文章目錄

• • • • 1、同步異常向量表-(smc)
      • • 1.1、handle_sync_exception調(diào)用smc_handler64處理同步異常
      • 2、異類步異常向量表-(irq,fiq...)
      • • 2.1、get_interrupt_type_handler獲取ATF注冊(cè)的中斷處理函數(shù)
        • 2.2、handle_interrupt_exception調(diào)用ATF中注冊(cè)的handler函數(shù)

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思考
（1）、smc是如何調(diào)用到ATF中的smc_handler64()函數(shù)的？
（2）、進(jìn)入EL3(ATF)的方式有幾種？

在ree或tee中執(zhí)行smc指令后，cpu將觸發(fā)同步異常，此時(shí)cpu進(jìn)入ATF的sync_exception_aarch64，在干函數(shù)中調(diào)用了handle_sync_exception()—>smc_handler64()

也就是說，進(jìn)入EL3(ATF)的方式有兩種：
（1）、同步異常：smc指令
（2）、異步異常：產(chǎn)生了routing到EL3的FIQ或IRQ
armv8異常：

• asynchronous exception 異步異常，例如IRQ、FIQ、Serror
• synchronous exception 同步異常，例如hyc、smc

1、同步異常向量表-(smc)

smc同步異常調(diào)用的都是handle_sync_exception

sync_exception_aarch64:/* -----------------------------------------------------* This exception vector will be the entry point for* SMCs and traps that are unhandled at lower ELs most* commonly. SP_EL3 should point to a valid cpu context* where the general purpose and system register state* can be saved.* -----------------------------------------------------*/handle_sync_exceptioncheck_vector_size sync_exception_aarch64 sync_exception_aarch32:/* -----------------------------------------------------* This exception vector will be the entry point for* SMCs and traps that are unhandled at lower ELs most* commonly. SP_EL3 should point to a valid cpu context* where the general purpose and system register state* can be saved.* -----------------------------------------------------*/handle_sync_exceptioncheck_vector_size sync_exception_aarch32

1.1、handle_sync_exception調(diào)用smc_handler64處理同步異常

.macro handle_sync_exception /* Enable the SError interrupt */ msr daifclr, #DAIF_ABT_BITstr x30, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_LR] mrs x30, esr_el3 ubfx x30, x30, #ESR_EC_SHIFT, #ESR_EC_LENGTHcmp x30, #EC_AARCH32_SMC b.eq smc_handler32cmp x30, #EC_AARCH64_SMC b.eq smc_handler64/* -----------------------------------------------------* The following code handles any synchronous exception* that is not an SMC.* -----------------------------------------------------*/bl report_unhandled_exception .endm

2、異類步異常向量表-(irq,fiq…)

irq/fiq異步異常調(diào)用的是handle_interrupt_exception

irq_aarch64:handle_interrupt_exception irq_aarch64check_vector_size irq_aarch64.align 7 fiq_aarch64:handle_interrupt_exception fiq_aarch64check_vector_size fiq_aarch64

2.1、get_interrupt_type_handler獲取ATF注冊(cè)的中斷處理函數(shù)

interrupt_type_handler_t get_interrupt_type_handler(uint32_t type) {if (validate_interrupt_type(type))return NULL;return intr_type_descs[type].handler; }

2.2、handle_interrupt_exception調(diào)用ATF中注冊(cè)的handler函數(shù)

.macro handle_interrupt_exception label/* Enable the SError interrupt */msr daifclr, #DAIF_ABT_BITstr x30, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_LR]bl save_gp_registers/** Save the EL3 system registers needed to return from* this exception.*/mrs x0, spsr_el3mrs x1, elr_el3stp x0, x1, [sp, #CTX_EL3STATE_OFFSET + CTX_SPSR_EL3]/* Switch to the runtime stack i.e. SP_EL0 */ldr x2, [sp, #CTX_EL3STATE_OFFSET + CTX_RUNTIME_SP]mov x20, spmsr spsel, #0mov sp, x2/** Find out whether this is a valid interrupt type. If the* interrupt controller reports a spurious interrupt then* return to where we came from.*/bl plat_ic_get_pending_interrupt_typecmp x0, #INTR_TYPE_INVALb.eq interrupt_exit_\label/** Get the registered handler for this interrupt type. A* NULL return value could be 'cause of the following* conditions:** a. An interrupt of a type was routed correctly but a* handler for its type was not registered.** b. An interrupt of a type was not routed correctly so* a handler for its type was not registered.** c. An interrupt of a type was routed correctly to EL3,* but was deasserted before its pending state could* be read. Another interrupt of a different type pended* at the same time and its type was reported as pending* instead. However, a handler for this type was not* registered.** a. and b. can only happen due to a programming error.* The occurrence of c. could be beyond the control of* Trusted Firmware. It makes sense to return from this* exception instead of reporting an error.*/bl get_interrupt_type_handlercbz x0, interrupt_exit_\labelmov x21, x0mov x0, #INTR_ID_UNAVAILABLE/* Set the current security state in the 'flags' parameter */mrs x2, scr_el3ubfx x1, x2, #0, #1/* Restore the reference to the 'handle' i.e. SP_EL3 */mov x2, x20/* x3 will point to a cookie (not used now) */mov x3, xzr/* Call the interrupt type handler */blr x21interrupt_exit_\label:/* Return from exception, possibly in a different security state */b el3_exit.endm

剖析該段匯編的關(guān)鍵代碼：

bl get_interrupt_type_handler //獲取注冊(cè)的中斷處理函數(shù), 返回函數(shù)地址，保存在X0中 cbz x0, interrupt_exit_\label mov x21, x0 //X0保存到了X21中 ..... blr x21 //跳轉(zhuǎn)到X21，就是跳轉(zhuǎn)到ATF中的中斷處理函數(shù)

總結(jié)

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