95 lines
3.4 KiB
C
95 lines
3.4 KiB
C
/* gen_offset.h - macros to generate structure member offset definitions */
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/*
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* Copyright (c) 2010, 2012, 2014 Wind River Systems, Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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/*
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* DESCRIPTION
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* This header contains macros to allow a nanokernel implementation to
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* generate absolute symbols whose values represents the member offsets for
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* various nanokernel structures. These absolute symbols are typically
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* utilized by assembly source files rather than hardcoding the values in
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* some local header 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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* 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 <nano_private.h>
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* GEN_ABS_SYM_BEGIN (_OffsetAbsSyms) /@ the name parameter is arbitrary @/
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* /@ tNANO structure member offsets @/
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*
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* GEN_OFFSET_SYM (tNANO, fiber);
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* GEN_OFFSET_SYM (tNANO, task);
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* GEN_OFFSET_SYM (tNANO, current);
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* GEN_OFFSET_SYM (tNANO, nested);
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* GEN_OFFSET_SYM (tNANO, common_isp);
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*
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* GEN_ABSOLUTE_SYM (__tNANO_SIZEOF, sizeof(tNANO));
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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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* 00000010 A __tNANO_common_isp_OFFSET
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* 00000008 A __tNANO_current_OFFSET
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* 0000000c A __tNANO_nested_OFFSET
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* 00000000 A __tNANO_fiber_OFFSET
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* 00000004 A __tNANO_task_OFFSET
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*/
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#ifndef _GEN_OFFSET_H
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#define _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 independant */
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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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#endif /* _GEN_OFFSET_H */
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