mirror of
https://github.com/apache/nuttx.git
synced 2026-08-11 15:35:10 +00:00
e47be608d5
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> |
||
|---|---|---|
| .. | ||
| aio | ||
| assert | ||
| audio | ||
| builtin | ||
| ctype | ||
| dirent | ||
| dlfcn | ||
| elf | ||
| errno | ||
| eventfd | ||
| fdt | ||
| fixedmath | ||
| gdbstub | ||
| gnssutils | ||
| grp | ||
| hex2bin | ||
| inttypes | ||
| libgen | ||
| locale | ||
| lzf | ||
| machine | ||
| misc | ||
| net | ||
| netdb | ||
| obstack | ||
| pthread | ||
| pwd | ||
| queue | ||
| regex | ||
| sched | ||
| search | ||
| semaphore | ||
| signal | ||
| spawn | ||
| stdio | ||
| stdlib | ||
| stream | ||
| string | ||
| symtab | ||
| syslog | ||
| termios | ||
| time | ||
| tls | ||
| uio | ||
| unistd | ||
| userfs | ||
| uuid | ||
| wchar | ||
| wctype | ||
| wqueue | ||
| zoneinfo | ||
| .gitignore | ||
| CMakeLists.txt | ||
| Kconfig | ||
| libc.csv | ||
| libc.h | ||
| limits_check.c | ||
| Makefile | ||