diff options
Diffstat (limited to 'nuttx/arch/arm/src/stm32/stm32_vectors.S')
-rw-r--r-- | nuttx/arch/arm/src/stm32/stm32_vectors.S | 82 |
1 files changed, 65 insertions, 17 deletions
diff --git a/nuttx/arch/arm/src/stm32/stm32_vectors.S b/nuttx/arch/arm/src/stm32/stm32_vectors.S index 91f530f05..1629dfc9f 100644 --- a/nuttx/arch/arm/src/stm32/stm32_vectors.S +++ b/nuttx/arch/arm/src/stm32/stm32_vectors.S @@ -211,16 +211,37 @@ stm32_common: */ adds r2, r14, #3 /* If R14=0xfffffffd, then r2 == 0 */ - ite ne /* Next two instructions are condition */ + ite ne /* Next two instructions are conditional */ mrsne r1, msp /* R1=The main stack pointer */ mrseq r1, psp /* R1=The process stack pointer */ #else mrs r1, msp /* R1=The main stack pointer */ #endif + /* r1 holds the value of the stack pointer AFTER the excption handling logic + * pushed the various registers onto the stack. Get r2 = the value of the + * stack pointer BEFORE the interrupt modified it. + */ + mov r2, r1 /* R2=Copy of the main/process stack pointer */ add r2, #HW_XCPT_SIZE /* R2=MSP/PSP before the interrupt was taken */ mrs r3, primask /* R3=Current PRIMASK setting */ + +#ifdef CONFIG_ARCH_FPU + /* Skip over the block of memory reserved for floating pointer register save. + * Lazy FPU register saving is used. FPU registers will be saved in this + * block only if a context switch occurs (this means, of course, that the FPU + * cannot be used in interrupt processing). + */ + + sub r1, #(4*SW_FPU_REGS) +#endif + + /* Save the the remaining registers on the stack after the registers pushed + * by the exception handling logic. r2=SP and r3=primask, r4-r11,r14=register + * values. + */ + #ifdef CONFIG_NUTTX_KERNEL stmdb r1!, {r2-r11,r14} /* Save the remaining registers plus the SP value */ #else @@ -257,36 +278,47 @@ stm32_common: 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, are within a TCB structure. We'll have to copy some - * values to the stack. + /* We are returning with a pending context switch. + * + * If the FPU is enabled, then we will need to restore FPU registers. + * This is not done in normal interrupt save/restore because the cost + * is prohibitive. This is only done when switching contexts. A + * consequence of this is that floating point operations may not be + * performed in interrupt handling logic. + * + * Here: + * r0 = Address of the register save area + + * NOTE: It is a requirement that up_restorefpu() preserve the value of + * r0! + */ + +#ifdef CONFIG_ARCH_FPU + bl up_restorefpu /* Restore the FPU registers */ +#endif + + /* Returning with a pending context switch is different from the normal + * return because in this case, the register save structure does not lie + * on the stack but, rather, are within a TCB structure. We'll have to + * copy somevalues to the new stack. */ 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 */ - ldr r1, [r0, #(4*REG_SP)] /* R1=Value of SP before interrupt */ + ldr r1, [r0, #(4*REG_SP)] /* R1=Value of SP before interrupt */ stmdb r1!, {r4-r11} /* Store eight registers in HW save area */ #ifdef CONFIG_NUTTX_KERNEL ldmia r0, {r2-r11,r14} /* Recover R4-R11, r14 + 2 temp values */ #else ldmia r0, {r2-r11} /* Recover R4-R11 + 2 temp values */ #endif - - /* We may also need to restore FPU registers. This is not done in - * normal interrupt save/restore because the cost is prohibitive. This - * is only done when switching contexts. A consequence of this is that - * floating point operations may not be performed in interrupt handling - * logic. - */ - -#ifdef CONFIG_ARCH_FPU - bl up_restorefpu /* Restore the FPU registers */ -#endif b 2f /* Re-join common logic */ /* We are returning with no context switch. We simply need to "unwind" * the same stack frame that we created + * + * Here: + * r1 = Address of the return stack (same as r0) */ 1: #ifdef CONFIG_NUTTX_KERNEL @@ -294,6 +326,22 @@ stm32_common: #else ldmia r1!, {r2-r11} /* Recover R4-R11 + 2 temp values */ #endif +#ifdef CONFIG_ARCH_FPU + /* Skip over the block of memory reserved for floating pointer register + * save. Then R1 is the address of the HW save area + */ + + add r1, #(4*SW_FPU_REGS) +#endif + + /* Set up to return from the exception + * + * Here: + * r1 = Address on the target thread's stack position at the start of + * the registers saved by hardware + * r3 = primask + * r4-r11 = restored register values + */ 2: #ifdef CONFIG_NUTTX_KERNEL /* The EXC_RETURN value will be 0xfffffff9 (privileged thread) or 0xfffffff1 |