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nuttx/libc/dllfcn/lib_dlopen.c

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/****************************************************************************
* libc/dllfcn/lib_dlopen.c
*
* Copyright (C) 2017 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <gnutt@nuttx.org>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* 3. Neither the name NuttX nor the names of its contributors may be
* used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <stdlib.h>
#include <string.h>
#include <libgen.h>
#include <dllfcn.h>
#include <assert.h>
#include <errno.h>
#include <nuttx/module.h>
#include <nuttx/lib/modlib.h>
#include "libc.h"
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: dldump_loadinfo
****************************************************************************/
#ifdef CONFIG_BUILD_PROTECTED
#if defined(CONFIG_DEBUG_INFO) && defined(CONFIG_DEBUG_BINFMT)
static void dldump_loadinfo(FAR struct mod_loadinfo_s *loadinfo)
{
int i;
binfo("LOAD_INFO:\n");
binfo(" textalloc: %08lx\n", (long)loadinfo->textalloc);
binfo(" datastart: %08lx\n", (long)loadinfo->datastart);
binfo(" textsize: %ld\n", (long)loadinfo->textsize);
binfo(" datasize: %ld\n", (long)loadinfo->datasize);
binfo(" filelen: %ld\n", (long)loadinfo->filelen);
binfo(" filfd: %d\n", loadinfo->filfd);
binfo(" symtabidx: %d\n", loadinfo->symtabidx);
binfo(" strtabidx: %d\n", loadinfo->strtabidx);
binfo("ELF Header:\n");
binfo(" e_ident: %02x %02x %02x %02x\n",
loadinfo->ehdr.e_ident[0], loadinfo->ehdr.e_ident[1],
loadinfo->ehdr.e_ident[2], loadinfo->ehdr.e_ident[3]);
binfo(" e_type: %04x\n", loadinfo->ehdr.e_type);
binfo(" e_machine: %04x\n", loadinfo->ehdr.e_machine);
binfo(" e_version: %08x\n", loadinfo->ehdr.e_version);
binfo(" e_entry: %08lx\n", (long)loadinfo->ehdr.e_entry);
binfo(" e_phoff: %d\n", loadinfo->ehdr.e_phoff);
binfo(" e_shoff: %d\n", loadinfo->ehdr.e_shoff);
binfo(" e_flags: %08x\n" , loadinfo->ehdr.e_flags);
binfo(" e_ehsize: %d\n", loadinfo->ehdr.e_ehsize);
binfo(" e_phentsize: %d\n", loadinfo->ehdr.e_phentsize);
binfo(" e_phnum: %d\n", loadinfo->ehdr.e_phnum);
binfo(" e_shentsize: %d\n", loadinfo->ehdr.e_shentsize);
binfo(" e_shnum: %d\n", loadinfo->ehdr.e_shnum);
binfo(" e_shstrndx: %d\n", loadinfo->ehdr.e_shstrndx);
if (loadinfo->shdr && loadinfo->ehdr.e_shnum > 0)
{
for (i = 0; i < loadinfo->ehdr.e_shnum; i++)
{
FAR Elf32_Shdr *shdr = &loadinfo->shdr[i];
binfo("Sections %d:\n", i);
binfo(" sh_name: %08x\n", shdr->sh_name);
binfo(" sh_type: %08x\n", shdr->sh_type);
binfo(" sh_flags: %08x\n", shdr->sh_flags);
binfo(" sh_addr: %08x\n", shdr->sh_addr);
binfo(" sh_offset: %d\n", shdr->sh_offset);
binfo(" sh_size: %d\n", shdr->sh_size);
binfo(" sh_link: %d\n", shdr->sh_link);
binfo(" sh_info: %d\n", shdr->sh_info);
binfo(" sh_addralign: %d\n", shdr->sh_addralign);
binfo(" sh_entsize: %d\n", shdr->sh_entsize);
}
}
}
#else
# define dldump_loadinfo(i)
#endif
#endif
/****************************************************************************
* Name: dldump_initializer
****************************************************************************/
#ifdef CONFIG_BUILD_PROTECTED
#ifdef CONFIG_MODLIB_DUMPBUFFER
static void dldump_initializer(mod_initializer_t initializer,
FAR struct mod_loadinfo_s *loadinfo)
{
modlib_dumpbuffer("Initializer code", (FAR const uint8_t *)initializer,
MIN(loadinfo->textsize - loadinfo->ehdr.e_entry, 512));
}
#else
# define dldump_initializer(b,l)
#endif
#endif
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: dlinsert
*
* Description:
* Verify that the file is an ELF module binary and, if so, load the
* shared library into user memory and initialize it for use.
*
* NOTE: modlib_setsymtab() had to have been called by application logic
* logic prior to calling this. Otherwise, dlinsert will be unable to
* resolve symbols in the OS module.
*
* Input Parameters:
* filename - Full path to the shared library file to be loaded
*
* Returned Value:
* A non-NULL module handle that can be used on subsequent calls to other
* shared library interfaces is returned on success. If insmod() was
* unable to load the module insmod() will return a NULL handle and the
* errno variable will be set appropriately.
*
****************************************************************************/
#ifdef CONFIG_BUILD_PROTECTED
static inline FAR void *dlinsert(FAR const char *filename)
{
struct mod_loadinfo_s loadinfo;
FAR struct module_s *modp;
mod_initializer_t initializer;
int ret;
binfo("Loading file: %s\n", filename);
/* Get exclusive access to the module registry */
modlib_registry_lock();
/* Initialize the ELF library to load the program binary. */
ret = modlib_initialize(filename, &loadinfo);
dldump_loadinfo(&loadinfo);
if (ret != 0)
{
serr("ERROR: Failed to initialize to load module: %d\n", ret);
goto errout_with_lock;
}
/* Allocate a module registry entry to hold the module data */
modp = (FAR struct module_s *)lib_zalloc(sizeof(struct module_s));
if (ret != 0)
{
binfo("Failed to initialize for load of ELF program: %d\n", ret);
goto errout_with_loadinfo;
}
/* Load the program binary */
ret = modlib_load(&loadinfo);
dldump_loadinfo(&loadinfo);
if (ret != 0)
{
binfo("Failed to load ELF program binary: %d\n", ret);
goto errout_with_registry_entry;
}
/* Bind the program to the kernel symbol table */
ret = modlib_bind(modp, &loadinfo);
if (ret != 0)
{
binfo("Failed to bind symbols program binary: %d\n", ret);
goto errout_with_load;
}
/* Save the load information */
modp->alloc = (FAR void *)loadinfo.textalloc;
#if defined(CONFIG_FS_PROCFS) && !defined(CONFIG_FS_PROCFS_EXCLUDE_MODULE)
modp->textsize = loadinfo.textsize;
modp->datasize = loadinfo.datasize;
#endif
/* Get the module initializer entry point */
initializer = (mod_initializer_t)(loadinfo.textalloc + loadinfo.ehdr.e_entry);
#if defined(CONFIG_FS_PROCFS) && !defined(CONFIG_FS_PROCFS_EXCLUDE_MODULE)
modp->initializer = initializer;
#endif
dldump_initializer(initializer, &loadinfo);
/* Call the module initializer */
ret = initializer(&modp->modinfo);
if (ret < 0)
{
binfo("Failed to initialize the module: %d\n", ret);
goto errout_with_load;
}
/* Add the new module entry to the registry */
modlib_registry_add(modp);
modlib_uninitialize(&loadinfo);
modlib_registry_unlock();
return (FAR void *)modp;
errout_with_load:
modlib_unload(&loadinfo);
(void)modlib_undepend(modp);
errout_with_registry_entry:
lib_free(modp);
errout_with_loadinfo:
modlib_uninitialize(&loadinfo);
errout_with_lock:
modlib_registry_unlock();
set_errno(-ret);
return NULL;
}
#endif
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: dlopen
*
* Description:
* dlopen() makes an executable object file specified by file available to
* the calling program. The class of files eligible for this operation and
* the manner of their construction are specified by the implementation,
* though typically such files are executable objects such as shared
* libraries, relocatable files or programs. Note that some implementations
* permit the construction of dependencies between such objects that are
* embedded within files. In such cases, a dlopen() operation will load
* such dependencies in addition to the object referenced by file.
* Implementations may also impose specific constraints on the construction
* of programs that can employ dlopen() and its related services.
*
* If a file is specified in multiple dlopen() invocations, mode is
* interpreted at each invocation. Note, however, that once RTLD_NOW has
* been specified all relocations will have been completed rendering
* further RTLD_NOW operations redundant and any further RTLD_LAZY
* operations irrelevant. Similarly note that once RTLD_GLOBAL has been
* specified the object will maintain the RTLD_GLOBAL status regardless
* of any previous or future specification of RTLD_LOCAL, so long as the
* object remains in the address space (see dlclose()).
*
* Symbols introduced into a program through calls to dlopen() may be
* used in relocation activities. Symbols so introduced may duplicate
* symbols already defined by the program or previous dlopen()
* operations. To resolve the ambiguities such a situation might
* present, the resolution of a symbol reference to symbol definition is
* based on a symbol resolution order. Two such resolution orders are
* defined: load or dependency ordering. Load order establishes an
* ordering among symbol definitions, such that the definition first
* loaded (including definitions from the image file and any dependent
* objects loaded with it) has priority over objects added later (via
* dlopen()). Load ordering is used in relocation processing. Dependency
* ordering uses a breadth-first order starting with a given object,
* then all of its dependencies, then any dependents of those, iterating
* until all dependencies are satisfied. With the exception of the global
* symbol object obtained via a dlopen() operation on a file of 0,
* dependency ordering is used by the dlsym() function. Load ordering is
* used in dlsym() operations upon the global symbol object.
*
* When an object is first made accessible via dlopen() it and its
* dependent objects are added in dependency order. Once all the objects
* are added, relocations are performed using load order. Note that if an
* object or its dependencies had been previously loaded, the load and
* dependency orders may yield different resolutions.
*
* The symbols introduced by dlopen() operations, and available through
* dlsym() are at a minimum those which are exported as symbols of global
* scope by the object. Typically such symbols will be those that were
* specified in (for example) C source code as having extern linkage. The
* precise manner in which an implementation constructs the set of
* exported symbols for a dlopen() object is specified by that
* implementation.
*
* Input Parameters:
* file - Used to construct a pathname to the object file. If file
* contains a slash character, the file argument is used as the
* pathname for the file. Otherwise, file is used in an
* implementation-dependent manner to yield a pathname.
*
* If the value of file is 0, dlopen() provides a handle on a
* global symbol object. This object provides access to the symbols
* from an ordered set of objects consisting of the original
* program image file, together with any objects loaded at program
* startup as specified by that process image file (for example,
* shared libraries), and the set of objects loaded using a
* dlopen() operation together with the RTLD_GLOBAL flag. As the
* latter set of objects can change during execution, the set
* identified by handle can also change dynamically.
*
* Only a single copy of an object file is brought into the address
* space, even if dlopen() is invoked multiple times in reference
* to the file, and even if different pathnames are used to
* reference the file.
* mode - Describes how dlopen() will operate upon file with respect to
* the processing of relocations and the scope of visibility of the
* symbols provided within file. When an object is brought into the
* address space of a process, it may contain references to symbols
* whose addresses are not known until the object is loaded. These
* references must be relocated before the symbols can be accessed.
* The mode parameter governs when these relocations take place.
* See definitions above for values of the mode parameter:.
*
* Returned Value:
* A successful dlopen() returns a handle which the caller may use on
* subsequent calls to dlsym() and dlclose(). The value of this handle
* should not be interpreted in any way by the caller.
*
* If file cannot be found, cannot be opened for reading, is not of an
* appropriate object format for processing by dlopen(), or if an error
* occurs during the process of loading file or relocating its symbolic
* references, dlopen() will return NULL. More detailed diagnostic
* information will be available through dlerror().
*
* Reference: OpenGroup.org
*
****************************************************************************/
FAR void *dlopen(FAR const char *file, int mode)
{
#if defined(CONFIG_BUILD_FLAT)
FAR void *handle;
FAR char *name;
DEBUGASSERT(file != NULL);
/* In the FLAT build, a shared library is essentially the same as a kernel
* module.
*
* REVIST: Missing functionality:
* - No automatic binding of symbols
* - No dependencies
* - mode is ignored.
*/
/* Use the basename of the file as the module name.
* REVISIT: This places an non-standard restriction. We cannot install
* two modules of the same name event though they lie in different
* directories.
*/
name = strdup(file);
if (name == NULL)
{
return NULL;
}
/* Then install the file using the basename of the file as the module name. */
handle = insmod(file, basename(name));
free(name);
return handle;
#elif defined(CONFIG_BUILD_PROTECTED)
/* The PROTECTED build is equivalent to the FLAT build EXCEPT that there
* 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.
*
* dlinsert() is essentially a clone of insmod().
*/
return dlinsert(file);
#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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