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dlopen() of a library that is already loaded fails. libelf_insert() rejects a name that is already in the module registry with EEXIST, and dlinsert() passes that straight out, so the second caller gets NULL. POSIX says dlopen() shall return a handle to the object, and there is no way today for two modules to hold the same library at once -- which is what a shared library is for. So dlopen() now takes another reference on a library that is already there, and dlclose() only tears it down when the last handle goes. The count lives in the dlfcn layer rather than in libelf_insert() so that insmod keeps its own behaviour: a second insmod of the same name still fails with EEXIST, which is right for a kernel module. The module name is what makes any of this possible, and a PROTECTED build did not have one. Names were defined for CONFIG_BUILD_FLAT or the kernel side of a split build, on the reasoning that only the kernel needed them, which predates dlopen() being usable from user space. Without a name the user-space copy of libelf cannot recognise a second open of a library, cannot count opens, and cannot make dlclose() mean anything -- two dlopen()s there produce two independent copies of the library and lose track of the first. Names are therefore defined wherever CONFIG_LIBC_DLFCN is, which costs NAME_MAX per loaded module in that configuration. The path no longer has to be copied either. The module name is the basename of the file and libelf_insert() takes it as a const string, so dlinsert() finds it with strrchr() instead of handing a writable duplicate of the whole path to basename(). BUILD_KERNEL is deliberately untouched. dlopen() returns NULL there unconditionally: dlinsert() is a stub, because sharing a library between processes with separate address spaces needs the text in a shared region and the data per process at a matching virtual address, which is a different problem from this one. Built for mps3-an547:picostest with and without CONFIG_LIBC_DLFCN, and for stm32f4discovery:kostest, a PROTECTED configuration, with it enabled. Assisted-by: Claude Opus 5 (1M context) <noreply@anthropic.com> Signed-off-by: Marco Casaroli <marco.casaroli@gmail.com>
82 lines
2.9 KiB
C
82 lines
2.9 KiB
C
/****************************************************************************
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* sched/module/mod_insmod.c
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*
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* SPDX-License-Identifier: Apache-2.0
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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 <errno.h>
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#include <nuttx/module.h>
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#include <nuttx/lib/elf.h>
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#ifdef CONFIG_MODULE
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: insmod
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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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* module into kernel memory and initialize it for use.
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*
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* NOTE: libelf_setsymtab() had to have been called in board-specific OS
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* logic prior to calling this function from application logic (perhaps via
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* boardctl(BOARDIOC_OS_SYMTAB). Otherwise, insmod 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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*
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* filename - Full path to the module binary to be loaded
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* modname - The name that can be used to refer to the module after
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* it has been 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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* module interfaces is returned on success. If insmod() was unable to
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* load the module insmod() will return a NULL handle and the errno
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* variable will be set appropriately.
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*
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****************************************************************************/
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FAR void *insmod(FAR const char *filename, FAR const char *modname)
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{
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/* A duplicate name is an error here, where it has always been.
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* libelf_insert() would take a reference instead, which is what
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* dlopen() wants and insmod() does not.
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*/
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if (libelf_gethandle(modname) != NULL)
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{
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set_errno(EEXIST);
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return NULL;
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}
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return libelf_insert(filename, modname);
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}
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#endif /* CONFIG_MODULE */
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