850a172bac Added lazy FPU stacking and QEMU functional tests for RV64 GNU port (#549)
* add lazy FPU stacking to context save/restore

Save mstatus/sstatus to stack slot 29 and skip floating-point register
save/restore when FS is Off (bits 14:13). This avoids unnecessary FP
context work for threads that do not use the FPU.

- context_save: check FS in nested and first-level interrupt paths
- context_restore: gate FP restore on nested, no-preempt, and preempt paths
- use sstatus when TX_RISCV_SMODE is defined, otherwise mstatus

* add QEMU virt CMake build and automated test runner
Wire the QEMU virt demo into the CMake build system and add a
Python/GDB functional test runner, mirroring the risc-v32/gnu port.
- Add qemu_virt/CMakeLists.txt to build kernel.elf and register the
  check-functional-riscv64 target (requires Python3; skipped if absent)
- Link kernel.elf with --whole-archive so all ThreadX symbols resolve
- Pin _start at 0x80000000 via .text.boot in entry.s and
  KEEP(*(.text.boot)) in link.lds
- Extend demo_threadx.c with fpu_test_val and shorten thread_0 sleep
  for GDB-driven FPU, timer, and preemption checks
- Add test/azrtos_test_tx_gnu_riscv64_qemu.py; verified passing on
  QEMU virt (FPU, timer interrupt, preemption)

* Clean up RV64 PR scope and remove QEMU test integration leftovers

Revert accidental RV64 qemu_virt test/CMake integration changes and keep this branch
focused on lazy FPU context handling only. Also remove unintended TX_RISCV_SMODE-based
mstatus/sstatus save path and align comments/logic to mstatus-only behavior.

* Initialize mstatus.FS in RV64 stack build so new threads start with clean FP state

Slot 29 was left uninitialized while context restore reads it as an FP-live
hint; garbage FS bits could make a new thread inherit the previous thread's
floating-point registers.

* Add RV64 regression test for the FP state of a newly created thread

The test dirties every floating point register, then creates a thread and
checks that the stack builder wrote the mstatus slot and that the new
thread starts with all floating point registers zeroed. It is registered
for RV64 only, since the RV32 stack builder still leaves the slot unwritten.

* Completed the RISC-V64 lazy FPU so the restore side matches the save side

The lazy FPU save in this branch skips the floating-point stores when
mstatus.FS is Off, and records the mstatus it judged that on in frame slot
29. Merged onto current dev, only the save side had that treatment: both
restore paths and the scheduler's interrupt-frame path still reloaded the
FP registers unconditionally, from slots the save had deliberately left
alone. A thread that never touched the FP unit would have had whatever the
frame happened to contain loaded into its registers, and FS driven to
Dirty on the way out.

The guard is added at the three places that consume an interrupt frame:
both paths in _tx_thread_context_restore, and _tx_thread_schedule_loop.
Each reads slot 29 and skips the FP block when FS was Off, which is the
same shape the risc-v32 port already uses.

The solicited path is deliberately left alone. _tx_thread_system_return
saves the callee-saved FP registers unconditionally, so restoring them
unconditionally is consistent; making that pair lazy as well is a separate
change, and risc-v32 is the model for it.

Verified with QEMU on all five configurations:

  risc-v64   96 of 96 passing, five configurations, nothing unlinkable
  risc-v32   95 of 95 passing, five configurations, unchanged
  functional check-functional-riscv64 passes every check

The ninety-sixth test is the one this branch adds. It is load bearing:
seeding stack build with FS = Off instead of Initial makes it fail, and
restoring the seed makes it pass, so it guards the behaviour the rest of
this branch is about rather than passing regardless.

Assisted-by: Claude Code (Opus 5) <noreply@anthropic.com>

---------

Co-authored-by: r <r@r>
Co-authored-by: Frédéric Desbiens <frederic.desbiens@eclipse-foundation.org>
2026-09-09 16:25:28 -04:00
…
2026-06-30 17:31:42 -04:00

Eclipse ThreadX RTOS

This advanced real-time operating system (RTOS) is designed specifically for deeply embedded applications. Among the multiple benefits it provides are advanced scheduling facilities, message passing, interrupt management, and messaging services. Eclipse ThreadX RTOS has many advanced features, including picokernel architecture, preemption threshold, event chaining, and a rich set of system services.

Here are the key features and modules of ThreadX:

ThreadX Key Features

Getting Started

Eclipse ThreadX has been integrated to the semiconductor's SDKs and development environment. You can develop using the tools of choice from STMicroelectronics, NXP, Renesas and Microchip.

We also provide getting started guide and samples using development boards from semiconductors you can build and test with.

See Overview of Eclipse ThreadX RTOS for the high-level overview.

Repository Structure and Usage

Directory layout

.
├── cmake                        # CMakelist files for building the project
├── common                       # Core ThreadX files
├── common_modules               # Core ThreadX module files
├── common_smp                   # Core ThreadX SMP files
├── docs                         # Documentation supplements
├── ports                        # Architecture and compiler specific files. See below for directory breakdown
│   ├── cortex_m7
│   │   ├── iar                  # Example IAR compiler sample project
│   │   │   ├── example build    # IAR workspace and sample project files
│   │   │   ├── inc              # tx_port.h for this architecture
│   │   │   └── src              # Source files for this architecture
│   │   ├── ac6                  # Example ac6/Keil sample project
│   │   ├── gnu                  # Example gnu sample project
│   │   └── ...
│   └── ...
├── ports_modules                # Architecture and compiler specific files for threadX modules
├── ports_smp                    # Architecture and compiler specific files for threadX SMP
├── samples                      # demo_threadx.c
└── utility                      # Test cases and utilities

Branches & Releases

The master branch has the most recent code with all new features and bug fixes. It does not represent the latest General Availability (GA) release of the library. Each official release (preview or GA) will be tagged to mark the commit and push it into the Github releases tab, e.g. v6.2-rel.

When you see xx-xx-xxxx, 6.x or x.x in function header, this means the file is not officially released yet. They will be updated in the next release. See example below.

/**************************************************************************/
/*                                                                        */
/*  FUNCTION                                               RELEASE        */
/*                                                                        */
/*    _tx_initialize_low_level                          Cortex-M23/GNU    */
/*                                                           6.x          */
/*  AUTHOR                                                                */
/*                                                                        */
/*    Scott Larson, Microsoft Corporation                                 */
/*                                                                        */
/*  DESCRIPTION                                                           */
/*                                                                        */
/*    This function is responsible for any low-level processor            */
/*    initialization, including setting up interrupt vectors, setting     */
/*    up a periodic timer interrupt source, saving the system stack       */
/*    pointer for use in ISR processing later, and finding the first      */
/*    available RAM memory address for tx_application_define.             */
/*                                                                        */
/*  INPUT                                                                 */
/*                                                                        */
/*    None                                                                */
/*                                                                        */
/*  OUTPUT                                                                */
/*                                                                        */
/*    None                                                                */
/*                                                                        */
/*  CALLS                                                                 */
/*                                                                        */
/*    None                                                                */
/*                                                                        */
/*  CALLED BY                                                             */
/*                                                                        */
/*    _tx_initialize_kernel_enter           ThreadX entry function        */
/*                                                                        */
/*  RELEASE HISTORY                                                       */
/*                                                                        */
/*    DATE              NAME                      DESCRIPTION             */
/*                                                                        */
/*  09-30-2020      Scott Larson            Initial Version 6.1           */
/*  xx-xx-xxxx      Scott Larson            Include tx_user.h,            */
/*                                            resulting in version 6.x    */
/*                                                                        */
/**************************************************************************/

Supported Architecture Ports

ThreadX

arc_em      cortex_a12        cortex_m0     cortex_r4
arc_hs      cortex_a15        cortex_m23    cortex_r5
arm11       cortex_a17        cortex_m3     cortex_r7
arm9        cortex_a34        cortex_m33
c667x       cortex_a35        cortex_m4
linux       cortex_a5         cortex_m55
risc-v32    cortex_a53        cortex_m7
rxv1        cortex_a55        cortex_m85
rxv2        cortex_a57
rxv3        cortex_a5x
win32       cortex_a65
xtensa      cortex_a65ae
            cortex_a7
            cortex_a72
            cortex_a73
            cortex_a75
            cortex_a76
            cortex_a76ae
            cortex_a77
            cortex_a8
            cortex_a9

ThreadX Modules

Eclipse ThreadX Modules component provides an infrastructure for applications to dynamically load modules that are built separately from the resident portion of the application.

cortex_a35
cortex_a35_smp
cortex_a7
cortex_m0+
cortex_m23
cortex_m3
cortex_m33
cortex_m4
cortex_m7
cortex_r4
rxv2

ThreadX SMP

Eclipse ThreadX SMP is a high-performance real-time SMP kernel designed specifically for embedded applications.

arc_hs_smp
cortex_a34_smp
cortex_a35_smp
cortex_a53_smp
cortex_a55_smp
cortex_a57_smp
cortex_a5x_smp
cortex_a5_smp
cortex_a65ae_smp
cortex_a65_smp
cortex_a72_smp
cortex_a73_smp
cortex_a75_smp
cortex_a76ae_smp
cortex_a76_smp
cortex_a77_smp
cortex_a78_smp
cortex_a7_smp
cortex_a9_smp
linux

Adaptation layer for ThreadX

ThreadX is an advanced real-time operating system (RTOS) designed specifically for deeply embedded applications. To help ease application migration to ThreadX RTOS, Eclipse ThreadX provides adaption layers for various legacy RTOS APIs (FreeRTOS, POSIX, OSEK, etc.).

Component dependencies

The main components of ThreadX RTOS are each provided in their own repository, but there are dependencies between them, as shown in the following graph. This is important to understand when setting up your builds.

dependency graph

You will have to take the dependency graph above into account when building anything other than ThreadX itself.

Building and using the library

Instruction for building the ThreadX as static library using Arm GNU Toolchain and CMake. If you are using toolchain and IDE from semiconductor, you might follow its own instructions to use ThreadX RTOS components as explained in the Getting Started section.

  1. Install the following tools:

  2. Cloning the repo

    $ git clone https://github.com/eclipse-threadx/threadx.git
    
  3. Define the features and addons you need in tx_user.h and build together with the component source code. You can refer to tx_user_sample.h as an example.

  4. Building as a static library

    Each component of ThreadX RTOS comes with a composable CMake-based build system that supports many different MCUs and host systems. Integrating any of these components into your device app code is as simple as adding a git submodule and then including it in your build using the CMake add_subdirectory().

    While the typical usage pattern is to include ThreadX into your device code source tree to be built & linked with your code, you can compile this project as a standalone static library to confirm your build is set up correctly.

    An example of building the library for Cortex-M4:

    $ cmake -Bbuild -GNinja -DCMAKE_TOOLCHAIN_FILE=cmake/cortex_m4.cmake .
    
    $ cmake --build ./build
    

Licensing

License terms for using Eclipse ThreadX are defined in the LICENSE.txt file of this repo. Please refer to this file for all definitive licensing information for all content, incl. the history of this repo.

Resources

The following are references to additional ThreadX RTOS resources:

You can also check previous questions or ask new ones on StackOverflow using the threadx-rtos and threadx tags.

Security

Eclipse ThreadX provides OEMs with components to secure communication and to create code and data isolation using underlying MCU/MPU hardware protection mechanisms. It is ultimately the responsibility of the device builder to ensure the device fully meets the evolving security requirements associated with its specific use case.

Contribution

Please follow the instructions provided in the CONTRIBUTING.md for the corresponding repository.

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