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cpu/avr8_common: Wrap stdio.h
This allows automatically moving format strings to flash, provided that code previously compiled fine with `-Wformat-nonliteral` (which in RIOT is the case due to `-Wformat=2`).
This commit is contained in:
Marian Buschsieweke
parent
75f17b4930
commit
c406f7ef42
145
cpu/avr8_common/include/stdio.h
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145
cpu/avr8_common/include/stdio.h
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/*
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* Copyright (C) 2023 Otto-von-Guericke-Universität Magdeburg
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*
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* This file is subject to the terms and conditions of the GNU Lesser General
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* Public License v2.1. See the file LICENSE in the top level directory for more
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* details.
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*/
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/**
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* @defgroup cpu_avr8_common_stdio_wrapper stdio wrapper for AVR8
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* @ingroup cpu_avr8_common
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*
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* This module a wrapper for the stdio.h header intended to make use of
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* flash_utils.h in printf() automatically
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*
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* @{
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*
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* @file
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* @brief stdio wrapper to extend the C libs stdio
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*
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* @author Marian Buschsieweke <marian.buschsieweke@ovgu.de>
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*/
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#ifndef STDIO_H
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#define STDIO_H
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#include_next "stdio.h"
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/* C++ does not support __flash. Hence, only wrap printf() and friends for
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* C and let C++ use them unmodified. */
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#ifdef __cplusplus
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extern "C" {
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}
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#else
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#include "flash_utils.h"
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#ifdef DOXYGEN
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/**
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* @brief A wrapper for the `printf()` function that passes arguments through
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* unmodified, but fails to compile if the first argument is not a
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* string literal.
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*
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* See e.g. `man 3 printf` or https://linux.die.net/man/3/printf for
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* documentation the printf function. This applies fully here, as it passes
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* through the arguments unmodified.
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*
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* The motivation for enforcing the first argument to be a string literal is
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* three-fold:
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*
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* 1. It prevents security issues due format strings controlled by adversaries.
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* 2. It makes sure that modern C compilers that do understand format
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* specifiers have knowledge of the format string and can verify that the
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* other arguments match what is given via format string specifiers
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* 3. It allows to force the format string to flash even for Harvard
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* architectures transparently
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*
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* Similar wrappers are also in place for `vprintf()`, `fprintf()`,
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* `vfprintf()`, `snprintf()`, `vsnprintf()`.
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*/
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#define printf(...) /* implementation details */
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#else
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/* this helper function-like macro takes at least 65 arguments and will
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* "return" the 65 argument unmodified. It is not useful by itself, but
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* needed to implement _SINGLEARG_OR_MULTIARG(). */
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#define _TAKE_65TH_TOKEN( _1, _2, _3, _4, _5, _6, _7, _8, _9, _10, \
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_11, _12, _13, _14, _15, _16, _17, _18, _19, _20, \
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_21, _22, _23, _24, _25, _26, _27, _28, _29, _30, \
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_31, _32, _33, _34, _35, _36, _37, _38, _39, _40, \
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_41, _42, _43, _44, _45, _46, _47, _48, _49, _50, \
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_51, _52, _53, _54, _55, _56, _57, _58, _59, _60, \
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_61, _62, _63, _64, N, ...) N
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#define _EXPAND_HELPER(x) x
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/* this function-like macro expands its argument */
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#define _EXPAND(x) _EXPAND_HELPER(x)
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/* This function-like macro will expand to `SINGLEARG` if called with one
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* argument and `MULTIARG` if called with more than one.
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*
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* (Implementation detail: It will not work with more than 64 arguments. But
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* 64 arguments to one printf call ought to be enough for everyone...)
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*/
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#define _SINGLEARG_OR_MULTIARG(...) \
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_TAKE_65TH_TOKEN(__VA_ARGS__, \
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MULTIARG, MULTIARG, MULTIARG, MULTIARG, \
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MULTIARG, MULTIARG, MULTIARG, MULTIARG, \
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MULTIARG, MULTIARG, MULTIARG, MULTIARG, \
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MULTIARG, MULTIARG, MULTIARG, MULTIARG, \
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MULTIARG, MULTIARG, MULTIARG, MULTIARG, \
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MULTIARG, MULTIARG, MULTIARG, MULTIARG, \
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MULTIARG, MULTIARG, MULTIARG, MULTIARG, \
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MULTIARG, MULTIARG, MULTIARG, MULTIARG, \
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MULTIARG, MULTIARG, MULTIARG, MULTIARG, \
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MULTIARG, MULTIARG, MULTIARG, MULTIARG, \
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MULTIARG, MULTIARG, MULTIARG, MULTIARG, \
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MULTIARG, MULTIARG, MULTIARG, MULTIARG, \
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MULTIARG, MULTIARG, MULTIARG, MULTIARG, \
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MULTIARG, MULTIARG, MULTIARG, MULTIARG, \
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MULTIARG, MULTIARG, MULTIARG, MULTIARG, \
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MULTIARG, MULTIARG, MULTIARG, SINGLEARG)
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#define _CONCAT_HELPER(a, b) a ## b
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#define _CONCAT(a, b) _CONCAT_HELPER(a, b)
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/* Implementation for `printf(fmt)` */
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#define _PRINTF_SINGLEARG(x) \
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flash_printf(TO_FLASH(x))
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/* Implementation for `printf(fmt, ...)` */
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#define _PRINTF_MULTIARG(x, ...) \
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flash_printf(TO_FLASH(x), __VA_ARGS__)
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/* Dispatch to _PRINTF_SINGLEARG() and _PRINTF_MULTIARG() depending on the
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* number of arguments. Special handling for `printf(fmt)` compared to
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* `printf(fmt, ...)` is needed because the `__VA_ARGS__` part must contain
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* at least one argument, which in case of `printf(fmt)` is not the case. */
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#define printf(...) \
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_EXPAND(_CONCAT(_PRINTF_, _SINGLEARG_OR_MULTIARG(__VA_ARGS__))(__VA_ARGS__))
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/* And now all other printf variants. For the v*printf() versions we do not
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* need to differentiate, because they have always the same number of arguments
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* (with the last being va_list). For the other printf variants, we again need
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* to dispatch to a _SINGLEARG and a _MULTIARG version. */
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#define vprintf(fmt, args) flash_vprintf(TO_FLASH(fmt), args)
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#define _FPRINTF_SINGLEARG(stream, x) \
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flash_fprintf(stream, TO_FLASH(x))
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#define _FPRINTF_MULTIARG(stream, x, ...) \
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flash_fprintf(stream, TO_FLASH(x), __VA_ARGS__)
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#define fprintf(stream, ...) \
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_EXPAND(_CONCAT(_FPRINTF_, _SINGLEARG_OR_MULTIARG(__VA_ARGS__))(stream, __VA_ARGS__))
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#define vfprintf(stream, fmt, args) flash_vfprintf(stream, TO_FLASH(fmt), args)
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#define _SNPRINTF_SINGLEARG(buf, buf_len, fmt) \
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flash_snprintf(buf, buf_len, TO_FLASH(fmt))
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#define _SNPRINTF_MULTIARG(buf, buf_len, fmt, ...) \
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flash_snprintf(buf, buf_len, TO_FLASH(fmt), __VA_ARGS__)
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#define snprintf(buf, buf_len, ...) \
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_EXPAND(_CONCAT(_SNPRINTF_, _SINGLEARG_OR_MULTIARG(__VA_ARGS__))(buf, buf_len, __VA_ARGS__))
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#define vsnprintf(buf, buf_len, fmt, args) flash_vsnprintf(buf, buf_len, TO_FLASH(fmt), args)
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#endif
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#endif
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#endif /* STDIO_H */
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/** @} */
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@ -414,6 +414,12 @@ ifneq (,$(filter log_%,$(USEMODULE)))
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USEMODULE += log
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endif
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ifneq (,$(filter log_color,$(USEMODULE)))
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# log_color fails to compile with -Wformat-nonliteral but this is required
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# for the wrapped stdio that pushes the format string into progmem
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FEATURES_BLACKLIST += arch_avr8
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endif
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ifneq (,$(filter cpp11-compat,$(USEMODULE)))
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USEMODULE += cpp_new_delete
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USEMODULE += xtimer
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@ -10,6 +10,9 @@ choice LOG
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config MODULE_LOG_COLOR
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bool "log_color: colored log output"
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select MODULE_LOG
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# log_color fails to compile with -Wformat-nonliteral but this is required
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# for the wrapped stdio that pushes the format string into progmem
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depends on !CPU_ARCH_AVR8
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help
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Implements a logging module with colored output.
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