/************************************************************************************ * arch/arm/src/armv6-m/up_exception.S * * Copyright (C) 2013 Gregory Nutt. All rights reserved. * Author: Gregory Nutt * * 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 #include #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_BUILD_PROTECTED 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, PRIMASK, 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, primask /* R3=Current PRIMASK setting */ mov r0, r1 /* Copy the context array pointer */ stmia r0!, {r2-r7} /* Save the SP, PRIMASK, 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_BUILD_PROTECTED 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_BUILD_PROTECTED 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), PRIMASK (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_BUILD_PROTECTED 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 primask, 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: g_intstackalloc/g_intstackbase * * Description: * Shouldn't happen * ************************************************************************************/ #if CONFIG_ARCH_INTERRUPTSTACK > 3 .bss .global g_intstackalloc .global g_intstackbase .align 4 g_intstackalloc: .skip (CONFIG_ARCH_INTERRUPTSTACK & ~3) g_intstackbase: .size g_intstackalloc, .-g_intstackalloc #endif .end