/************************************************************************************
* arch/arm/src/armv7-m/up_exception.S
*
* Copyright (C) 2009-2013 Gregory Nutt. All rights reserved.
* Copyright (C) 2012 Michael Smith. All rights reserved.
* Author: Gregory Nutt <gnutt@nuttx.org>
*
* 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
.syntax unified
.thumb
.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
*
* If CONFIG_ARCH_FPU is defined, the volatile FP registers and FPSCR are on the
* return stack immediately above REG_XPSR.
*/
.text
.type exception_common, function
.thumb_func
exception_common:
mrs r0, ipsr /* R0=exception number */
/* Complete the context save */
/* The EXC_RETURN value tells us whether the context is on the MSP or PSP */
tst r14, #EXC_RETURN_PROCESS_STACK /* nonzero if context on process stack */
ite eq /* next two instructions conditional */
mrseq r1, msp /* R1=The main stack pointer */
mrsne r1, psp /* R1=The process stack pointer */
mov r2, r1 /* R2=Copy of the main/process stack pointer */
add r2, #HW_XCPT_SIZE /* R2=MSP/PSP before the interrupt was taken */
/* (ignoring the xPSR[9] alignment bit) */
#ifdef CONFIG_ARMV7M_USEBASEPRI
mrs r3, basepri /* R3=Current BASEPRI setting */
#else
mrs r3, primask /* R3=Current PRIMASK setting */
#endif
#ifdef CONFIG_ARCH_FPU
/* Save the non-volatile FP registers here.
*
* This routine is the only point where we can save these registers; either before
* or after calling up_doirq. The compiler is free to use them at any time as long
* as they are restored before returning, so we can't assume that we can get at the
* true values of these registers in any routine called from here.
*
* XXX we could do all this saving lazily on the context switch side if we knew where to put
* the registers.
*/
vstmdb r1!, {s16-s31} /* Save the non-volatile FP context */
#endif
stmdb r1!, {r2-r11,r14} /* Save the remaining registers plus the SP/PRIMASK values */
/* 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 1f /* 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 stack, and restore the software
* saved context directly.
*
* XXX In the normal case, it appears that this entire operation is unnecessary;
* context switch time would be improved if we could work out when the stack
* is dirty and avoid the work...
*/
add r1, r0, #SW_XCPT_SIZE /* R1=Address of HW save area in reg array */
ldmia r1!, {r4-r11} /* Fetch eight registers in HW save area */
#ifdef CONFIG_ARCH_FPU
vldmia r1!, {s0-s15} /* Fetch sixteen FP registers in HW save area */
ldmia r1, {r2-r3} /* Fetch FPSCR and Reserved in HW save area */
#endif
ldr r1, [r0, #(4*REG_SP)] /* R1=Value of SP before interrupt */
#ifdef CONFIG_ARCH_FPU
stmdb r1!, {r2-r3} /* Store FPSCR and Reserved on the return stack */
vstmdb r1!, {s0-s15} /* Store sixteen FP registers on the return stack */
#endif
stmdb r1!, {r4-r11} /* Store eight registers on the return stack */
ldmia r0!, {r2-r11,r14} /* Recover R4-R11, r14 + 2 temp values */
#ifdef CONFIG_ARCH_FPU
vldmia r0, {s16-s31} /* Recover S16-S31 */
#endif
b 2f /* Re-join common logic */
1:
/* We are returning with no context switch. We simply need to "unwind"
* the same stack frame that we created at entry.
*/
ldmia r1!, {r2-r11,r14} /* Recover R4-R11, r14 + 2 temp values */
#ifdef CONFIG_ARCH_FPU
vldmia r1!, {s16-s31} /* Recover S16-S31 */
#endif
2:
/* The EXC_RETURN value tells us whether we are returning on the MSP or PSP
*/
tst r14, #EXC_RETURN_PROCESS_STACK /* nonzero if context on process stack */
ite eq /* next two instructions conditional */
msreq msp, r1 /* R1=The main stack pointer */
msrne psp, r1 /* R1=The process stack pointer */
/* Restore the interrupt state */
#ifdef CONFIG_ARMV7M_USEBASEPRI
msr basepri, r3 /* Restore interrupts priority masking*/
cpsie i /* Re-enable interrupts */
#else
msr primask, r3 /* Restore interrupts */
#endif
/* 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
