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Documentation/components/fdpic.rst covers what someone building or loading an FDPIC module needs: how the format works and what the loader does with it, how it differs from NXFLAT and from the ELF loader's own PIC/XIP path, what the target and toolchain have to provide, how to build a module, a shared library and a C++ module, and what a firmware entry point must do to accept a module callback. The comparison is the part worth stating plainly, because two of the three properties are shared. All three formats run position-independent code from flash with no MMU and give several instances of one module a shared .text with private .data. NXFLAT needs its own tools and cannot export symbols, so it has no shared libraries. ELF PIC needs no extra tools at all, but one base register per task means a shared object is loaded as a single allocation -- its text cannot stay in flash -- and there is no DT_NEEDED walk. FDPIC costs an arm-uclinuxfdpiceabi linker and buys a pointer that carries its own data base, which is what makes shared libraries and callbacks on a thread the module never created possible. The reference material at the end is the part that is expensive to rediscover: the FDPIC marker being in EI_OSABI rather than e_flags, the three relocation types that survive a static link, why both relocation tables are bound eagerly, why .rofixup is skipped, and the two binfmt contract details that fail as a panic or a bare -EINVAL. Also adds the fdpic and reject sections to the xipfs test suite document, which apps/testing/fs/xipfs grows in the matching apps change. Assisted-by: Claude Code:claude-opus-5 Signed-off-by: Marco Casaroli <marco.casaroli@gmail.com> |
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| .github | ||
| arch | ||
| audio | ||
| binfmt | ||
| boards | ||
| cmake | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| dummy | ||
| fs | ||
| graphics | ||
| include | ||
| libs | ||
| mm | ||
| net | ||
| openamp | ||
| pass1 | ||
| sched | ||
| syscall | ||
| tools | ||
| video | ||
| wireless | ||
| .asf.yaml | ||
| .codespell-ignore-lines | ||
| .codespellrc | ||
| .editorconfig | ||
| .gitignore | ||
| .gitmessage | ||
| .pre-commit-config.yaml | ||
| .yamllint | ||
| AUTHORS | ||
| CMakeLists.txt | ||
| CONTRIBUTING.md | ||
| INVIOLABLES.md | ||
| Kconfig | ||
| LICENSE | ||
| Makefile | ||
| NOTICE | ||
| README.md | ||
| ReleaseNotes | ||
Apache NuttX is a real-time operating system (RTOS) with an emphasis on standards compliance and small footprint. Scalable from 8-bit to 64-bit microcontroller environments, the primary governing standards in NuttX are POSIX and ANSI standards. Additional standard APIs from Unix and other common RTOSs (such as VxWorks) are adopted for functionality not available under these standards, or for functionality that is not appropriate for deeply-embedded environments (such as fork()).
For brevity, many parts of the documentation will refer to Apache NuttX as simply NuttX.
Getting Started
First time on NuttX? Read the Getting Started guide! If you don't have a board available, NuttX has its own simulator that you can run on terminal.
Documentation
You can find the current NuttX documentation on the Documentation Page.
Alternatively, you can build the documentation yourself by following the Documentation Build Instructions.
The old NuttX documentation is still available in the Apache wiki.
Supported Boards
NuttX supports a wide variety of platforms. See the full list on the Supported Platforms page.
Contributing
If you wish to contribute to the NuttX project, read the Contributing guidelines for information on Git usage, coding standard, workflow and the NuttX principles.
License
The code in this repository is under either the Apache 2 license, or a license compatible with the Apache 2 license. See the License Page for more information.