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Aleksandr Anisimovjforissier
Aleksandr Anisimov
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jforissier
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plugins: example of using the tee-supplicant plugin framework
TEE clients can add to the tee-supplicant own plugins. This feature makes the supplicant a bit more flexible in terms of providing services. Any external TEE services can be designed as a tee-supplicant plugin. User TAs can interact with the plugins using libutee and the OP-TEE kernel code can use a special plugin PRC for it. This patch adds example of using the plugin framework. 'syslog' plugin is used as an example. It can write log messages from OP-TEE (TAs or kernel) to system log. Also patch adds a new TA, which interacts with the 'syslog' plugin with the help of 'tee_invoke_supp_plugin()'. This TA increments a value and prints some strings to the syslog. Also patch adds a host CA, which calls the TA 'TA_PING_CNT' times. If the example works successfully, we can find the following strings in the log file (for qemu it's '/var/log/messages' file): ``` 21:18:05 buildroot daemon.info tee-supplicant[92]: Hello, plugin! value = 0x0 21:18:07 buildroot daemon.info tee-supplicant[92]: Hello, plugin! value = 0x1 21:18:09 buildroot daemon.info tee-supplicant[92]: Hello, plugin! value = 0x2 21:18:11 buildroot daemon.info tee-supplicant[92]: Hello, plugin! value = 0x3 21:18:13 buildroot daemon.info tee-supplicant[92]: Hello, plugin! value = 0x4 ``` Signed-off-by: Aleksandr Anisimov <[email protected]> Reviewed-by: Jens Wiklander <[email protected]>
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‎.gitignore‎

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@@ -18,3 +18,4 @@ random/host/optee_example_random
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aes/host/optee_example_aes
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hotp/host/optee_example_hotp
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secure_storage/host/optee_example_secure_storage
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plugins/host/optee_example_plugins

‎plugins/Android.mk‎

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###################### optee-plugins ######################
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LOCAL_PATH := $(call my-dir)
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OPTEE_CLIENT_EXPORT = $(LOCAL_PATH)/../../optee_client/out/export
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include $(CLEAR_VARS)
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LOCAL_CFLAGS += -DANDROID_BUILD
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LOCAL_CFLAGS += -Wall
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LOCAL_SRC_FILES += host/main.c
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LOCAL_C_INCLUDES := $(LOCAL_PATH)/ta/include \
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$(OPTEE_CLIENT_EXPORT)/include \
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LOCAL_SHARED_LIBRARIES := libteec
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LOCAL_MODULE := optee_example_plugins
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LOCAL_VENDOR_MODULE := true
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LOCAL_MODULE_TAGS := optional
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include $(BUILD_EXECUTABLE)
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include $(LOCAL_PATH)/ta/Android.mk

‎plugins/CMakeLists.txt‎

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project (optee_example_plugins C)
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set (SRC host/main.c)
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add_executable (${PROJECT_NAME} ${SRC})
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target_include_directories(${PROJECT_NAME}
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PRIVATE ta/include
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PRIVATE include)
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target_compile_definitions (${PROJECT_NAME}
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PRIVATE -DBINARY_PREFIX="TEE-EXMPL"
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)
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target_link_libraries (${PROJECT_NAME}
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PRIVATE teec)
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install (TARGETS ${PROJECT_NAME} DESTINATION ${CMAKE_INSTALL_BINDIR})
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add_subdirectory (syslog)

‎plugins/Makefile‎

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export V?=0
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# If _HOST or _TA specific compilers are not specified, then use CROSS_COMPILE
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HOST_CROSS_COMPILE ?= $(CROSS_COMPILE)
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TA_CROSS_COMPILE ?= $(CROSS_COMPILE)
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.PHONY: all
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all:
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$(MAKE) -C host CROSS_COMPILE="$(HOST_CROSS_COMPILE)" --no-builtin-variables
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$(MAKE) -C ta CROSS_COMPILE="$(TA_CROSS_COMPILE)" LDFLAGS=""
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$(MAKE) -C syslog CROSS_COMPILE="$(HOST_CROSS_COMPILE)"
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.PHONY: clean
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clean:
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$(MAKE) -C host clean
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$(MAKE) -C ta clean
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$(MAKE) -C syslog clean

‎plugins/host/Makefile‎

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CC ?= $(CROSS_COMPILE)gcc
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LD ?= $(CROSS_COMPILE)ld
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AR ?= $(CROSS_COMPILE)ar
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NM ?= $(CROSS_COMPILE)nm
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OBJCOPY ?= $(CROSS_COMPILE)objcopy
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OBJDUMP ?= $(CROSS_COMPILE)objdump
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READELF ?= $(CROSS_COMPILE)readelf
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OBJS = main.o
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CFLAGS += -Wall -I../ta/include -I$(TEEC_EXPORT)/include -I./include
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CFLAGS += -DBINARY_PREFIX=\"TEE-EXMPL\"
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#Add/link other required libraries here
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LDADD += -lteec -L$(TEEC_EXPORT)/lib
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BINARY = optee_example_plugins
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.PHONY: all
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all: $(BINARY)
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$(BINARY): $(OBJS)
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$(CC) -o $@ $< $(LDADD)
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.PHONY: clean
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clean:
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rm -f $(OBJS) $(BINARY)
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%.o: %.c
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$(CC) $(CFLAGS) -c $< -o $@

‎plugins/host/main.c‎

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// SPDX-License-Identifier: BSD-2-Clause
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/*
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* Copyright (c) 2020, Open Mobile Platform LLC
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*/
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#include <err.h>
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#include <inttypes.h>
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#include <stdio.h>
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#include <string.h>
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#include <stdbool.h>
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#include <unistd.h>
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/* OP-TEE TEE client API (built by optee_client) */
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#include <tee_client_api.h>
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/* For the UUID (found in the TA's h-file(s)) */
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#include <plugin_ta.h>
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#define SLEEP_SEC 2
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#define TA_PING_CNT 5
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int main(void)
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{
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int i = 0;
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TEEC_Result res = TEEC_SUCCESS;
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TEEC_Context ctx = { };
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TEEC_Session sess = { };
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TEEC_Operation op = { };
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TEEC_UUID uuid = PLUGIN_TA_UUID;
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uint32_t err_origin = 0;
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/* Initialize a context connecting us to the TEE */
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res = TEEC_InitializeContext(NULL, &ctx);
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if (res != TEEC_SUCCESS)
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errx(1, "TEEC_InitializeContext failed with code %#" PRIx32,
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res);
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/* Open a session to the "plugin" TA */
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res = TEEC_OpenSession(&ctx, &sess, &uuid, TEEC_LOGIN_PUBLIC, NULL,
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NULL, &err_origin);
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if (res != TEEC_SUCCESS)
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errx(1, "TEEC_Opensession failed with code %#" PRIx32 "origin %#" PRIx32,
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res, err_origin);
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/* Clear the TEEC_Operation struct */
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memset(&op, 0, sizeof(op));
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op.paramTypes =
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TEEC_PARAM_TYPES(TEEC_NONE, TEEC_NONE, TEEC_NONE, TEEC_NONE);
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/*
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* TA will refer to the syslog plugin to print some log messages to REE.
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*
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* See the plugin code in the optee-client.
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* See the log through 'journalctl'.
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*/
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printf("Work logic: REE --> plugin TA --> syslog plugin in REE --> syslog\n");
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printf("See the log from TEE through 'journalctl'\n\n");
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for (i = 0; i < TA_PING_CNT; ++i) {
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res = TEEC_InvokeCommand(&sess, PLUGIN_TA_PING, &op,
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&err_origin);
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printf("Attempt #%d: TEEC_InvokeCommand() %s; res=%#" PRIx32 " orig=%#" PRIx32 "\n",
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i + 1, (res == TEEC_SUCCESS) ? "success" : "failed",
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res, err_origin);
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sleep(SLEEP_SEC);
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}
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/*
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* We're done with the TA, close the session and
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* destroy the context.
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*/
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TEEC_CloseSession(&sess);
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TEEC_FinalizeContext(&ctx);
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return 0;
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}

‎plugins/syslog/CMakeLists.txt‎

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project (96bcf744-4f72-4866-bf1d-8634fd9c65e5.plugin C)
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set (CFG_TEE_PLUGIN_LOAD_PATH "/usr/lib/tee-supplicant/plugins/")
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set (CMAKE_SHARED_LIBRARY_PREFIX "")
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add_library(${PROJECT_NAME} SHARED syslog_plugin.c)
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install (TARGETS ${PROJECT_NAME} DESTINATION ${CFG_TEE_PLUGIN_LOAD_PATH})

‎plugins/syslog/Makefile‎

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PLUGIN_UUID = 96bcf744-4f72-4866-bf1d-8634fd9c65e5
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PLUGIN = $(PLUGIN_UUID).plugin
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PLUGIN_SRS = $(wildcard ./*.c)
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PLUGIN_OBJ = $(patsubst %.c, %.o, $(PLUGIN_SRS))
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PLUGIN_INCLUDES_DIR = $(CURDIR) $(TEEC_EXPORT)/include
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PLUGIN_INCLUDES = $(addprefix -I, $(PLUGIN_INCLUDES_DIR))
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PLUGIN_CCFLAGS = -Wall -fPIC
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PLUGIN_LDFLAGS = -shared
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.PHONY: all
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all: $(PLUGIN)
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$(PLUGIN): $(PLUGIN_OBJ)
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$(CROSS_COMPILE)gcc $(PLUGIN_LDFLAGS) $(PLUGIN_OBJ) -o $@
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%.o: %.c
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$(CROSS_COMPILE)gcc $(PLUGIN_CCFLAGS) $(PLUGIN_INCLUDES) -c $*.c -o $*.o
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.PHONY: clean
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clean:
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$(RM) $(PLUGIN_OBJ) $(PLUGIN_UUID).plugin
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‎plugins/syslog/syslog_plugin.c‎

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// SPDX-License-Identifier: BSD-2-Clause
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/*
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* Copyright (c) 2020, Open Mobile Platform LLC
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*/
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#include <stddef.h>
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#include <syslog.h>
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#include <tee_plugin_method.h>
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/*
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* OPTEE has access to the plugin by the UUID
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*/
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#define SYSLOG_PLUGIN_UUID { 0x96bcf744, 0x4f72, 0x4866, \
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{ 0xbf, 0x1d, 0x86, 0x34, 0xfd, 0x9c, 0x65, 0xe5 } }
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/* plugin cmd */
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#define TO_SYSLOG 0
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static TEEC_Result syslog_plugin_init(void)
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{
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return TEEC_SUCCESS;
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}
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static TEEC_Result write_syslog(unsigned int sub_cmd, void *data, size_t data_len)
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{
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/* 'sub_cmd' in this case means priority according syslog.h */
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openlog(NULL, LOG_CONS | LOG_PID, LOG_DAEMON);
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syslog(sub_cmd, "%*s", (int)data_len, (const char *)data);
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closelog();
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return TEEC_SUCCESS;
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}
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static TEEC_Result syslog_plugin_invoke(unsigned int cmd, unsigned int sub_cmd,
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void *data, size_t data_len,
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size_t *out_len)
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{
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/*
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* The pointer 'out_len' is used to save length of
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* output data from the plugin for TEE, when TEE will be needed
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* by the data.
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*
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* Buffer 'data' is used like input and output.
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*/
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(void)out_len;
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switch (cmd) {
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case TO_SYSLOG:
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return write_syslog(sub_cmd, data, data_len);
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default:
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break;
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}
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return TEEC_ERROR_NOT_SUPPORTED;
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}
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struct plugin_method plugin_method = {
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"syslog",
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SYSLOG_PLUGIN_UUID,
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syslog_plugin_init, /* can be NULL */
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syslog_plugin_invoke,
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};

‎plugins/ta/Android.mk‎

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LOCAL_PATH := $(call my-dir)
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local_module := 2a287631-de1b-4fdd-a55c-b9312e40769a.ta
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include $(BUILD_OPTEE_MK)

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