optee的fast call的介绍

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1、optee的fast call调用的代码导读

如果调用的是fast call，在ATF的代码中，将会把optee_vector_table->fast_smc_entry地址赋给ELR_EL3寄存器，el3_exit退出后，PC将会跳转到该地址处，对应着optee_os中的线程向量表vector_fast_smc_entry地址

static uintptr_t opteed_smc_handler(uint32_t smc_fid,
             u_register_t x1,
             u_register_t x2,
             u_register_t x3,
             u_register_t x4,
             void *cookie,
             void *handle,
             u_register_t flags)
{
...
        if (GET_SMC_TYPE(smc_fid) == SMC_TYPE_FAST) {
            cm_set_elr_el3(SECURE, (uint64_t)
                    &optee_vector_table->fast_smc_entry);
        } else {
            cm_set_elr_el3(SECURE, (uint64_t)
                    &optee_vector_table->yield_smc_entry);
        }
...
}

optee_os中的线程向量表的定义

/*
 * Vector table supplied to ARM Trusted Firmware (ARM-TF) at
 * initialization.
 *
 * Note that ARM-TF depends on the layout of this vector table, any change
 * in layout has to be synced with ARM-TF.
 */
FUNC thread_vector_table , : , .identity_map
    b    vector_std_smc_entry
    b    vector_fast_smc_entry
    b    vector_cpu_on_entry
    b    vector_cpu_off_entry
    b    vector_cpu_resume_entry
    b    vector_cpu_suspend_entry
    b    vector_fiq_entry
    b    vector_system_off_entry
    b    vector_system_reset_entry
END_FUNC thread_vector_table
DECLARE_KEEP_PAGER thread_vector_table

vector_fast_smc_entry的实现

LOCAL_FUNC vector_fast_smc_entry , : , .identity_map
    readjust_pc
    sub    sp, sp, #THREAD_SMC_ARGS_SIZE
    store_xregs sp, THREAD_SMC_ARGS_X0, 0, 7
    mov    x0, sp
    bl    thread_handle_fast_smc
    load_xregs sp, THREAD_SMC_ARGS_X0, 1, 8
    add    sp, sp, #THREAD_SMC_ARGS_SIZE
    ldr    x0, =TEESMC_OPTEED_RETURN_CALL_DONE
    smc    #0
    b    .    /* SMC should not return */
END_FUNC vector_fast_smc_entry

optee_os中fast call的实现

void thread_handle_fast_smc(struct thread_smc_args *args)
{
    thread_check_canaries();

#ifdef CFG_VIRTUALIZATION
    if (!virt_set_guest(args->a7)) {
        args->a0 = OPTEE_SMC_RETURN_ENOTAVAIL;
        goto out;
    }
#endif

    tee_entry_fast(args);

#ifdef CFG_VIRTUALIZATION
    virt_unset_guest();
#endif
    /* Fast handlers must not unmask any exceptions */
out:
    __maybe_unused;
    assert(thread_get_exceptions() == THREAD_EXCP_ALL);
}

/* Note: this function is weak to let platforms add special handling */
void __weak tee_entry_fast(struct thread_smc_args *args)
{
    __tee_entry_fast(args);
}

/*
 * If tee_entry_fast() is overridden, it's still supposed to call this
 * function.
 */
void __tee_entry_fast(struct thread_smc_args *args)
{
    switch (args->a0) {

    /* Generic functions */
    case OPTEE_SMC_CALLS_COUNT:
        tee_entry_get_api_call_count(args);
        break;
    case OPTEE_SMC_CALLS_UID:
        tee_entry_get_api_uuid(args);
        break;
    case OPTEE_SMC_CALLS_REVISION:
        tee_entry_get_api_revision(args);
        break;
    case OPTEE_SMC_CALL_GET_OS_UUID:
        tee_entry_get_os_uuid(args);
        break;
    case OPTEE_SMC_CALL_GET_OS_REVISION:
        tee_entry_get_os_revision(args);
        break;

    /* OP-TEE specific SMC functions */
#ifdef CFG_CORE_RESERVED_SHM
    case OPTEE_SMC_GET_SHM_CONFIG:
        tee_entry_get_shm_config(args);
        break;
#endif
    case OPTEE_SMC_L2CC_MUTEX:
        tee_entry_fastcall_l2cc_mutex(args);
        break;
    case OPTEE_SMC_EXCHANGE_CAPABILITIES:
        tee_entry_exchange_capabilities(args);
        break;
    case OPTEE_SMC_DISABLE_SHM_CACHE:
        tee_entry_disable_shm_cache(args);
        break;
    case OPTEE_SMC_ENABLE_SHM_CACHE:
        tee_entry_enable_shm_cache(args);
        break;
    case OPTEE_SMC_BOOT_SECONDARY:
        tee_entry_boot_secondary(args);
        break;
    case OPTEE_SMC_GET_THREAD_COUNT:
        tee_entry_get_thread_count(args);
        break;

#if defined(CFG_VIRTUALIZATION)
    case OPTEE_SMC_VM_CREATED:
        tee_entry_vm_created(args);
        break;
    case OPTEE_SMC_VM_DESTROYED:
        tee_entry_vm_destroyed(args);
        break;
#endif

    default:
        args->a0 = OPTEE_SMC_RETURN_UNKNOWN_FUNCTION;
        break;
    }
}

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