前言

（默认你对optee有一点点点点了解）

一、hello_world分析

在\optee_examples\hello_world目录下，optee给出了一个简单的CA/TA示例。

hello_world的结构如下：

1、CA端

A.main.c

main.c文件有效代码如下：

#include <err.h>
#include <stdio.h>
#include <string.h>
#include <tee_client_api.h>
#include <hello_world_ta.h>

int main(void)
{
	TEEC_Result res;
	TEEC_Context ctx;
	TEEC_Session sess;
	TEEC_Operation op;
	TEEC_UUID uuid = TA_HELLO_WORLD_UUID;
	uint32_t err_origin;

	res = TEEC_InitializeContext(NULL, &ctx);
	if (res != TEEC_SUCCESS)
		errx(1, "TEEC_InitializeContext failed with code 0x%x", res);

	res = TEEC_OpenSession(&ctx, &sess, &uuid,TEEC_LOGIN_PUBLIC, NULL, NULL, &err_origin);
	if (res != TEEC_SUCCESS)
		errx(1, "TEEC_Opensession failed with code 0x%x origin 0x%x", res, err_origin);

	memset(&op, 0, sizeof(op));
	
	op.paramTypes = TEEC_PARAM_TYPES(TEEC_VALUE_INOUT, TEEC_NONE, TEEC_NONE, TEEC_NONE);
	op.params[0].value.a = 42;

	printf("Invoking TA to increment %d\n", op.params[0].value.a);
	res = TEEC_InvokeCommand(&sess, TA_HELLO_WORLD_CMD_INC_VALUE, &op, &err_origin);
	if (res != TEEC_SUCCESS)
		errx(1, "TEEC_InvokeCommand failed with code 0x%x origin 0x%x", res, err_origin);
	printf("TA incremented value to %d\n", op.params[0].value.a);

	TEEC_CloseSession(&sess);
	TEEC_FinalizeContext(&ctx);

	return 0;
}

真的是个很简单的程序，由调用的指令id=TA_HELLO_WORLD_CMD_INC_VALUE来看，我们猜测这是一个加法相关操作。

整个函数只调用了一次InvokeCommand，之前和之后都打印出op.params[0].value.a。

B.Makefile

makefile源文件如下，我们可以看到make后会生成名为main的可执行文件。

CC      ?= $(CROSS_COMPILE)gcc
LD      ?= $(CROSS_COMPILE)ld
AR      ?= $(CROSS_COMPILE)ar
NM      ?= $(CROSS_COMPILE)nm
OBJCOPY ?= $(CROSS_COMPILE)objcopy
OBJDUMP ?= $(CROSS_COMPILE)objdump
READELF ?= $(CROSS_COMPILE)readelf

OBJS = main.o

CFLAGS += -Wall -I../ta/include -I$(TEEC_EXPORT)/include -I./include
#Add/link other required libraries here
LDADD += -lteec -L$(TEEC_EXPORT)/lib

BINARY = optee_example_hello_world

.PHONY: all
all: $(BINARY)

$(BINARY): $(OBJS)
	$(CC) $(LDFLAGS) -o $@ $< $(LDADD)

.PHONY: clean
clean:
	rm -f $(OBJS) $(BINARY)

%.o: %.c
	$(CC) $(CFLAGS) -c $< -o $@

2、TA端

A.android.mk

android.mk源文件如下，我们可以看到make后生成的是8aaaf200-2450-11e4-abe2-0002a5d5c51b.ta。

LOCAL_PATH := $(call my-dir)

local_module := 8aaaf200-2450-11e4-abe2-0002a5d5c51b.ta
include $(BUILD_OPTEE_MK)

B.hello_world_ta.c

hello_world_ta.c有效代码如下，我们可以看到原子操作不只是加法操作inc_value，还有减法操作dec_value，还有必备的TA_CreateEntryPoint、TA_DestroyEntryPoint、TA_OpenSessionEntryPoint、TA_CloseSessionEntryPoint、TA_InvokeCommandEntryPoint五个函数。

#include <tee_internal_api.h>
#include <tee_internal_api_extensions.h>

#include <hello_world_ta.h>

TEE_Result TA_CreateEntryPoint(void)
{
	DMSG("has been called");

	return TEE_SUCCESS;
}

void TA_DestroyEntryPoint(void)
{
	DMSG("has been called");
}


TEE_Result TA_OpenSessionEntryPoint(uint32_t param_types,
		TEE_Param __maybe_unused params[4],
		void __maybe_unused **sess_ctx)
{
	uint32_t exp_param_types = TEE_PARAM_TYPES(TEE_PARAM_TYPE_NONE,
						   TEE_PARAM_TYPE_NONE,
						   TEE_PARAM_TYPE_NONE,
						   TEE_PARAM_TYPE_NONE);

	DMSG("has been called");

	if (param_types != exp_param_types)
		return TEE_ERROR_BAD_PARAMETERS;

	(void)&params;
	(void)&sess_ctx;


	IMSG("Hello World!\n");

	return TEE_SUCCESS;
}



void TA_CloseSessionEntryPoint(void __maybe_unused *sess_ctx)
{
	(void)&sess_ctx; /* Unused parameter */
	IMSG("Goodbye!\n");
}

static TEE_Result inc_value(uint32_t param_types,
	TEE_Param params[4])
{
	uint32_t exp_param_types = TEE_PARAM_TYPES(TEE_PARAM_TYPE_VALUE_INOUT,
						   TEE_PARAM_TYPE_NONE,
						   TEE_PARAM_TYPE_NONE,
						   TEE_PARAM_TYPE_NONE);

	DMSG("has been called");

	if (param_types != exp_param_types)
		return TEE_ERROR_BAD_PARAMETERS;

	IMSG("Got value: %u from NW", params[0].value.a);
	params[0].value.a++;
	IMSG("Increase value to: %u", params[0].value.a);

	return TEE_SUCCESS;
}

static TEE_Result dec_value(uint32_t param_types,
	TEE_Param params[4])
{
	uint32_t exp_param_types = TEE_PARAM_TYPES(TEE_PARAM_TYPE_VALUE_INOUT,
						   TEE_PARAM_TYPE_NONE,
						   TEE_PARAM_TYPE_NONE,
						   TEE_PARAM_TYPE_NONE);

	DMSG("has been called");

	if (param_types != exp_param_types)
		return TEE_ERROR_BAD_PARAMETERS;

	IMSG("Got value: %u from NW", params[0].value.a);
	params[0].value.a--;
	IMSG("Decrease value to: %u", params[0].value.a);

	return TEE_SUCCESS;
}


TEE_Result TA_InvokeCommandEntryPoint(void __maybe_unused *sess_ctx,
			uint32_t cmd_id,
			uint32_t param_types, TEE_Param params[4])
{
	(void)&sess_ctx; 

	switch (cmd_id) {
	case TA_HELLO_WORLD_CMD_INC_VALUE:
		return inc_value(param_types, params);
	case TA_HELLO_WORLD_CMD_DEC_VALUE:
		return dec_value(param_types, params);
	default:
		return TEE_ERROR_BAD_PARAMETERS;
	}
}

C.user_ta_header_defines.h

#ifndef USER_TA_HEADER_DEFINES_H
#define USER_TA_HEADER_DEFINES_H

#include <hello_world_ta.h>

#define TA_UUID				TA_HELLO_WORLD_UUID
#define TA_FLAGS			TA_FLAG_EXEC_DDR

#define TA_STACK_SIZE			(2 * 1024)
#define TA_DATA_SIZE			(32 * 1024)

#define TA_VERSION	"1.0"

#define TA_DESCRIPTION	"Example of OP-TEE Hello World Trusted Application"

#define TA_CURRENT_TA_EXT_PROPERTIES \
    { "org.linaro.optee.examples.hello_world.property1", \
	USER_TA_PROP_TYPE_STRING,  "Some string" }, \
    { "org.linaro.optee.examples.hello_world.property2", \
	USER_TA_PROP_TYPE_U32, &(const uint32_t){ 0x0010 } }

D.Makefile

CFG_TEE_TA_LOG_LEVEL ?= 4

BINARY=8aaaf200-2450-11e4-abe2-0002a5d5c51b

-include $(TA_DEV_KIT_DIR)/mk/ta_dev_kit.mk

ifeq ($(wildcard $(TA_DEV_KIT_DIR)/mk/ta_dev_kit.mk), )
clean:
	@echo 'Note: $$(TA_DEV_KIT_DIR)/mk/ta_dev_kit.mk not found, cannot clean TA'
	@echo 'Note: TA_DEV_KIT_DIR=$(TA_DEV_KIT_DIR)'
endif

E.sub.mk

global-incdirs-y += include
srcs-y += hello_world_ta.c

F.include/hello_world_ta.h

#ifndef TA_HELLO_WORLD_H
#define TA_HELLO_WORLD_H

#define TA_HELLO_WORLD_UUID \
	{ 0x8aaaf200, 0x2450, 0x11e4, { 0xab, 0xe2, 0x00, 0x02, 0xa5, 0xd5, 0xc5, 0x1b} }

#define TA_HELLO_WORLD_CMD_INC_VALUE		0
#define TA_HELLO_WORLD_CMD_DEC_VALUE		1

#endif /*TA_HELLO_WORLD_H*/