102 lines
3.2 KiB
C
102 lines
3.2 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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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. Consequently,
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changes made to such symbols may require modifications to the associated
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tool(s). Typically, relocating a member of a structure merely requires
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that a tool be rebuilt; however, moving a member to another structure
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(or to a new sub-structure within an existing structure) may require that
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the tool itself be modified. Likewise, deleting, renaming, or changing the
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meaning of an absolute symbol may require modifications to a tool.
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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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__<structure>_<member>_OFFSET
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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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The following sample file illustrates the usage of the macros available
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in this file:
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<START of sample source file: offsets.c>
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#include <gen_offset.h>
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/@ include struct definitions for which offsets symbols are to be generated @/
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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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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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GEN_ABSOLUTE_SYM (__tNANO_SIZEOF, sizeof(tNANO));
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GEN_ABS_SYM_END
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<END of sample source file: offsets.c>
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Compiling the sample offsets.c results in the following symbols in offsets.o:
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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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\NOMANUAL
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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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