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Chapter 20 SAINT The Standalone Initialization Utility (SAINT) is an interactive utility program that analyzes system libraries (which contain system object modules, or SOMs) to produce executable images known as boot images. A bootable image is a file that can be copied directly to memory and executed without modification. The SAINT utility's primary function is to produce a boot image for the operating system. The input file upon which the SAINT utility is primarily dependent is the system library file. The format of the library file is defined in the SOM Architecture Control Document.
WARNING Do not use this utility without service center support. Unauthorized use will void your warranty and may cause data loss.
The following terms are used in this chapter: CME Compatibility mode environment. This file contains the environment required to run a compatibility mode program file created by the MPE segmenter. IODC I/O-dependent code. This I/O-device-specific code tests and accesses I/O devices, particularly the boot device device (system disk). IPL Initial program load. This is the first code to be executed from outside the SPU. It is usually code residing on the system disk (the boot device) and is brought into the system by the PDC and IODC code. It provides a user interface to boot image or SOM files into the system to be executed. LIF Logical interchange format. This is a common format used to identify the contents of diverse media. LST Library symbol table. This symbol table is contained in SOM library files and defines the meaning and location of symbols contained in the SOMs that are part of the system library file. The library file is defined in the SOM Architecture Control Document. PIT Page information table. This table contains entries identical to the page table entries required by the system architecture. These entries describe the physical page layout of the bootable image contained in the boot image file. PDC Processor-dependent code. This code is contained in ROM and invokes processor self-tests, locates the boot channel, and checks the condition of the boot device path (including the CPU, main memory, and access to the boot device). PME Primary macro environment. The historical name for MPE boot images. This document uses only the term boot image. RFI Return from interrupt. This system instruction restores the processor state by resetting the values of the PSW, PC space, and PC offset registers to the values contained in the IPSW and PC space and offset queues. This instruction can be used to switch instruction execution from real addressing mode to virtual addressing mode. SOM System object module. The SOM is the file used as the output of system compilers, the input and output of the system linker and MPE/iX loader. Its format is defined in the SOM Architecture Control Document. XRT Cross reference table. This is a process-local table built by the MPE/iX loader, which contains information required to make intermodule procedure calls. There is also a system XRT (SXRT) residing in system space that is used to make system calls. file offset A byte offset relative to the beginning of the file. virtual offset A byte offset relative to the beginning of the space. space offset The same as virtual offset. Preparation for use To bring up the operating system, the START boot image contains the code that builds the required software structures and initializes the various components of MPE/iX, such as the virtual space manager, memory manager, IPC, compatibility mode emulator, and so forth. The first code to be executed is in real addressing mode and builds the page table and hash table required to use virtual addressing mode. It then transfers to virtual addressing mode during the call to the virtual entry point. When the operating system is running, some parts of it are required to be in main memory at all times. This code is part of the system library, and is identified by the memory-resident bit in the library's initialization pointers and subspace dictionary entries. All code that is defined as being memory-resident is contained in the start boot image. The operating system code, which must reside in memory while the system is being initialized, must also be contained in the boot image. This code is identified by the initially frozen bit contained in the initialization pointers and subspace dictionary entries. All code read is defined as being initially resident and is also contained in the start boot image. During system initialization, the initially frozen code is locked in memory until the system library is fully mapped into virtual space. At that point, the code resets to allow the memory manager to swap it out, if necessary. Input files The input files accepted by the SAINT utility consist of system library files, CME files, SXRT declaration files, and millicode files. The MPE/iX system library contains MPE/iX system code and data structures. The system millicode is also contained in a SOM, and the compatibility mode definition is contained in a CME file. The input files required to build the boot image are all identified by one of the load commands (LOADCME, LOADMILLI, LOADSXRT, or LOADSYSLIB). SOMs and system libraries The system library is the primary input file used by the SAINT utility to produce boot images. Libraries contain SOM files, which are the primary output files of system compilers and assemblers, as well as the system linker. Libraries are built by the link editor, which invokes the linker. In addition to executable code, SOMs contain an initialization pointer area, which is used to define the page allocation and access rights of both code and data. An initialization pointer record defines either the location of code or data within the SOM, or the value and length of a data area required by the SOM. These records are used to allocate pages within the boot image file and to build the page information table, or PIT, for the boot image. The library symbol table, or LST, contains records defining the location of procedures within the SOMs contained in the library, and these records are copied directly over to the boot image for use by a symbolic debugger when the system is being booted up. The system object module ACD defines the format of the SOM and the system library.