nuttx/libs
Neale Ferguson 5d7f2fdf16 Fix loading of ET_DYN type of shared objects
* build-globals.sh
  - Only look in the nuttx for external symbols used when loading
    dynamic shared objects

* include/elf64.h
  - Correct the type of fields in the Elf64_Phdr structure

* libs/libc/dlfcn/lib_dlclose.c
  - Distinguish between ET_DYN and other objects as the former
    has both text and data in a single allocation to reserve
    GOT offsets

* libs/libc/dlfcn/lib_dlopen.c
  - Code formatting

* libs/libc/modlib/modlib_bind.c
  - Distinguish between relocation entry sizes by section type
  - Handle RELA style relocations

* libs/libc/modlib/modlib_globals.S
  - Formatting fixes
  - Symbols should not be weak - they exist or they don't

* include/nuttx/lib/modlib.h
  - Add an inidcator to module_s to distinguish between ET_DYN and other

* libs/libc/modlib/modlib_load.c
  - ET_DYN objects need to keep the relative displacement between the text
    and data sections due to GOT references from the former to the latter.
    This also implies that linking may require modification from the default
    for the shared objects being produced. For example, default alignment may
    mean nearly 64K of wasted space.

* libs/libc/modlib/modlib_unload.c
  sched/module/mod_rmmod.c
  - Distingusih between freeing of ET_DYN storage and other as the former
    is a single allocation.

* libs/libc/modlib/mod_insmod.c
  - Cater for ET_DYN objects having init and preinit sections
2023-09-20 09:35:28 -04:00
..
libc Fix loading of ET_DYN type of shared objects 2023-09-20 09:35:28 -04:00
libdsp build: add initial cmake build system 2023-07-08 13:50:48 +08:00
libm nxstyle: cleanup UTF-8 Unicode to ASCII 2023-09-18 11:54:17 -04:00
libnx cmake:support nxlib cmake compilation 2023-08-10 23:18:56 +08:00
libxx libs/libxx/libcxx: fix CI compilation issue reported on MACOS 2023-09-19 01:17:17 +08:00
CMakeLists.txt build: add initial cmake build system 2023-07-08 13:50:48 +08:00
README.txt libs/README.txt: Fix a typo 2020-01-27 08:46:46 +01:00

README
======

This directory holds NuttX libraries.  Libraries in NuttX are very special
creatures.  They have these properties:

1. They can be shared by both application logic and logic within the OS when
   using the FLAT build.

2. But in PROTECTED and KERNEL modes, they must be built differently:  The
   copies used by applications and the OS cannot be the same.  Rather,
   separate versions of libraries must be built for the kernel and for
   applications.

3. When used by the OS, some special care must be taken to assure that the
   OS logic does not disrupt the user's errno value and that the OS does
   not create inappropriate cancellation points.

   For example, sem_wait() is both a cancellation point and modifies the
   errno value.  So within the FLAT build and without kernel version for
   the PROTECTED and KERNEL builds, the special internal OS interface
   nxsem_wait() must be used.  Within libraries, the macro _SEM_WAIT()
   (as defined in include/nuttx/semaphore.h) is used instead.  The
   definition of this macro accounts for the different usage environments.

NOTE:  The libraries under libs/ build differently from other NuttX
components:  There are no build-related files in the libs/ directory; it
is simply a container for other well-known, individual library directories.
The upper level Makefile logic is aware of the libraries within the libs/
container.

The only real function of the libs/ directory is to prevent the top-level
directory from becoming cluttered with individual libraries.