System Page

Updated: April 19, 2023

The system page contains essential information about the system, including the system page's size, information about the hardware platform (including IRQs and the CPU), the cache size, and the location of kernel callouts in memory.

The system page is implemented by a data structure containing constants, references to other data structures, and a union shared by the different processor architectures that QNX Neutrino RTOS supports.

One of the startup program's main tasks is to initialize the system page with the information that the OS needs to run on the current hardware (see Startup tasks in the Startup Programs chapter). After the startup program initializes the system page, it is populated with data that describes the current system and OS, allowing applications to retrieve the information they need.

System page location

The standard location for header files, including sys/syspage.h, is on your host system in ${QNX_TARGET}/usr/include, where ${QNX_TARGET} is the directory that holds the target-related components. Architecture-specific header files are kept in ${QNX_TARGET}/usr/include/arch, where arch is the architecture of the target system. For example, ${QNX_TARGET}/usr/include/x86_64/syspage.h contains the architecture-specific definitions for x86 64-bit. Note, however, that the correct header file to include is the general one that contains definitions for all architectures and is stored in the standard header file location (e.g., /my_qnx_sdp/target/qnx71/usr/include/sys/syspage.h).

A QNX SDP product patch or OS update can replace this and other header files (and other components such as binaries and libraries) with newer versions.

However, because QNX regularly updates header files between patches and updates, a specific BSP component often requires a newer version of a header file. When an updated header file is required, it is included with the BSP and the version in the QNX SDP exists independently. When you build the BSP, the build process automatically uses the version shipped with it. Any other coding operations you do outside the context of that specific BSP use the QNX SDP version of the header file.

System page contents

The sys/syspage.h header file defines the system page structure. Although the contents of this structure vary with the platform, it always has the following members:
struct syspage_entry {
    _Uint16t            size;
    _Uint16t            total_size;
    _Uint16t            type;
    _Uint16t            num_cpu;
    syspage_entry_info  system_private;
    syspage_entry_info  DEPRECATED_SECTION_NAME(meminfo);
    syspage_entry_info  hwinfo;
    syspage_entry_info  qtime;
    syspage_entry_info  callout;
    syspage_entry_info  callin;
    syspage_entry_info  typed_strings;
    syspage_entry_info  strings;
    syspage_entry_info  smp;
    syspage_entry_info  pminfo;
    _Uint32t            spare0[1];
    union {
        struct {
            _Uint32t        __x86_spacer;
            struct x86_syspage_entry     x86;
        struct {
            _Uint32t        __arm_spacer;
            struct arm_syspage_entry    arm;
        struct x86_64_syspage_entry     x86_64;
        struct aarch64_syspage_entry    aarch64;
        _Uint64t        filler[20];
    } un;
Note: The startup library code initializes some of the system page fields. Depending on the amount of customization you require, you may need to initialize some fields as well.
The members of the syspage_entry data structure are:
The size of the system page entry. The startup library sets this member automatically.

The size of the system page entry plus the referenced substructures; effectively the size of the entire system-page database.

The startup library sets this member automatically, but other library calls may adjust (grow) it later as required.


This member is used to indicate the CPU family for determining which union member in the un element to use. It can be SYSPAGE_ARM for supported ARM 32-bit CPU architectures, or one of SYSPAGE_X86_64 or SYSPAGE_AARCH64, for the supported 64-bit architectures.

The library sets this member automatically.

The number of CPUs on the system. The startup library initializes it to the default value of 1. If additional CPUs are detected during startup, the startup program should call init_smp() to set this member to the correct value.
See system_private.
See asinfo.
Deprecated; do not use.
See hwinfo.
See cpuinfo.
See cacheattr.
See qtime.
See callout.
For internal use.

A literal pool used for typed strings. Each entry consists of a four-byte number and a NULL-terminated string. The number represents the string type and corresponds to a specific constant from the system header file <confname.h> (see the C library function confstr()).

Usually, the init_*() library functions populate the typed strings literal pool. However, if you need to add something, you can call the add_typed_string() function from the startup library.


A literal pool used for non-typed strings. To use one of these strings, specify the appropriate index in strings (e.g., cpuinfo's name member).

Usually, the init_*() library functions populate the non-typed strings literal pool. However, if you need to add something, you can call the add_string() function from the startup library.

See intrinfo.
See smp.
Not currently supported.
See un.


The _SP_NEW_ARRAY macro defines the data structures for several syspage_entry members, including asinfo, cpuinfo, cacheattr, intrinfo, and mdriver. It is a union of the old and the new syspage_array_info structures:

#define _SP_NEW_ARRAY(__sect)				\
	union {					\
		syspage_array_info	new_##__sect;	\
		syspage_array_info	__sect;	\


The _SP_OLD_ARRAY macro defines pre-64-bit data structures for the same syspage_entry members as are defined by _SP_NEW_ARRAY:

#define _SP_OLD_ARRAY(__sect)	syspage_entry_info	old_##__sect


The syspage_array_info data structure is used by _SP_NEW_ARRAY and _SP_OLD_ARRAY. It is defined as follows:

typedef struct {
	_Uint16t		entry_off;
	_Uint16t		entry_size;
	_Uint16t		element_size;
} syspage_array_info;

64-bit support

QNX SDP 7.0 introduces support for 64-bit processing on x86 and ARM platforms. This support introduces changes to the system page, including the addition of new definitions for system page types:

 *	System page types
enum {
	/* additional 32 bit architectures go here */

	SYSPAGE_64BIT = 0x100,
	/* additional 64 bit architectures go here */
Note: Some definitions are for architectures that are no longer supported (e.g., X86, PPC, MIPS, SH).