Apache NuttX is a mature, real-time embedded operating system (RTOS) https://nuttx.apache.org/
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liang.huang bdfa666f3e arch/risc-v: fix stale ustkptr used for backtrace in kernel stack mode
xcp.ustkptr is only assigned once in up_initial_state() when a task is
created and, since the syscall fast path was optimized in
e6973c764c, is never updated afterwards. up_backtrace() used
"ustkptr != NULL" to decide whether a task is currently blocked
inside a syscall, and *(ustkptr + 1) as the frame pointer to resume
tracing from. Since ustkptr is now a dead value fixed at task
creation time, the check is always true and the "frame pointer" it
derives points at stale data near the initial stack top, unrelated
to where the task is actually blocked.

Use rtcb->flags & TCB_FLAG_SYSCALL together with xcp.sregs, which
dispatch_syscall() maintains precisely across the entire syscall
execution window (including any nested context switches caused by
blocking), to locate the frame pointer/return address saved at
syscall entry instead.

Signed-off-by: liang.huang <liang.huang@houmo.ai>
2026-08-03 20:58:32 +08:00
.github !arch/stm32: move stm32l1 and finalize the directory split 2026-07-03 10:27:27 +08:00
arch arch/risc-v: fix stale ustkptr used for backtrace in kernel stack mode 2026-08-03 20:58:32 +08:00
audio drivers/efuse/efuse: Drivers Registered With World Write Permissions(Part 1) 2026-08-03 17:23:22 +08:00
binfmt fs/binfmt: Enforce POSIX execute permissions prior to binary load 2026-06-17 17:11:07 +08:00
boards boards/raspberrypi-4b: Fix nxinit configuration SD issues 2026-08-03 20:57:47 +08:00
cmake !boards: enforce secure ROMFS passwd and TEA key setup 2026-07-06 12:04:07 -03:00
crypto drivers/efuse/efuse: Drivers Registered With World Write Permissions(Part 1) 2026-08-03 17:23:22 +08:00
Documentation docs/raspberrypi-4b: Documentation about the SD card updated 2026-08-03 20:57:47 +08:00
drivers drivers/: Multiple Drivers Are Registered With World Writable Part 3 2026-08-03 17:23:22 +08:00
dummy build: add initial cmake build system 2023-07-08 13:50:48 +08:00
fs drivers/: Multiple Drivers Are Registered With World Writable - Part 2 2026-08-03 17:23:22 +08:00
graphics drivers/: Multiple Drivers Are Registered With World Writable - Part 2 2026-08-03 17:23:22 +08:00
include drivers/crypto: add Microchip RNG90 driver 2026-08-03 17:23:22 +08:00
libs libc/stream: Check lowout bounds before access 2026-07-06 19:55:11 +08:00
mm mm/gran: reject pools with too many granules 2026-07-03 10:32:15 +08:00
net fix(net/igmp): restore General Query handling broken by pointer compare 2026-08-03 17:22:28 +08:00
openamp openamp: fix CMake dcache option 2026-05-10 15:03:24 +02:00
pass1 Makefile: Remove make depend files by make distclean 2026-02-16 16:27:57 +01:00
sched sched/misc/assert: Add CONFIG_SCHED_DUMP_TASKS and CONFIG_SCHED_DUMP_STACK 2026-07-04 13:29:32 -04:00
syscall syscall: fcntl param3 type to uintptr_t 2026-04-27 12:01:55 -03:00
tools !boards: enforce secure ROMFS passwd and TEA key setup 2026-07-06 12:04:07 -03:00
video video: ensure video library is non-empty 2026-05-08 19:51:39 +08:00
wireless drivers/: Multiple Drivers Are Registered With World Writable - Part 2 2026-08-03 17:23:22 +08:00
.asf.yaml github: master branch protection tune. 2025-05-07 18:37:13 -05:00
.codespell-ignore-lines !boards: Remove NSH_ARCHINIT and board_app_initialize 2026-05-02 18:36:46 +08:00
.codespellrc arch/sim: replace macOS C++ constructor runtime hack with post-link patch 2026-05-19 07:08:55 -03:00
.editorconfig .editorconfig: fix character encoding property specification 2025-11-28 19:12:13 +08:00
.gitignore git: Specify multiple build directories in .gitignore. 2026-05-20 03:06:58 +08:00
.gitmessage docs/contributing: Add a commit message template 2025-06-03 17:33:24 +08:00
.pre-commit-config.yaml pre-commit: enable codespell checks 2025-05-05 12:34:39 +08:00
.yamllint feat: add a GitHub action to lint the YAML files 2020-12-15 09:52:04 -06:00
AUTHORS AUTHORS: add Eren Terzioglu 2026-05-20 15:17:00 +08:00
CMakeLists.txt tools/rust: Fix aarch64 NuttX Rust target specs 2026-05-29 10:25:10 +02:00
CONTRIBUTING.md docs: Fix typos, formatting, and numbering in README.md and CONTRIBUTING.md. 2026-03-23 12:05:24 +01:00
INVIOLABLES.md INVIOLABLES.md: Fix a simple alignment and change occurrences of Nuttx 2020-09-03 01:33:05 +08:00
Kconfig sched/misc/assert: Add CONFIG_SCHED_DUMP_TASKS and CONFIG_SCHED_DUMP_STACK 2026-07-04 13:29:32 -04:00
LICENSE !arch/stm32: move stm32l1 and finalize the directory split 2026-07-03 10:27:27 +08:00
Makefile !boards: enforce secure ROMFS passwd and TEA key setup 2026-07-06 12:04:07 -03:00
NOTICE Remove the double blank line from source files 2022-02-20 20:10:14 +01:00
README.md docs: Fix typos, formatting, and numbering in README.md and CONTRIBUTING.md. 2026-03-23 12:05:24 +01:00
ReleaseNotes Documentation: move ReleaseNotes 2023-09-26 20:41:00 +08:00

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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.