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QNX Software Development Platform
QNX SDP is a cross-compiling and debugging environment, including an IDE and command-line tools, for building binary images and programs for target boards running the QNX OS 8.0.
OS Components & Operations
Building Embedded Systems
The Building Embedded Systems guide is intended for developers who are developing or building BSPs for QNX OS embedded systems.
Kernel Callouts
Kernel callouts are standalone pieces of code (or code fragments) that the kernel uses to perform hardware-specific functions. These callouts don't need to be statically linked to the kernel.
Kernel callout categories
The startup library provides kernel callouts that look after different categories of tasks. You can use these callouts as models when you write your own.
Kernel debug
The kernel uses the debug callouts when it needs to print out some internal debugging information or encounters a fault.

QNX Momentics IDE User's Guide
This User's Guide describes version 8.0 of the Integrated Development Environment (IDE) that's part of the QNX Tool Suite.
QNX Software Development Platform
QNX SDP is a cross-compiling and debugging environment, including an IDE and command-line tools, for building binary images and programs for target boards running the QNX OS 8.0.
- Quickstart Guide
- System Architecture
  The System Architecture guide accompanies the QNX OS and is intended for both application developers and end-users.
- OS Components & Operations
  - Boot Optimization Guide
    The Boot Optimization Guide describes techniques you can use to reduce the time from your board's initial power on until you have a fully functional QNX system running on the board.
  - Building Embedded Systems
    The Building Embedded Systems guide is intended for developers who are developing or building BSPs for QNX OS embedded systems.
    - Overview
      QNX systems are built from the QNX OS standard release components, the architecture- and board-specific files provided in QNX BSPs, and customer and third-party components.
    - Working with QNX BSPs
      Before you attempt to write a new BSP or modify an existing one, it is helpful to know how to use a BSP.
    - Initial Program Loaders (IPLs)
      IPLs first set up the minimum environment needed to execute their compiled C code, then find the OS image and load it into memory, and then jump to the QNX startup code.
    - Startup Programs
      The first program to run in a bootable OS image is the startup program; it completes the system configuration, then launches the OS kernel.
    - Kernel Callouts
      Kernel callouts are standalone pieces of code (or code fragments) that the kernel uses to perform hardware-specific functions. These callouts don't need to be statically linked to the kernel.
      - Kernel callout categories
        The startup library provides kernel callouts that look after different categories of tasks. You can use these callouts as models when you write your own.
        Kernel debug
        The kernel uses the debug callouts when it needs to print out some internal debugging information or encounters a fault.
        Interrupt controller
        The interrupt controller interface includes kernel callouts and stubs.
        Timer and clock
        The kernel uses the timer callouts to work with the hardware timer (i.e., the timer/counter chip).
        System reboot
        The kernel invokes the reboot() callout to reboot the system.
        Cache control
        The cache controller circuitry in your system determines whether you need to provide a callout for the kernel to interface to the cache controller.
        Custom
        You can use the custom() callout to define a function to be invoked synchronously when a kernel call with the value __KER_SYS_CUSTOM (defined in <sys/kercalls.h>) is invoked by a process.
      - Writing a kernel callout
        If your hardware platform isn't supported by the kernel callouts in the startup library, or by any of the available board-specific kernel callouts, you will need to write your own callout.
    - System Page
      The system page contains essential information about the system, including the system page's size, information about the hardware platform (including IRQs and the CPUs), the cache size, and the location of kernel callouts in memory.
    - OS Images
      OS images are files that contains the OS, your executables, and any data files that might be related to your programs.
    - OS Image Buildfiles
      You can edit OS image buildfiles to configure OS images.
    - IPL Library
      The IPL library contains a set of routines for building a custom IPL.
    - Startup Library
      The startup library contains a rich set of routines ranging from high-level functions called by main() to utility functions for performing specific startup tasks.
    - Debugging QNX Embedded Systems
      The microkernel architecture of QNX OS means that debugging QNX embedded systems can be different from debugging other embedded systems.
    - Sample Buildfiles
      This appendix contains sample buildfiles that you can modify to support your hardware platform and your implementation requirements.
    - Glossary
  - Customizing a BSP
    While QNX provides Board Support Packages (BSPs) for many common platforms and their individual variants, in some cases, you need a BSP for a board that QNX does not provide. If this is the case, you can modify a QNX BSP or develop your own.
  - Device Publishers Developer's Guide
  - High Availability Framework Developer's Guide
  - High-Performance Networking Stack (io-sock) User's Guide
    This guide contains instructions for implementing and using the QNX OS High-Performance Networking Stack and its manager, io-sock.
  - PCI Server User's Guide
  - Performance Tuning User's Guide
  - QNX Filesystem for Safety User's Guide
  - SMMUMAN User's Guide
  - System Analysis Toolkit (SAT) User's Guide
  - Technotes
  - User's Guide
    The QNX OS User's Guide is intended for all users of a QNX OS system, from system administrators to end users.
- Graphics
- Programming
- System Security Guide
  The QNX System Security Guide is intended for both system integrators who are responsible for the security of a QNX OS system and developers who want to create a QNX OS resource manager free from vulnerabilities.
- Utilities & Libraries
- Migrating to QNX OS 8.0
QNX Software in the Cloud
QNX Software in the Cloud enables developers to use the QNX OS in the Amazon cloud environment.
QNX Toolkit for Visual Studio Code
This User's Guide describes the QNX^® Toolkit for Visual Studio Code. The guide introduces you to the QNX Toolkit by explaining the QNX development environment and how to build, run, and debug your QNX^® Operating System (OS) applications and systems.
QNX Hypervisor User's Guide
This User's Guide explains the QNX hypervisor architecture and provides instructions for installing and running a QNX Hypervisor system, changing system components and configuration, and using hypervisor features such as virtual devices (vdevs).
Typographical Conventions, Support, and Licensing
This section describes the typographical conventions used throughout the documentation, explains how to obtain technical support, and provides some information about licensing.

Kernel debug

QNX SDP8.0Building Embedded SystemsConfigurationDeveloper

The kernel uses the debug callouts when it needs to print out some internal debugging information or encounters a fault.

The kernel uses these callouts to interact with a serial port, console, or other device to output debug or instrumentation information. For example, a display_msg command in a boot image startup script can make procnto use a debug kernel callout to output a message like the following one:

Running default qnxbasedma.build...

We recommend that when working on a startup program, you start by getting a debug kernel callout working. The ability to output messages to a device helps you debug code as you add or modify it.

Kernel callouts

break_detect(): Check if a break has been detected.
display_char(): Receive a char from the kernel and output it to a device.
poll_key(): Pass a char, if available, to the kernel. If no char is available, pass back -1.
spare(): Currently unused by the kernel; reserved for future usage.

Only the display_char() callout is required; the others are optional.

Example

This kernel callout takes a character passed in through register r4 and outputs it to the serial controller.

The CALLOUT_START macro's third argument invokes the patch_debug() routine. This routine replaces the 0x1234 and 0x5678 memory locations with the base address of the serial controller register. The lis (load immediate and shift) and ori (OR immediate) instructions load the base address of the device registers into r6:

CALLOUT_START display_char_5200, 0, patch_debug
lis   %r6,0x1234
ori   %r6,%r6,0x5678

Disable interrupts:

loadi  %r9,PPC_MSR_EE
mfmsr  %r8
andc   %r9,%r8,%r9
mtmsr  %r9
isync

Loop until the Transmit Ready bit has been set:

1:
lwz    %r0,MGT5200_PSC_SR(%r6)
andis. %r0,%r0,MGT5200_PSC_SR_TXRDY
beq    1b

Store the byte (the char passed in by the kernel in r4) in the Transmit Byte register:

stb    %r4,MGT5200_PSC_TB(%r6)
eieio

Re-enable interrupts, then branch to the link register and continue executing at the instruction that follows the call to this routine:

mtmsr  %r8
isync
blr

End of callout marker:

CALLOUT_END display_char_5200

Note:

The startup code must look after some specific debug tasks in addition to those handled by the kernel callouts (see Debug startup tasks in the Startup Programs chapter).

Page updated: August 11, 2025