lib: os: cbprintf: Add static packaging

Extend cbprintf with static packaging.

Signed-off-by: Krzysztof Chruscinski <krzysztof.chruscinski@nordicsemi.no>

include/sys/cbprintf.h

@@ -11,6 +11,7 @@
 #include <stddef.h>
 #include <stdint.h>
 #include <toolchain.h>
+#include <sys/cbprintf_internal.h>
 
 #ifdef CONFIG_CBPRINTF_LIBC_SUBSTS
 #include <stdio.h>
@@ -20,12 +21,32 @@
 extern "C" {
 #endif
 
+/* Determine if _Generic is supported.
+ * In general it's a C11 feature but it was added also in:
+ * - GCC 4.9.0 https://gcc.gnu.org/gcc-4.9/changes.html
+ * - Clang 3.0 https://releases.llvm.org/3.0/docs/ClangReleaseNotes.html
+ */
+#ifndef Z_C_GENERIC
+#if ((__STDC_VERSION__ >= 201112L) || \
+	((__GNUC__ * 10000 + __GNUC_MINOR__ * 100 + __GNUC_PATCHLEVEL__) >= 40900) || \
+	((__clang_major__ * 10000 + __clang_minor__ * 100 + __clang_patchlevel__) >= 30000))
+#define Z_C_GENERIC 1
+#else
+#define Z_C_GENERIC 0
+#endif
+#endif
+
 /**
  * @defgroup cbprintf_apis Formatted Output APIs
  * @ingroup support_apis
  * @{
  */
 
+/** @brief Required alignment of the buffer used for packaging. */
+#define CBPRINTF_PACKAGE_ALIGNMENT \
+	(IS_ENABLED(CONFIG_CBPRINTF_PACKAGE_LONGDOUBLE) ? \
+		sizeof(long double) : MAX(sizeof(double), sizeof(long long)))
+
 /** @brief Signature for a cbprintf callback function.
  *
  * This function expects two parameters:
@@ -45,6 +66,50 @@ extern "C" {
  */
 typedef int (*cbprintf_cb)(/* int c, void *ctx */);
 
+/** @brief Determine if string must be packaged in run time.
+ *
+ * Static packaging can be applied if size of the package can be determined
+ * at compile time. In general, package size can be determined at compile time
+ * if there are no string arguments which might be copied into package body if
+ * they are considered transient.
+ *
+ * @param skip number of read only string arguments in the parameter list. It
+ * shall be non-zero if there are known read only string arguments present
+ * in the string (e.g. function name prefix in the log message).
+ *
+ * @param ... String with arguments.
+ *
+ * @retval 1 if string must be packaged in run time.
+ * @retval 0 string can be statically packaged.
+ */
+#define CBPRINTF_MUST_RUNTIME_PACKAGE(skip, .../* fmt, ... */) \
+	Z_CBPRINTF_MUST_RUNTIME_PACKAGE(skip, __VA_ARGS__)
+
+/** @brief Statically package string.
+ *
+ * Build string package from formatted string. It assumes that formatted
+ * string is in the read only memory.
+ *
+ * If _Generic is not supported then runtime packaging is performed.
+ *
+ * @param packaged pointer to where the packaged data can be stored. Pass a null
+ * pointer to skip packaging but still calculate the total space required.
+ * The data stored here is relocatable, that is it can be moved to another
+ * contiguous block of memory. It must be aligned to the size of the longest
+ * argument. It is recommended to use CBPRINTF_PACKAGE_ALIGNMENT for alignment.
+ *
+ * @param inlen set to the number of bytes available at @p packaged. If
+ * @p packaged is NULL the value is ignored.
+ *
+ * @param outlen variable updated to the number of bytes required to completely
+ * store the packed information. If input buffer was too small it is set to
+ * -ENOSPC.
+ *
+ * @param ... formatted string with arguments. Format string must be constant.
+ */
+#define CBPRINTF_STATIC_PACKAGE(packaged, inlen, outlen, ... /* fmt, ... */) \
+		Z_CBPRINTF_STATIC_PACKAGE(packaged, inlen, outlen, __VA_ARGS__)
+
 /** @brief Capture state required to output formatted data later.
  *
  * Like cbprintf() but instead of processing the arguments and emitting the

include/sys/cbprintf_internal.h

@@ -0,0 +1,292 @@
+/*
+ * Copyright (c) 2020 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#ifndef ZEPHYR_INCLUDE_SYS_CBPRINTF_INTERNAL_H_
+#define ZEPHYR_INCLUDE_SYS_CBPRINTF_INTERNAL_H_
+
+#include <stdarg.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <toolchain.h>
+#include <sys/util.h>
+#include <sys/__assert.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*
+ * Special alignment cases
+ */
+
+#if defined(__i386__)
+/* there are no gaps on the stack */
+#define VA_STACK_ALIGN(type)	1
+#elif defined(__sparc__)
+/* there are no gaps on the stack */
+#define VA_STACK_ALIGN(type)	1
+#elif defined(__x86_64__)
+#define VA_STACK_MIN_ALIGN	8
+#elif defined(__aarch64__)
+#define VA_STACK_MIN_ALIGN	8
+#elif defined(__riscv)
+#define VA_STACK_MIN_ALIGN	(__riscv_xlen / 8)
+#endif
+
+/*
+ * Default alignment values if not specified by architecture config
+ */
+
+#ifndef VA_STACK_MIN_ALIGN
+#define VA_STACK_MIN_ALIGN	1
+#endif
+
+#ifndef VA_STACK_ALIGN
+#define VA_STACK_ALIGN(type)	MAX(VA_STACK_MIN_ALIGN, __alignof__(type))
+#endif
+
+/** @brief Return 1 if argument is a pointer to char or wchar_t
+ *
+ * @param x argument.
+ *
+ * @return 1 if char * or wchar_t *, 0 otherwise.
+ */
+#define Z_CBPRINTF_IS_PCHAR(x) _Generic((x), \
+			char * : 1, \
+			const char * : 1, \
+			volatile char * : 1, \
+			const volatile char * : 1, \
+			wchar_t * : 1, \
+			const wchar_t * : 1, \
+			volatile wchar_t * : 1, \
+			const volatile wchar_t * : 1, \
+			default : \
+				0)
+
+/** @brief Calculate number of char * or wchar_t * arguments in the arguments.
+ *
+ * @param fmt string.
+ *
+ * @param ... string arguments.
+ *
+ * @return number of arguments which are char * or wchar_t *.
+ */
+#define Z_CBPRINTF_HAS_PCHAR_ARGS(fmt, ...) \
+	(FOR_EACH(Z_CBPRINTF_IS_PCHAR, (+),  __VA_ARGS__))
+
+/**
+ * @brief Check if formatted string must be packaged in runtime.
+ *
+ * @param skip number of char/wchar_t pointers in the argument list which are
+ * accepted for static packaging.
+ *
+ * @param ... String with arguments (fmt, ...).
+ *
+ * @retval 1 if string must be packaged at runtime.
+ * @retval 0 if string can be statically packaged.
+ */
+#if Z_C_GENERIC
+#define Z_CBPRINTF_MUST_RUNTIME_PACKAGE(skip, ...) \
+	COND_CODE_0(NUM_VA_ARGS_LESS_1(__VA_ARGS__), \
+			(0), \
+			(((Z_CBPRINTF_HAS_PCHAR_ARGS(__VA_ARGS__) - skip) > 0)))
+#else
+#define Z_CBPRINTF_MUST_RUNTIME_PACKAGE(skip, ...) 1
+#endif
+
+/** @brief Get storage size for given argument.
+ *
+ * Floats are promoted to double so they use size of double, others int storage
+ * or it's own storage size if it is bigger than int. Strings are stored in
+ * the package with 1 byte header indicating if string is stored as pointer or
+ * by value.
+ *
+ * @param x argument.
+ *
+ * @return Number of bytes used for storing the argument.
+ */
+#define Z_CBPRINTF_ARG_SIZE(v) \
+	_Generic((v), \
+		float : sizeof(double), \
+		default : \
+			_Generic((v), \
+				void * : 0, \
+				default : \
+					sizeof((v)+0) \
+				) \
+		)
+
+/** @brief Promote and store argument in the buffer.
+ *
+ * @param buf Buffer.
+ *
+ * @param arg Argument.
+ */
+#define Z_CBPRINTF_STORE_ARG(buf, arg) \
+	*_Generic((arg) + 0, \
+		char : (int *)buf, \
+		unsigned char: (int *)buf, \
+		short : (int *)buf, \
+		unsigned short : (int *)buf, \
+		int : (int *)buf, \
+		unsigned int : (unsigned int *)buf, \
+		long : (long *)buf, \
+		unsigned long : (unsigned long *)buf, \
+		long long : (long long *)buf, \
+		unsigned long long : (unsigned long long *)buf, \
+		float : (double *)buf, \
+		double : (double *)buf, \
+		long double : (long double *)buf, \
+		default : \
+			(const void **)buf) = arg
+
+/** @brief Return alignment needed for given argument.
+ *
+ * @param _arg Argument
+ *
+ * @return Alignment in bytes.
+ */
+#define Z_CBPRINTF_ALIGNMENT(_arg) \
+	MAX(_Generic((_arg) + 0, \
+		float : VA_STACK_ALIGN(double), \
+		double : VA_STACK_ALIGN(double), \
+		long double : VA_STACK_ALIGN(long double), \
+		long long : VA_STACK_ALIGN(long long), \
+		unsigned long long : VA_STACK_ALIGN(long long), \
+		default : \
+			__alignof__((_arg) + 0)), VA_STACK_MIN_ALIGN)
+
+/** @brief Detect long double variable.
+ *
+ * @param x Argument.
+ *
+ * @return 1 if @p x is a long double, 0 otherwise.
+ */
+#define Z_CBPRINTF_IS_LONGDOUBLE(x) \
+	_Generic((x) + 0, long double : 1, default : 0)
+
+/** @brief Safely package arguments to a buffer.
+ *
+ * Argument is put into the buffer if capable buffer is provided. Length is
+ * incremented even if data is not packaged.
+ *
+ * @param _buf buffer.
+ *
+ * @param _idx index. Index is postincremented.
+ *
+ * @param _max maximum index (buffer capacity).
+ *
+ * @param _arg argument.
+ */
+#define Z_CBPRINTF_PACK_ARG2(_buf, _idx, _max, _arg) do { \
+	BUILD_ASSERT(!((sizeof(double) < VA_STACK_ALIGN(long double)) && \
+			Z_CBPRINTF_IS_LONGDOUBLE(_arg) && \
+			!IS_ENABLED(CONFIG_CBPRINTF_PACKAGE_LONGDOUBLE)),\
+			"Packaging of long double not enabled in Kconfig."); \
+	while (_idx % Z_CBPRINTF_ALIGNMENT(_arg)) { \
+		_idx += sizeof(int); \
+	}; \
+	uint32_t _arg_size = Z_CBPRINTF_ARG_SIZE(_arg); \
+	if (_buf && _idx < _max) { \
+		Z_CBPRINTF_STORE_ARG(&_buf[_idx], _arg); \
+	} \
+	_idx += _arg_size; \
+} while (0)
+
+/** @brief Package single argument.
+ *
+ * Macro is called in a loop for each argument in the string.
+ *
+ * @param arg argument.
+ */
+#define Z_CBPRINTF_PACK_ARG(arg) \
+	Z_CBPRINTF_PACK_ARG2(_pbuf, _pkg_len, _pmax, arg)
+
+/** @brief Package descriptor.
+ *
+ * @param len Package length.
+ *
+ * @param str_cnt Number of strings stored in the package.
+ */
+struct z_cbprintf_desc {
+	uint8_t len;
+	uint8_t str_cnt;
+};
+
+/** @brief Package header. */
+union z_cbprintf_hdr {
+	struct z_cbprintf_desc desc;
+	void *raw;
+};
+
+/** @brief Statically package a formatted string with arguments.
+ *
+ * @param buf buffer. If null then only length is calculated.
+ *
+ * @param _inlen buffer capacity on input. Ignored when @p buf is null.
+ *
+ * @param _outlen number of bytes required to store the package.
+ *
+ * @param ... String with variable list of arguments.
+ */
+#define Z_CBPRINTF_STATIC_PACKAGE_GENERIC(buf, _inlen, _outlen, \
+					  ... /* fmt, ... */) \
+do { \
+	_Pragma("GCC diagnostic push") \
+	_Pragma("GCC diagnostic ignored \"-Wpointer-arith\"") \
+	if (IS_ENABLED(CONFIG_CBPRINTF_STATIC_PACKAGE_CHECK_ALIGNMENT)) { \
+		__ASSERT(!((uintptr_t)buf & (CBPRINTF_PACKAGE_ALIGNMENT - 1)), \
+			"Buffer must be aligned."); \
+	} \
+	uint8_t *_pbuf = buf; \
+	size_t _pmax = (buf != NULL) ? *_inlen : SIZE_MAX; \
+	size_t _pkg_len = 0; \
+	union z_cbprintf_hdr *_len_loc; \
+	/* package starts with string address and field with length */ \
+	if (_pmax < sizeof(char *) + 2 * sizeof(uint16_t)) { \
+		break; \
+	} \
+	_len_loc = (union z_cbprintf_hdr *)_pbuf; \
+	_pkg_len += sizeof(union z_cbprintf_hdr); \
+	if (_pbuf) { \
+		*(char **)&_pbuf[_pkg_len] = GET_ARG_N(1, __VA_ARGS__); \
+	} \
+	_pkg_len += sizeof(char *); \
+	/* Pack remaining arguments */\
+	COND_CODE_0(NUM_VA_ARGS_LESS_1(__VA_ARGS__), (), ( \
+	    FOR_EACH(Z_CBPRINTF_PACK_ARG, (;), GET_ARGS_LESS_N(1, __VA_ARGS__));\
+	)) \
+	/* Store length */ \
+	_outlen = (_pkg_len > _pmax) ? -ENOSPC : _pkg_len; \
+	/* Store length in the header, set number of dumped strings to 0 */ \
+	if (_pbuf) { \
+		union z_cbprintf_hdr hdr = { .desc = {.len = _pkg_len }}; \
+		*_len_loc = hdr; \
+	} \
+	_Pragma("GCC diagnostic pop") \
+} while (0)
+
+#if Z_C_GENERIC
+#define Z_CBPRINTF_STATIC_PACKAGE(packaged, inlen, outlen, ... /* fmt, ... */) \
+	Z_CBPRINTF_STATIC_PACKAGE_GENERIC(packaged, inlen, outlen, __VA_ARGS__)
+#else
+#define Z_CBPRINTF_STATIC_PACKAGE(packaged, inlen, outlen, ... /* fmt, ... */) \
+do { \
+	/* Small trick needed to avoid warning on always true */ \
+	if (((uintptr_t)packaged + 1) != 1) { \
+		outlen = cbprintf_package(packaged, inlen, __VA_ARGS__); \
+	} else { \
+		outlen = cbprintf_package(NULL, 0, __VA_ARGS__); \
+	} \
+} while (0)
+#endif /* Z_C_GENERIC */
+
+#ifdef __cplusplus
+}
+#endif
+
+
+#endif /* ZEPHYR_INCLUDE_SYS_CBPRINTF_INTERNAL_H_ */

lib/os/Kconfig.cbprintf

@@ -115,3 +115,19 @@ config CBPRINTF_LIBC_SUBSTS
 
 	  When used with CBPRINTF_NANO this increases the implementation code
 	  size by a small amount.
+
+config CBPRINTF_PACKAGE_LONGDOUBLE
+	bool "Support packaging of long doubles"
+	help
+	  Option impact required alignment for buffers used for packaging
+	  (CBPRINTF_PACKAGE_ALIGNMENT). On most platforms long doubles
+	  requires buffer to be 16 bytes aligned. Long doubles are rarely used
+	  so such alignment is an unnecessary waste. If option is disabled,
+	  then compilation fails if long double is used.
+
+config CBPRINTF_STATIC_PACKAGE_CHECK_ALIGNMENT
+	bool "Validate alignment of a static package buffer"
+	help
+	  When enabled, CBPRINTF_STATIC_PACKAGE asserts when buffer is not
+	  properly aligned. If macro is widely used then assert may impact
+	  memory footprint.

lib/os/cbprintf_packaged.c

@@ -94,8 +94,6 @@ static int cbprintf_via_va_list(cbprintf_cb out, void *ctx,
 	return cbvprintf(out, ctx, fmt, u.ap);
 }
 
-#define VA_STACK_MIN_ALIGN	8
-
 #elif defined(__x86_64__)
 /*
  * Reference:
@@ -131,8 +129,6 @@ static int cbprintf_via_va_list(cbprintf_cb out, void *ctx,
 	return cbvprintf(out, ctx, fmt, u.ap);
 }
 
-#define VA_STACK_MIN_ALIGN	8
-
 #elif defined(__xtensa__)
 /*
  * Reference:
@@ -193,38 +189,10 @@ static int cbprintf_via_va_list(cbprintf_cb out, void *ctx,
 
 #endif
 
-/*
- * Special alignment cases
- */
-
-#if defined(__i386__)
-/* there are no gaps on the stack */
-#define VA_STACK_ALIGN(type)	1
-#endif
-
-#if defined(__riscv)
-#define VA_STACK_MIN_ALIGN	(__riscv_xlen / 8)
-#endif
-
 #if defined(__sparc__)
-/* no gaps on the stack even though the CPU can't do unaligned accesses */
+/* CPU can't do unaligned accesses even though no gaps on the stack.*/
-#define VA_STACK_ALIGN(type)	1
 #define VA_STACK_LL_DBL_MEMCPY	true
-#endif
+#else
-
-/*
- * Default alignment values if not specified by architecture config
- */
-
-#ifndef VA_STACK_MIN_ALIGN
-#define VA_STACK_MIN_ALIGN	1
-#endif
-
-#ifndef VA_STACK_ALIGN
-#define VA_STACK_ALIGN(type)	MAX(VA_STACK_MIN_ALIGN, __alignof__(type))
-#endif
-
-#ifndef VA_STACK_LL_DBL_MEMCPY
 #define VA_STACK_LL_DBL_MEMCPY	false
 #endif