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/*

 * Copyright (c) 2007 Petr Stepan

 * All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions

 * are met:

 *

 * - Redistributions of source code must retain the above copyright

 *   notice, this list of conditions and the following disclaimer.

 * - Redistributions in binary form must reproduce the above copyright

 *   notice, this list of conditions and the following disclaimer in the

 *   documentation and/or other materials provided with the distribution.

 * - The name of the author may not be used to endorse or promote products

 *   derived from this software without specific prior written permission.

 *

 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR

 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES

 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.

 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,

 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT

 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,

 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY

 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF

 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 */

/** @addtogroup arm32

 * @{

 */

/** @file

    @brief	Exception handlers and exception initialization routines.

 */

#include <arch/exception.h>

#include <arch/debug/print.h>

#include <arch/memstr.h>

#include <arch/regutils.h>

#include <interrupt.h>

#include <arch/machine.h>

#include <arch/mm/page_fault.h>

#include <print.h>

#include <syscall/syscall.h>

/** Offset used in calculation of exception handler's relative address.

 *

 * @see install_handler()

 */

#define PREFETCH_OFFSET      0x8

/** LDR instruction's code */

#define LDR_OPCODE           0xe59ff000

/** Number of exception vectors. */

#define EXC_VECTORS          8

/** Size of memory block occupied by exception vectors. */

#define EXC_VECTORS_SIZE     (EXC_VECTORS * 4)

/** Kernel stack pointer.

 *

 * It is set when thread switches to user mode,

 * and then used for exception handling.

 */

extern uintptr_t supervisor_sp;

/** Temporary exception stack pointer.

 *

 * Temporary stack is used in exceptions handling routines

 * before switching to thread's kernel stack.

 */

extern uintptr_t exc_stack;

/** Switches to kernel stack and saves all registers there.

 *

 * Temporary exception stack is used to save a few registers

 * before stack switch takes place.

 */

inline static void setup_stack_and_save_regs()

{

asm volatile("ldr r13, =exc_stack		\n\

	stmfd r13!, {r0}			\n\

	mrs r0, spsr				\n\

	and r0, r0, #0x1f			\n\

	cmp r0, #0x10				\n\

	bne 1f					\n\

						\n\

	@prev mode was usermode			\n\

	ldmfd r13!, {r0}			\n\

	ldr r13, =supervisor_sp			\n\

	ldr r13, [r13]				\n\

	stmfd r13!, {lr}			\n\

	stmfd r13!, {r0-r12}			\n\

	stmfd r13!, {r13, lr}^			\n\

	mrs r0, spsr				\n\

	stmfd r13!, {r0}			\n\

	b 2f					\n\

						\n\

	@prev mode was not usermode		\n\

1:						\n\

	stmfd r13!, {r1, r2, r3}		\n\

	mrs r1, cpsr				\n\

	mov r2, lr				\n\

	bic r1, r1, #0x1f			\n\

	orr r1, r1, r0				\n\

	mrs r0, cpsr				\n\

	msr cpsr_c, r1				\n\

						\n\

	mov r3, r13				\n\

	stmfd r13!, {r2}			\n\

	mov r2, lr				\n\

	stmfd r13!, {r4-r12}			\n\

	mov r1, r13				\n\

	@following two lines are for debugging	\n\

	mov sp, #0				\n\

	mov lr, #0				\n\

	msr cpsr_c, r0				\n\

						\n\

	ldmfd r13!, {r4, r5, r6, r7}		\n\

	stmfd r1!, {r4, r5, r6}			\n\

	stmfd r1!, {r7}				\n\

	stmfd r1!, {r2}				\n\

	stmfd r1!, {r3}				\n\

	mrs r0, spsr				\n\

	stmfd r1!, {r0}				\n\

	mov r13, r1				\n\

2:"

);

}

/** Returns from exception mode.

 * 

 * Previously saved state of registers (including control register)

 * is restored from the stack.

 */

inline static void load_regs()

{

asm volatile(	"ldmfd r13!, {r0}		\n\

	msr spsr, r0				\n\

	and r0, r0, #0x1f			\n\

	cmp r0, #0x10				\n\

	bne 3f					\n\

						\n\

	@return to user mode			\n\

	ldmfd r13!, {r13, lr}^			\n\

	b 4f					\n\

						\n\

	@return to non-user mode		\n\

3:						\n\

	ldmfd r13!, {r1, r2}			\n\

	mrs r3, cpsr				\n\

	bic r3, r3, #0x1f			\n\

	orr r3, r3, r0				\n\

	mrs r0, cpsr				\n\

	msr cpsr_c, r3				\n\

						\n\

	mov r13, r1				\n\

	mov lr, r2				\n\

	msr cpsr_c, r0				\n\

						\n\

	@actual return				\n\

4:	ldmfd r13, {r0-r12, pc}^"

);

}

/** Switch CPU to mode in which interrupts are serviced (currently it 

 * is Undefined mode).

 *

 * The default mode for interrupt servicing (Interrupt Mode)

 * can not be used because of nested interrupts (which can occur

 * because interrupt are enabled in higher levels of interrupt handler).

 */

inline static void switchToIrqServicingMode()

{

	/* switch to Undefined mode */

	asm volatile(

		/* save regs used during switching */

		"stmfd sp!, {r0-r3}		\n"

		/* save stack pointer and link register to r1, r2 */

		"mov r1, sp			\n"

		"mov r2, lr			\n"

		/* mode switch */

		"mrs r0, cpsr			\n"

		"bic r0, r0, #0x1f		\n"

		"orr r0, r0, #0x1b		\n"

		"msr cpsr_c, r0			\n"

		/* restore saved sp and lr */

		"mov sp, r1			\n"

		"mov lr, r2			\n"

		/* restore original regs */

		"ldmfd sp!, {r0-r3}		\n"

	);

}

/** Calls exception dispatch routine. */

#define CALL_EXC_DISPATCH(exception)		\

	asm("mov r0, %0" : : "i" (exception));	\

	asm("mov r1, r13");			\

	asm("bl exc_dispatch");		

/** General exception handler.

 *

 *  Stores registers, dispatches the exception,

 *  and finally restores registers and returns from exception processing.

 *

 *  @param exception Exception number.

 */

#define PROCESS_EXCEPTION(exception)		\

	setup_stack_and_save_regs();		\

	CALL_EXC_DISPATCH(exception)		\

	load_regs();

/** Updates specified exception vector to jump to given handler.

 *

 *  Addresses of handlers are stored in memory following exception vectors.

 */

static void install_handler (unsigned handler_addr, unsigned* vector)

{

	/* relative address (related to exc. vector) of the word

	 * where handler's address is stored

	*/

	volatile uint32_t handler_address_ptr = EXC_VECTORS_SIZE - PREFETCH_OFFSET;

	/* make it LDR instruction and store at exception vector */

	*vector = handler_address_ptr | LDR_OPCODE;

	/* store handler's address */

	*(vector + EXC_VECTORS) = handler_addr;

}

/** Low-level Reset Exception handler. */

static void reset_exception_entry()

{

	PROCESS_EXCEPTION(EXC_RESET);

}

/** Low-level Software Interrupt Exception handler. */

static void swi_exception_entry()

{

	PROCESS_EXCEPTION(EXC_SWI);

}

/** Low-level Undefined Instruction Exception handler. */

static void undef_instr_exception_entry()

{

	PROCESS_EXCEPTION(EXC_UNDEF_INSTR);

}

/** Low-level Fast Interrupt Exception handler. */

static void fiq_exception_entry()

{

	PROCESS_EXCEPTION(EXC_FIQ);

}

/** Low-level Prefetch Abort Exception handler. */

static void prefetch_abort_exception_entry()

{

	asm("sub lr, lr, #4");

	PROCESS_EXCEPTION(EXC_PREFETCH_ABORT);

} 

/** Low-level Data Abort Exception handler. */

static void data_abort_exception_entry()

{

	asm("sub lr, lr, #8");

	PROCESS_EXCEPTION(EXC_DATA_ABORT);

}

/** Low-level Interrupt Exception handler.

 *

 * CPU is switched to Undefined mode before further interrupt processing

 * because of possible occurence of nested interrupt exception, which

 * would overwrite (and thus spoil) stack pointer.

 */

static void irq_exception_entry()

{

	asm("sub lr, lr, #4");

	setup_stack_and_save_regs();

	switchToIrqServicingMode();

	CALL_EXC_DISPATCH(EXC_IRQ)

	load_regs();

}

/** Software Interrupt handler.

 *

 * Dispatches the syscall.

 */

static void swi_exception(int exc_no, istate_t *istate)

{

	/*

	dprintf("SYSCALL: r0-r4: %x, %x, %x, %x, %x; pc: %x\n", istate->r0, 

		istate->r1, istate->r2, istate->r3, istate->r4, istate->pc);

	*/

	istate->r0 = syscall_handler(

		istate->r0,

		istate->r1,

		istate->r2,

		istate->r3,

		istate->r4);

}

/** Interrupt Exception handler.

 *

 * Determines the sources of interrupt, and calls their handlers.

 */

static void irq_exception(int exc_no, istate_t *istate)

{

	machine_irq_exception(exc_no, istate);

}

/** Fills exception vectors with appropriate exception handlers. */

void install_exception_handlers(void)

{

	install_handler((unsigned)reset_exception_entry,

			 (unsigned*)EXC_RESET_VEC);

	install_handler((unsigned)undef_instr_exception_entry,

			 (unsigned*)EXC_UNDEF_INSTR_VEC);

	install_handler((unsigned)swi_exception_entry,

			 (unsigned*)EXC_SWI_VEC);

	install_handler((unsigned)prefetch_abort_exception_entry,

			 (unsigned*)EXC_PREFETCH_ABORT_VEC);

	install_handler((unsigned)data_abort_exception_entry,

			 (unsigned*)EXC_DATA_ABORT_VEC);

	install_handler((unsigned)irq_exception_entry,

			 (unsigned*)EXC_IRQ_VEC);

	install_handler((unsigned)fiq_exception_entry,

			 (unsigned*)EXC_FIQ_VEC);

}

#ifdef HIGH_EXCEPTION_VECTORS

/** Activates use of high exception vectors addresses. */

static void high_vectors() 

{

	uint32_t control_reg;

	asm volatile( "mrc p15, 0, %0, c1, c1": "=r" (control_reg));

	//switch on the high vectors bit

	control_reg |= CP15_R1_HIGH_VECTORS_BIT;

	asm volatile( "mcr p15, 0, %0, c1, c1" : : "r" (control_reg));

}

#endif

/** Initializes exception handling.

 * 

 * Installs low-level exception handlers and then registers

 * exceptions and their handlers to kernel exception dispatcher.

 */

void exception_init(void)

{

#ifdef HIGH_EXCEPTION_VECTORS

	high_vectors();

#endif

	install_exception_handlers();

	exc_register(EXC_IRQ, "interrupt", (iroutine) irq_exception);

	exc_register(EXC_PREFETCH_ABORT, "prefetch abort", (iroutine) prefetch_abort);

	exc_register(EXC_DATA_ABORT, "data abort", (iroutine) data_abort);

	exc_register(EXC_SWI, "software interrupt", (iroutine) swi_exception);

}

/** Prints #istate_t structure content.

 *

 * @param istate Structure to be printed.

 */

void print_istate(istate_t *istate)

{

	dprintf("istate dump:\n");

	dprintf(" r0: %x    r1: %x    r2: %x    r3: %x\n",

		istate->r0, istate->r1, istate->r2, istate->r3);

	dprintf(" r4: %x    r5: %x    r6: %x    r7: %x\n", 

		istate->r4, istate->r5, istate->r6, istate->r7);

	dprintf(" r8: %x    r8: %x   r10: %x   r11: %x\n", 

		istate->r8, istate->r9, istate->r10, istate->r11);

	dprintf(" r12: %x    sp: %x    lr: %x  spsr: %x\n",

		istate->r12, istate->sp, istate->lr, istate->spsr);

	dprintf(" pc: %x\n", istate->pc);

}

/** @}

 */