281 lines
11 KiB
C
281 lines
11 KiB
C
/****************************************************************************
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* libs/libc/dlfcn/lib_dlopen.c
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. 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, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*
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****************************************************************************/
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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 <libgen.h>
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#include <dlfcn.h>
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#include <nuttx/envpath.h>
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#include <nuttx/lib/modlib.h>
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#include <nuttx/lib/lib.h>
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/****************************************************************************
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* Private Functions
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****************************************************************************/
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: dlinsert
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*
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* Description:
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* Verify that the file is an ELF module binary and, if so, load the
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* shared library into user memory and initialize it for use.
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*
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* NOTE: modlib_setsymtab() had to have been called by application logic
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* logic prior to calling this. Otherwise, dlinsert will be unable to
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* resolve symbols in the OS module.
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*
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* Input Parameters:
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* filename - Full path to the shared library file to be loaded
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*
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* Returned Value:
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* A non-NULL module handle that can be used on subsequent calls to other
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* shared library interfaces is returned on success. If insmod() was
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* unable to load the module insmod() will return a NULL handle and the
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* errno variable will be set appropriately.
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*
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****************************************************************************/
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#if defined(CONFIG_BUILD_FLAT) || defined(CONFIG_BUILD_PROTECTED)
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/* In the FLAT build, a shared library is essentially the same as a kernel
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* module.
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*
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* REVISIT: Missing functionality:
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* - No automatic binding of symbols
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* - No dependencies
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* - mode is ignored.
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*
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* The PROTECTED build is equivalent to the FLAT build EXCEPT that there
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* must be two copies of the module logic: One residing in kernel
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* space and using the kernel symbol table and one residing in user space
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* using the user space symbol table.
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*
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* dlinsert() is essentially a clone of insmod().
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*/
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static inline FAR void *dlinsert(FAR const char *filename)
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{
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FAR void *handle;
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FAR char *name;
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DEBUGASSERT(filename != NULL);
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name = strdup(filename);
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if (name == NULL)
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{
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return NULL;
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}
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/* Then install the file using the basename of the file as the module
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* name.
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*/
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handle = modlib_insert(filename, basename(name));
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lib_free(name);
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return handle;
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}
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#else /* if defined(CONFIG_BUILD_KERNEL) */
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/* The KERNEL build is considerably more complex: In order to be shared,
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* the .text portion of the module must be (1) build for PIC/PID operation
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* and (2) must like in a shared memory region accessible from all
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* processes. The .data/.bss portion of the module must be allocated in
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* the user space of each process, but must lie at the same virtual address
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* so that it can be referenced from the one copy of the text in the shared
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* memory region.
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*/
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static inline FAR void *dlinsert(FAR const char *filename)
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{
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/* #warning Missing logic */
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return NULL;
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}
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#endif
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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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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FAR void *handle = NULL;
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#ifdef CONFIG_LIBC_ENVPATH
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if (file[0] != '/')
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{
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FAR const char *relpath;
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FAR char *fullpath;
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ENVPATH_HANDLE env;
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/* Set aside the relative path */
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relpath = file;
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/* Initialize to traverse the LD_LIBRARY_PATH variable */
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env = envpath_init("LD_LIBRARY_PATH");
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if (env)
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{
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/* Get the next absolute file path */
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while ((fullpath = envpath_next(env, relpath)) != NULL)
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{
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/* Try to load the file at this path */
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handle = dlinsert(fullpath);
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/* Free the allocated fullpath */
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lib_free(fullpath);
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/* Break out of the loop with handle != NULL on success */
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if (handle != NULL)
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{
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break;
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}
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}
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/* Release the traversal handle */
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envpath_release(env);
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}
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}
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else
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#endif
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{
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/* We already have the one and only absolute path to the file to
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* be loaded.
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*/
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handle = dlinsert(file);
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}
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return handle;
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}
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