open TA

• • • • 1、open TA的兩種方式
      • 2、TA的分類 & 查詢TA的順序
      • • (1)、Look for already loaded TA
        • (2)、Look for pseudo TA
        • (3)、Look for user TA

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1、open TA的兩種方式

• 在CA中TEEC_OpenSession()打開一個TA
• 在TA中TEE_OpenSession()打開一個TA

如下圖所示，是打開一個user_ta的過程，最終都是調用了rpc_load，然后再調用shdr_verify_signature()驗證TA簽名.

2、TA的分類 & 查詢TA的順序

• Look for already loaded TA
• Look for pseudo TA
• Look for user TA

如代碼所示在tee_ta_manage.c的tee_ta_init_session中，先去查找已經loaded的TA，再去尋址PTA，最好才去找user TA

static TEE_Result tee_ta_init_session(TEE_ErrorOrigin *err,struct tee_ta_session_head *open_sessions,const TEE_UUID *uuid,struct tee_ta_session **sess) {TEE_Result res;struct tee_ta_ctx *ctx;struct tee_ta_session *s = calloc(1, sizeof(struct tee_ta_session));*err = TEE_ORIGIN_TEE;if (!s)return TEE_ERROR_OUT_OF_MEMORY;s->cancel_mask = true;condvar_init(&s->refc_cv);condvar_init(&s->lock_cv);s->lock_thread = THREAD_ID_INVALID;s->ref_count = 1;/** We take the global TA mutex here and hold it while doing* RPC to load the TA. This big critical section should be broken* down into smaller pieces.*/mutex_lock(&tee_ta_mutex);TAILQ_INSERT_TAIL(open_sessions, s, link);/* Look for already loaded TA */ctx = tee_ta_context_find(uuid);if (ctx) {res = tee_ta_init_session_with_context(ctx, s);if (res == TEE_SUCCESS || res != TEE_ERROR_ITEM_NOT_FOUND)goto out;}/* Look for pseudo TA */res = tee_ta_init_pseudo_ta_session(uuid, s);if (res == TEE_SUCCESS || res != TEE_ERROR_ITEM_NOT_FOUND)goto out;/* Look for user TA */res = tee_ta_init_user_ta_session(uuid, s);out:if (res == TEE_SUCCESS) {*sess = s;} else {TAILQ_REMOVE(open_sessions, s, link);free(s);}mutex_unlock(&tee_ta_mutex);return res; }

(1)、Look for already loaded TA

其實就是遍歷鏈表link，查看TA是否已經被loaded了

/* Look for already loaded TA */ctx = tee_ta_context_find(uuid);if (ctx) {res = tee_ta_init_session_with_context(ctx, s);if (res == TEE_SUCCESS || res != TEE_ERROR_ITEM_NOT_FOUND)goto out;} static struct tee_ta_ctx *tee_ta_context_find(const TEE_UUID *uuid) {struct tee_ta_ctx *ctx;TAILQ_FOREACH(ctx, &tee_ctxes, link) {if (memcmp(&ctx->uuid, uuid, sizeof(TEE_UUID)) == 0)return ctx;}return NULL; }

(2)、Look for pseudo TA

其實就算去rodata中的__start_ta_head_section段就尋找PTA

/* Look for pseudo TA */res = tee_ta_init_pseudo_ta_session(uuid, s);if (res == TEE_SUCCESS || res != TEE_ERROR_ITEM_NOT_FOUND)goto out;*(.rodata .rodata.*)/** 8 to avoid unwanted padding between __start_ta_head_section* and the first structure in ta_head_section, in 64-bit* builds*/. = ALIGN(8);__start_ta_head_section = . ;KEEP(*(ta_head_section))__stop_ta_head_section = . ;. = ALIGN(8);__start_phys_mem_map_section = . ;KEEP(*(phys_mem_map_section))__end_phys_mem_map_section = . ;. = ALIGN(8);__start_phys_sdp_mem_section = . ;KEEP(*(phys_sdp_mem_section))__end_phys_sdp_mem_section = . ;. = ALIGN(8);__start_phys_nsec_ddr_section = . ;KEEP(*(phys_nsec_ddr_section))__end_phys_nsec_ddr_section = . ;. = ALIGN(8);__start_phys_ddr_overall_section = . ;KEEP(*(phys_ddr_overall_section))__end_phys_ddr_overall_section = . ;

(3)、Look for user TA

通過RPC調用，從REE側的文件系統中讀取TA Binary

總結

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