baeedc5009
mmu_write_ttbr0() writes TTBR0_EL1 and then invalidates the TLB. A write to TTBR0_EL1 takes effect only at the next context synchronization event, so until the ISB at the end of the invalidation, a table walk can still use the old table. The instruction fetches of the invalidation sequence itself do such walks. An entry that they cache after the TLBI completes stays valid: walk cache entries are not tagged with the table base, and the kernel and every process use ASID 0. A kernel build then translates a user address of the new process through a level 0 entry of the old table, and gets a level 1 translation fault. Under QEMU with HVF on Apple silicon this happens on every boot of qemu-armv8a:knsh: up_addrenv_va_to_pa() fails for the first user buffer, and virtio gets a descriptor with address 0. TCG has no walk caches, so it does not show the problem. Add an ISB after the write, as the Arm ARM sequence for a TTBR change without an ASID change requires: write, ISB, TLBI, DSB, ISB. Assisted-by: Claude Code:claude-opus-5-5 Signed-off-by: Marco Casaroli <marco.casaroli@gmail.com> |
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| 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 | ||
| .mcp.json | ||
| .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.