fix(esp_tee): Add standard newlib function stubs to resolve build warnings

- Disable C++ exceptions for TEE build to reduce flash footprint

components/cxx/CMakeLists.txt

@@ -1,16 +1,23 @@
 idf_build_get_property(target IDF_TARGET)
+idf_build_get_property(esp_tee_build ESP_TEE_BUILD)
 
 if(${target} STREQUAL "linux")
     return() # This component is not necessary on the POSIX/Linux simulator
 endif()
 
-idf_component_register(SRCS "cxx_exception_stubs.cpp"
+set(srcs "cxx_exception_stubs.cpp")
-                            "cxx_guards.cpp"
+set(priv_requires esp_system)
-                            "cxx_init.cpp"
-                        # Make sure that pthread is in component list
-                        PRIV_REQUIRES pthread esp_system)
 
-if(NOT CONFIG_CXX_EXCEPTIONS)
+if(NOT esp_tee_build)
+    list(APPEND srcs "cxx_guards.cpp" "cxx_init.cpp")
+    # Make sure that pthread is in component list
+    list(APPEND priv_requires pthread)
+endif()
+
+idf_component_register(SRCS ${srcs}
+                       PRIV_REQUIRES ${priv_requires})
+
+if(esp_tee_build OR NOT CONFIG_CXX_EXCEPTIONS)
     set(WRAP_FUNCTIONS
         __register_frame_info_bases
         __register_frame_info
@@ -55,25 +62,31 @@ if(CMAKE_C_COMPILER_ID MATCHES "Clang")
 else()
     target_link_libraries(${COMPONENT_LIB} PUBLIC stdc++ gcc)
 endif()
-target_link_libraries(${COMPONENT_LIB} INTERFACE "-u __cxa_guard_dummy")
-target_link_libraries(${COMPONENT_LIB} INTERFACE "-u __cxx_init_dummy")
 
-# Force libpthread to appear later than libstdc++ in link line since libstdc++ depends on libpthread.
-# Furthermore, force libcxx to appear later than libgcc because some libgcc unwind code is wrapped, if C++
-# exceptions are disabled. libcxx (this component) provides the unwind code wrappers.
-# This is to prevent linking of libgcc's unwind code which considerably increases the binary size.
-# Also force libnewlib to appear later than libstdc++ in link line since libstdc++ depends on
-# some functions in libnewlib, e.g. getentropy().
-idf_component_get_property(pthread pthread COMPONENT_LIB)
-idf_component_get_property(newlib newlib COMPONENT_LIB)
-idf_component_get_property(cxx cxx COMPONENT_LIB)
 add_library(stdcpp_deps INTERFACE)
-if(CMAKE_C_COMPILER_ID MATCHES "Clang")
-    target_link_libraries(stdcpp_deps INTERFACE stdc++ c $<TARGET_FILE:${pthread}> $<TARGET_FILE:${newlib}>)
-else()
-    target_link_libraries(stdcpp_deps INTERFACE stdc++ $<TARGET_FILE:${pthread}> $<TARGET_FILE:${newlib}>)
-endif()
 target_link_libraries(${COMPONENT_LIB} PUBLIC stdcpp_deps)
+
+if(NOT esp_tee_build)
+    target_link_libraries(${COMPONENT_LIB} INTERFACE "-u __cxa_guard_dummy")
+    target_link_libraries(${COMPONENT_LIB} INTERFACE "-u __cxx_init_dummy")
+
+    # Force libpthread to appear later than libstdc++ in link line since libstdc++ depends on libpthread.
+    # Furthermore, force libcxx to appear later than libgcc because some libgcc unwind code is wrapped, if C++
+    # exceptions are disabled. libcxx (this component) provides the unwind code wrappers.
+    # This is to prevent linking of libgcc's unwind code which considerably increases the binary size.
+    # Also force libnewlib to appear later than libstdc++ in link line since libstdc++ depends on
+    # some functions in libnewlib, e.g. getentropy().
+    idf_component_get_property(pthread pthread COMPONENT_LIB)
+    idf_component_get_property(newlib newlib COMPONENT_LIB)
+
+    if(CMAKE_C_COMPILER_ID MATCHES "Clang")
+        target_link_libraries(stdcpp_deps INTERFACE stdc++ c $<TARGET_FILE:${pthread}> $<TARGET_FILE:${newlib}>)
+    else()
+        target_link_libraries(stdcpp_deps INTERFACE stdc++ $<TARGET_FILE:${pthread}> $<TARGET_FILE:${newlib}>)
+    endif()
+endif()
+
+idf_component_get_property(cxx cxx COMPONENT_LIB)
 add_library(libgcc_cxx INTERFACE)
 target_link_libraries(libgcc_cxx INTERFACE ${CONFIG_COMPILER_RT_LIB_NAME} $<TARGET_FILE:${cxx}>)
 target_link_libraries(${COMPONENT_LIB} PUBLIC libgcc_cxx)

components/esp_tee/subproject/main/CMakeLists.txt

@@ -46,6 +46,9 @@ list(APPEND include "${heap_dir}/tlsf")
 # esp_app_desc_t configuration structure for TEE
 list(APPEND srcs "common/esp_app_desc_tee.c")
 
+# Newlib syscalls stub implementation
+list(APPEND srcs "common/syscall_stubs.c")
+
 idf_component_register(SRCS ${srcs}
                        INCLUDE_DIRS ${include})
 
@@ -57,6 +60,9 @@ include(${CMAKE_CURRENT_LIST_DIR}/ld/esp_tee_ld.cmake)
 # esp_app_desc_t configuration structure for TEE: Linking symbol and trimming project version and name
 target_link_libraries(${COMPONENT_LIB} PRIVATE "-u esp_app_desc_tee_include_impl")
 
+# Newlib syscalls stub implementation: Linking symbol
+target_link_libraries(${COMPONENT_LIB} PRIVATE "-u esp_tee_include_syscalls_impl")
+
 # cut PROJECT_VER and PROJECT_NAME to required 32 characters.
 idf_build_get_property(project_ver PROJECT_VER)
 idf_build_get_property(project_name PROJECT_NAME)

components/esp_tee/subproject/main/common/syscall_stubs.c

@@ -0,0 +1,136 @@
+/*
+ * SPDX-FileCopyrightText: 2025 Espressif Systems (Shanghai) CO LTD
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <errno.h>
+#include <pthread.h>
+#include <unistd.h>
+
+#include "esp_random.h"
+
+// NOTE: Remove compile-time warnings for the below newlib-provided functions
+struct _reent *__getreent(void)
+{
+    return _GLOBAL_REENT;
+}
+
+int _fstat_r(struct _reent *r, int fd, struct stat *st)
+{
+    errno = ENOSYS;
+    return -1;
+}
+
+int _close_r(struct _reent *r, int fd)
+{
+    errno = ENOSYS;
+    return -1;
+}
+
+off_t _lseek_r(struct _reent *r, int fd, off_t offset, int whence)
+{
+    errno = ENOSYS;
+    return -1;
+}
+
+ssize_t _read_r(struct _reent *r, int fd, void *ptr, size_t len)
+{
+    errno = ENOSYS;
+    return -1;
+}
+
+ssize_t _write_r(struct _reent *r, int fd, const void *ptr, size_t len)
+{
+    errno = ENOSYS;
+    return -1;
+}
+
+int _getpid_r(struct _reent *r)
+{
+    return 1;
+}
+
+int _kill_r(struct _reent *r, int pid, int sig)
+{
+    errno = ENOSYS;
+    return -1;
+}
+
+int _getentropy_r(struct _reent *r, void *buffer, size_t length)
+{
+    esp_fill_random(buffer, length);
+    return 0;
+}
+
+void *pthread_getspecific(pthread_key_t key)
+{
+    return NULL;
+}
+
+int pthread_setspecific(pthread_key_t key, const void *value)
+{
+    return 0;
+}
+
+int pthread_key_create(pthread_key_t *key, void (*destructor)(void*))
+{
+    errno = ENOSYS;
+    return -1;
+}
+
+int pthread_key_delete(pthread_key_t key)
+{
+    errno = ENOSYS;
+    return -1;
+}
+
+int pthread_mutex_init(pthread_mutex_t *mutex, const pthread_mutexattr_t *attr)
+{
+    errno = ENOSYS;
+    return -1;
+}
+
+int pthread_mutex_destroy(pthread_mutex_t *mutex)
+{
+    errno = ENOSYS;
+    return -1;
+}
+
+int pthread_mutex_lock(pthread_mutex_t *mutex)
+{
+    errno = ENOSYS;
+    return -1;
+}
+
+int pthread_mutex_unlock(pthread_mutex_t *mutex)
+{
+    errno = ENOSYS;
+    return -1;
+}
+
+void *__cxa_get_globals(void)
+{
+    return NULL;
+}
+
+void *__cxa_get_globals_fast(void)
+{
+    return NULL;
+}
+
+int __cxa_thread_atexit(void (*func)(void *), void *arg, void *dso)
+{
+    return 0;
+}
+
+void esp_tee_include_syscalls_impl(void)
+{
+
+}

components/esp_tee/subproject/main/core/esp_tee_init.c

@@ -187,19 +187,3 @@ void __attribute__((noreturn)) esp_tee_init(uint32_t ree_entry_addr, uint32_t re
     /* App entry function should not return here. */
     ESP_INFINITE_LOOP(); /* WDT will reset us */
 }
-
-// NOTE: Remove compile-time warnings for the below newlib-provided functions
-struct _reent *__getreent(void)
-{
-    return _GLOBAL_REENT;
-}
-
-void _fstat_r(void) {}
-
-void _close_r(void) {}
-
-void _lseek_r(void) {}
-
-void _read_r(void) {}
-
-void _write_r(void) {}

components/nvs_flash/CMakeLists.txt

@@ -32,7 +32,7 @@ elseif(esp_tee_build)
              "src/nvs_platform.cpp")
 
     set(requires esp_partition mbedtls)
-    set(priv_requires spi_flash newlib)
+    set(priv_requires spi_flash newlib cxx)
 
     idf_component_register(SRCS "${srcs}"
                     REQUIRES "${requires}"