ac7b5f5218
A SIGEV_THREAD notification -- from mq_notify() or timer_create() -- runs its callback on a shared signal-notification work queue, not in the registering task. That worker carries no FDPIC data base, so a module's callback reaches it with the wrong base and cannot touch its own globals. This is unlike every other callback entry point, where the callback runs in a task that inherited the module's data space and resolving the code address is enough. The base is knowable exactly once, at registration, when the call is still in the module's own context: capture it there with fdpic_base() into the persisted work structure (mq's ntwork, the timer's pt_work). At send or expiry the descriptor is resolved to its code address -- a plain memory read that needs no base -- and stored in work->func. The worker, seeing a non-zero base, installs it in the FDPIC register around the call and restores it after; a zero base, which is every non-module callback, takes the direct path unchanged. fdpic_base() exposes the test fdpic_callback() already makes internally -- whether the caller is a module -- for a site that has to decide before it stores a pointer somewhere the register will no longer be correct. fdpic_invoke() is the install-call-restore, in the same ARM-thumb inline asm as the rest of fdpic.h. It saves the register on the stack and keeps the push 8-byte aligned, and pins the argument in r0, so it asks the allocator for only two free registers -- enough on builds that also reserve a frame pointer. It is safe against preemption: the FDPIC register is REG_PIC in the saved context, preserved across a context switch, and base firmware reserves it so no interrupt handler disturbs it. A context switch or interrupt while the callback runs therefore keeps the module's base. Verified with CONFIG_SIG_EVTHREAD on two ARM cores: an RP2350 (Cortex-M33, armv8-m) on hardware and mps2-an500 (Cortex-M7, armv7e-m) under QEMU. On each a module's mq_notify and timer_create SIGEV_THREAD callbacks run on the worker and write a distinctive value into a module global, proving the base was installed. Removing just the register install makes the same callback HardFault the board, confirming it is load-bearing. 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.