Security hardening ================== This page contains guidance on what to check for additional security measures, including build options that can be modified to improve security or catch issues early in development. Build options ------------- Several build options can be used to check for security issues. Refer to the `user guide`_ for detailed information on the specific build options. - The ``BRANCH_PROTECTION`` build flag can be used to enable Pointer Authentication and Branch Target Identification. - The ``ENABLE_STACK_PROTECTOR`` build flag can be used to identify buffer overflows. - The ``W`` build flag can be used to enable a number of compiler warning options to detect potentially incorrect code. - W=0 (default value) The ``Wunused`` with ``Wno-unused-parameter``, ``Wdisabled-optimization`` and ``Wvla`` flags are enabled. The ``Wunused-but-set-variable``, ``Wmaybe-uninitialized`` and ``Wpacked-bitfield-compat`` are GCC specific flags that are also enabled. - W=1 Adds ``Wextra``, ``Wmissing-declarations``, ``Wmissing-format-attribute``, ``Wmissing-prototypes``, ``Wold-style-definition`` and ``Wunused-const-variable``. - W=2 Adds ``Waggregate-return``, ``Wcast-align``, ``Wnested-externs``, ``Wshadow``, ``Wlogical-op``, ``Wmissing-field-initializers`` and ``Wsign-compare``. - W=3 Adds ``Wbad-function-cast``, ``Wcast-qual``, ``Wconversion``, ``Wpacked``, ``Wpadded``, ``Wpointer-arith``, ``Wredundant-decls`` and ``Wswitch-default``. Refer to the GCC or Clang documentation for more information on the individual options: https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html and https://clang.llvm.org/docs/DiagnosticsReference.html. NB: The ``Werror`` flag is enabled by default in TF-A and can be disabled by setting the ``E`` build flag to 0. *Copyright (c) 2019, Arm Limited. All rights reserved.* .. _user guide: ../getting_started/user-guide.rst