[ATF]-ATF代码分析

目录

• • • • 1、ATF里都有什么？
      • 2、ATF的rt_svc介绍(runtime service)
      • • (1)、SMC Calling convention文档
        • (2)、DECLARE_RT_SVC的使用
        • (3)、DECLARE_RT_SVC的定义
        • （4）、在同步异常中smc_handler64，跳转到响应的rt_svc
        • (5)、smc在驱动中的调用
      • 4、进入ATF的方式
      • • 5、smc流程下的代码分析

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1、ATF里都有什么？

ATF的Current features Overview

• 安全世界的初始化，例如异常向量表、一些控制寄存器和中断寄
• CPU reset和power down的时序。包括Arm DynamIQ cpu的支持。
• 标准的system IP的驱动，例如Generic Interrupt Controller (GIC), Cache Coherent Interconnect (CCI), Cache Coherent Network (CCN), Network Interconnect (NIC) and TrustZone Controller (TZC).
• 一种通用的SCMI驱动程序, 适用于电源控制接口，例如ARM SYSTEM Control Processor(SCP)
• smc处理，using an EL3 runtime services framework
• PSCI库的支持，用于CPU/Cluster/system的电源管理，这个库集成到了aarch64 el3的runtime中，也适用于aarch32 el3
• secure monitor代码，用于world切换、中断routing
• SPDs for the OP-TEE Secure OS, NVIDIA Trusted Little Kernel and Trusty Secure OS
• SecureBoot实现
• 预集成TBB与Arm CryptoCell产品，利用其硬件Root的信任和加密加速服务。

2、ATF的rt_svc介绍(runtime service)

(1)、SMC Calling convention文档

我们重点看下这张表，对应smc id的定义

• bit31决定是fast call，还是std call(yield对应的就是std call)
• bit30表示是以32位传参，还是以64位传参， 注意我们看了optee在linux的driver，都是以32位方式
• bit29:24 决定服务的类型
• bit23:16 reserved
• bit15:0 每种call类型下，表示range

bit31、bit30、bit23:16、bit15:0 都是很好理解，我们来讲一下bit29:24
在ATF中定义rt_svc（runtime service）时，需按照该文档的描述来定义

例如在opteed_main.c中，定义了一个service，它的call类型是OEN_TOS_START–OEN_TOS_END，对应的恰好是bit29:24 = 50–63

DECLARE_RT_SVC(
	opteed_fast,

	OEN_TOS_START,
	OEN_TOS_END,
	SMC_TYPE_FAST,
	opteed_setup,
	opteed_smc_handler
);

那么我们在linux kernel中，调用smc时的smc id的bit29:24需要等于50，那么此次的smc调用才会调用到这个runtime service的handler程序

例如在arm_arch_svc_setup.c中，定义了一个service，它的call类型是OEN_ARM_START–OEN_ARM_END，对应的恰好是bit29:24 = 0–0

/* Register Standard Service Calls as runtime service */
DECLARE_RT_SVC(
		arm_arch_svc,
		OEN_ARM_START,
		OEN_ARM_END,
		SMC_TYPE_FAST,
		NULL,
		arm_arch_svc_smc_handler
);

那么我们在linux kernel中，调用smc时的smc id的bit29:24需要等于0，那么此次的smc调用才会调用到这个runtime service的handler程序

例如mtk代码中，mtk_sip_svc.c中，定义了一个service，它的call类型是OEN_SIP_START–OEN_SIP_END，对应的恰好是bit29:24 = 2–2

/* Define a runtime service descriptor for fast SMC calls */
DECLARE_RT_SVC(
	mediatek_sip_svc,
	OEN_SIP_START,
	OEN_SIP_END,
	SMC_TYPE_FAST,
	NULL,
	sip_smc_handler
);

那么我们在linux kernel中，调用smc时的smc id的bit29:24需要等于2，那么此次的smc调用才会调用到这个runtime service的handler程序

(2)、DECLARE_RT_SVC的使用

DECLARE_RT_SVC是一个宏，用于定义一组service，例如在opteed_main.c中的使用

/* Define an OPTEED runtime service descriptor for fast SMC calls */
DECLARE_RT_SVC(
	opteed_fast,

	OEN_TOS_START,
	OEN_TOS_END,
	SMC_TYPE_FAST,
	opteed_setup,
	opteed_smc_handler
);

/* Define an OPTEED runtime service descriptor for yielding SMC calls */
DECLARE_RT_SVC(
	opteed_std,

	OEN_TOS_START,
	OEN_TOS_END,
	SMC_TYPE_YIELD,
	NULL,
	opteed_smc_handler
);

其中OEN_TOS_START和OEN_TOS_END、SMC_TYPE_FAST和SMC_TYPE_YIELD都是按照SMC Calling convention文档来定义的

#define OEN_ARM_START			U(0)
#define OEN_ARM_END			U(0)
#define OEN_CPU_START			U(1)
#define OEN_CPU_END			U(1)
#define OEN_SIP_START			U(2)
#define OEN_SIP_END			U(2)
#define OEN_OEM_START			U(3)
#define OEN_OEM_END			U(3)
#define OEN_STD_START			U(4)	/* Standard Service Calls */
#define OEN_STD_END			U(4)
#define OEN_STD_HYP_START		U(5)	/* Standard Hypervisor Service calls */
#define OEN_STD_HYP_END			U(5)
#define OEN_VEN_HYP_START		U(6)	/* Vendor Hypervisor Service calls */
#define OEN_VEN_HYP_END			U(6)
#define OEN_TAP_START			U(48)	/* Trusted Applications */
#define OEN_TAP_END			U(49)
#define OEN_TOS_START			U(50)	/* Trusted OS */
#define OEN_TOS_END			U(63)
#define OEN_LIMIT			U(64)

#define SMC_TYPE_FAST			ULL(1)
#define SMC_TYPE_YIELD			ULL(0)

SMC_TYPE_FAST和SMC_TYPE_YIELD也是根据SMC Calling convention文档定义

(3)、DECLARE_RT_SVC的定义

在runtime_svc.h中，其实就是在section(“rt_svc_descs”)段中定义了一个全局变量.

/*
 * Convenience macros to declare a service descriptor
 */
#define DECLARE_RT_SVC(_name, _start, _end, _type, _setup, _smch)	\
	static const rt_svc_desc_t __svc_desc_ ## _name			\
		__section("rt_svc_descs") __used = {			\
			.start_oen = (_start),				\
			.end_oen = (_end),				\
			.call_type = (_type),				\
			.name = #_name,					\
			.init = (_setup),				\
			.handle = (_smch)				\
		}

section “rt_svc_descs”在RT_SVC_DESCS宏中

#define RT_SVC_DESCS					\
	. = ALIGN(STRUCT_ALIGN);			\
	__RT_SVC_DESCS_START__ = .;			\
	KEEP(*(rt_svc_descs))				\
	__RT_SVC_DESCS_END__ = .;

而在rodata_common的宏中，定义了RT_SVC_DESCS

#define RODATA_COMMON					\
	RT_SVC_DESCS					\
	FCONF_POPULATOR					\
	PMF_SVC_DESCS					\
	PARSER_LIB_DESCS				\
	CPU_OPS						\
	GOT						\
	BASE_XLAT_TABLE_RO

在bl31.ld.S中，将RODATA_COMMON放入了rodata段

    .rodata . : {
        __RODATA_START__ = .;
        *(SORT_BY_ALIGNMENT(.rodata*))

	RODATA_COMMON

        /* Place pubsub sections for events */
        . = ALIGN(8);
#include <lib/el3_runtime/pubsub_events.h>

        . = ALIGN(PAGE_SIZE);
        __RODATA_END__ = .;
    } >RAM

（4）、在同步异常中smc_handler64，跳转到响应的rt_svc

附上完整代码和注释

smc_handler64:
	/* NOTE: The code below must preserve x0-x4 */

	/*
	 * Save general purpose and ARMv8.3-PAuth registers (if enabled).
	 * If Secure Cycle Counter is not disabled in MDCR_EL3 when
	 * ARMv8.5-PMU is implemented, save PMCR_EL0 and disable Cycle Counter.
	 */
	bl	save_gp_pmcr_pauth_regs

#if ENABLE_PAUTH
	/* Load and program APIAKey firmware key */
	bl	pauth_load_bl31_apiakey
#endif

	/*
	 * Populate the parameters for the SMC handler.
	 * We already have x0-x4 in place. x5 will point to a cookie (not used
	 * now). x6 will point to the context structure (SP_EL3) and x7 will
	 * contain flags we need to pass to the handler.
	 */
	mov	x5, xzr
	mov	x6, sp

	/*
	 * Restore the saved C runtime stack value which will become the new
	 * SP_EL0 i.e. EL3 runtime stack. It was saved in the 'cpu_context'
	 * structure prior to the last ERET from EL3.
	 */
	ldr	x12, [x6, #CTX_EL3STATE_OFFSET + CTX_RUNTIME_SP]

	/* Switch to SP_EL0 */
	msr	spsel, #MODE_SP_EL0

	/*
	 * Save the SPSR_EL3, ELR_EL3, & SCR_EL3 in case there is a world
	 * switch during SMC handling.
	 * TODO: Revisit if all system registers can be saved later.
	 */
	mrs	x16, spsr_el3
	mrs	x17, elr_el3
	mrs	x18, scr_el3
	stp	x16, x17, [x6, #CTX_EL3STATE_OFFSET + CTX_SPSR_EL3]
	str	x18, [x6, #CTX_EL3STATE_OFFSET + CTX_SCR_EL3]

	/* Copy SCR_EL3.NS bit to the flag to indicate caller's security */
	bfi	x7, x18, #0, #1

	mov	sp, x12

	/* Get the unique owning entity number */
	ubfx	x16, x0, #FUNCID_OEN_SHIFT, #FUNCID_OEN_WIDTH  ---------------- 获取FUNCID_OEN_SHIFT，对应第一节中的OEN_TOS_START
	ubfx	x15, x0, #FUNCID_TYPE_SHIFT, #FUNCID_TYPE_WIDTH  ---------------- 获取FUNCID_TYPE_SHIFT，对应第一节中的SMC_TYPE_FAST(fast还是yield,yield其实就是standard)
	orr	x16, x16, x15, lsl #FUNCID_OEN_WIDTH

	/* Load descriptor index from array of indices */
	adrp	x14, rt_svc_descs_indices  ----在runtime_svc_init()中会将所有的section rt_svc_descs段放入rt_svc_descs_indices数组，这里获取该数组地址
	add	x14, x14, :lo12:rt_svc_descs_indices
	ldrb	w15, [x14, x16]   ---找到rt_svc在rt_svc_descs_indices数组中的index

	/* Any index greater than 127 is invalid. Check bit 7. */
	tbnz	w15, 7, smc_unknown

	/*
	 * Get the descriptor using the index
	 * x11 = (base + off), w15 = index    -------------------------重要的注释
	 *
	 * handler = (base + off) + (index << log2(size))  ------ 这句注释特别重要，整段汇编看不懂没关系，这句注释看懂就行
	 */
	adr	x11, (__RT_SVC_DESCS_START__ + RT_SVC_DESC_HANDLE)
	lsl	w10, w15, #RT_SVC_SIZE_LOG2
	ldr	x15, [x11, w10, uxtw]    ------------------------------这句话对应的就是上述注释:handler = (base + off) + (index << log2(size))

	/*
	 * Call the Secure Monitor Call handler and then drop directly into
	 * el3_exit() which will program any remaining architectural state
	 * prior to issuing the ERET to the desired lower EL.
	 */
#if DEBUG
	cbz	x15, rt_svc_fw_critical_error
#endif
	blr	x15     -------------------------------------跳转到handler

	b	el3_exit

(5)、smc在驱动中的调用

在optee_smc.h中，我们可以查看linux kernel中给driver定义的smc的类型有：

首先是两个宏，一个用于定义fast call，一个用于定义std call

#define OPTEE_SMC_STD_CALL_VAL(func_num) \
	ARM_SMCCC_CALL_VAL(ARM_SMCCC_STD_CALL, ARM_SMCCC_SMC_32, \
			   ARM_SMCCC_OWNER_TRUSTED_OS, (func_num))
#define OPTEE_SMC_FAST_CALL_VAL(func_num) \
	ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, ARM_SMCCC_SMC_32, \
			   ARM_SMCCC_OWNER_TRUSTED_OS, (func_num))

std call只有两个cmd，一个用于正向调用，一个用于rpc调用

#define OPTEE_SMC_FUNCID_RETURN_FROM_RPC	3
#define OPTEE_SMC_CALL_RETURN_FROM_RPC \
	OPTEE_SMC_STD_CALL_VAL(OPTEE_SMC_FUNCID_RETURN_FROM_RPC)

#define OPTEE_SMC_FUNCID_CALL_WITH_ARG OPTEE_MSG_FUNCID_CALL_WITH_ARG
#define OPTEE_SMC_CALL_WITH_ARG \
	OPTEE_SMC_STD_CALL_VAL(OPTEE_SMC_FUNCID_CALL_WITH_ARG)

fast call有5个分别用于: get_os_uuid、get_shm_config、exchange_capabilities、disable_shm_cache、enable_shm_cache

#define OPTEE_SMC_FUNCID_GET_OS_UUID OPTEE_MSG_FUNCID_GET_OS_UUID
#define OPTEE_SMC_CALL_GET_OS_UUID \
	OPTEE_SMC_FAST_CALL_VAL(OPTEE_SMC_FUNCID_GET_OS_UUID)

#define OPTEE_SMC_FUNCID_GET_SHM_CONFIG	7
#define OPTEE_SMC_GET_SHM_CONFIG \
	OPTEE_SMC_FAST_CALL_VAL(OPTEE_SMC_FUNCID_GET_SHM_CONFIG)

#define OPTEE_SMC_FUNCID_EXCHANGE_CAPABILITIES	9
#define OPTEE_SMC_EXCHANGE_CAPABILITIES \
	OPTEE_SMC_FAST_CALL_VAL(OPTEE_SMC_FUNCID_EXCHANGE_CAPABILITIES)

#define OPTEE_SMC_FUNCID_DISABLE_SHM_CACHE	10
#define OPTEE_SMC_DISABLE_SHM_CACHE \
	OPTEE_SMC_FAST_CALL_VAL(OPTEE_SMC_FUNCID_DISABLE_SHM_CACHE)

#define OPTEE_SMC_FUNCID_ENABLE_SHM_CACHE	11
#define OPTEE_SMC_ENABLE_SHM_CACHE \
	OPTEE_SMC_FAST_CALL_VAL(OPTEE_SMC_FUNCID_ENABLE_SHM_CACHE)

4、进入ATF的方式

透过事务看本质, 进入ATF的方式：触发异常：同步异常SMC、异步异常(irq,fiq)

如果是同步异常，那么一定是在linux或tee中发生了smc调用，此时进入跳转ATF中异常向量表中的同步异常程序smc_handler64或smc_handler32

在该程序中，解析smc id，来选择跳转到具体哪一个rt-svc(runtime service)

如果是异步异常，那么一定是触发了irq或fiq或serror中断等，此时进入跳转ATF中异常向量表中的异步异常程序，进而跳转到响应的中断处理函数.

在ATF中仅实现irq_aarch64、fiq_aarch64、irq_aarch32、fiq_aarch32 四个异常中断处理函数

vector_entry irq_aarch64
	check_and_unmask_ea
	handle_interrupt_exception irq_aarch64
end_vector_entry irq_aarch64

vector_entry fiq_aarch64
	check_and_unmask_ea
	handle_interrupt_exception fiq_aarch64
end_vector_entry fiq_aarch64

vector_entry irq_aarch32
	check_and_unmask_ea
	handle_interrupt_exception irq_aarch32
end_vector_entry irq_aarch32

vector_entry fiq_aarch32
	check_and_unmask_ea
	handle_interrupt_exception fiq_aarch32
end_vector_entry fiq_aarch32

在中断函数中，先调用plat_ic_get_pending_interrupt_type获取interrupt_type，其实就是通过读取寄存器read_icc_hppir0_el1() ，判断中断是从那里来的，然后返回下面三种interrupt_type:
#define INTR_TYPE_S_EL1 U(0)
#define INTR_TYPE_EL3 U(1)
#define INTR_TYPE_NS U(2)

有了type，再get_interrupt_type_handler获取handler程序，进而跳转到相应的handler程序。 而在三种类型的handler程序的注册，以INTR_TYPE_S_EL1为例：
在opteed_setup()时，将opteed_sel1_interrupt_handler()函数注册成了INTR_TYPE_S_EL1类型中断，也就是当CPU运行在TEE时，来了一个rounting到EL3的中断，则会跳转到ATF中的opteed_sel1_interrupt_handler()函数

5、smc流程下的代码分析

标签：ATF,分析,OPTEE,smc,代码,svc,OEN,SMC,define
来源： https://blog.51cto.com/u_15278218/2931173