333 lines
16 KiB
C
333 lines
16 KiB
C
/****************************************************************************
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* include/dlfcn.h
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*
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* Copyright (C) 2017, 2019 Gregory Nutt. All rights reserved.
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* Author: Gregory Nutt <gnutt@nuttx.org>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* 3. Neither the name NuttX nor the names of its contributors may be
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* used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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****************************************************************************/
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#ifndef __INCLUDE_DLFCN_H
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#define __INCLUDE_DLFCN_H
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <sys/types.h>
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/****************************************************************************
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* Pre-processor Definitions
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****************************************************************************/
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/* The dlfcn.h header defines at least the following macros for use in the
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* construction of a dlopen() mode argument:
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*
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* RTLD_LAZY - Relocations are performed at an implementation-dependent
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* time, ranging from the time of the dlopen() call until
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* the first reference to a given symbol occurs. Specifying
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* RTLD_LAZY should improve performance on implementations
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* supporting dynamic symbol binding as a process may not
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* reference all of the functions in any given object. And,
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* for systems supporting dynamic symbol resolution for
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* normal process execution, this behaviour mimics the
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* normal handling of process execution.
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* RTLD_NOW - All necessary relocations are performed when the object
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* is first loaded. This may waste some processing if
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* relocations are performed for functions that are never
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* referenced. This behaviour may be useful for
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* applications that need to know as soon as an object is
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* loaded that all symbols referenced during execution will
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* be available.
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*
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* Any object loaded by dlopen() that requires relocations against global
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* symbols can reference the symbols in the original process image file,
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* any objects loaded at program startup, from the object itself as well as
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* any other object included in the same dlopen() invocation, and any
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* objects that were loaded in any dlopen() invocation and which specified
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* the RTLD_GLOBAL flag. To determine the scope of visibility for the
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* symbols loaded with a dlopen() invocation, the mode parameter should be
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* bitwise or'ed with one of the following values:
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*
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* RTLD_GLOBAL - The object's symbols are made available for the
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* relocation processing of any other object. In addition,
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* symbol lookup using dlopen(0, mode) and an associated
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* dlsym() allows objects loaded with this mode to be
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* searched.
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* RTLD_LOCAL - All symbols are not made available for relocation
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* processing by other modules.
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*
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* Reference: OpenGroup.org
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*/
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#define RTLD_LAZY (0 << 0)
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#define RTLD_NOW (1 << 0)
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#define RTLD_GLOBAL (1 << 1)
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#define RTLD_LOCAL (1 << 2)
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/****************************************************************************
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* Public Function Prototypes
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****************************************************************************/
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#ifdef __cplusplus
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#define EXTERN extern "C"
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extern "C"
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{
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#else
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#define EXTERN extern
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#endif
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/****************************************************************************
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* Name: dlsymtab
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*
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* Description:
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* dlsymtab() is a non-standard shared library interface. It selects the
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* symbol table to use when binding a shared library to the base firmware
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* which may be in FLASH memory.
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*
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* Input Parameters:
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* symtab - The new symbol table.
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* nsymbols - The number of symbols in the symbol table.
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*
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* Returned Value:
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* Always returns OK.
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*
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****************************************************************************/
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struct symtab_s;
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int dlsymtab(FAR const struct symtab_s *symtab, int nsymbols);
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/****************************************************************************
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* Name: dlopen
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*
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* Description:
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* dlopen() makes an executable object file specified by file available to
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* the calling program. The class of files eligible for this operation and
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* the manner of their construction are specified by the implementation,
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* though typically such files are executable objects such as shared
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* libraries, relocatable files or programs. Note that some implementations
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* permit the construction of dependencies between such objects that are
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* embedded within files. In such cases, a dlopen() operation will load
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* such dependencies in addition to the object referenced by file.
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* Implementations may also impose specific constraints on the construction
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* of programs that can employ dlopen() and its related services.
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*
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* If a file is specified in multiple dlopen() invocations, mode is
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* interpreted at each invocation. Note, however, that once RTLD_NOW has
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* been specified all relocations will have been completed rendering
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* further RTLD_NOW operations redundant and any further RTLD_LAZY
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* operations irrelevant. Similarly note that once RTLD_GLOBAL has been
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* specified the object will maintain the RTLD_GLOBAL status regardless
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* of any previous or future specification of RTLD_LOCAL, so long as the
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* object remains in the address space (see dlclose()).
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*
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* Symbols introduced into a program through calls to dlopen() may be
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* used in relocation activities. Symbols so introduced may duplicate
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* symbols already defined by the program or previous dlopen()
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* operations. To resolve the ambiguities such a situation might
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* present, the resolution of a symbol reference to symbol definition is
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* based on a symbol resolution order. Two such resolution orders are
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* defined: load or dependency ordering. Load order establishes an
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* ordering among symbol definitions, such that the definition first
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* loaded (including definitions from the image file and any dependent
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* objects loaded with it) has priority over objects added later (via
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* dlopen()). Load ordering is used in relocation processing. Dependency
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* ordering uses a breadth-first order starting with a given object,
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* then all of its dependencies, then any dependents of those, iterating
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* until all dependencies are satisfied. With the exception of the global
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* symbol object obtained via a dlopen() operation on a file of 0,
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* dependency ordering is used by the dlsym() function. Load ordering is
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* used in dlsym() operations upon the global symbol object.
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*
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* When an object is first made accessible via dlopen() it and its
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* dependent objects are added in dependency order. Once all the objects
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* are added, relocations are performed using load order. Note that if an
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* object or its dependencies had been previously loaded, the load and
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* dependency orders may yield different resolutions.
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*
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* The symbols introduced by dlopen() operations, and available through
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* dlsym() are at a minimum those which are exported as symbols of global
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* scope by the object. Typically such symbols will be those that were
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* specified in (for example) C source code as having extern linkage. The
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* precise manner in which an implementation constructs the set of
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* exported symbols for a dlopen() object is specified by that
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* implementation.
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*
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* Input Parameters:
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* file - Used to construct a pathname to the object file. If file
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* contains a slash character, the file argument is used as the
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* pathname for the file. Otherwise, file is used in an
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* implementation-dependent manner to yield a pathname.
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*
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* If the value of file is 0, dlopen() provides a handle on a
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* global symbol object. This object provides access to the symbols
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* from an ordered set of objects consisting of the original
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* program image file, together with any objects loaded at program
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* startup as specified by that process image file (for example,
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* shared libraries), and the set of objects loaded using a
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* dlopen() operation together with the RTLD_GLOBAL flag. As the
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* latter set of objects can change during execution, the set
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* identified by handle can also change dynamically.
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*
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* Only a single copy of an object file is brought into the address
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* space, even if dlopen() is invoked multiple times in reference
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* to the file, and even if different pathnames are used to
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* reference the file.
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* mode - Describes how dlopen() will operate upon file with respect to
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* the processing of relocations and the scope of visibility of the
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* symbols provided within file. When an object is brought into the
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* address space of a process, it may contain references to symbols
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* whose addresses are not known until the object is loaded. These
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* references must be relocated before the symbols can be accessed.
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* The mode parameter governs when these relocations take place.
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* See definitions above for values of the mode parameter:.
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*
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* Returned Value:
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* A successful dlopen() returns a handle which the caller may use on
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* subsequent calls to dlsym() and dlclose(). The value of this handle
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* should not be interpreted in any way by the caller.
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*
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* If file cannot be found, cannot be opened for reading, is not of an
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* appropriate object format for processing by dlopen(), or if an error
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* occurs during the process of loading file or relocating its symbolic
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* references, dlopen() will return NULL. More detailed diagnostic
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* information will be available through dlerror().
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*
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* Reference: OpenGroup.org
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*
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* ****************************************************************************/
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FAR void *dlopen(FAR const char *file, int mode);
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/****************************************************************************
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* Name: dlsym
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*
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* Description:
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* dlsym() allows a process to obtain the address of a symbol defined
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* within an object made accessible through a dlopen() call. handle is the
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* value returned from a call to dlopen() (and which has not since been
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* released via a call to dlclose()), name is the symbol's name as a
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* character string.
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*
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* dlsym() will search for the named symbol in all objects loaded
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* automatically as a result of loading the object referenced by handle
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* (see dlopen()). Load ordering is used in dlsym() operations upon the
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* global symbol object. The symbol resolution algorithm used will be
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* dependency order as described in dlopen().
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*
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* Input Parameters:
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* handle - The opaque, non-NULL value returned by a previous successful
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* call to dlopen().
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* name - A pointer to the symbol name string.
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*
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* Returned Value:
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* If handle does not refer to a valid object opened by dlopen(), or if
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* the named symbol cannot be found within any of the objects associated
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* with handle, dlsym() will return NULL. More detailed diagnostic
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* information will be available through dlerror().
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*
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* Reference: OpenGroup.org
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*
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****************************************************************************/
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FAR void *dlsym(FAR void *handle, FAR const char *name);
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/****************************************************************************
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* Name: dlclose
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*
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* Description:
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* dlclose() is used to inform the system that the object referenced by a
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* handle returned from a previous dlopen() invocation is no longer needed
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* by the application.
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*
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* The use of dlclose() reflects a statement of intent on the part of the
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* process, but does not create any requirement upon the implementation,
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* such as removal of the code or symbols referenced by handle. Once an
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* object has been closed using dlclose() an application should assume
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* that its symbols are no longer available to dlsym(). All objects loaded
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* automatically as a result of invoking dlopen() on the referenced object
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* are also closed.
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*
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* Although a dlclose() operation is not required to remove structures
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* from an address space, neither is an implementation prohibited from
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* doing so. The only restriction on such a removal is that no object will
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* be removed to which references have been relocated, until or unless all
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* such references are removed. For instance, an object that had been
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* loaded with a dlopen() operation specifying the RTLD_GLOBAL flag might
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* provide a target for dynamic relocations performed in the processing of
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* other objects - in such environments, an application may assume that no
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* relocation, once made, will be undone or remade unless the object
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* requiring the relocation has itself been removed.
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*
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* Input Parameters:
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* handle - The opaque, non-NULL value returned by a previous successful
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* call to dlopen().
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*
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* Returned Value:
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* If the referenced object was successfully closed, dlclose() returns 0.
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* If the object could not be closed, or if handle does not refer to an
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* open object, dlclose() returns a non-zero value. More detailed
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* diagnostic information will be available through dlerror().
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*
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* Reference: OpenGroup.org
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* ****************************************************************************/
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int dlclose(FAR void *handle);
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/****************************************************************************
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* Name: dlerror
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*
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* Description:
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* dlerror() returns a null-terminated character string (with no trailing
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* newline) that describes the last error that occurred during dynamic
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* linking processing. If no dynamic linking errors have occurred since
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* the last invocation of dlerror(), dlerror() returns NULL. Thus,
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* invoking dlerror() a second time, immediately following a prior
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* invocation, will result in NULL being returned.
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*
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* Input Parameters:
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* If successful, dlerror() returns a null-terminated character string.
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* Otherwise, NULL is returned.
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*
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* Returned Value:
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*
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* Reference: OpenGroup.org
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*
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****************************************************************************/
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FAR char *dlerror(void);
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#undef EXTERN
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#ifdef __cplusplus
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}
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#endif
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#endif /* __INCLUDE_DLFCN_H */
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