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通用MCU Bootloader - KBOOT之IAP API
今天痞子衡给大家介绍的是飞思卡尔Kinetis系列MCU的KBOOT之ROM API特性。
KBOOT的ROM API特性主要存在于ROM Bootloader形态中,KBOOT内部集成了一些Kinetis内部IP模块driver,这些IP模块driver首要目的是用于实现KBOOT的功能,但由于这些IP模块driver会随着KBOOT一起被固化在ROM空间里,所以如果这些IP driver能够被外部(主要是运行于Flash中的Application)调用,那么肯定会节省Application代码空间,这么看起来将ROM Bootloader里的一些IP driver以API的形式export出去是很有意义的,这么有意义的事,KBOOT当然是会做的。下面痞子衡给大家介绍KBOOT里的ROM API特性:
一、API tree原型
KBOOT中声明了如下一个名叫bootloader_tree_t的结构体来组织那些可被export出去的IP模块driver,结构体前4个成员记录了版本、版权以及Bootloader等信息,从第5个成员开始便是那些IP模块driver API,目前支持导出的模块API并不多,一共4个:Flash、AES、Kboot、USB。
- //! @brief Structure of version property.
- typedef union StandardVersion
- {
- struct {
- uint8_t bugfix; //!< bugfix version [7:0]
- uint8_t minor; //!< minor version [15:8]
- uint8_t major; //!< major version [23:16]
- char name; //!< name [31:24]
- };
- uint32_t version; //!< combined version numbers
- } standard_version_t;
- //! @brief Root of the bootloader API tree.
- //!
- //! An instance of this struct resides in read-only memory in the bootloader. It
- //! provides a user application access to APIs exported by the bootloader.
- //!
- //! @note The order of existing fields must not be changed.
- typedef struct BootloaderTree
- {
- void (*runBootloader)(void *arg); //!< Function to start the bootloader executing.
- standard_version_t version; //!< Bootloader version number.
- const char *copyright; //!< Copyright string.
- const bootloader_context_t *runtimeContext; //!< Pointer to the bootloader's runtime context.
- const flash_driver_interface_t *flashDriver; //!< Flash driver API.
- const aes_driver_interface_t *aesDriver; //!< AES driver API.
- const kb_interface_t *kbApi; //!< Bootloader API.
- const usb_driver_interface_t *usbDriver; //!< USB driver API.
- } bootloader_tree_t;
复制代码 在所有导出的模块driver API中,Flash driver API是使用最广泛的,其API原型如下(不同芯片中Flash driver API版本可能不一致,截止目前共有3个版本:F1.0.x、F1.1.x、F1.2.x):
- //! @brief Interface for the flash driver.
- typedef struct FlashDriverInterface {
- #if !defined(FLASH_API_TREE_1_0)
- standard_version_t version; //!< flash driver API version number.
- #endif
- status_t (*flash_init)(flash_driver_t * driver);
- #if defined(FLASH_API_TREE_1_0)
- status_t (*flash_erase_all)(flash_config_t *config);
- status_t (*flash_erase_all_unsecure)(flash_config_t *config);
- status_t (*flash_erase)(flash_config_t *config, uint32_t start, uint32_t lengthInBytes);
- #else
- status_t (*flash_erase_all)(flash_config_t *config, uint32_t key);
- status_t (*flash_erase_all_unsecure)(flash_config_t *config, uint32_t key);
- status_t (*flash_erase)(flash_config_t *config, uint32_t start, uint32_t lengthInBytes, uint32_t key);
- #endif
- status_t (*flash_program)(flash_driver_t * driver, uint32_t start, uint32_t * src, uint32_t lengthInBytes);
- status_t (*flash_get_security_state)(flash_driver_t * driver, flash_security_state_t * state);
- status_t (*flash_security_bypass)(flash_driver_t * driver, const uint8_t * backdoorKey);
- status_t (*flash_verify_erase_all)(flash_driver_t * driver, flash_margin_value_t margin);
- status_t (*flash_verify_erase)(flash_driver_t * driver, uint32_t start, uint32_t lengthInBytes, flash_margin_value_t margin);
- status_t (*flash_verify_program)(flash_driver_t * driver, uint32_t start, uint32_t lengthInBytes, const uint8_t * expectedData, flash_margin_value_t margin, uint32_t * failedAddress, uint32_t * failedData);
- status_t (*flash_get_property)(flash_driver_t * driver, flash_property_t whichProperty, uint32_t * value);
- #if (!defined(FLASH_API_TREE_1_0)) && (!defined(FLASH_API_TREE_1_1))
- status_t (*flash_register_callback)(flash_driver_t * driver, flash_callback_t callback);
- status_t (*flash_program_once)(flash_driver_t * driver, uint32_t index, uint32_t * src, uint32_t lengthInBytes);
- status_t (*flash_read_once)(flash_driver_t * driver, uint32_t index, uint32_t * dst, uint32_t lengthInBytes);
- status_t (*flash_read_resource)(flash_driver_t * driver, uint32_t start, uint32_t *dst, uint32_t lengthInBytes, flash_read_resource_option_t option);
- #endif
- } flash_driver_interface_t;
复制代码 下表列出了所有含ROM空间的芯片中Flash driver API的版本:
Note: 模块driver API设计必须满足几个条件:一、API里不能使用全局变量;二、模块IRQHandler不能直接当做API
二、API tree位置
声明好了bootloader_tree_t结构体原型以及各IP模块driver API原型,下一步便是在KBOOT中定义如下常量g_bootloaderTree以创建对象分配内存(不同芯片中g_bootloaderTree版本可能不一致,下面是用于K80芯片上的K1.3.0版)。
- //! @brief Static API tree.
- const bootloader_tree_t g_bootloaderTree =
- {
- .runBootloader = bootloader_user_entry,
- .version = {
- .name = kBootloader_Version_Name,
- .major = kBootloader_Version_Major,
- .minor = kBootloader_Version_Minor,
- .bugfix = kBootloader_Version_Bugfix
- },
- .copyright = bootloaderCopyright,
- .runtimeContext = &g_bootloaderContext,
- .flashDriver = &g_flashDriverInterface,
- .aesDriver = &g_aesInterface
- };
复制代码 只要找到g_bootloaderTree地址,便可以访问到那些IP模块driver API,现在的问题是如何找到g_bootloaderTree地址?我们知道在KBOOT工程中,如果不在链接文件里明确指定g_bootloaderTree地址,链接器会随机分配一个地址来存放g_bootloaderTree,这会导致在不同芯片中g_bootloaderTree地址是不一样的;但即使强制指定g_bootloaderTree链接地址,如果ROM空间起始地址不一定是从0x1c000000开始,那么还是难以做到g_bootloaderTree地址统一。到底该怎么解决这个问题?KBOOT使用了一个巧妙的方法,下面是KBOOT工程的startup文件(IAR版),KBOOT将g_bootloaderTree的地址放到了中断向量表第8个向量的位置处(该向量为ARM Cortex-M未定义的系统向量),因此只要知道了ROM空间的起始地址,那么偏移0x1c处开始的4bytes便是g_bootloaderTree地址。
- MODULE ?cstartup
- ;; Forward declaration of sections.
- SECTION CSTACK:DATA:NOROOT(3)
- SECTION .intvec:CODE:NOROOT(2)
- EXTERN g_bootloaderTree
- PUBLIC __vector_table
- PUBLIC __vector_table_0x1c
- DATA
- __vector_table
- DCD sfe(CSTACK)
- DCD Reset_Handler
- DCD NMI_Handler
- DCD HardFault_Handler
- DCD MemManage_Handler
- DCD BusFault_Handler
- DCD UsageFault_Handler
- __vector_table_0x1c
- DCD g_bootloaderTree
- DCD 0
- DCD 0
- DCD 0
- DCD SVC_Handler
- DCD DebugMon_Handler
- DCD 0
- DCD PendSV_Handler
- DCD SysTick_Handler
- ;; ...
复制代码 三、调用API的方法
KBOOT中的ROM API调用方法非常简单,以K80芯片中Flash driver API调用为例,首先需要按以下步骤定义s_flashInterface指针:
- #define BOOTLOADER_TREE_LOCATION (0x1c00001cul)
- #define BOOTLOADER_API_TREE_POINTER (*(bootloader_tree_t **)BOOTLOADER_TREE_LOCATION)
- static const flash_driver_interface_t *s_flashInterface = BOOTLOADER_API_TREE_POINTER->flashDriver;
复制代码 有了s_flashInterface指针便可以随意访问Flash driver API:
- const uint32_t test_program_buffer[2] = { 0x01234567, 0x89abcdef };
- flash_config_t flashInstance;
- s_flashInterface->flash_init(&flashInstance);
- s_flashInterface->flash_erase(&flashInstance, 0x8000, 0x1000);
- s_flashInterface->flash_program(&flashInstance, 0x8000, (uint32_t *)test_program_buffer, 8);
复制代码
作者:痞子衡
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