/*
* 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);
}
/** @}
*/