91 lines
3.2 KiB
C
91 lines
3.2 KiB
C
/*
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* Copyright (c) 2010, 2012, 2014 Wind River Systems, Inc.
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*
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* SPDX-License-Identifier: Apache-2.0
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*/
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/**
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* @file
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* @brief Macros to generate structure member offset definitions
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*
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* This header contains macros to allow a kernel implementation to generate
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* absolute symbols whose values represents the member offsets for various
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* kernel structures. These absolute symbols are typically utilized by
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* assembly source files rather than hardcoding the values in some local header
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* file.
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*
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* WARNING: Absolute symbols can potentially be utilized by external tools --
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* for example, to locate a specific field within a data structure.
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* Consequently, changes made to such symbols may require modifications to the
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* associated tool(s). Typically, relocating a member of a structure merely
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* requires that a tool be rebuilt; however, moving a member to another
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* structure (or to a new sub-structure within an existing structure) may
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* require that the tool itself be modified. Likewise, deleting, renaming, or
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* changing the meaning of an absolute symbol may require modifications to a
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* tool.
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*
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* The macro "GEN_OFFSET_SYM(structure, member)" is used to generate a single
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* absolute symbol. The absolute symbol will appear in the object module
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* generated from the source file that utilizes the GEN_OFFSET_SYM() macro.
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* Absolute symbols representing a structure member offset have the following
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* form:
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*
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* __<structure>_<member>_OFFSET
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*
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* The macro "GEN_NAMED_OFFSET_SYM(structure, member, name)" is also provided
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* to create the symbol with the following form:
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*
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* __<structure>_<name>_OFFSET
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*
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* This header also defines the GEN_ABSOLUTE_SYM macro to simply define an
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* absolute symbol, irrespective of whether the value represents a structure
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* or offset.
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*
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* The following sample file illustrates the usage of the macros available
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* in this file:
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*
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* <START of sample source file: offsets.c>
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*
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* #include <gen_offset.h>
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* /@ include struct definitions for which offsets symbols are to be
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* generated @/
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*
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* #include <kernel_structs.h>
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* GEN_ABS_SYM_BEGIN (_OffsetAbsSyms) /@ the name parameter is arbitrary @/
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* /@ _kernel_t structure member offsets @/
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*
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* GEN_OFFSET_SYM (_kernel_t, nested);
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* GEN_OFFSET_SYM (_kernel_t, irq_stack);
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* GEN_OFFSET_SYM (_kernel_t, current);
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* GEN_OFFSET_SYM (_kernel_t, idle);
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*
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* GEN_ABSOLUTE_SYM (___kernel_t_SIZEOF, sizeof(_kernel_t));
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*
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* GEN_ABS_SYM_END
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* <END of sample source file: offsets.c>
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*
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* Compiling the sample offsets.c results in the following symbols in offsets.o:
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*
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* $ nm offsets.o
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* 00000000 A ___kernel_t_nested_OFFSET
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* 00000004 A ___kernel_t_irq_stack_OFFSET
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* 00000008 A ___kernel_t_current_OFFSET
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* 0000000c A ___kernel_t_idle_OFFSET
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*/
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#ifndef ZEPHYR_KERNEL_INCLUDE_GEN_OFFSET_H_
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#define ZEPHYR_KERNEL_INCLUDE_GEN_OFFSET_H_
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#include <toolchain.h>
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#include <stddef.h>
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/* definition of the GEN_OFFSET_SYM() macros is toolchain independent */
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#define GEN_OFFSET_SYM(S, M) \
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GEN_ABSOLUTE_SYM(__##S##_##M##_##OFFSET, offsetof(S, M))
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#define GEN_NAMED_OFFSET_SYM(S, M, N) \
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GEN_ABSOLUTE_SYM(__##S##_##N##_##OFFSET, offsetof(S, M))
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#endif /* ZEPHYR_KERNEL_INCLUDE_GEN_OFFSET_H_ */
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