/************************************************************************************
* arch/arm/src/armv6-m/up_exception.S
*
* Copyright (C) 2013 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <gnutt@nuttx.org>
*
* This file was leveraged from the ARMv7-M version which has, in addition:
*
* Copyright (C) 2012 Michael Smith. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. 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.
* 3. Neither the name NuttX nor the names of its contributors may be
* used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "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
* COPYRIGHT OWNER OR CONTRIBUTORS 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.
*
************************************************************************************/
/************************************************************************************
* Included Files
************************************************************************************/
#include <nuttx/config.h>
#include <arch/irq.h>
#include "exc_return.h"
#include "chip.h"
/************************************************************************************
* Global Symbols
************************************************************************************/
.globl exception_common
.cpu cortex-m0
.file "up_exception.S"
/************************************************************************************
* .text
************************************************************************************/
/* Common exception handling logic. On entry here, the return stack is on either
* the PSP or the MSP and looks like the following:
*
* REG_XPSR
* REG_R15
* REG_R14
* REG_R12
* REG_R3
* REG_R2
* REG_R1
* MSP->REG_R0
*
* And
* IPSR contains the IRQ number
* R14 Contains the EXC_RETURN value
* We are in handler mode and the current SP is the MSP
*/
.text
.align 2
.code 16
.thumb_func
.type exception_common, function
exception_common:
/* Complete the context save */
/* Get the current stack pointer. The EXC_RETURN value tells us whether
* the context is on the MSP or PSP.
*/
#ifdef CONFIG_NUTTX_KERNEL
mov r0, r14 /* Copy high register to low register */
lsl r0, #(31 - EXC_RETURN_PROCESS_BITNO) /* Move to bit 31 */
bmi 1f /* Test bit 31 */
mrs r1, msp /* R1=The main stack pointer */
b 2f
1:
mrs r1, psp /* R1=The process stack pointer */
#else
mrs r1, msp /* R1=The main stack pointer */
#endif
/* R1 is the current stack pointer. HW_XCPT_REGS were pushed onto the stack
* when the interrupt was taken so (R1)+HW_XCPT_SIZE is the value of the
* stack pointer before the interrupt. The total size of the context save
* area is XCPTCONTEXT_SIZE = SW_XCPT_SIZE + HW_XCPT_SIZE so (R1)-SW_XCPT_SIZE
* is the address of the beginning of the context save area.
*/
2:
/* Save SP, BASEPRI, and R4-R7 in the context array */
sub r1, #SW_XCPT_SIZE /* R1=Beginning of context array on the stack */
mov r2, #XCPTCONTEXT_SIZE /* R2=Size of the context array */
add r2, r1 /* R2=MSP/PSP before the interrupt was taken */
/* (ignoring the xPSR[9] alignment bit) */
mrs r3, basepri /* R3=Current BASEPRI setting */
mov r0, r1 /* Copy the context array pointer */
stmia r0!, {r2-r7} /* Save the SP, BASEPRI, and R4-R7 in the context array */
/* Save R8-R11 and the EXEC_RETURN value in the context array */
mov r2, r8 /* Copy high registers to low */
mov r3, r9
mov r4, r10
mov r5, r11
#ifdef CONFIG_NUTTX_KERNEL
mov r6, r14
stmia r0!, {r2-r6} /* Save the high registers r8-r11 and r14 */
#else
stmia r0!, {r2-r5} /* Save the high registers r8-r11 */
#endif
/* Get the exception number in R0=IRQ, R1=register save area on stack */
mrs r0, ipsr /* R0=exception number */
/* Disable interrupts, select the stack to use for interrupt handling
* and call up_doirq to handle the interrupt
*/
cpsid i /* Disable further interrupts */
/* If CONFIG_ARCH_INTERRUPTSTACK is defined, we will use a special interrupt
* stack pointer. The way that this is done here prohibits nested interrupts!
* Otherwise, we will use the stack that was current when the interrupt was taken.
*/
#if CONFIG_ARCH_INTERRUPTSTACK > 3
ldr sp, =g_intstackbase
push {r1} /* Save the MSP on the interrupt stack */
bl up_doirq /* R0=IRQ, R1=register save area on stack */
pop {r1} /* Recover R1=main stack pointer */
#else
msr msp, r1 /* We are using the main stack pointer */
bl up_doirq /* R0=IRQ, R1=register save area on stack */
mrs r1, msp /* Recover R1=main stack pointer */
#endif
/* On return from up_doirq, r0 will hold a pointer to register context
* array to use for the interrupt return. If that return value is the same
* as current stack pointer, then things are relatively easy.
*/
cmp r0, r1 /* Context switch? */
beq 3f /* Branch if no context switch */
/* We are returning with a pending context switch. This case is different
* because in this case, the register save structure does not lie on the
* stack but, rather within a TCB structure. We'll have to copy some
* values to the stack.
*/
/* Copy the hardware-saved context to the new stack */
mov r2, #SW_XCPT_SIZE /* R2=Size of software-saved portion of the context array */
add r1, r0, r2 /* R1=Address of HW save area in reg array */
ldr r2, [r0, #(4*REG_SP)] /* R2=Value of SP before the interrupt */
sub r2, #HW_XCPT_SIZE /* R2=Address of HW save area on the return stack */
ldmia r1!, {r4-r7} /* Fetch four registers from the HW save area */
stmia r2!, {r4-r7} /* Copy four registers to the return stack */
ldmia r1!, {r4-r7} /* Fetch four registers from the HW save area */
stmia r2!, {r4-r7} /* Copy four registers to the return stack */
/* Restore the register contents */
mov r1, r0
3:
/* We are returning with no context switch. We simply need to "unwind"
* the same stack frame that we created at entry.
*/
/* Recover R8-R11 and EXEC_RETURN (5 registers) */
mov r2, #(4*REG_R8) /* R2=Offset to R8 storage */
add r0, r1, r2 /* R0=Address of R8 storage */
#ifdef CONFIG_NUTTX_KERNEL
ldmia r0!, {r2-r6} /* Recover R8-R11 and R14 (5 registers)*/
mov r8, r2 /* Move to position in high registers */
mov r9, r3
mov r10, r4
mov r11, r5
mov r14, r6 /* EXEC_RETURN */
#else
ldmia r0!, {r2-r5} /* Recover R8-R11 and R14 (5 registers)*/
mov r8, r2 /* Move to position in high registers */
mov r9, r3
mov r10, r4
mov r11, r5
#endif
/* Recover SP (R2), BASEPRI (R3), and R4-R7. Determine the value of
* the stack pointer as it was on entry to the exception handler.
*/
ldmia r1!, {r2-r7} /* Recover R4-R7 + 2 temp values */
mov r1, #HW_XCPT_SIZE /* R1=Size of hardware-saved portion of the context array */
sub r1, r2, r1 /* R1=Value of MSP/PSP on exception entry */
/* Restore the stack pointer. The EXC_RETURN value tells us whether the
* context is on the MSP or PSP.
*/
#ifdef CONFIG_NUTTX_KERNEL
mov r0, r14 /* Copy high register to low register */
lsl r0, #(31 - EXC_RETURN_PROCESS_BITNO) /* Move to bit 31 */
bmi 5f /* Test bit 31 */
msr msp, r1 /* R1=The main stack pointer */
b 6f
5:
msr psp, r1 /* R1=The process stack pointer */
6:
#else
msr msp, r1 /* R1=The main stack pointer */
ldr r0, =EXC_RETURN_PRIVTHR /* R0=EXC_RETURN to privileged mode */
mov r14, r0 /* R14=EXC_RETURN to privileged mode */
#endif
/* Restore the interrupt state */
msr basepri, r3 /* Restore interrupts priority masking*/
cpsie i /* Re-enable interrupts */
/* Always return with R14 containing the special value that will: (1)
* return to thread mode, and (2) select the correct stack.
*/
bx r14 /* And return */
.size exception_common, .-exception_common
/************************************************************************************
* Name: up_interruptstack/g_intstackbase
*
* Description:
* Shouldn't happen
*
************************************************************************************/
#if CONFIG_ARCH_INTERRUPTSTACK > 3
.bss
.global g_intstackbase
.align 4
up_interruptstack:
.skip (CONFIG_ARCH_INTERRUPTSTACK & ~3)
g_intstackbase:
.size up_interruptstack, .-up_interruptstack
#endif
.end
