Merge "doc: Split and expand coding style documentation" into integration
This commit is contained in:
commit
cf96f2ed03
|
@ -2763,6 +2763,19 @@ build system.
|
|||
to ``no``. If any of the options ``EL3_PAYLOAD_BASE`` or ``PRELOADED_BL33_BASE``
|
||||
are used, this flag will be set to ``no`` automatically.
|
||||
|
||||
Platform include paths
|
||||
----------------------
|
||||
|
||||
Platforms are allowed to add more include paths to be passed to the compiler.
|
||||
The ``PLAT_INCLUDES`` variable is used for this purpose. This is needed in
|
||||
particular for the file ``platform_def.h``.
|
||||
|
||||
Example:
|
||||
|
||||
.. code:: c
|
||||
|
||||
PLAT_INCLUDES += -Iinclude/plat/myplat/include
|
||||
|
||||
C Library
|
||||
---------
|
||||
|
||||
|
@ -2844,7 +2857,7 @@ amount of open resources per driver.
|
|||
|
||||
--------------
|
||||
|
||||
*Copyright (c) 2013-2019, Arm Limited and Contributors. All rights reserved.*
|
||||
*Copyright (c) 2013-2020, Arm Limited and Contributors. All rights reserved.*
|
||||
|
||||
.. _PSCI: http://infocenter.arm.com/help/topic/com.arm.doc.den0022c/DEN0022C_Power_State_Coordination_Interface.pdf
|
||||
.. _Arm Generic Interrupt Controller version 2.0 (GICv2): http://infocenter.arm.com/help/topic/com.arm.doc.ihi0048b/index.html
|
||||
|
|
|
@ -1,18 +1,61 @@
|
|||
Coding Style & Guidelines
|
||||
=========================
|
||||
Coding Guidelines
|
||||
=================
|
||||
|
||||
The following sections contain TF coding guidelines. They are continually
|
||||
evolving and should not be considered "set in stone". Feel free to question them
|
||||
and provide feedback.
|
||||
This document provides some additional guidelines to consider when writing
|
||||
|TF-A| code. These are not intended to be strictly-enforced rules like the
|
||||
contents of the :ref:`Coding Style`.
|
||||
|
||||
Some of the guidelines may also apply to other codebases.
|
||||
Automatic Editor Configuration
|
||||
------------------------------
|
||||
|
||||
Many of the rules given below (such as indentation size, use of tabs, and
|
||||
newlines) can be set automatically using the `EditorConfig`_ configuration file
|
||||
in the root of the repository: ``.editorconfig``. With a supported editor, the
|
||||
rules set out in this file can be automatically applied when you are editing
|
||||
files in the |TF-A| repository.
|
||||
|
||||
Several editors include built-in support for EditorConfig files, and many others
|
||||
support its functionality through plugins.
|
||||
|
||||
Use of the EditorConfig file is suggested but is not required.
|
||||
|
||||
|
||||
Automatic Compliance Checking
|
||||
-----------------------------
|
||||
|
||||
To assist with coding style compliance, the project Makefile contains two
|
||||
targets which both utilise the `checkpatch.pl` script that ships with the Linux
|
||||
source tree. The project also defines certain *checkpatch* options in the
|
||||
``.checkpatch.conf`` file in the top-level directory.
|
||||
|
||||
.. note::
|
||||
The existing TF codebase does not necessarily comply with all the
|
||||
below guidelines but the intent is for it to do so eventually.
|
||||
Checkpatch errors will gate upstream merging of pull requests.
|
||||
Checkpatch warnings will not gate merging but should be reviewed and fixed if
|
||||
possible.
|
||||
|
||||
Checkpatch overrides
|
||||
--------------------
|
||||
To check the entire source tree, you must first download copies of
|
||||
``checkpatch.pl``, ``spelling.txt`` and ``const_structs.checkpatch`` available
|
||||
in the `Linux master tree`_ *scripts* directory, then set the ``CHECKPATCH``
|
||||
environment variable to point to ``checkpatch.pl`` (with the other 2 files in
|
||||
the same directory) and build the `checkcodebase` target:
|
||||
|
||||
.. code:: shell
|
||||
|
||||
make CHECKPATCH=<path-to-linux>/linux/scripts/checkpatch.pl checkcodebase
|
||||
|
||||
To just check the style on the files that differ between your local branch and
|
||||
the remote master, use:
|
||||
|
||||
.. code:: shell
|
||||
|
||||
make CHECKPATCH=<path-to-linux>/linux/scripts/checkpatch.pl checkpatch
|
||||
|
||||
If you wish to check your patch against something other than the remote master,
|
||||
set the ``BASE_COMMIT`` variable to your desired branch. By default,
|
||||
``BASE_COMMIT`` is set to ``origin/master``.
|
||||
|
||||
Ignored Checkpatch Warnings
|
||||
^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
||||
|
||||
Some checkpatch warnings in the TF codebase are deliberately ignored. These
|
||||
include:
|
||||
|
@ -23,210 +66,61 @@ include:
|
|||
|
||||
- ``**WARNING: Use of volatile is usually wrong``: see
|
||||
`Why the “volatile” type class should not be used`_ . Although this document
|
||||
contains some very useful information, there are several legitimate uses of
|
||||
the volatile keyword within the TF codebase.
|
||||
contains some very useful information, there are several legimate uses of the
|
||||
volatile keyword within the TF codebase.
|
||||
|
||||
Headers and inclusion
|
||||
---------------------
|
||||
Performance considerations
|
||||
--------------------------
|
||||
|
||||
Header guards
|
||||
^^^^^^^^^^^^^
|
||||
Avoid printf and use logging macros
|
||||
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
||||
|
||||
For a header file called "some_driver.h" the style used by the Trusted Firmware
|
||||
is:
|
||||
``debug.h`` provides logging macros (for example, ``WARN`` and ``ERROR``)
|
||||
which wrap ``tf_log`` and which allow the logging call to be compiled-out
|
||||
depending on the ``make`` command. Use these macros to avoid print statements
|
||||
being compiled unconditionally into the binary.
|
||||
|
||||
Each logging macro has a numerical log level:
|
||||
|
||||
.. code:: c
|
||||
|
||||
#ifndef SOME_DRIVER_H
|
||||
#define SOME_DRIVER_H
|
||||
#define LOG_LEVEL_NONE 0
|
||||
#define LOG_LEVEL_ERROR 10
|
||||
#define LOG_LEVEL_NOTICE 20
|
||||
#define LOG_LEVEL_WARNING 30
|
||||
#define LOG_LEVEL_INFO 40
|
||||
#define LOG_LEVEL_VERBOSE 50
|
||||
|
||||
<header content>
|
||||
By default, all logging statements with a log level ``<= LOG_LEVEL_INFO`` will
|
||||
be compiled into debug builds and all statements with a log level
|
||||
``<= LOG_LEVEL_NOTICE`` will be compiled into release builds. This can be
|
||||
overridden from the command line or by the platform makefile (although it may be
|
||||
necessary to clean the build directory first). For example, to enable
|
||||
``VERBOSE`` logging on FVP:
|
||||
|
||||
#endif /* SOME_DRIVER_H */
|
||||
``make PLAT=fvp LOG_LEVEL=50 all``
|
||||
|
||||
Include statement ordering
|
||||
^^^^^^^^^^^^^^^^^^^^^^^^^^
|
||||
Use const data where possible
|
||||
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
||||
|
||||
All header files that are included by a source file must use the following,
|
||||
grouped ordering. This is to improve readability (by making it easier to quickly
|
||||
read through the list of headers) and maintainability.
|
||||
|
||||
#. *System* includes: Header files from the standard *C* library, such as
|
||||
``stddef.h`` and ``string.h``.
|
||||
|
||||
#. *Project* includes: Header files under the ``include/`` directory within TF
|
||||
are *project* includes.
|
||||
|
||||
#. *Platform* includes: Header files relating to a single, specific platform,
|
||||
and which are located under the ``plat/<platform_name>`` directory within TF,
|
||||
are *platform* includes.
|
||||
|
||||
Within each group, ``#include`` statements must be in alphabetical order,
|
||||
taking both the file and directory names into account.
|
||||
|
||||
Groups must be separated by a single blank line for clarity.
|
||||
|
||||
The example below illustrates the ordering rules using some contrived header
|
||||
file names; this type of name reuse should be otherwise avoided.
|
||||
For example, the following code:
|
||||
|
||||
.. code:: c
|
||||
|
||||
#include <string.h>
|
||||
|
||||
#include <a_dir/example/a_header.h>
|
||||
#include <a_dir/example/b_header.h>
|
||||
#include <a_dir/test/a_header.h>
|
||||
#include <b_dir/example/a_header.h>
|
||||
|
||||
#include "./a_header.h"
|
||||
|
||||
Include statement variants
|
||||
^^^^^^^^^^^^^^^^^^^^^^^^^^
|
||||
|
||||
Two variants of the ``#include`` directive are acceptable in the TF codebase.
|
||||
Correct use of the two styles improves readability by suggesting the location
|
||||
of the included header and reducing ambiguity in cases where generic and
|
||||
platform-specific headers share a name.
|
||||
|
||||
For header files that are in the same directory as the source file that is
|
||||
including them, use the ``"..."`` variant.
|
||||
|
||||
For header files that are **not** in the same directory as the source file that
|
||||
is including them, use the ``<...>`` variant.
|
||||
|
||||
Example (bl1_fwu.c):
|
||||
|
||||
.. code:: c
|
||||
|
||||
#include <assert.h>
|
||||
#include <errno.h>
|
||||
#include <string.h>
|
||||
|
||||
#include "bl1_private.h"
|
||||
|
||||
Platform include paths
|
||||
^^^^^^^^^^^^^^^^^^^^^^
|
||||
|
||||
Platforms are allowed to add more include paths to be passed to the compiler.
|
||||
The ``PLAT_INCLUDES`` variable is used for this purpose. This is needed in
|
||||
particular for the file ``platform_def.h``.
|
||||
|
||||
Example:
|
||||
|
||||
.. code:: c
|
||||
|
||||
PLAT_INCLUDES += -Iinclude/plat/myplat/include
|
||||
|
||||
Types and typedefs
|
||||
------------------
|
||||
|
||||
Use of built-in *C* and *libc* data types
|
||||
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
||||
|
||||
The TF codebase should be kept as portable as possible, especially since both
|
||||
64-bit and 32-bit platforms are supported. To help with this, the following data
|
||||
type usage guidelines should be followed:
|
||||
|
||||
- Where possible, use the built-in *C* data types for variable storage (for
|
||||
example, ``char``, ``int``, ``long long``, etc) instead of the standard *C99*
|
||||
types. Most code is typically only concerned with the minimum size of the
|
||||
data stored, which the built-in *C* types guarantee.
|
||||
|
||||
- Avoid using the exact-size standard *C99* types in general (for example,
|
||||
``uint16_t``, ``uint32_t``, ``uint64_t``, etc) since they can prevent the
|
||||
compiler from making optimizations. There are legitimate uses for them,
|
||||
for example to represent data of a known structure. When using them in struct
|
||||
definitions, consider how padding in the struct will work across architectures.
|
||||
For example, extra padding may be introduced in AArch32 systems if a struct
|
||||
member crosses a 32-bit boundary.
|
||||
|
||||
- Use ``int`` as the default integer type - it's likely to be the fastest on all
|
||||
systems. Also this can be assumed to be 32-bit as a consequence of the
|
||||
`Procedure Call Standard for the Arm Architecture`_ and the `Procedure Call
|
||||
Standard for the Arm 64-bit Architecture`_ .
|
||||
|
||||
- Avoid use of ``short`` as this may end up being slower than ``int`` in some
|
||||
systems. If a variable must be exactly 16-bit, use ``int16_t`` or
|
||||
``uint16_t``.
|
||||
|
||||
- Avoid use of ``long``. This is guaranteed to be at least 32-bit but, given
|
||||
that `int` is 32-bit on Arm platforms, there is no use for it. For integers of
|
||||
at least 64-bit, use ``long long``.
|
||||
|
||||
- Use ``char`` for storing text. Use ``uint8_t`` for storing other 8-bit data.
|
||||
|
||||
- Use ``unsigned`` for integers that can never be negative (counts,
|
||||
indices, sizes, etc). TF intends to comply with MISRA "essential type" coding
|
||||
rules (10.X), where signed and unsigned types are considered different
|
||||
essential types. Choosing the correct type will aid this. MISRA static
|
||||
analysers will pick up any implicit signed/unsigned conversions that may lead
|
||||
to unexpected behaviour.
|
||||
|
||||
- For pointer types:
|
||||
|
||||
- If an argument in a function declaration is pointing to a known type then
|
||||
simply use a pointer to that type (for example: ``struct my_struct *``).
|
||||
|
||||
- If a variable (including an argument in a function declaration) is pointing
|
||||
to a general, memory-mapped address, an array of pointers or another
|
||||
structure that is likely to require pointer arithmetic then use
|
||||
``uintptr_t``. This will reduce the amount of casting required in the code.
|
||||
Avoid using ``unsigned long`` or ``unsigned long long`` for this purpose; it
|
||||
may work but is less portable.
|
||||
|
||||
- For other pointer arguments in a function declaration, use ``void *``. This
|
||||
includes pointers to types that are abstracted away from the known API and
|
||||
pointers to arbitrary data. This allows the calling function to pass a
|
||||
pointer argument to the function without any explicit casting (the cast to
|
||||
``void *`` is implicit). The function implementation can then do the
|
||||
appropriate casting to a specific type.
|
||||
|
||||
- Use ``ptrdiff_t`` to compare the difference between 2 pointers.
|
||||
|
||||
- Use ``size_t`` when storing the ``sizeof()`` something.
|
||||
|
||||
- Use ``ssize_t`` when returning the ``sizeof()`` something from a function that
|
||||
can also return an error code; the signed type allows for a negative return
|
||||
code in case of error. This practice should be used sparingly.
|
||||
|
||||
- Use ``u_register_t`` when it's important to store the contents of a register
|
||||
in its native size (32-bit in AArch32 and 64-bit in AArch64). This is not a
|
||||
standard *C99* type but is widely available in libc implementations,
|
||||
including the FreeBSD version included with the TF codebase. Where possible,
|
||||
cast the variable to a more appropriate type before interpreting the data. For
|
||||
example, the following struct in ``ep_info.h`` could use this type to minimize
|
||||
the storage required for the set of registers:
|
||||
|
||||
.. code:: c
|
||||
|
||||
typedef struct aapcs64_params {
|
||||
u_register_t arg0;
|
||||
u_register_t arg1;
|
||||
u_register_t arg2;
|
||||
u_register_t arg3;
|
||||
u_register_t arg4;
|
||||
u_register_t arg5;
|
||||
u_register_t arg6;
|
||||
u_register_t arg7;
|
||||
} aapcs64_params_t;
|
||||
|
||||
If some code wants to operate on ``arg0`` and knows that it represents a 32-bit
|
||||
unsigned integer on all systems, cast it to ``unsigned int``.
|
||||
|
||||
These guidelines should be updated if additional types are needed.
|
||||
|
||||
Avoid anonymous typedefs of structs/enums in headers
|
||||
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
||||
|
||||
For example, the following definition:
|
||||
|
||||
.. code:: c
|
||||
|
||||
typedef struct {
|
||||
struct my_struct {
|
||||
int arg1;
|
||||
int arg2;
|
||||
} my_struct_t;
|
||||
};
|
||||
|
||||
void init(struct my_struct *ptr);
|
||||
|
||||
void main(void)
|
||||
{
|
||||
struct my_struct x;
|
||||
x.arg1 = 1;
|
||||
x.arg2 = 2;
|
||||
init(&x);
|
||||
}
|
||||
|
||||
is better written as:
|
||||
|
||||
|
@ -237,31 +131,18 @@ is better written as:
|
|||
int arg2;
|
||||
};
|
||||
|
||||
This allows function declarations in other header files that depend on the
|
||||
struct/enum to forward declare the struct/enum instead of including the
|
||||
entire header:
|
||||
void init(const struct my_struct *ptr);
|
||||
|
||||
.. code:: c
|
||||
void main(void)
|
||||
{
|
||||
const struct my_struct x = { 1, 2 };
|
||||
init(&x);
|
||||
}
|
||||
|
||||
#include <my_struct.h>
|
||||
void my_func(my_struct_t *arg);
|
||||
|
||||
instead of:
|
||||
|
||||
.. code:: c
|
||||
|
||||
struct my_struct;
|
||||
void my_func(struct my_struct *arg);
|
||||
|
||||
Some TF definitions use both a struct/enum name **and** a typedef name. This
|
||||
is discouraged for new definitions as it makes it difficult for TF to comply
|
||||
with MISRA rule 8.3, which states that "All declarations of an object or
|
||||
function shall use the same names and type qualifiers".
|
||||
|
||||
The Linux coding standards also discourage new typedefs and checkpatch emits
|
||||
a warning for this.
|
||||
|
||||
Existing typedefs will be retained for compatibility.
|
||||
This allows the linker to put the data in a read-only data section instead of a
|
||||
writeable data section, which may result in a smaller and faster binary. Note
|
||||
that this may require dependent functions (``init()`` in the above example) to
|
||||
have ``const`` arguments, assuming they don't need to modify the data.
|
||||
|
||||
Libc functions that are banned or to be used with caution
|
||||
---------------------------------------------------------
|
||||
|
@ -410,14 +291,14 @@ error. This situation should be handled in one of the following ways:
|
|||
then emit an ``ERROR`` message and call the platform-specific function
|
||||
``plat_error_handler()``.
|
||||
|
||||
Cases 1 and 2 are subtly different. A platform may implement ``plat_panic_handler``
|
||||
and ``plat_error_handler`` in the same way (for example, by waiting for a secure
|
||||
watchdog to time-out or by invoking an interface on the platform's power
|
||||
controller to reset the platform). However, ``plat_error_handler`` may take
|
||||
additional action for some errors (for example, it may set a flag so the
|
||||
platform resets into a different mode). Also, ``plat_panic_handler()`` may
|
||||
implement additional debug functionality (for example, invoking a hardware
|
||||
breakpoint).
|
||||
Cases 1 and 2 are subtly different. A platform may implement
|
||||
``plat_panic_handler`` and ``plat_error_handler`` in the same way (for example,
|
||||
by waiting for a secure watchdog to time-out or by invoking an interface on the
|
||||
platform's power controller to reset the platform). However,
|
||||
``plat_error_handler`` may take additional action for some errors (for example,
|
||||
it may set a flag so the platform resets into a different mode). Also,
|
||||
``plat_panic_handler()`` may implement additional debug functionality (for
|
||||
example, invoking a hardware breakpoint).
|
||||
|
||||
Examples of unexpected unrecoverable errors:
|
||||
|
||||
|
@ -456,131 +337,115 @@ Examples:
|
|||
- Secure world is waiting for a hardware response that is critical for continued
|
||||
operation.
|
||||
|
||||
Security considerations
|
||||
-----------------------
|
||||
Use of built-in *C* and *libc* data types
|
||||
-----------------------------------------
|
||||
|
||||
Part of the security of a platform is handling errors correctly, as described in
|
||||
the previous section. There are several other security considerations covered in
|
||||
this section.
|
||||
The |TF-A| codebase should be kept as portable as possible, especially since
|
||||
both 64-bit and 32-bit platforms are supported. To help with this, the following
|
||||
data type usage guidelines should be followed:
|
||||
|
||||
Do not leak secrets to the normal world
|
||||
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
||||
- Where possible, use the built-in *C* data types for variable storage (for
|
||||
example, ``char``, ``int``, ``long long``, etc) instead of the standard *C99*
|
||||
types. Most code is typically only concerned with the minimum size of the
|
||||
data stored, which the built-in *C* types guarantee.
|
||||
|
||||
The secure world **must not** leak secrets to the normal world, for example in
|
||||
response to an SMC.
|
||||
- Avoid using the exact-size standard *C99* types in general (for example,
|
||||
``uint16_t``, ``uint32_t``, ``uint64_t``, etc) since they can prevent the
|
||||
compiler from making optimizations. There are legitimate uses for them,
|
||||
for example to represent data of a known structure. When using them in struct
|
||||
definitions, consider how padding in the struct will work across architectures.
|
||||
For example, extra padding may be introduced in |AArch32| systems if a struct
|
||||
member crosses a 32-bit boundary.
|
||||
|
||||
Handling Denial of Service attacks
|
||||
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
||||
- Use ``int`` as the default integer type - it's likely to be the fastest on all
|
||||
systems. Also this can be assumed to be 32-bit as a consequence of the
|
||||
`Procedure Call Standard for the Arm Architecture`_ and the `Procedure Call
|
||||
Standard for the Arm 64-bit Architecture`_ .
|
||||
|
||||
The secure world **should never** crash or become unusable due to receiving too
|
||||
many normal world requests (a *Denial of Service* or *DoS* attack). It should
|
||||
have a mechanism for throttling or ignoring normal world requests.
|
||||
- Avoid use of ``short`` as this may end up being slower than ``int`` in some
|
||||
systems. If a variable must be exactly 16-bit, use ``int16_t`` or
|
||||
``uint16_t``.
|
||||
|
||||
Performance considerations
|
||||
--------------------------
|
||||
- Avoid use of ``long``. This is guaranteed to be at least 32-bit but, given
|
||||
that `int` is 32-bit on Arm platforms, there is no use for it. For integers of
|
||||
at least 64-bit, use ``long long``.
|
||||
|
||||
Avoid printf and use logging macros
|
||||
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
||||
- Use ``char`` for storing text. Use ``uint8_t`` for storing other 8-bit data.
|
||||
|
||||
``debug.h`` provides logging macros (for example, ``WARN`` and ``ERROR``)
|
||||
which wrap ``tf_log`` and which allow the logging call to be compiled-out
|
||||
depending on the ``make`` command. Use these macros to avoid print statements
|
||||
being compiled unconditionally into the binary.
|
||||
- Use ``unsigned`` for integers that can never be negative (counts,
|
||||
indices, sizes, etc). TF intends to comply with MISRA "essential type" coding
|
||||
rules (10.X), where signed and unsigned types are considered different
|
||||
essential types. Choosing the correct type will aid this. MISRA static
|
||||
analysers will pick up any implicit signed/unsigned conversions that may lead
|
||||
to unexpected behaviour.
|
||||
|
||||
Each logging macro has a numerical log level:
|
||||
- For pointer types:
|
||||
|
||||
- If an argument in a function declaration is pointing to a known type then
|
||||
simply use a pointer to that type (for example: ``struct my_struct *``).
|
||||
|
||||
- If a variable (including an argument in a function declaration) is pointing
|
||||
to a general, memory-mapped address, an array of pointers or another
|
||||
structure that is likely to require pointer arithmetic then use
|
||||
``uintptr_t``. This will reduce the amount of casting required in the code.
|
||||
Avoid using ``unsigned long`` or ``unsigned long long`` for this purpose; it
|
||||
may work but is less portable.
|
||||
|
||||
- For other pointer arguments in a function declaration, use ``void *``. This
|
||||
includes pointers to types that are abstracted away from the known API and
|
||||
pointers to arbitrary data. This allows the calling function to pass a
|
||||
pointer argument to the function without any explicit casting (the cast to
|
||||
``void *`` is implicit). The function implementation can then do the
|
||||
appropriate casting to a specific type.
|
||||
|
||||
- Avoid pointer arithmetic generally (as this violates MISRA C 2012 rule
|
||||
18.4) and especially on void pointers (as this is only supported via
|
||||
language extensions and is considered non-standard). In TF-A, setting the
|
||||
``W`` build flag to ``W=3`` enables the *-Wpointer-arith* compiler flag and
|
||||
this will emit warnings where pointer arithmetic is used.
|
||||
|
||||
- Use ``ptrdiff_t`` to compare the difference between 2 pointers.
|
||||
|
||||
- Use ``size_t`` when storing the ``sizeof()`` something.
|
||||
|
||||
- Use ``ssize_t`` when returning the ``sizeof()`` something from a function that
|
||||
can also return an error code; the signed type allows for a negative return
|
||||
code in case of error. This practice should be used sparingly.
|
||||
|
||||
- Use ``u_register_t`` when it's important to store the contents of a register
|
||||
in its native size (32-bit in |AArch32| and 64-bit in |AArch64|). This is not a
|
||||
standard *C99* type but is widely available in libc implementations,
|
||||
including the FreeBSD version included with the TF codebase. Where possible,
|
||||
cast the variable to a more appropriate type before interpreting the data. For
|
||||
example, the following struct in ``ep_info.h`` could use this type to minimize
|
||||
the storage required for the set of registers:
|
||||
|
||||
.. code:: c
|
||||
|
||||
#define LOG_LEVEL_NONE 0
|
||||
#define LOG_LEVEL_ERROR 10
|
||||
#define LOG_LEVEL_NOTICE 20
|
||||
#define LOG_LEVEL_WARNING 30
|
||||
#define LOG_LEVEL_INFO 40
|
||||
#define LOG_LEVEL_VERBOSE 50
|
||||
typedef struct aapcs64_params {
|
||||
u_register_t arg0;
|
||||
u_register_t arg1;
|
||||
u_register_t arg2;
|
||||
u_register_t arg3;
|
||||
u_register_t arg4;
|
||||
u_register_t arg5;
|
||||
u_register_t arg6;
|
||||
u_register_t arg7;
|
||||
} aapcs64_params_t;
|
||||
|
||||
If some code wants to operate on ``arg0`` and knows that it represents a 32-bit
|
||||
unsigned integer on all systems, cast it to ``unsigned int``.
|
||||
|
||||
By default, all logging statements with a log level ``<= LOG_LEVEL_INFO`` will
|
||||
be compiled into debug builds and all statements with a log level
|
||||
``<= LOG_LEVEL_NOTICE`` will be compiled into release builds. This can be
|
||||
overridden from the command line or by the platform makefile (although it may be
|
||||
necessary to clean the build directory first). For example, to enable
|
||||
``VERBOSE`` logging on FVP:
|
||||
These guidelines should be updated if additional types are needed.
|
||||
|
||||
``make PLAT=fvp LOG_LEVEL=50 all``
|
||||
--------------
|
||||
|
||||
Use const data where possible
|
||||
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
||||
|
||||
For example, the following code:
|
||||
|
||||
.. code:: c
|
||||
|
||||
struct my_struct {
|
||||
int arg1;
|
||||
int arg2;
|
||||
};
|
||||
|
||||
void init(struct my_struct *ptr);
|
||||
|
||||
void main(void)
|
||||
{
|
||||
struct my_struct x;
|
||||
x.arg1 = 1;
|
||||
x.arg2 = 2;
|
||||
init(&x);
|
||||
}
|
||||
|
||||
is better written as:
|
||||
|
||||
.. code:: c
|
||||
|
||||
struct my_struct {
|
||||
int arg1;
|
||||
int arg2;
|
||||
};
|
||||
|
||||
void init(const struct my_struct *ptr);
|
||||
|
||||
void main(void)
|
||||
{
|
||||
const struct my_struct x = { 1, 2 };
|
||||
init(&x);
|
||||
}
|
||||
|
||||
This allows the linker to put the data in a read-only data section instead of a
|
||||
writeable data section, which may result in a smaller and faster binary. Note
|
||||
that this may require dependent functions (``init()`` in the above example) to
|
||||
have ``const`` arguments, assuming they don't need to modify the data.
|
||||
|
||||
Library and driver code
|
||||
-----------------------
|
||||
|
||||
TF library code (under ``lib/`` and ``include/lib``) is any code that provides a
|
||||
reusable interface to other code, potentially even to code outside of TF.
|
||||
|
||||
In some systems drivers must conform to a specific driver framework to provide
|
||||
services to the rest of the system. TF has no driver framework and the
|
||||
distinction between a driver and library is somewhat subjective.
|
||||
|
||||
A driver (under ``drivers/`` and ``include/drivers/``) is defined as code that
|
||||
interfaces with hardware via a memory mapped interface.
|
||||
|
||||
Some drivers (for example, the Arm CCI driver in ``include/drivers/arm/cci.h``)
|
||||
provide a general purpose API to that specific hardware. Other drivers (for
|
||||
example, the Arm PL011 console driver in ``drivers/arm/pl011/pl011_console.S``)
|
||||
provide a specific hardware implementation of a more abstract library API. In
|
||||
the latter case there may potentially be multiple drivers for the same hardware
|
||||
device.
|
||||
|
||||
Neither libraries nor drivers should depend on platform-specific code. If they
|
||||
require platform-specific data (for example, a base address) to operate then
|
||||
they should provide an initialization function that takes the platform-specific
|
||||
data as arguments.
|
||||
|
||||
TF common code (under ``common/`` and ``include/common/``) is code that is re-used
|
||||
by other generic (non-platform-specific) TF code. It is effectively internal
|
||||
library code.
|
||||
*Copyright (c) 2020, Arm Limited and Contributors. All rights reserved.*
|
||||
|
||||
.. _`Linux master tree`: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/
|
||||
.. _`Procedure Call Standard for the Arm Architecture`: https://developer.arm.com/docs/ihi0042/latest/
|
||||
.. _`Procedure Call Standard for the Arm 64-bit Architecture`: https://developer.arm.com/docs/ihi0055/latest/
|
||||
.. _`EditorConfig`: http://editorconfig.org/
|
||||
.. _`Why the “volatile” type class should not be used`: https://www.kernel.org/doc/html/latest/process/volatile-considered-harmful.html
|
||||
.. _`Procedure Call Standard for the Arm Architecture`: http://infocenter.arm.com/help/topic/com.arm.doc.ihi0042f/IHI0042F_aapcs.pdf
|
||||
.. _`Procedure Call Standard for the Arm 64-bit Architecture`: http://infocenter.arm.com/help/topic/com.arm.doc.ihi0055b/IHI0055B_aapcs64.pdf
|
||||
.. _`MISRA C:2012 Guidelines`: https://www.misra.org.uk/Activities/MISRAC/tabid/160/Default.aspx
|
||||
.. _`a spreadsheet`: https://developer.trustedfirmware.org/file/download/lamajxif3w7c4mpjeoo5/PHID-FILE-fp7c7acszn6vliqomyhn/MISRA-and-TF-Analysis-v1.3.ods
|
||||
|
|
|
@ -0,0 +1,468 @@
|
|||
Coding Style
|
||||
============
|
||||
|
||||
The following sections outline the |TF-A| coding style for *C* code. The style
|
||||
is based on the `Linux kernel coding style`_, with a few modifications.
|
||||
|
||||
The style should not be considered *set in stone*. Feel free to provide feedback
|
||||
and suggestions.
|
||||
|
||||
.. note::
|
||||
You will almost certainly find code in the |TF-A| repository that does not
|
||||
follow the style. The intent is for all code to do so eventually.
|
||||
|
||||
File Encoding
|
||||
-------------
|
||||
|
||||
The source code must use the **UTF-8** character encoding. Comments and
|
||||
documentation may use non-ASCII characters when required (e.g. Greek letters
|
||||
used for units) but code itself is still limited to ASCII characters.
|
||||
|
||||
Newlines must be in **Unix** style, which means that only the Line Feed (``LF``)
|
||||
character is used to break a line and reset to the first column.
|
||||
|
||||
Language
|
||||
--------
|
||||
|
||||
The primary language for comments and naming must be International English. In
|
||||
cases where there is a conflict between the American English and British English
|
||||
spellings of a word, the American English spelling is used.
|
||||
|
||||
Exceptions are made when referring directly to something that does not use
|
||||
international style, such as the name of a company. In these cases the existing
|
||||
name should be used as-is.
|
||||
|
||||
C Language Standard
|
||||
-------------------
|
||||
|
||||
The C language mode used for TF-A is *GNU99*. This is the "GNU dialect of ISO
|
||||
C99", which implies the *ISO C99* standard with GNU extensions.
|
||||
|
||||
Both GCC and Clang compiler toolchains have support for *GNU99* mode, though
|
||||
Clang does lack support for a small number of GNU extensions. These
|
||||
missing extensions are rarely used, however, and should not pose a problem.
|
||||
|
||||
MISRA Compliance
|
||||
----------------
|
||||
|
||||
TF-A attempts to comply with the `MISRA C:2012 Guidelines`_. Coverity
|
||||
Static Analysis is used to regularly generate a report of current MISRA defects
|
||||
and to prevent the addition of new ones.
|
||||
|
||||
It is not possible for the project to follow all MISRA guidelines. We maintain
|
||||
`a spreadsheet`_ that lists all rules and directives and whether we aim to
|
||||
comply with them or not. A rationale is given for each deviation.
|
||||
|
||||
.. note::
|
||||
Enforcing a rule does not mean that the codebase is free of defects
|
||||
of that rule, only that they would ideally be removed.
|
||||
|
||||
.. note::
|
||||
Third-party libraries are not considered in our MISRA analysis and we do not
|
||||
intend to modify them to make them MISRA compliant.
|
||||
|
||||
Indentation
|
||||
-----------
|
||||
|
||||
Use **tabs** for indentation. The use of spaces for indentation is forbidden
|
||||
except in the case where a term is being indented to a boundary that cannot be
|
||||
achieved using tabs alone.
|
||||
|
||||
Tab spacing should be set to **8 characters**.
|
||||
|
||||
Trailing whitespace is not allowed and must be trimmed.
|
||||
|
||||
Spacing
|
||||
-------
|
||||
|
||||
Single spacing should be used around most operators, including:
|
||||
|
||||
- Arithmetic operators (``+``, ``-``, ``/``, ``*``)
|
||||
- Assignment operators (``=``, ``+=``, etc)
|
||||
- Boolean operators (``&&``, ``||``)
|
||||
- Comparison operators (``<``, ``>``, ``==``, etc)
|
||||
|
||||
A space should also be used to separate parentheses and braces when they are not
|
||||
already separated by a newline, such as for the ``if`` statement in the
|
||||
following example:
|
||||
|
||||
.. code:: c
|
||||
|
||||
int function_foo(bool bar)
|
||||
{
|
||||
if (bar) {
|
||||
function_baz();
|
||||
}
|
||||
}
|
||||
|
||||
Note that there is no space between the name of a function and the following
|
||||
parentheses.
|
||||
|
||||
Control statements (``if``, ``for``, ``switch``, ``while``, etc) must be
|
||||
separated from the following open paranthesis by a single space. The previous
|
||||
example illustrates this for an ``if`` statement.
|
||||
|
||||
Line Length
|
||||
-----------
|
||||
|
||||
Line length *should* be at most **80 characters**. This limit does not include
|
||||
non-printing characters such as the line feed.
|
||||
|
||||
This rule is a *should*, not a must, and it is acceptable to exceed the limit
|
||||
**slightly** where the readability of the code would otherwise be significantly
|
||||
reduced. Use your judgement in these cases.
|
||||
|
||||
Blank Lines
|
||||
-----------
|
||||
|
||||
Functions are usually separated by a single blank line. In certain cases it is
|
||||
acceptable to use additional blank lines for clarity, if required.
|
||||
|
||||
The file must end with a single newline character. Many editors have the option
|
||||
to insert this automatically and to trim multiple blank lines at the end of the
|
||||
file.
|
||||
|
||||
Braces
|
||||
------
|
||||
|
||||
Opening Brace Placement
|
||||
^^^^^^^^^^^^^^^^^^^^^^^
|
||||
|
||||
Braces follow the **Kernighan and Ritchie (K&R)** style, where the opening brace
|
||||
is **not** placed on a new line.
|
||||
|
||||
Example for a ``while`` loop:
|
||||
|
||||
.. code:: c
|
||||
|
||||
while (condition) {
|
||||
foo();
|
||||
bar();
|
||||
}
|
||||
|
||||
This style applies to all blocks except for functions which, following the Linux
|
||||
style, **do** place the opening brace on a new line.
|
||||
|
||||
Example for a function:
|
||||
|
||||
.. code:: c
|
||||
|
||||
int my_function(void)
|
||||
{
|
||||
int a;
|
||||
|
||||
a = 1;
|
||||
return a;
|
||||
}
|
||||
|
||||
Conditional Statement Bodies
|
||||
^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
||||
|
||||
Where conditional statements (such as ``if``, ``for``, ``while`` and ``do``) are
|
||||
used, braces must be placed around the statements that form the body of the
|
||||
conditional. This is the case regardless of the number of statements in the
|
||||
body.
|
||||
|
||||
.. note::
|
||||
This is a notable departure from the Linux coding style that has been
|
||||
adopted to follow MISRA guidelines more closely and to help prevent errors.
|
||||
|
||||
For example, use the following style:
|
||||
|
||||
.. code:: c
|
||||
|
||||
if (condition) {
|
||||
foo++;
|
||||
}
|
||||
|
||||
instead of omitting the optional braces around a single statement:
|
||||
|
||||
.. code:: c
|
||||
|
||||
/* This is violating MISRA C 2012: Rule 15.6 */
|
||||
if (condition)
|
||||
foo++;
|
||||
|
||||
The reason for this is to prevent accidental changes to control flow when
|
||||
modifying the body of the conditional. For example, at a quick glance it is easy
|
||||
to think that the value of ``bar`` is only incremented if ``condition``
|
||||
evaluates to ``true`` but this is not the case - ``bar`` will always be
|
||||
incremented regardless of the condition evaluation. If the developer forgets to
|
||||
add braces around the conditional body when adding the ``bar++;`` statement then
|
||||
the program execution will not proceed as intended.
|
||||
|
||||
.. code:: c
|
||||
|
||||
/* This is violating MISRA C 2012: Rule 15.6 */
|
||||
if (condition)
|
||||
foo++;
|
||||
bar++;
|
||||
|
||||
Naming
|
||||
------
|
||||
|
||||
Functions
|
||||
^^^^^^^^^
|
||||
|
||||
Use lowercase for function names, separating multiple words with an underscore
|
||||
character (``_``). This is sometimes referred to as *Snake Case*. An example is
|
||||
given below:
|
||||
|
||||
.. code:: c
|
||||
|
||||
void bl2_arch_setup(void)
|
||||
{
|
||||
...
|
||||
}
|
||||
|
||||
Local Variables and Parameters
|
||||
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
||||
|
||||
Local variables and function parameters use the same format as function names:
|
||||
lowercase with underscore separation between multiple words. An example is
|
||||
given below:
|
||||
|
||||
.. code:: c
|
||||
|
||||
static void set_scr_el3_from_rm(uint32_t type,
|
||||
uint32_t interrupt_type_flags,
|
||||
uint32_t security_state)
|
||||
{
|
||||
uint32_t flag, bit_pos;
|
||||
|
||||
...
|
||||
|
||||
}
|
||||
|
||||
Preprocessor Macros
|
||||
^^^^^^^^^^^^^^^^^^^
|
||||
|
||||
Identifiers that are defined using preprocessor macros are written in all
|
||||
uppercase text.
|
||||
|
||||
.. code:: c
|
||||
|
||||
#define BUFFER_SIZE_BYTES 64
|
||||
|
||||
Function Attributes
|
||||
-------------------
|
||||
|
||||
Place any function attributes after the function type and before the function
|
||||
name.
|
||||
|
||||
.. code:: c
|
||||
|
||||
void __init plat_arm_interconnect_init(void);
|
||||
|
||||
Alignment
|
||||
---------
|
||||
|
||||
Alignment should be performed primarily with tabs, adding spaces if required to
|
||||
achieve a granularity that is smaller than the tab size. For example, with a tab
|
||||
size of eight columns it would be necessary to use one tab character and two
|
||||
spaces to indent text by ten columns.
|
||||
|
||||
Switch Statement Alignment
|
||||
^^^^^^^^^^^^^^^^^^^^^^^^^^
|
||||
|
||||
When using ``switch`` statements, align each ``case`` statement with the
|
||||
``switch`` so that they are in the same column.
|
||||
|
||||
.. code:: c
|
||||
|
||||
switch (condition) {
|
||||
case A:
|
||||
foo();
|
||||
case B:
|
||||
bar();
|
||||
default:
|
||||
baz();
|
||||
}
|
||||
|
||||
Pointer Alignment
|
||||
^^^^^^^^^^^^^^^^^
|
||||
|
||||
The reference and dereference operators (ampersand and *pointer star*) must be
|
||||
aligned with the name of the object on which they are operating, as opposed to
|
||||
the type of the object.
|
||||
|
||||
.. code:: c
|
||||
|
||||
uint8_t *foo;
|
||||
|
||||
foo = &bar;
|
||||
|
||||
|
||||
Comments
|
||||
--------
|
||||
|
||||
The general rule for comments is that the double-slash style of comment (``//``)
|
||||
is not allowed. Examples of the allowed comment formats are shown below:
|
||||
|
||||
.. code:: c
|
||||
|
||||
/*
|
||||
* This example illustrates the first allowed style for multi-line comments.
|
||||
*
|
||||
* Blank lines within multi-lines are allowed when they add clarity or when
|
||||
* they separate multiple contexts.
|
||||
*
|
||||
*/
|
||||
|
||||
.. code:: c
|
||||
|
||||
/**************************************************************************
|
||||
* This is the second allowed style for multi-line comments.
|
||||
*
|
||||
* In this style, the first and last lines use asterisks that run the full
|
||||
* width of the comment at its widest point.
|
||||
*
|
||||
* This style can be used for additional emphasis.
|
||||
*
|
||||
*************************************************************************/
|
||||
|
||||
.. code:: c
|
||||
|
||||
/* Single line comments can use this format */
|
||||
|
||||
.. code:: c
|
||||
|
||||
/***************************************************************************
|
||||
* This alternative single-line comment style can also be used for emphasis.
|
||||
**************************************************************************/
|
||||
|
||||
Headers and inclusion
|
||||
---------------------
|
||||
|
||||
Header guards
|
||||
^^^^^^^^^^^^^
|
||||
|
||||
For a header file called "some_driver.h" the style used by |TF-A| is:
|
||||
|
||||
.. code:: c
|
||||
|
||||
#ifndef SOME_DRIVER_H
|
||||
#define SOME_DRIVER_H
|
||||
|
||||
<header content>
|
||||
|
||||
#endif /* SOME_DRIVER_H */
|
||||
|
||||
Include statement ordering
|
||||
^^^^^^^^^^^^^^^^^^^^^^^^^^
|
||||
|
||||
All header files that are included by a source file must use the following,
|
||||
grouped ordering. This is to improve readability (by making it easier to quickly
|
||||
read through the list of headers) and maintainability.
|
||||
|
||||
#. *System* includes: Header files from the standard *C* library, such as
|
||||
``stddef.h`` and ``string.h``.
|
||||
|
||||
#. *Project* includes: Header files under the ``include/`` directory within
|
||||
|TF-A| are *project* includes.
|
||||
|
||||
#. *Platform* includes: Header files relating to a single, specific platform,
|
||||
and which are located under the ``plat/<platform_name>`` directory within
|
||||
|TF-A|, are *platform* includes.
|
||||
|
||||
Within each group, ``#include`` statements must be in alphabetical order,
|
||||
taking both the file and directory names into account.
|
||||
|
||||
Groups must be separated by a single blank line for clarity.
|
||||
|
||||
The example below illustrates the ordering rules using some contrived header
|
||||
file names; this type of name reuse should be otherwise avoided.
|
||||
|
||||
.. code:: c
|
||||
|
||||
#include <string.h>
|
||||
|
||||
#include <a_dir/example/a_header.h>
|
||||
#include <a_dir/example/b_header.h>
|
||||
#include <a_dir/test/a_header.h>
|
||||
#include <b_dir/example/a_header.h>
|
||||
|
||||
#include "a_header.h"
|
||||
|
||||
Include statement variants
|
||||
^^^^^^^^^^^^^^^^^^^^^^^^^^
|
||||
|
||||
Two variants of the ``#include`` directive are acceptable in the |TF-A|
|
||||
codebase. Correct use of the two styles improves readability by suggesting the
|
||||
location of the included header and reducing ambiguity in cases where generic
|
||||
and platform-specific headers share a name.
|
||||
|
||||
For header files that are in the same directory as the source file that is
|
||||
including them, use the ``"..."`` variant.
|
||||
|
||||
For header files that are **not** in the same directory as the source file that
|
||||
is including them, use the ``<...>`` variant.
|
||||
|
||||
Example (bl1_fwu.c):
|
||||
|
||||
.. code:: c
|
||||
|
||||
#include <assert.h>
|
||||
#include <errno.h>
|
||||
#include <string.h>
|
||||
|
||||
#include "bl1_private.h"
|
||||
|
||||
Typedefs
|
||||
--------
|
||||
|
||||
Avoid anonymous typedefs of structs/enums in headers
|
||||
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
||||
|
||||
For example, the following definition:
|
||||
|
||||
.. code:: c
|
||||
|
||||
typedef struct {
|
||||
int arg1;
|
||||
int arg2;
|
||||
} my_struct_t;
|
||||
|
||||
|
||||
is better written as:
|
||||
|
||||
.. code:: c
|
||||
|
||||
struct my_struct {
|
||||
int arg1;
|
||||
int arg2;
|
||||
};
|
||||
|
||||
This allows function declarations in other header files that depend on the
|
||||
struct/enum to forward declare the struct/enum instead of including the
|
||||
entire header:
|
||||
|
||||
.. code:: c
|
||||
|
||||
struct my_struct;
|
||||
void my_func(struct my_struct *arg);
|
||||
|
||||
instead of:
|
||||
|
||||
.. code:: c
|
||||
|
||||
#include <my_struct.h>
|
||||
void my_func(my_struct_t *arg);
|
||||
|
||||
Some TF definitions use both a struct/enum name **and** a typedef name. This
|
||||
is discouraged for new definitions as it makes it difficult for TF to comply
|
||||
with MISRA rule 8.3, which states that "All declarations of an object or
|
||||
function shall use the same names and type qualifiers".
|
||||
|
||||
The Linux coding standards also discourage new typedefs and checkpatch emits
|
||||
a warning for this.
|
||||
|
||||
Existing typedefs will be retained for compatibility.
|
||||
|
||||
--------------
|
||||
|
||||
*Copyright (c) 2020, Arm Limited. All rights reserved.*
|
||||
|
||||
.. _`Linux kernel coding style`: https://www.kernel.org/doc/html/latest/process/coding-style.html
|
||||
.. _`MISRA C:2012 Guidelines`: https://www.misra.org.uk/Activities/MISRAC/tabid/160/Default.aspx
|
||||
.. _`a spreadsheet`: https://developer.trustedfirmware.org/file/download/lamajxif3w7c4mpjeoo5/PHID-FILE-fp7c7acszn6vliqomyhn/MISRA-and-TF-Analysis-v1.3.ods
|
|
@ -23,7 +23,7 @@ Making Changes
|
|||
|
||||
- Make commits of logical units. See these general `Git guidelines`_ for
|
||||
contributing to a project.
|
||||
- Follow the :ref:`Coding Style & Guidelines`.
|
||||
- Follow the :ref:`Coding Style` and :ref:`Coding Guidelines`.
|
||||
|
||||
- Use the checkpatch.pl script provided with the Linux source tree. A
|
||||
Makefile target is provided for convenience.
|
||||
|
@ -128,7 +128,7 @@ Binary Components
|
|||
|
||||
--------------
|
||||
|
||||
*Copyright (c) 2013-2019, Arm Limited and Contributors. All rights reserved.*
|
||||
*Copyright (c) 2013-2020, Arm Limited and Contributors. All rights reserved.*
|
||||
|
||||
.. _developer.trustedfirmware.org: https://developer.trustedfirmware.org
|
||||
.. _issue: https://developer.trustedfirmware.org/project/board/1/
|
||||
|
|
|
@ -8,6 +8,7 @@ Processes & Policies
|
|||
|
||||
security
|
||||
platform-compatibility-policy
|
||||
coding-style
|
||||
coding-guidelines
|
||||
contributing
|
||||
faq
|
||||
|
|
|
@ -1,10 +1,30 @@
|
|||
Security hardening
|
||||
==================
|
||||
Secure Development Guidelines
|
||||
=============================
|
||||
|
||||
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.
|
||||
|
||||
Security considerations
|
||||
-----------------------
|
||||
|
||||
Part of the security of a platform is handling errors correctly, as described in
|
||||
the previous section. There are several other security considerations covered in
|
||||
this section.
|
||||
|
||||
Do not leak secrets to the normal world
|
||||
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
||||
|
||||
The secure world **must not** leak secrets to the normal world, for example in
|
||||
response to an SMC.
|
||||
|
||||
Handling Denial of Service attacks
|
||||
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
||||
|
||||
The secure world **should never** crash or become unusable due to receiving too
|
||||
many normal world requests (a *Denial of Service* or *DoS* attack). It should
|
||||
have a mechanism for throttling or ignoring normal world requests.
|
||||
|
||||
Build options
|
||||
-------------
|
||||
|
||||
|
@ -53,4 +73,4 @@ Several build options can be used to check for security issues. Refer to the
|
|||
|
||||
--------------
|
||||
|
||||
*Copyright (c) 2019, Arm Limited. All rights reserved.*
|
||||
*Copyright (c) 2019-2020, Arm Limited. All rights reserved.*
|
||||
|
|
Loading…
Reference in New Issue