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/**
* @file
*
* @ingroup RTEMSScoreCPUARM
*
* @brief ARM interrupt exception prologue and epilogue.
*/
/*
* Copyright (c) 2009, 2022 embedded brains GmbH. All rights reserved.
*
* embedded brains GmbH
* Dornierstr. 4
* 82178 Puchheim
* Germany
* <rtems@embedded-brains.de>
*
* The license and distribution terms for this file may be
* found in the file LICENSE in this distribution or at
* http://www.rtems.org/license/LICENSE.
*/
/*
* The upper EXCHANGE_SIZE bytes of the INT stack area are used for data
* exchange between INT and SVC mode. Below of this is the actual INT stack.
* The exchange area is only accessed if INT is disabled.
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include <rtems/asm.h>
#ifdef ARM_MULTILIB_ARCH_V4
#define STACK_POINTER_ADJUST r7
#define NON_VOLATILE_SCRATCH r9
#define EXCHANGE_LR r4
#define EXCHANGE_SPSR r5
#define EXCHANGE_CPSR r6
#define EXCHANGE_INT_SP r8
#define EXCHANGE_LIST {EXCHANGE_LR, EXCHANGE_SPSR, EXCHANGE_CPSR, EXCHANGE_INT_SP}
#define EXCHANGE_SIZE 16
#define CONTEXT_LIST {r0, r1, r2, r3, EXCHANGE_LR, EXCHANGE_SPSR, NON_VOLATILE_SCRATCH, r12}
#define CONTEXT_SIZE 32
.arm
.globl _ARMV4_Exception_interrupt
_ARMV4_Exception_interrupt:
/* Save exchange registers to exchange area */
stmdb sp, EXCHANGE_LIST
/* Set exchange registers */
mov EXCHANGE_LR, lr
mrs EXCHANGE_SPSR, SPSR
mrs EXCHANGE_CPSR, CPSR
sub EXCHANGE_INT_SP, sp, #EXCHANGE_SIZE
/* Switch to SVC mode */
orr EXCHANGE_CPSR, EXCHANGE_CPSR, #0x1
msr CPSR_c, EXCHANGE_CPSR
/*
* Save context. We save the link register separately because it has
* to be restored in SVC mode. The other registers can be restored in
* INT mode. Ensure that the size of the saved registers is an
* integral multiple of 8 bytes. Provide a non-volatile scratch
* register which may be used accross function calls.
*/
push CONTEXT_LIST
push {STACK_POINTER_ADJUST, lr}
/*
* On a public interface, the stack pointer must be aligned on an
* 8-byte boundary. However, it may temporarily be only aligned on a
* 4-byte boundary. Make sure the stack pointer is aligned on an
* 8-byte boundary.
*/
and STACK_POINTER_ADJUST, sp, #0x4
sub sp, sp, STACK_POINTER_ADJUST
/* Get per-CPU control of current processor */
GET_SELF_CPU_CONTROL r0
#ifdef ARM_MULTILIB_VFP
/* Save VFP context */
vmrs r2, FPSCR
vpush {d0-d7}
#ifdef ARM_MULTILIB_VFP_D32
vpush {d16-d31}
#endif
push {r2, r3}
#endif /* ARM_MULTILIB_VFP */
/* Remember INT stack pointer */
mov r1, EXCHANGE_INT_SP
/* Restore exchange registers from exchange area */
ldmia r1, EXCHANGE_LIST
/* Get interrupt nest level */
ldr r2, [r0, #PER_CPU_ISR_NEST_LEVEL]
/* Switch stack if necessary and save original stack pointer */
mov NON_VOLATILE_SCRATCH, sp
cmp r2, #0
moveq sp, r1
/* Increment interrupt nest and thread dispatch disable level */
ldr r3, [r0, #PER_CPU_THREAD_DISPATCH_DISABLE_LEVEL]
add r2, r2, #1
add r3, r3, #1
str r2, [r0, #PER_CPU_ISR_NEST_LEVEL]
str r3, [r0, #PER_CPU_THREAD_DISPATCH_DISABLE_LEVEL]
/* Call BSP dependent interrupt dispatcher */
#ifdef RTEMS_PROFILING
cmp r2, #1
bne .Lskip_profiling
BLX_TO_THUMB_1 _CPU_Counter_read
push {r0, r1}
GET_SELF_CPU_CONTROL r0
BLX_TO_THUMB_1 bsp_interrupt_dispatch
BLX_TO_THUMB_1 _CPU_Counter_read
pop {r1, r3}
mov r2, r0
GET_SELF_CPU_CONTROL r0
BLX_TO_THUMB_1 _Profiling_Outer_most_interrupt_entry_and_exit
.Lprofiling_done:
#else
BLX_TO_THUMB_1 bsp_interrupt_dispatch
#endif
/* Get per-CPU control of current processor */
GET_SELF_CPU_CONTROL r0
/* Load some per-CPU variables */
ldr r12, [r0, #PER_CPU_THREAD_DISPATCH_DISABLE_LEVEL]
ldrb r1, [r0, #PER_CPU_DISPATCH_NEEDED]
ldr r2, [r0, #PER_CPU_ISR_DISPATCH_DISABLE]
ldr r3, [r0, #PER_CPU_ISR_NEST_LEVEL]
/* Restore stack pointer */
mov sp, NON_VOLATILE_SCRATCH
/* Decrement levels and determine thread dispatch state */
eor r1, r1, r12
sub r12, r12, #1
orr r1, r1, r12
orr r1, r1, r2
sub r3, r3, #1
/* Store thread dispatch disable and ISR nest levels */
str r12, [r0, #PER_CPU_THREAD_DISPATCH_DISABLE_LEVEL]
str r3, [r0, #PER_CPU_ISR_NEST_LEVEL]
/*
* Check thread dispatch necessary, ISR dispatch disable and thread
* dispatch disable level.
*/
cmp r1, #0
bne .Lthread_dispatch_done
/* Save CPSR in non-volatile register */
mrs NON_VOLATILE_SCRATCH, CPSR
/* Thread dispatch */
.Ldo_thread_dispatch:
/* Set ISR dispatch disable and thread dispatch disable level to one */
mov r12, #1
str r12, [r0, #PER_CPU_ISR_DISPATCH_DISABLE]
str r12, [r0, #PER_CPU_THREAD_DISPATCH_DISABLE_LEVEL]
/* Call _Thread_Do_dispatch(), this function will enable interrupts */
bic r1, NON_VOLATILE_SCRATCH, #0x80
BLX_TO_THUMB_1 _Thread_Do_dispatch
/* Disable interrupts */
msr CPSR, NON_VOLATILE_SCRATCH
/*
* Get per-CPU control of current processor. In SMP configurations, we
* may run on another processor after the _Thread_Do_dispatch() call.
*/
GET_SELF_CPU_CONTROL r0
/* Check if we have to do the thread dispatch again */
ldrb r12, [r0, #PER_CPU_DISPATCH_NEEDED]
cmp r12, #0
bne .Ldo_thread_dispatch
/* We are done with thread dispatching */
mov r12, #0
str r12, [r0, #PER_CPU_ISR_DISPATCH_DISABLE]
.Lthread_dispatch_done:
#ifdef ARM_MULTILIB_VFP
/* Restore VFP context */
pop {r2, r3}
#ifdef ARM_MULTILIB_VFP_D32
vpop {d16-d31}
#endif
vpop {d0-d7}
vmsr FPSCR, r2
#endif /* ARM_MULTILIB_VFP */
/* Undo stack pointer adjustment */
add sp, sp, STACK_POINTER_ADJUST
/* Restore STACK_POINTER_ADJUST register and link register */
pop {STACK_POINTER_ADJUST, lr}
/*
* XXX: Remember and restore stack pointer. The data on the stack is
* still in use. So the stack is now in an inconsistent state. The
* FIQ handler implementation must not use this area.
*/
mov r12, sp
add sp, #CONTEXT_SIZE
/* Get INT mode program status register */
mrs r1, CPSR
bic r1, r1, #0x1
/* Switch to INT mode */
msr CPSR_c, r1
/* Save EXCHANGE_LR and EXCHANGE_SPSR registers to exchange area */
push {EXCHANGE_LR, EXCHANGE_SPSR}
/* Restore context */
ldmia r12, CONTEXT_LIST
/* Set return address and program status */
mov lr, EXCHANGE_LR
msr SPSR_fsxc, EXCHANGE_SPSR
/* Restore EXCHANGE_LR and EXCHANGE_SPSR registers from exchange area */
pop {EXCHANGE_LR, EXCHANGE_SPSR}
#ifdef ARM_MULTILIB_HAS_LOAD_STORE_EXCLUSIVE
/*
* We must clear reservations here, since otherwise compare-and-swap
* atomic operations with interrupts enabled may yield wrong results.
* A compare-and-swap atomic operation is generated by the compiler
* like this:
*
* .L1:
* ldrex r1, [r0]
* cmp r1, r3
* bne .L2
* strex r3, r2, [r0]
* cmp r3, #0
* bne .L1
* .L2:
*
* Consider the following scenario. A thread is interrupted right
* before the strex. The interrupt updates the value using a
* compare-and-swap sequence. Everything is fine up to this point.
* The interrupt performs now a compare-and-swap sequence which fails
* with a branch to .L2. The current processor has now a reservation.
* The interrupt returns without further strex. The thread updates the
* value using the unrelated reservation of the interrupt.
*/
clrex
#endif
/* Return from interrupt */
subs pc, lr, #4
#ifdef RTEMS_PROFILING
.Lskip_profiling:
BLX_TO_THUMB_1 bsp_interrupt_dispatch
b .Lprofiling_done
#endif
#endif /* ARM_MULTILIB_ARCH_V4 */
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