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ChorusOS 5.0 Board Support Package Developer's Guide

Chapter 7 Configuring the ChorusOS System Image

This chapter describes how to configure your system image to specify the new BSP component. The configuration of the ChorusOS system image depends on a number of configuration files written in ECML but for the purpose of adding a BSP you will mainly need to create and edit the target.xml and target_action.xml files.

Note -

On some platforms, target.xml is split into multiple file: drvlist.xml, drivers.xml which are included in target.xml.

Overview of Creating a System Image

This section explains what the system image is and how to create it using the tools and configuration files provided.

The system image is the initial state of the target board's physical memory. It contains a set of files that are organized into one or more memory banks. For more information on the complete set of ChorusOS configuration files see "Configuration Files" in ChorusOS 5.0 System Administrator's Guide.

When the target system is deployed, some of the system image memory banks are burnt into non-volatile physical memory. The rest can be downloaded from a local device or from the network by the initial loader (boot monitor or firmware).

To build the system image, you use an XML-based system. This system has two components:

The board-specific configuration must be stored in the board BSP directory: source_dir/nucleus/bsp/family/board. For example, the board-specific configuration files for the SBC8260 board are stored in source_dir/nucleus/bsp/powerpc/sbc8260, and those for the PC/AT are stored in source_dir/nucleus/bsp/x86/i386at.

There are two configuration files that define the BSP and driver configuration of the system image:

The configuration must specify the list of memory banks and, for each particular bank, a symbolic name, a base address, and a size limit. Also, the configuration can request mkimage to organize any particular memory bank as a file system volume. The current ChorusOS operating system release supports FAT MS-DOS format only.

The configuration must also specify a list of files to be included in the system image and, for each particular file, the bank where the file must be stored. In addition, for relocatable ELF files, the configuration can specify how the file must be relocated when stored in the memory bank.

Most of the examples in this chapter use the SBC8260 board. To understand the examples, the following information about the SBC8260 board is useful:

Imported Objects

The following objects are predefined and can be used within the board-specific configuration files. They can be used to specify conditions that enable different configurations to be set up for different situations, for example you can set up two different configurations for the two deployment schemes, that would depend on the object BOOT_MODE:

Summary of Required Definitions

A board-specific configuration must define the following objects. They are defined in the ECML target.xml file using variables and folders. More information on how to define these objects is given in the following sections:

The target.xml File Structure

This section describes the content and structure of the target.xml file. The main folders and the variables that they contain are shown in examples.

target.xml Definition

A target.xml file contains a number of hierarchical folders. The top level of folders is the following:

Global Variables

The Global variables folder contains definitions of global system image configuration variables.

Some of them are board-specific and used within the board-specific configuration files only. For example, a configuration for a PC/AT target defines the LOADER configuration variable, with a value specifying which of the two initial loaders (SVR4 boot and Linux LILO boot) will be used to load the system image. The format of the system image is tailored to match the requirements of the initial loader specified by LOADER.

There is one mandatory global variable, IMAGE_DIR. This variable specifies the working directory to be used by the mkimage tool to store the files created during the generation of the ChorusOS system image.

Example 7-1 is an extract of the SBC8260 board-specific configuration file, and defines two global configuration variables, IMAGE_DIR and RESULT.

Example 7-1 SBC8260 Global Variable Configuration

<definition name='IMAGE_DIR'>
		<description>'mkimage' tool output repository</description>
		<string/>
		<vstring>${BUILD_DIR}/image/${BOOT_MODE}/${SYSTEM}</vstring>
</definition>

<definition name='RESULT'>
		<description>the resulting system image file pathname</description>
		<string/>
		<vstring>${BUILD_DIR}/${SYSTEM}.${BOOT_MODE}</vstring>
</definition>

The value of IMAGE_DIR specifies the mkimage working directory as a function of the BOOT_MODE and SYSTEM configuration variables. For example, the working directory for RAM-based chorus system image generation is ${BUILD_DIR}/image/RAM/chorus.

The value of RESULT specifies the filename of the resulting (bootable) system image file. The filename also depends on the BOOT_MODE and SYSTEM configuration variables. For example, the bootable RAM-based chorus system image file will be stored in ${BUILD_DIR}/chorus.RAM.

Banks

The Banks folder contains definitions of the system image memory banks.

A system image memory bank is specified by an object of the type Bank. The following fields of a Bank object must be defined in the target.xml file in order to define the properties of each bank:

The board-specific configuration can define any number of memory banks. A board-specific configuration must define a Bank object named sys_bank.

For example, the SBC8260 board-specific configuration defines two memory banks trampoline_bank and sys_bank.

The trampoline_bank memory bank will contain the power-up initialization (trampoline) program (see "Power-up Program Implementation"). The sys_bank memory bank will contain the remains of the system image.

Code Example 7-2 is an extract of the SBC8260 board-specific configuration file, and defines the trampoline_bank and sys_bank objects.

Example 7-2 SBC8260 Bank Configuration

	
<folder name='Banks'>

    <description>system image memory banks</description>

    <definition name='sys_bank'>
      <description>default system image memory bank</description>
      <condition>
        <equal><var name='BOOT_MODE' /><const>RAM</const></equal>
      </condition>

      <type name='Bank' />
      <value field='ram'><true /></value>
      <value field='addr'><const>0x00100000</const></value>
      <value field='size'><const>0x00f00000</const></value>
    </definition>

    <definition name='trampoline_bank'>
      <description>memory bank for a 'trampoline' 
              (eg. power-up) binary</description>
      <condition>
        <equal><var name='BOOT_MODE' /><const>ROM</const></equal>
      </condition>
      <type name='Bank' />
      <value field='ram'><false /></value>
      <value field='addr'><const>0xfff00000</const></value>
      <value field='size'><const>0x00001000</const></value>
    </definition>

    <definition name='sys_bank'>
      <description>default system image memory bank</description>
      <condition>
        <equal><var name='BOOT_MODE' /><const>ROM</const></equal>
      </condition>
      <type name='Bank' />
      <value field='ram'><false /></value>
      <value field='addr'><const>0xfff01000</const></value>
      <value field='size'><const>0x000ff000</const></value>
    </definition>

  </folder>

Two bank configurations are provided. The first configuration is used when the system is configured to boot from ROM. This configuration is selected when the value of the BOOT_MODE configuration variable is set to ROM. In this case, trampoline_bank will start at the address 0xfff00000 and can contain up to 4K bytes, sufficient for the trampoline program to run. sys_bank starts immediately after trampoline_bank at the address 0xfff01000 and it can contain up to 0xff000 bytes.

The second configuration is used when the system is configured to boot from RAM. In this case, trampoline_bank is not defined. sys_bank starts at the address 0x00100000 and it can contain up to 0xf00000 bytes. The RAM occupied by the bank will be tagged as allocated when the initial state of the RAM allocator is generated, because the value of the ram field is true.

For more information on the resulting system image bank description structure see "Banks".

Areas

This folder contains definitions of the linking areas used during system image link-edit. A linking area is specified by an object of the type Area which defines the following fields:

The board-specific configuration can define any number of linking areas. A board-specific configuration must define an Area object named ram_area.

For example, the SBC8260 board-specific configuration defines three linking areas: ram_area, supervisor_actor_area, and user_actor_area.

When the microkernel is configured with the memory management module implementing the flat memory model (that is, when the value of the VIRTUAL_ADDRESS_SPACE configuration variable is false), only ram_area is defined. It is used to link-edit all non-XIP data segments.

Code Example 7-3 is an extract of the SBC8260 board-specific configuration file, and defines the ram_area object.

Example 7-3 SBC8260 ram_area Configuration

    <definition name='ram_area'>
      <description>default system image linking area  
          (used for bss only)</description>
      <condition>
        <equal><var name='BOOT_MODE' /><const>RAM</const></equal>
      </condition>
      <type name='Area' />
      <value field='addr'><const>0x00004000</const></value>
      <value field='size'><const>0x000fc000</const></value>
      <value field='private'><false/></value>
      <value field='virtual'><false/></value>
    </definition>

    <definition name='ram_area'>
      <description>default system image linking area
          (used for data segments)</description>
      <condition>
        <equal><var name='BOOT_MODE' /><const>ROM</const></equal>
      </condition>
      <type name='Area' />
      <value field='addr'><const>0x00004000</const></value>
      <value field='size'><const>0x00ffc000</const></value>
      <value field='private'><false/></value>
      <value field='virtual'><false/></value>
    </definition>

When the microkernel is configured with one of the memory management modules implementing the virtual memory model (that is, when the value of the VIRTUAL_ADDRESS_SPACE configuration variable is true), three linking areas are defined:

Code Example 7-4 is an extract of the SBC2860 board-specific configuration file, and defines the supervisor_actor_area and user_actor_area objects.

Example 7-4 SBC8260 supervisor_actor_area and user_actor_area Objects

   <definition name='supervisor_actor_area'>
      <description>linking area for supervisor actors</description>
      <condition><var name='VIRTUAL_ADDRESS_SPACE' /></condition>
      <type name='Area' />
      <value field='virtual'><true /></value>
      <value field='private'><false /></value>
      <value field='addr'><const>0xa0000000</const></value>
      <value field='size'><const>0x40000000</const></value>
    </definition>

    <definition name='user_actor_area'>
      <description>linking area for user actors</description>
      <condition><var name='VIRTUAL_ADDRESS_SPACE' /></condition>
      <type name='Area' />
      <value field='virtual'><true /></value>
      <value field='private'><true /></value>
      <value field='addr'><const>0x00000000</const></value>
      <value field='size'><const>0x80000000</const></value>
    </definition>

System Control Blocks

A board-specific configuration must define two references to linking area objects where global system control blocks are allocated:

For example, the SBC8260 board-specific configuration defines supervisor_context_area_ref as a reference to ram_area: 

<definition name='supervisor_context_area_ref'>
			<description>reference to the address range where global system 
				control blocks must be allocated</description>
			<type name='Area' ref-only='yes' />
			<ref name='ram_area' />
</definition>

The mkimage tool will allocate an address range for supervisor address space control blocks in ram_area (as well as the address ranges for all segments link-edited into it).

Two configurations for user_context_area_ref are defined for the SBC8260 board.

Microkernel Address Space

A board-specific configuration can specify the initial microkernel address space layout. If specified, the object that defines it must be named ksp and is usually contained in the folder named KSP. The exact semantics and requirements for the initial microkernel address space specifications are family dependent. For more information on the resulting system image data see "The Initial Address Space"

An MPC60x family-dependent configuration must specify the initial microkernel address space layout.

The SBC8260 board-dependent configuration specifies the initial microkernel address space as follows:

Example 7-5 SBC8260 Board-Dependent Configuration

  <folder name='Kernel address SPace'>
    <description>kernel address space configurations</description>

    <definition name='ksp'>
      <description>flat memory management: system address space layout
               virtual memory management: see PPC 60x BKI</description>

      <type name='AddrSpaceMap' />
<!--
        PowerPC 60x bus SDRAM: 0x00000000 .. 0x00ffffff
-->
      <value index='size'>
        <value field='vaddr'><const>0x00000000</const></value>
        <value field='valid'><true/></value>
        <value field='paddr'><const>0x00000000</const></value>
        <value field='attr'>
          <const>KSP_PPC60x_BAT|KSP_PPC60x_M|KSP_PPC60x_RW</const>
        </value>
      </value>
<!--
        Local bus 32-bit SDRAM: 0x01000000 .. 0x0effffff
-->
      <value index='size'>
        <value field='vaddr'><const>0x01000000</const></value>
        <value field='valid'><false/></value>
      </value>
<!--
        8260 internal memory map (IMMR): 0x0f000000 .. 0x0f01ffff
-->
      <value index='size'>
        <value field='vaddr'><const>0x0f000000</const></value>
        <value field='valid'><true/></value>
        <value field='paddr'><const>0x0f000000</const></value>
        <value field='attr'>
          <const>KSP_PPC60x_BAT|KSP_PPC60x_G|KSP_PPC60x_I|KSP_PPC60x_RW
          </const>
        </value>
      </value>

      <value index='size'>
        <value field='vaddr'><const>0x0f020000</const></value>
        <value field='valid'><false/></value>
      </value>
<!--
        8-bits general purpose FLASH memory: 0xe0000000 .. 0xe0ffffff
-->
<!--
        32-bits general purpose FLASH memory.
                expandable : 0xfc000000 .. 0xfcffffff
                boot       : 0xfe000000 .. 0xffffffff
-->
      <value index='size'>
        <value field='vaddr'><const>0xfc000000</const></value>
        <value field='valid'><true/></value>
        <value field='paddr'><const>0xfc000000</const></value>
        <value field='attr'>
          <const>KSP_PPC60x_BAT|KSP_PPC60x_RO</const></value>
      </value>
    </definition>

  </folder>

According to this definition, the microkernel will initially map the RAM space from physical address 0 to 0x01000000, to the virtual address 0, using one pair of BATs. It will also map the flash memory space from physical address 0xfc000000 to 0xffffffff, to the virtual address 0xfc000000 using another pair of BATs. Finally, the microkernel will map 0x00020000 bytes of 8260 Internal Memory Mapped Registers based at the physical address 0x0f000000 to the virtual address 0x0f000000. The rest of the virtual address space will be invalid.

Link-Edit Models

The link-edit models folder contains a set of link-edit models, each one describing how to link-edit a particular type of binary file.

The models.xml file contains the standard set of link-edit models:

Usually, the board-specific configuration includes the models defined in model.xml and defines a small number of board-specific models.

A link-edit model is specified by an object of type Binary which defines the following fields:

The values of the ro, rw, and bss fields are objects of the type Segment. A Segment object specifies link-edit instructions for the set of sections held by the segment and instructions for the segment loading for execution. In the Segment object:

Therefore, if for a given segment a linking area is not defined (for instance, the segment is to be link-edited at its place in the memory bank) , the xip attribute must be true.

If, for a segment, a linking area is defined, the xip attribute can be either:

Code Example 7-6 is an extract of the SBC8260 board-specific configuration file, and contains the standard link-edit models and the link-edit model definition which contains the trampoline program.

Example 7-6 SBC8260 Link-Edit Model Configuration

<folder name='Link-edit models'>
			<description>layouts of executable binary files</description>

		<folderRef href='model.xml' />  

		<folder name='Genesis2-specific link-edit models'>
			<description>layouts of executable binary files</description>

			<definition name='trampoline_model'>
				<description>trampoline (eg. power-up) program 
                                link-edit model</description>
				<type name='Binary' />
				<value field='ro'>
					<value field='xip'><true/></value>
				</value>
				<value field='strip'><const>ALL</const></value>
			</definition>
		</folder>
</folder>

The trampoline program does not contain any data and its text section must be link-edited at its place in its memory bank, trampoline_bank.

Files

The Files folder contains the specification of the set of BSP files that can be included in the system image. Each file is specified by an object of the type File which contains the following fields:

Code Example 7-7 is an extract of the SBC8260 board-specific configuration file, and contains the definitions of the File objects.

Example 7-7 SBC8260 File Configuration

  <folder name='Files'>
    <description>files that system image can potentially 
                     contain</description>

    <definition name='powerup'>
      <description>powerup initialization program</description>
      <condition>
        <equal><var name='BOOT_MODE' /><const>ROM</const></equal>
      </condition>

      <type name='File' />
      <value field='path'>
        <vstring>${BSP_DIR}/bin/sbc8260/boot/trampoline</vstring>
      </value>
      <value field='bank'><ref name='trampoline_bank' /></value>
      <value field='binary'><ref name='trampoline_model' /></value>
    </definition>

    <definition name='bootstrap'>
      <description>bootstrap program</description>
      <type name='File' />
      <value field='path'>
        <vstring>${BSP_DIR}/bin/sbc8260/boot/boot</vstring>
      </value>
      <value field='bank'><ref name='sys_bank' /></value>
      <value field='binary'><ref name='bootstrap_model' /></value>
    </definition>

    <definition name='debug_driver'>
      <description>system debug agent driver</description>
      <type name='File' />
      <value field='path'>
        <vstring>${BSP_DIR}/bin/sbc8260/dbg/dbgBsp</vstring>
      </value>
      <value field='bank'><ref name='sys_bank' /></value>
      <value field='binary'><ref name='debug_driver_model' /></value>
    </definition>

    <definition name='debug_agent'>
      <description>system debug agent</description>
      <type name='File' />
      <value field='path'>
        <vstring>${BUILD_DIR}/obj/dbg/dbgAgent</vstring>
      </value>
      <value field='bank'><ref name='sys_bank' /></value>
      <value field='binary'><ref name='debug_agent_model' /></value>
    </definition>

    <definition name='microkernel'>
      <description>ChorusOS microkernel</description>
        <type name='File' />
      <value field='path'>
        <vstring>${BUILD_DIR}/obj/kern/kern</vstring>
      </value>
      <value field='bank'><ref name='sys_bank' /></value>
      <value field='binary'><ref name='microkernel_model' /></value>
    </definition>

    <definition name='tbdec'>
      <description>built-in driver</description>
      <type name='File' />
      <value field='path'>
        <vstring>${DRV_F_DIR}/bin/drv/timer/tbDec/D_tbDec</vstring>
      </value>
      <value field='bank'><ref name='sys_bank' /></value>
      <value field='binary'><ref name='driver_model' /></value>
    </definition>

    <definition name='quicc8260'>
      <description>built-in driver</description>
      <type name='File' />
      <value field='path'>
        <vstring>${DRV_F_DIR}/bin/drv/quicc/8260/D_quicc8260</vstring>
      </value>
      <value field='bank'><ref name='sys_bank' /></value>
      <value field='binary'><ref name='driver_model' /></value>
    </definition>

    <definition name='fccEther'>
      <description>built-in driver</description>
      <type name='File' />
      <value field='path'>
        <vstring>${DRV_DIR}/bin/drv/net/ether/fcc/D_fccEther</vstring>
      </value>
      <value field='bank'><ref name='sys_bank' /></value>
      <value field='binary'><ref name='driver_model' /></value>
    </definition>

    <definition name='sccEther'>
      <description>built-in driver</description>
      <type name='File' />
      <value field='path'>
        <vstring>${DRV_DIR}/bin/drv/net/ether/scc/D_sccEther</vstring>
      </value>
      <value field='bank'><ref name='sys_bank' /></value>
      <value field='binary'><ref name='driver_model' /></value>
    </definition>

    <definition name='quiccMii'>
      <description>built-in driver</description>
      <type name='File' />
      <value field='path'>
        <vstring>${DRV_DIR}/bin/drv/mii/quiccMii/D_quiccMii</vstring>
      </value>
      <value field='bank'><ref name='sys_bank' /></value>
      <value field='binary'><ref name='driver_model' /></value>
    </definition>

    <definition name='lxt970'>
      <description>built-in driver</description>
      <type name='File' />
      <value field='path'>
        <vstring>${DRV_DIR}/bin/drv/phy/lxt970/D_lxt970</vstring>
      </value>
      <value field='bank'><ref name='sys_bank' /></value>
      <value field='binary'><ref name='driver_model' /></value>
    </definition>

    <definition name='sccUart'>
      <description>built-in driver</description>
      <type name='File' />
      <value field='path'>
        <vstring>${DRV_DIR}/bin/drv/uart/scc/D_sccUart</vstring>
      </value>
      <value field='bank'><ref name='sys_bank' /></value>
      <value field='binary'><ref name='driver_model' /></value>
    </definition>

    <definition name='reboot'>
      <description>reboot program</description>
      <type name='File' />
      <value field='path'>
        <vstring>${BSP_DIR}/bin/sbc8260/reboot/reboot</vstring>
      </value>
      <value field='bank'><ref name='sys_bank' /></value>
      <value field='binary'><ref name='reboot_model' /></value>
    </definition>
  </folder>

System Image

The system image folder contains three sub-folders:

Files

The files folder contains the definition of a BSP_files object, which is a list of references to File objects specifying the files that must be included in the system image.

A board-specific configuration must define a BSP_files object.

Code Example 7-8 is an extract of the SBC8260 board-specific configuration file, and contains the BSP_files definition.

Example 7-8 SBC8260 BSP_files Configuration

      <definition name='BSP_files'>
        <description>system image BSP files</description>
        <type name='FileList' />
        <value index='size'><ref name='debug_driver' /></value>
        <value index='size'><ref name='debug_agent' /></value>
        <value index='size'><ref name='bootstrap' /></value>
        <value index='size'><ref name='reboot' /></value>
        <value index='size'><ref name='microkernel' /></value>
        <value index='size'><ref name='tbdec' /></value>
        <value index='size'><ref name='quicc8260' /></value>
        <value index='size'><ref name='fccEther' /></value>
      </definition>

      <setting name='BSP_files'>
        <condition>
          <equal><var name='BOOT_MODE' /><const>ROM</const></equal>
        </condition>
        <value index='size'><ref name='powerup' /></value>
      </setting>

Files Generated Automatically

The mkimage tool generates three files:

The Auto-generated files folder contains definitions of File objects corresponding to these three files. The File objects must be named bootconf, symb, and env_file, respectively.

Code Example 7-9 is an extract of the SBC8260 board-specific configuration file, and contains the Auto-generated files definition.

Example 7-9 SBC8260 Auto-generated Files Configuration

      <folder name='Auto-generated files'>
        <description>system image files automatically \
         generated by 'mkimage' tool</description>

        <definition name='env_file'>
          <description>initial state of system environment \
           variables</description>
          <type name='File' />
          <value field='path'>
            <vstring>${IMAGE_DIR}/environ</vstring>
          </value>
          <value field='bank'><ref name='sys_bank' /></value>
        </definition>

        <definition name='symb'>
          <description>kernel debuger (kdb) symbols</description>
          <type name='File' />
          <value field='path'>
            <vstring>${IMAGE_DIR}/symb/${SYSTEM}_symb</vstring>
          </value>
          <value field='bank'><ref name='sys_bank' /></value>
          <value field='binary'><ref name='debug_agent_model' /></value>
        </definition>

        <definition name='bootconf'>
          <description>bootconf program</description>
          <type name='File' />
          <value field='path'>
            <vstring>${IMAGE_DIR}/bconf/${SYSTEM}_bconf</vstring>
          </value>
          <value field='bank'><ref name='sys_bank' /></value>
          <value field='binary'><ref name='bootconf_model' /></value>
        </definition>

      </folder>

Miscellaneous Information

The misc folder contains the following:

Code Example 7-10 is an extract of the SBC8260 board-specific configuration file, and contains the Misc definition.

Example 7-10 SBC8260 Misc Configuration

    <folder name='Misc'>
      <description>Misc configuration variables</description>
        
      <definition name='banks'>
        <description>list of system image banks</description>
        <type name='BankList'/>
      </definition>

      <definition name='heap_size'>
        <description>bootconf heap size</description>
        <int/>
        <const>0x00002000</const>
      </definition>

      <setting name='banks'>
        <condition>
          <equal><var name='BOOT_MODE' /><const>ROM</const></equal>
        </condition>
        <value index='size'><ref name='trampoline_bank' /></value>
      </setting>

      <setting name='banks'>
        <value index='size'><ref name='sys_bank' /></value>
      </setting>

    </folder>

The mkimage System Image

This section contains more information on the output from the mkimage tool and the target-specific configuration files that are described in the previous section.

Relocating ELF Files

If relocation is specified for a given file, mkimage relocates it and stores the resulting absolute binary file in the memory bank. You can specify how many program segments must contain the resulting binary file and, for each individual segment, how it must be relocated.

A segment can be relocated to a linking area or to the segment image's base address within the memory bank.

A linking area is a named range of addresses specified by an id, a base address, and a size. You can specify a different linking area for each program segment. mkimage relocates a segment to the lowest available range of addresses of a suitable size within the linking area. mkimage guarantees that different segments relocated to the same linking area will never overlap. However, segments relocated to private linking areas can overlap.

Execution in Place (XIP)

For any particular segment you can specify whether the segment must be executed at its place within the memory bank (in this document this segment is refered to as the "XIP segment") or whether it must be copied into the RAM before it is executed.

bootconf Binary

The mkimage command builds a binary file called bootconf. The bootconf file contains a data structure called BootConf, which describes the system image contents and layout. mkimage includes the bootconf binary file in one of the system image memory banks.

The initial loader boots the ChorusOS operating system, jumping to the entry point of the bootconf binary (see "Overview" for more details).

bootconf is a board-independent program that gets control from the board-specific initial loader and transfers control to the board-specific bootstrap program. In some cases, the initial loader needs to pass a board-dependent parameter to the bootstrap. This parameter can be loaded into a specific CPU register, and bootconf passes the entry value of the register to the bootstrap program as an opaque parameter. The register is:

When the bootconf binary is entered, it sets up a program stack in a stack area within its data segment, finds the descriptor of the bootstrap binary in the BootConf structure, and jumps to this entry point, passing the following parameters:

To jump to the bootstrap entry point, bootconf uses the standard C function invocation conventions. The bootstrap entry point is:

typedef void (*BootEntry) (struct BootConf*, void* cookie);

BootConf Structure

The bootconf file contains an object of type BootConf and all the objects it points to. It describes the structure of the system image in terms of its components.

typedef struct BootConf { 
    unsigned int        stamp;          /* identification stamp */
    PhMap*              kernelSpace;    /* initial address space 
															   descriptor */
    VmAddr              spaceBarrier;   /* frontier between user and 
                                           supervisor address space */
    int                 numBanks;       /* number of system image memory 
                                           banks */
    BankDesc*           bankDesc;       /* system image memory bank 
                                           descriptors */
    int                 numBins;        /* number of binaries */     
    BinDesc*            binDesc;        /* array of binary descriptors */
    int                 numSegs;        /* number of segments */ 
    BinSegDesc*         segDesc;        /* array of segment descriptors */ 
    RamDesc             ramAllocator;   /* ram occupation */ 
    KnSymbolTable*      symbols;        /* symbols for kdb */  
    EnvDesc*            env;            /* environment descriptor */ 
    void*               heapStart;      /* memory heap: */
    void*               heapCur;        /* occupied from heapStart to 
                                           heapCur */
    void*               heapLimit;      /* available from heapCur to 
                                           heapLimit */
    unsigned int        siteNumber;     /* site number used for remote 
                                           IPC */
    DevNode             rootDevice;     /* device tree */ 
    IdleFunc            idleFunc;       /* function to be executed in the 
                                           idle loop */
    DbgBsp              dbgBsp;         /* bsp for Debug Agent */     
    DbgOps              dbgOps;         /* debug Agent interface */
    BootConfRebootEntry rebootEntry;    /* reboot entry */
    RebootDesc*         rebootDesc;     /* reboot descriptor */
    void*               f_bootConf;     /* a processor-specific 
                                           descriptor */
} BootConf;

Code Example 7-11 contains an example of a BootConf structure.

The Initial Address Space

The kernelSpace field describes the initial address space. The exact interpretation of this descriptor is architecture dependent:

Other architecture-dependent requirements for the initial address space layout may be specified. See "The Boot-Kernel Interface" for details.

If required, the initial virtual address space is specified by the PhMap structure:

typedef struct PhChunk {     
                PhAddr       start;  /* chunk physical start address */     
                PhSize       size;   /* chunk size in bytes */     
                unsigned int tag;    /* chunk attributes */ 
} PhChunk;  

typedef struct PhMap {     
                int      numChunks;  /* number of items in the array */     
                PhChunk* chunk;      /* array of chunk descriptors */ 
} PhMap;

PhMap and PhChunk are declared in source_dir/nucleus/sys/common/src/kern/bki/phMap.h and source_dir/nucleus/sys/common/src/kern/bki/phChunk.h respectively. The PhMap structure is a series of PhChunk entries, each entry describing the virtual-to-physical translation of a contiguous range of virtual addresses. The size field of a PhChunk descriptor indicates the size of the range. The starting address of the range is given by the sum of the size values of the previous ranges. Therefore, the PhMap structure must describe the entire virtual address space.

If the tag value in PhChunk is equal to KSP_INVALID the translation is invalid and access to any address in the range described by PhChunk is prohibited.

Otherwise, the start field of a PhChunk structure gives the starting address of the physical address range that the virtual address is mapped to. The tag field of a PhChunk structure specifies the attributes associated with the mapping. The highest 24 bits of tag are used to store architecture-dependent attribute sets, such as memory access rights and cache control. See "The Boot-Kernel Interface" for details of architecture-specific BKI. The lowest 8 bits are reserved for use by the microkernel, and are set to 0 by mkimage.

The value of the spaceBarrier field may influence the dimensions of the supervisor and the user virtual address spaces. The exact meaning of this field is architecture dependent.

Banks

The bankDesc structure points to an array of BankDesc system image memory bank descriptors.

typedef struct BankDesc {     
        char*    id;      /* bank's symbolic name */ 
        BankType type;    /* bank's type */ 
        char*    fs;      /* files system type symbolic name */
        VmAddr   vaddr;   /* address required for the bank's image */
        VmSize   size;    /* bank's size */ 
} BankDesc;

The bankDesc structure is declared in source_dir/nucleus/sys/common/src/kern/bki/bki.h. A memory bank is specified by vaddr, indicating the starting address within the initial address space, and size.

The type field value is a combination of the bits listed in Table 7-1.

Table 7-1 type Bits
type Bit Meaning
BANK_KSP always "1" in this version
BANK_DEVICE bank is a memory device
BANK_DEVICE_READ data from the memory device can be read
BANK_DEVICE_WRITE data from the memory device can be modified
BANK_DEVICE_EXEC instructions from the memory device can be executed

If any of the last three bits is set, the BANK_DEVICE bit must also be set.

Files in a memory bank can be organized as a volume of a file system. In this case, the fs field points to a string containing the name of the file system type (for example, "FAT" stands for MS-DOS FAT file system). Otherwise, fs is 0.

When the initial loader jumps to the bootconf entry point, the memory banks containing the BIN_BOOTCONF and BIN_BOOTSTRAP program binaries must already be installed at the address indicated by vaddr.

When the bootstrap program transfers control to the microkernel, all memory banks must be installed at the address indicated by vaddr.

Binaries

The binDesc array points to an array of BinDesc structures. Each structure describes an absolute executable binary involved in the system deployment procedure, such as a bootconf, bootstrap, microkernel, or a driver. These binaries are part of the system image.

typedef struct BinDesc {     
                char*        name;      /* binary symbolic name */     
                int          firstSeg;  /* first segment index */     
                int          lastSeg;   /* last segment index */     
                KnPc         entry;     /* binary entry point */     
                BinType      type;      /* binary type */     
                BinMode      mode;      /* binary loading mode */     
                void*        actor;     /* private for the u-kernel */ 
} BinDesc;

Each binary is composed of a set of segments. The firstSeg and lastSeg fields specify the range of segments within the array of segment descriptors, pointed to by segDesc, that store the binary described by BinDesc.

The type field specifies the binary's type and is set to one of the binType values listed in Table 7-2.

Table 7-2 binType Values
BinType Value Type of Binary
BIN_BOOTCONFbootconf program
BIN_BOOTSTRAP bootstrap program
BIN_REBOOT reboot program
BIN_DBG_AGENT system debug agent
BIN_DBG_DRIVER debug agent communication driver
BIN_KERNEL microkernel
BIN_DRIVER a ChorusOS device driver
BIN_SUPERVISOR a supervisor actor
BIN_USER a user actor

BinType values are defined in such a way that:

The mode specifies the binary activation mode and can be any combination of the BinMode flags listed in Table 7-3.

Table 7-3 BinMode Flags
BinMode Flag Meaning
BIN_DEBUGGED The binary must be launched in debug mode.
BIN_STOPPED The binary must be loaded but not started.

These flags only have meaning for BIN_SUPERVISOR and BIN_USER binaries. The value of mode is ignored for all other binary types.

The numBins field specifies the number of elements in the array pointed to by binDesc.

segDesc points to an array of segment descriptors. Each item in the array is a SegDesc data structure and describes a segment of the system image. SegDesc is declared in source_dir/nucleus/sys/common/src/kern/bki/bki.h. 

typedef struct SegDesc {     
              VmAddr    kaddr;  /* image address */     
              VmAddr    vaddr;  /* execution address (from link editor) */
              VmSize    ksize;  /* image size */     
              VmSize    vsize;  /* execution size */     
              SegType   type;   /* code or data */     
              SegSpace  space;  /* address space type */ 
} SegDesc;

The descriptor specifies two things:

The segment image is stored in the memory bank containing the segment's binary. When the memory bank is installed at the required address, as specified in the BankDesc structure, the segment image can be found at kaddr. The ksize field specifies the size of the segment image contained in the memory bank.

When executed, the segment must be installed at the address specified by the vaddr field and its size must be equal to vsize. If vsize is greater than ksize, the memory from vaddr+ksize to vaddr+vsize must be initialized to zero.

The space field indicates whether a segment belongs to the initial address space. It can be set to one of the values listed in Table 7-4.

Table 7-4 SegSpace Values
SegSpace Value Meaning
SEG_KSP segment belongs to the initial microkernel address space
SEG_VIRTUAL segment does not belong to the initial microkernel address space

Only binaries of the BIN_ACTOR type can hold SEG_VIRTUAL segments.

The value of the type field can be any combination of the bits listed in Table 7-5.

Table 7-5 SegType Bit Values
SegType Bit Meaning
SEG_XIP Segment must be executed at its place in the memory bank
SEG_EXEC Segment contains instructions
SEG_READ Segment contains read-only data
SEG_WRITE Segment contains write data

If a segment is executable in place (XIP), and belongs to the initial kernel address space (for example, the SEG_XIP bit is set in the type field and the space field is equal to SEG_KSP), the segment's execution address will be the same as the segment's image address and the segment's execution size will be equal the segment's image size. Therefore, when a memory bank is installed at the address specified by its descriptor (BankDesc::vaddr), all XIP KSP segments that belong to the memory bank will have no particular installation procedure and will be ready for execution.

The numSegs field specifies the number of elements in the array pointed to by SegDesc.

RAM Occupation

The ramAllocator field describes RAM occupation by the system image. The mkbootconf tool initializes the ramAllocator state. It tags as allocated the memory dedicated to:

The ChorusOS operating system provides a library of functions to manipulate the RamDesc objects (see "RAM Allocator interface"). RamDesc is declared in source_dir/nucleus/sys/common/src/kern/bki/ram.h. These functions allow the bootstrap program to tag any range of physical addresses with an attribute.

Environment Variables

The env field points to an EnvDesc structure. The EnvDesc structure is declared in source_dir/nucleus/sys/common/src/lib/util/env.h.

typedef struct EnvDesc {     
                int     envSize;    /* current size of environment */
                int     envMaxSize; /* memory available for environment */
                char*   envPtr;     /* pointer to the environment */
} EnvDesc;

The system image contains a data file with the initial state of the system environment variables. The env field of the BootConf structure references the contents of this file.

The envPtr field points to a sequence of environment variable definitions. Each definition is a concatenation of two strings, envVariable and envValue, where envVariable is the null-terminated string name of an environment variable, and envValue is the null-terminated string value of the environment variable.

The envSize field is the size in bytes of the environment variable definition sequence.

The envMaxSize field is the environment file size. It must not exceed envMaxSize.

Heap and Stack

The heapStart field points to the beginning of a block of statically allocated memory. The block can be used by the bootstrap program for dynamic memory allocation. For instance, the heap is used by the device tree library memory allocator (see "Initial Device Tree") to build the initial state of the board's device tree.

The heapCur field points to the first byte available for future allocation. The mkbootconf tool sets heapCur to heapStart.

The heapLimit field points to the heap memory limit. The size of the heap memory is equal to heapLimit-heapStart.

The heap is also used for the initial stack. The bootconf start-up procedure initializes the current stack pointer with the heapLimit value.

All other fields of the BootConf structure are initialized dynamically during the system bootstrap.

Example BootConf Structure

This section contains an example of a BootConf structure for the SBC8260 PPC8260 EC603e-based board.

Example 7-11 BootConf Structure

#include bki/bki.h
#include bki/f_bki.h
PhChunk __mkimage__label__kernelSpace[] = {
        { 0x0, 0x1000000, KSP_PPC60x_BAT|KSP_PPC60x_M|KSP_PPC60x_RW },
        { 0x0, 0xe000000, KSP_INVALID },
        { 0xf000000, 0x20000, KSP_PPC60x_BAT|KSP_PPC60x_G|KSP_PPC60x_I|
            KSP_PPC60x_RW },
        { 0x0, 0xecfe0000, KSP_INVALID },
        { 0xfc000000, 0x4000000, KSP_PPC60x_BAT|KSP_PPC60x_RO }
};
BankDesc __mkimage__label__banks[] = {
        { "sys_bank", BANK_KSP, 0, 0x100000, 0xb3000}
};
BinDesc __mkimage__label__binDesc[] = {
        {
                "dbgBsp",
                0,
                0,
                0x10042c,
                BIN_DBG_DRIVER,
                0 | 0
        },
        {
                "dbgAgent",
                1,
                1,
                0x104494,
                BIN_DBG_AGENT,
                0 | 0
        },
        {
                "boot",
                2,
                2,
                0x108000,
                BIN_BOOTSTRAP,
                0 | 0
        },
        {
                "reboot",
                3,
                3,
                0x10d27c,
                BIN_REBOOT,
                0 | 0
        },
        {
                "kern",
                4,
                5,
                0x125418,
                BIN_KERNEL,
                0 | 0
        },
        {
                "D_tbDec",
                6,
                6,
                0x186000,
                BIN_DRIVER,
                0 | 0
        },
        {
                "D_quicc8260",
                7,
                8,
                0x188000,
                BIN_DRIVER,
                0 | 0
        },
        {
                "D_fccEther",
                9,
                9,
                0x18e000,
                BIN_DRIVER,
                0 | 0
        },
        {
                "PD",
                10,
                11,
                0x195000,
                BIN_SUPERVISOR,
                0 | 0
        },
        {
                "kernonly_symb",
                12,
                12,
                0x198000,
                BIN_DBG_AGENT,
                0 | 0
        },
        {
                "kernonly_bconf",
                13,
                13,
                0x1b0000,
                BIN_BOOTCONF,
                0 | 0
        }
};
BinSegDesc __mkimage__label__segDesc[] = {
        {
                0x100000,
                0x100000,
                0x608,
                0x608,
                SEG_XIP | SEG_EXEC | SEG_READ | SEG_WRITE,
                SEG_KSP
        },
        {
                0x101000,
                0x101000,
                0x6234,
                0x6234,
                SEG_XIP | SEG_EXEC | SEG_READ | SEG_WRITE,
                SEG_KSP
        },
        {
                0x108000,
                0x108000,
                0x4358,
                0x4358,
                SEG_XIP | SEG_EXEC | SEG_READ | SEG_WRITE,
                SEG_KSP
        },
        {
                0x10d000,
                0x10d000,
                0x2200,
                0x2200,
                SEG_XIP | SEG_EXEC | SEG_READ | SEG_WRITE,
                SEG_KSP
        },
        {
                0x110000,
                0x110000,
                0x75920,
                0x75920,
                SEG_XIP | SEG_EXEC | SEG_READ | SEG_WRITE,
                SEG_KSP
        },
        {
                0x186000,
                0x8000,
                0x0,
                0x1a000,
                SEG_READ | SEG_WRITE,
                SEG_KSP
        },
        {
                0x186000,
                0x186000,
                0x1be4,
                0x1be4,
                SEG_XIP | SEG_EXEC | SEG_READ | SEG_WRITE,
                SEG_KSP
        },
        {
                0x188000,
                0x188000,
                0x50dc,
                0x50dc,
                SEG_XIP | SEG_EXEC | SEG_READ | SEG_WRITE,
                SEG_KSP
        },
        {
                0x18e000,
                0x22000,
                0x0,
                0x10,
                SEG_READ | SEG_WRITE,
                SEG_KSP
        },
        {
                0x18e000,
                0x18e000,
                0x6654,
                0x6654,
                SEG_XIP | SEG_EXEC | SEG_READ | SEG_WRITE,
                SEG_KSP
        },
        {
                0x195000,
                0x195000,
                0x22c4,
                0x22c4,
                SEG_XIP | SEG_EXEC | SEG_READ | SEG_WRITE,
                SEG_KSP
        },
        {
                0x198000,
                0x23000,
                0x0,
                0xc04,
                SEG_READ | SEG_WRITE,
                SEG_KSP
        },
        {
                0x198000,
                0x198000,
                0x170c8,
                0x170c8,
                SEG_XIP | SEG_EXEC | SEG_READ | SEG_WRITE,
                SEG_KSP
        },
        {
                0x1b0000,
                0x1b0000,
                0x2c10,
                0x2c10,
                SEG_XIP | SEG_EXEC | SEG_READ | SEG_WRITE,
                SEG_KSP
        },
        {
                0,
                0,
                0,
                0,
                0,
                0
        },
        {
                0,
                0,
                0,
                0,
                0,
                0
        }
};
PhChunk __mkimage__label__ramChunks[64] = {
        { 0x0, 0x4000, PH_RAM_NONEXISTENT },
        { 0x4000, 0x20000, PH_RAM_ALLOCATED },
        { 0x24000, 0xdc000, PH_RAM_NONEXISTENT },
        { 0x100000, 0xb3000, PH_RAM_ALLOCATED },
        { 0x1b3000, 0xffe4d000, PH_RAM_NONEXISTENT }
};
EnvDesc __mkimage__label__environ = {   0x0, 0x0, (char*) 0x100000};
int heapSize = 0x2000;
char heap[0x2000];
BootConf __mkimage__label__bootConf = {
        0x38216b39,
        0,
        {
                5,
                __mkimage__label__kernelSpace
        },
        0x0,
        1,
        __mkimage__label__banks,
        11,
        __mkimage__label__binDesc,
        14,
        __mkimage__label__segDesc,
        {
                64,
                5,
                __mkimage__label__ramChunks
        },
        0,
        &__mkimage__label__environ,
        heap,
        heap,
        heap + 8192,
};
BootConf* bootConf= &__mkimage__label__bootConf;

The kernelSpace field of the BootConf structure contains the description of the kernel address space that must be established by the microkernel's memory management module.

The descriptor specifies that the first 16M of the physical address space, which corresponds to RAM potentially available on the board, must be mapped to the first 16M of the virtual address space using one Block Address Translation register pairs (IBAT and DBAT). The space must be mapped read/write enforcing memory coherency (that is, the memory control bit M must be set in the BATs).

Another pair of BATs must be used to map to the virtual address range from 0x0f000000 to 0x0f020000. These are the PPC8260 internal memory mapped registers which occupy the physical addresses from 0xf000000 to 0x0f020000. The space must be mapped read-only, bypassing the memory cache.

The system image is stored in one memory bank that must be installed at the address 0x00100000. The size of the bank is 0x00b3000 bytes.

A third pair of BATs must be used to map the last 64M of the physical address space, which corresponds to ROM (FLASH) potentially available on the board. This space must be mapped read-only.

The system image contains 11 binaries:

Some binaries (for example, boot) have just one XIP segment which includes all text and data. Others (for instance, kern) have zero-initialized data (bss), link-edited in a separate segment.

The RAM allocator specifies that the RAM from address 0x00004000 to address 0x00024000 and from address 0x00100000 to address 0x001b3000 is allocated. The memory from 0x00100000 to 0x001b3000 is occupied by the system image memory bank, and the memory from 0x00004000 to 0x00024000 by the system control blocks and bss.