICSR]
+	tst	r0, V7M_SCB_ICSR_RETTOBASE
+	beq	2f
+
+	get_thread_info tsk
+	ldr	r2, [tsk, #TI_FLAGS]
+	tst	r2, #_TIF_WORK_MASK
+	beq	2f			@ no work pending
+	mov	r0, #V7M_SCB_ICSR_PENDSVSET
+	str	r0, [r1, V7M_SCB_ICSR]	@ raise PendSV
+
+2:
+	@ registers r0-r3 and r12 are automatically restored on exception
+	@ return. r4-r7 were not clobbered in v7m_exception_entry so for
+	@ correctness they don't need to be restored. So only r8-r11 must be
+	@ restored here. The easiest way to do so is to restore r0-r7, too.
+	ldmia	sp!, {r0-r11}
+	add	sp, #S_FRAME_SIZE-S_IP
+	cpsie	i
+	bx	lr
+ENDPROC(__irq_entry)
+
+__pendsv_entry:
+	v7m_exception_entry
+
+	ldr	r1, =BASEADDR_V7M_SCB
+	mov	r0, #V7M_SCB_ICSR_PENDSVCLR
+	str	r0, [r1, V7M_SCB_ICSR]	@ clear PendSV
+
+	@ execute the pending work, including reschedule
+	get_thread_info tsk
+	mov	why, #0
+	b	ret_to_user
+ENDPROC(__pendsv_entry)
+
+/*
+ * Register switch for ARMv7-M processors.
+ * r0 = previous task_struct, r1 = previous thread_info, r2 = next thread_info
+ * previous and next are guaranteed not to be the same.
+ */
+ENTRY(__switch_to)
+	.fnstart
+	.cantunwind
+	add	ip, r1, #TI_CPU_SAVE
+	stmia	ip!, {r4 - r11}		@ Store most regs on stack
+	str	sp, [ip], #4
+	str	lr, [ip], #4
+	mov	r5, r0
+	add	r4, r2, #TI_CPU_SAVE
+	ldr	r0, =thread_notify_head
+	mov	r1, #THREAD_NOTIFY_SWITCH
+	bl	atomic_notifier_call_chain
+	mov	ip, r4
+	mov	r0, r5
+	ldmia	ip!, {r4 - r11}		@ Load all regs saved previously
+	ldr	sp, [ip]
+	ldr	pc, [ip, #4]!
+	.fnend
+ENDPROC(__switch_to)
+
+	.data
+	.align	8
+/*
+ * Vector table (64 words => 256 bytes natural alignment)
+ */
+ENTRY(vector_table)
+	.long	0			@ 0 - Reset stack pointer
+	.long	__invalid_entry		@ 1 - Reset
+	.long	__invalid_entry		@ 2 - NMI
+	.long	__invalid_entry		@ 3 - HardFault
+	.long	__invalid_entry		@ 4 - MemManage
+	.long	__invalid_entry		@ 5 - BusFault
+	.long	__invalid_entry		@ 6 - UsageFault
+	.long	__invalid_entry		@ 7 - Reserved
+	.long	__invalid_entry		@ 8 - Reserved
+	.long	__invalid_entry		@ 9 - Reserved
+	.long	__invalid_entry		@ 10 - Reserved
+	.long	vector_swi		@ 11 - SVCall
+	.long	__invalid_entry		@ 12 - Debug Monitor
+	.long	__invalid_entry		@ 13 - Reserved
+	.long	__pendsv_entry		@ 14 - PendSV
+	.long	__invalid_entry		@ 15 - SysTick
+	.rept	64 - 16
+	.long	__irq_entry		@ 16..64 - External Interrupts
+	.endr