nuttx/libs/libc/dlfcn/lib_dlsym.c

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/****************************************************************************
* libs/libc/dlfcn/lib_dlsym.c
*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership. The
* ASF licenses this file to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance with the
* License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <dlfcn.h>
#include <assert.h>
#include <debug.h>
#include <errno.h>
#include <nuttx/module.h>
#include <nuttx/symtab.h>
#include <nuttx/lib/modlib.h>
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: dlgetsym
*
* Description:
* dlgetsym() implements dlsym() for the PROTECTED build.
*
* Input Parameters:
* handle - The opaque, non-NULL value returned by a previous successful
* call to insmod().
* name - A pointer to the symbol name string.
*
* Returned Value:
* See dlsym().
*
****************************************************************************/
#ifdef CONFIG_BUILD_PROTECTED
static inline FAR const void *dlgetsym(FAR void *handle,
FAR const char *name)
{
FAR struct module_s *modp = (FAR struct module_s *)handle;
FAR const struct symtab_s *symbol;
int err;
int ret;
/* Verify that the module is in the registry */
modlib_registry_lock();
ret = modlib_registry_verify(modp);
if (ret < 0)
{
serr("ERROR: Failed to verify module: %d\n", ret);
err = -ret;
goto errout_with_lock;
}
/* Does the module have a symbol table? */
if (modp->modinfo.exports == NULL || modp->modinfo.nexports == 0)
{
serr("ERROR: Module has no symbol table\n");
err = ENOENT;
goto errout_with_lock;
}
/* Search the symbol table for the matching symbol */
symbol = symtab_findbyname(modp->modinfo.exports, name,
modp->modinfo.nexports);
if (symbol == NULL)
{
serr("ERROR: Failed to find symbol in symbol \"%s\" in table\n", name);
err = ENOENT;
goto errout_with_lock;
}
/* Return the address within the module associated with the symbol */
modlib_registry_unlock();
DEBUGASSERT(symbol->sym_value != NULL);
return symbol->sym_value;
errout_with_lock:
modlib_registry_unlock();
set_errno(err);
return NULL;
}
#endif
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: dlsym
*
* Description:
* dlsym() allows a process to obtain the address of a symbol defined
* within an object made accessible through a dlopen() call. handle is the
* value returned from a call to dlopen() (and which has not since been
* released via a call to dlclose()), name is the symbol's name as a
* character string.
*
* dlsym() will search for the named symbol in all objects loaded
* automatically as a result of loading the object referenced by handle
* (see dlopen()). Load ordering is used in dlsym() operations upon the
* global symbol object. The symbol resolution algorithm used will be
* dependency order as described in dlopen().
*
* Input Parameters:
* handle - The opaque, non-NULL value returned by a previous successful
* call to dlopen().
* name - A pointer to the symbol name string.
*
* Returned Value:
* If handle does not refer to a valid object opened by dlopen(), or if
* the named symbol cannot be found within any of the objects associated
* with handle, dlsym() will return NULL. More detailed diagnostic
* information will be available through dlerror().
*
* Reference: OpenGroup.org
*
****************************************************************************/
FAR void *dlsym(FAR void *handle, FAR const char *name)
{
#if defined(CONFIG_BUILD_FLAT)
/* In the FLAT build, a shared library is essentially the same as a kernel
* module.
*/
return (FAR void *)modsym(handle, name);
#elif defined(CONFIG_BUILD_PROTECTED)
/* 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
* space and using the kernel symbol table and one residing in user space
* using the user space symbol table.
*
* dlgetsem() is essentially a clone of modsym().
*/
return (FAR void *)dlgetsym(handle, name);
#else /* if defined(CONFIG_BUILD_KERNEL) */
/* The KERNEL build is considerably more complex: In order to be shared,
* the .text portion of the module must be (1) build for PIC/PID operation
* and (2) must like in a shared memory region accessible from all
* processes. The .data/.bss portion of the module must be allocated in
* the user space of each process, but must lie at the same virtual address
* so that it can be referenced from the one copy of the text in the shared
* memory region.
*/
#warning Missing logic
return NULL;
#endif
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}