原子不要骂我哈！分享一个stm32之qemu仿真开发板

2019-07-20 04:36发布

本帖最后由 huayuguo 于 2018-12-13 08:25 编辑

原文作者地址：https://www.cnblogs.com/89yanyu/p/7537902.html

想搞搞想到的东西但是，现在手里没有板子！所以想到了之前用过的qemu 嘿嘿就发现这个了，原子看了会不会骂我！

最关键的是这句话 qemu-system-gnuarmeclipse --board STM32F429I-Discovery说明还有其他板子！哈哈所以大家去发现吧，我准备下上班了，回头把具体搭建过程发上来！

QEMU无法仿真Cortex-M4内核基于陈老师提供的Hello_RTOS工程：　　qemu 2.8.0　　arm-none-eabi-gcc 4.8.2下载工程并编译1 git clone https://github.com/cbhust/STM32F429_Discovery_FreeRTOS_9.git2 cd STM32F429_Discovery_FreeRTOS_9/Projects/Hello_RTOS/3 make

选用STM32F429I-Discovery为系统板，调用qemu仿真。1 qemu-system-gnuarmeclipse --board STM32F429I-Discovery -d unimp,guest_errors --image hello_rtos.elf
--board STM32F429I-Discovery 选择系统板
-d unimp,guest_errors 设置需要记录的项目
--image hello_rtos.elf 选择系统镜像
出现如下错误：Attempt to set CP10/11 in SCB->CPACR, but FP is not supported yet.

经查询，这条错误信息是由于qemu不支持硬浮点https://sourceforge.net/p/gnuarmeclipse/bugs/159/

可以通过设置编译选项来选择软浮点，还是硬浮点。 http://blog.csdn.net/gujintong1110/article/details/23038217

将Hello_RTOS拷贝一份，到Qemu_with_M4修改Makefile中的MCFLAGS，改为：MCFLAGS=-mcpu=cortex-m4 -mthumb -mlittle-endian -mfpu=fpv4-sp-d16 -mfloat-abi=soft -mthumb-interworkDEFS=-DUSE_STDPERIPH_DRIVER -DSTM32F4XX
再次编译后，仍然出现错误：Error: selected processor does not support `vstmdbeq r0!,{s16-s31}' in Thumb mode
Error: instruction not allowed in IT block -- `stmdb r0!,{r4-r11,r14}'
Error: selected processor does not support `vldmiaeq r0!,{s16-s31}' in Thumb mode
Error: instruction not allowed in IT block -- `msr psp,r0'

查询后发现，这些代码不支持软浮点。https://sourceforge.net/p/freertos/discussion/382005/thread/9abf4160/

直接查看STM32F429_Discovery_FreeRTOS_9/FreeRTOS/Source/portable/GCC/ARM_CM4F/port.c发现：#ifndef __VFP_FP__ #error This port can only be used when the project options are configured to enable hardware floating point support.#endif
代码的确不支持软浮点。经过多次尝试决定，使用兼容软浮点的接口，并修改部分代码。阅读代码后发现三处涉及硬浮点的代码：[url=]

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1 /* This is a naked function. */ 2 static void vPortEnableVFP( void ) 3 { 4 __asm volatile 5 ( 6 " ldr.w r0, =0xE000ED88 " /* The FPU enable bits are in the CPACR. */ 7 " ldr r1, [r0] " 8 " " 9 " orr r1, r1, #( 0xf << 20 ) " /* Enable CP10 and CP11 coprocessors, then save back. */10 " str r1, [r0] "11 " bx r14 "12 );13 }14 /*-----------------------------------------------------------*/[url=]

[/url]

第9行就是硬浮点时，仿真出错的位置实际上是任务在初始化时对浮点处理器的初始化[url=]

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1 void xPortPendSVHandler( void ) 2 { 3 /* This is a naked function. */ 4 5 __asm volatile 6 ( 7 " mrs r0, psp " 8 " isb " 9 " "10 " ldr r3, pxCurrentTCBConst " /* Get the location of the current TCB. */11 " ldr r2, [r3] "12 " "13 " tst r14, #0x10 " /* Is the task using the FPU context? If so, push high vfp registers. */14 " it eq "15 " vstmdbeq r0!, {s16-s31} "16 " "17 " stmdb r0!, {r4-r11, r14} " /* Save the core registers. */18 " "19 " str r0, [r2] " /* Save the new top of stack into the first member of the TCB. */20 " "21 " stmdb sp!, {r3} "22 " mov r0, %0 "23 " msr basepri, r0 "24 " dsb "25 " isb "26 " bl vTaskSwitchContext "27 " mov r0, #0 "28 " msr basepri, r0 "29 " ldmia sp!, {r3} "30 " "31 " ldr r1, [r3] " /* The first item in pxCurrentTCB is the task top of stack. */32 " ldr r0, [r1] "33 " "34 " ldmia r0!, {r4-r11, r14} " /* Pop the core registers. */35 " "36 " tst r14, #0x10 " /* Is the task using the FPU context? If so, pop the high vfp registers too. */37 " it eq "38 " vldmiaeq r0!, {s16-s31} "39 " "40 " msr psp, r0 "41 " isb "42 " "43 #ifdef WORKAROUND_PMU_CM001 /* XMC4000 specific errata workaround. */44 #if WORKAROUND_PMU_CM001 == 145 " push { r14 } "46 " pop { pc } "47 #endif48 #endif49 " "50 " bx r14 "51 " "52 " .align 4 "53 "pxCurrentTCBConst: .word pxCurrentTCB "54 ::"i"(configMAX_SYSCALL_INTERRUPT_PRIORITY)55 );56 }[url=]