devbox
Gausst松鼠会
这个屌丝很懒，什么也没留下！
关注作者
热门标签
热门文章
当前位置:   article > 正文

5. ATF（ARM Trusted firmware）启动---bl31_atf bl31 无法启动

作者：Gausst松鼠会 | 2024-05-22 22:05:36

赞

踩

atf bl31 无法启动

    　

在bl2中通过调用smc指令后会跳转到bl31中进行执行，bl31最终主要的作用是建立EL3 runtime software，在该阶段会建立各种类型的smc调用注册并完成对应的cortex状态切换。该阶段主要执行在monitor中。

1. bl31_entrypoint

通过bl31.ld.S文件可知， bl31的入口函数是：bl31_entrypoint函数，该函数的内容如下：

  1. func bl31_entrypoint
  2. #if !RESET_TO_BL31
  3. 	/* ---------------------------------------------------------------
  4. 	 * Preceding bootloader has populated x0 with a pointer to a
  5. 	 * 'bl31_params' structure & x1 with a pointer to platform
  6. 	 * specific structure
  7. 	 * ---------------------------------------------------------------
  8. 	 */
  9. 	mov	x20, x0
  10. 	mov	x21, x1
  11.  
  12. 	/* ---------------------------------------------------------------------
  13. 	 * For !RESET_TO_BL31 systems, only the primary CPU ever reaches
  14. 	 * bl31_entrypoint() during the cold boot flow, so the cold/warm boot
  15. 	 * and primary/secondary CPU logic should not be executed in this case.
  16. 	 *
  17. 	 * Also, assume that the previous bootloader has already set up the CPU
  18. 	 * endianness and has initialised the memory.
  19. 	 * ---------------------------------------------------------------------
  20. 	 */
  21. /* el3初始化操作，该el3_entrypoint_common函数在上面已经介绍过，其中runtime_exceptions为el3 runtime software的异常向量表，内容定义在bl31/aarch64/runtime_exceptions.S文件中 */
  22. 	el3_entrypoint_common					\
  23. 		_set_endian=0					\
  24. 		_warm_boot_mailbox=0				\
  25. 		_secondary_cold_boot=0				\
  26. 		_init_memory=0					\
  27. 		_init_c_runtime=1				\
  28. 		_exception_vectors=runtime_exceptions
  29.  
  30. 	/* ---------------------------------------------------------------------
  31. 	 * Relay the previous bootloader's arguments to the platform layer
  32. 	 * ---------------------------------------------------------------------
  33. 	 */
  34. 	mov	x0, x20
  35. 	mov	x1, x21
  36. #else
  37. 	/* ---------------------------------------------------------------------
  38. 	 * For RESET_TO_BL31 systems which have a programmable reset address,
  39. 	 * bl31_entrypoint() is executed only on the cold boot path so we can
  40. 	 * skip the warm boot mailbox mechanism.
  41. 	 * ---------------------------------------------------------------------
  42. 	 */
  43. 	el3_entrypoint_common					\
  44. 		_set_endian=1					\
  45. 		_warm_boot_mailbox=!PROGRAMMABLE_RESET_ADDRESS	\
  46. 		_secondary_cold_boot=!COLD_BOOT_SINGLE_CPU	\
  47. 		_init_memory=1					\
  48. 		_init_c_runtime=1				\
  49. 		_exception_vectors=runtime_exceptions
  50.  
  51. 	/* ---------------------------------------------------------------------
  52. 	 * For RESET_TO_BL31 systems, BL31 is the first bootloader to run so
  53. 	 * there's no argument to relay from a previous bootloader. Zero the
  54. 	 * arguments passed to the platform layer to reflect that.
  55. 	 * ---------------------------------------------------------------------
  56. 	 */
  57. 	mov	x0, 0
  58. 	mov	x1, 0
  59. #endif /* RESET_TO_BL31 */
  60.  
  61. 	/* ---------------------------------------------
  62. 	 * Perform platform specific early arch. setup
  63. 	 * ---------------------------------------------
  64. 	 */
  65. /* 平台架构相关的初始化设置 */
  66. 	bl	bl31_early_platform_setup
  67. 	bl	bl31_plat_arch_setup
  68.  
  69. 	/* ---------------------------------------------
  70. 	 * Jump to main function.
  71. 	 * ---------------------------------------------
  72. 	 */
  73. 	bl	bl31_main	//跳转到bl31_main函数，执行该阶段需要的主要操作
  74.  
  75. 	/* -------------------------------------------------------------
  76. 	 * Clean the .data & .bss sections to main memory. This ensures
  77. 	 * that any global data which was initialised by the primary CPU
  78. 	 * is visible to secondary CPUs before they enable their data
  79. 	 * caches and participate in coherency.
  80. 	 * -------------------------------------------------------------
  81. 	 */
  82. 	adr	x0, __DATA_START__
  83. 	adr	x1, __DATA_END__
  84. 	sub	x1, x1, x0
  85. 	bl	clean_dcache_range
  86.  
  87. 	adr	x0, __BSS_START__
  88. 	adr	x1, __BSS_END__
  89. 	sub	x1, x1, x0
  90. 	bl	clean_dcache_range
  91.  
  92. 	b	el3_exit	//执行完成将跳转到bl33中执行，即执行bootloader
  93. endfunc bl31_entrypoint
	//执行完成将跳转到bl33中执行，即执行bootloader
endfunc bl31_entrypoint

2. bl31_main

该函数主要完成必要初始化操作，配置EL3中的各种smc操作，以便在后续顺利响应在CA和TA中产生的smc操作

  1. void bl31_main(void)
  2. {
  3. 	NOTICE("BL31: %s\n", version_string);
  4. 	NOTICE("BL31: %s\n", build_message);
  5.  
  6. 	/* Perform platform setup in BL31 */
  7. 	bl31_platform_setup();	//初始化相关驱动，时钟等
  8.  
  9. 	/* Initialise helper libraries */
  10. 	bl31_lib_init();	//用于执行bl31软件中相关全局变量的初始化
  11.  
  12. 	/* Initialize the runtime services e.g. psci. */
  13. 	INFO("BL31: Initializing runtime services\n");
  14. 	runtime_svc_init();	//初始化el3中的service，通过在编译时指定特定的section来确定哪些service会被作为el3 service
  15.  
  16. 	/*
  17. 	 * All the cold boot actions on the primary cpu are done. We now need to
  18. 	 * decide which is the next image (BL32 or BL33) and how to execute it.
  19. 	 * If the SPD runtime service is present, it would want to pass control
  20. 	 * to BL32 first in S-EL1. In that case, SPD would have registered a
  21. 	 * function to intialize bl32 where it takes responsibility of entering
  22. 	 * S-EL1 and returning control back to bl31_main. Once this is done we
  23. 	 * can prepare entry into BL33 as normal.
  24. 	 */
  25.  
  26. 	/*
  27. 	 * If SPD had registerd an init hook, invoke it.
  28. 	 */
  29. /* 如果注册了TEE OS支持，在调用完成run_service_init之后会使用TEE OS的入口函数初始化bl32_init变量，然后执行对应的Init函数，以OP-TEE为例，bl32_init将会被初始化成opteed_init，到此将会执行 opteed_init函数来进入OP-TEE OS的Image，当OP-TEE image OS执行完了image后，将会产生一个TEESMC_OPTEED_RETURN_ENTRY_DONE的smc来通过bl31已经完成了OP-TEE的初始化*/
  30. 	if (bl32_init) {
  31. 		INFO("BL31: Initializing BL32\n");
  32. 		(*bl32_init)();
  33. 	}
  34. 	/*
  35. 	 * We are ready to enter the next EL. Prepare entry into the image
  36. 	 * corresponding to the desired security state after the next ERET.
  37. 	 */
  38. 	bl31_prepare_next_image_entry();		//准备跳转到bl33，在执行runtime_service的时候会存在一个spd service，该在service的init函数中将会去执行bl32的image完成TEE OS初始化
  39.  
  40. 	console_flush();
  41.  
  42. 	/*
  43. 	 * Perform any platform specific runtime setup prior to cold boot exit
  44. 	 * from BL31
  45. 	 */
  46. 	bl31_plat_runtime_setup();
  47. }

3. runtime_svc_init

该函数主要用来建立smc索引表并执行EL3中提供的service的初始化操作
 

  1. void runtime_svc_init(void)
  2. {
  3. 	int rc = 0, index, start_idx, end_idx;
  4.  
  5. 	/* Assert the number of descriptors detected are less than maximum indices */
  6. /*判定rt_svc_descs段中的是否超出MAX_RT_SVCS条*/
  7. 	assert((RT_SVC_DESCS_END >= RT_SVC_DESCS_START) &&
  8. 			(RT_SVC_DECS_NUM < MAX_RT_SVCS));
  9.  
  10. 	/* If no runtime services are implemented then simply bail out */
  11. 	if (RT_SVC_DECS_NUM == 0)
  12. 		return;
  13.  
  14. 	/* Initialise internal variables to invalid state */
  15. /* 初始化 t_svc_descs_indices数组中的数据成-1，表示当前所有的service无效*/
  16. 	memset(rt_svc_descs_indices, -1, sizeof(rt_svc_descs_indices));
  17.  
  18. /* 获取第一条EL3 service在RAM中的起始地址，通过获取RT_SVC_DESCS_START的值来确定，该值在链接文件中有定义 */
  19. 	rt_svc_descs = (rt_svc_desc_t *) RT_SVC_DESCS_START;
  20.  
  21. /* 遍历整个rt_svc_des段，将其call type与rt_svc_descs_indices中的index建立对应关系 */
  22. 	for (index = 0; index < RT_SVC_DECS_NUM; index++) {
  23. 		rt_svc_desc_t *service = &rt_svc_descs[index];
  24.  
  25. 		/*
  26. 		 * An invalid descriptor is an error condition since it is
  27. 		 * difficult to predict the system behaviour in the absence
  28. 		 * of this service.
  29. 		 */
  30. /* 判定在编译的时候注册的service是否有效 */
  31. 		rc = validate_rt_svc_desc(service);
  32. 		if (rc) {
  33. 			ERROR("Invalid runtime service descriptor %p\n",
  34. 				(void *) service);
  35. 			panic();
  36. 		}
  37.  
  38. 		/*
  39. 		 * The runtime service may have separate rt_svc_desc_t
  40. 		 * for its fast smc and standard smc. Since the service itself
  41. 		 * need to be initialized only once, only one of them will have
  42. 		 * an initialisation routine defined. Call the initialisation
  43. 		 * routine for this runtime service, if it is defined.
  44. 		 */
  45. /* 执行当前service的init的操作 */
  46. 		if (service->init) {
  47. 			rc = service->init();
  48. 			if (rc) {
  49. 				ERROR("Error initializing runtime service %s\n",
  50. 						service->name);
  51. 				continue;
  52. 			}
  53. 		}
  54.  
  55. 		/*
  56. 		 * Fill the indices corresponding to the start and end
  57. 		 * owning entity numbers with the index of the
  58. 		 * descriptor which will handle the SMCs for this owning
  59. 		 * entity range.
  60. 		 */
  61. /* 根据该service的call type以及start oen来确定一个唯一的index,并且将该service中支持的所有的call type生成的唯一表示映射到同一个index中 */
  62. 		start_idx = get_unique_oen(rt_svc_descs[index].start_oen,
  63. 				service->call_type);
  64. 		assert(start_idx < MAX_RT_SVCS);
  65. 		end_idx = get_unique_oen(rt_svc_descs[index].end_oen,
  66. 				service->call_type);
  67. 		assert(end_idx < MAX_RT_SVCS);
  68. 		for (; start_idx <= end_idx; start_idx++)
  69. 			rt_svc_descs_indices[start_idx] = index;
  70. 	}
  71. }

4. DECLARE_RT_SVC

该宏用来在编译的时候将EL3中的service编译进rt_svc_descs段中，该宏定义如下：

  1. #define DECLARE_RT_SVC(_name, _start, _end, _type, _setup, _smch) \
  2. 	static const rt_svc_desc_t __svc_desc_ ## _name \
  3. 		__section("rt_svc_descs") __used = { \
  4. 			.start_oen = _start, \
  5. 			.end_oen = _end, \
  6. 			.call_type = _type, \
  7. 			.name = #_name, \
  8. 			.init = _setup, \
  9. 			.handle = _smch }


start_oen：该service的起始内部number

end.oen: 该service的末尾number

call_type: 调用的smc的类型

name: 该service的名字

init: 该service在执行之前需要被执行的初始化操作

handle: 当触发了call type的调用时调用的handle该请求的函数

5.以OP-TEE为例从bl31跳转到OP-TEE

实现从bl31到OP-TEE的跳转是通过执行opteed_setup函数来实现的，该函数在执行runtime_svc_int中对各service做service->init()函数来实现，而OPTEE这个service就是通过DECALARE_RT_SVC被注册到tr_svc_descs段中，代码存在service/spd/opteed/opteed_main.c文件中，内容如下：

声明：本文内容由网友自发贡献，版权归原作者所有，本站不承担相应法律责任。如您发现有侵权的内容，请联系我们。转载请注明出处：【wpsshop博客】
推荐阅读
相关标签

Copyright © 2003-2013 www.wpsshop.cn 版权所有，并保留所有权利。

  

闽ICP备14008679号