JPH02231639A - Calling system for service program - Google Patents

Abstract

PURPOSE:To attain the execution of a service program that can be executed in a non-priviledge mode by performing a calling procedure which shifts the control to an inlet address of the service program stored in an entry table with a jump or call instruction. CONSTITUTION:The inlet addresses 11 - 13 of service programs 41 - 43 are stored in an entry table 1 set in an address space 5 where the reference is possible to an application program. When the service program 42 is called out of an application program 3 stored in the space 5, a calling procedure 2 substitutes the contents of the inlet address 12 in the table 1 storing the inlet address of the program 42 for a variable X. Then the control is shifted to an address shown by the variable X with a jump or call instruction. Thus the service programs which are executed by calls are processed in the non-priviledge mode.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to program calling when data processing is performed in an electronic computer, and in particular to a calling method when an application program uses a service program prepared by an operating system. Regarding. [Prior Art] Conventionally, this type of service program calling method includes:
There was a method as follows. (1) Shift to privileged mode using a special command such as an SVC command and execute the service program. (2) It is statically linked with the application as a compilation unit library and called as a normal subroutine. (3) It is dynamically linked in the same way as 2 and called as a normal subroutine. (4) Jump between segments or Calling with a call instruction. [Problems to be solved by the invention] The conventional service program calling method described above has the following drawbacks: (1) In the method of shifting to privileged mode by issuing a special command,
Even if the contents of the service program can be in non-privileged mode, it is executed in privileged mode, which may cause the service program's program system to go down, reducing reliability. (2) In the method of statically linking and calling as a normal subroutine, the application program becomes large and relinking is required when updating the service program.

(3) In the method of dynamically linking and calling as a normal subroutine, the linking work for address resolution is performed at load time or by a link instruction, similar to static linking, so overhead is incurred during execution.

(4) The method of jumping between segments using a call gate or calling using a call instruction requires the CPU to have these functions, so it cannot be applied in general systems. [Means for Solving the Problems] The structure of the service program calling method of the present invention is such that the entrance address of a service program that can be executed in a non-privileged mode is stored in a service program prepared by an operating system, and an application An entry table placed at a specific address in an address space that can be referenced by a program, and a jump instruction or call instruction to the entry address of the service program stored in the entry table in order to call the service program executed in the non-privileged mode. It is characterized in that it includes a calling procedure that transfers control.

〔Example〕

Next, the present invention will be explained with reference to the drawings. FIG. 1 is a diagram showing an address space for explaining one embodiment of the present invention, and FIG. 2 is a block flowchart of the service program calling procedure of FIG. 1, where 1 is an entry table, 2 is a calling procedure, and 3 is an application program, 5 is a space that can be referenced by the application program, and 41 to 43 are service programs. Address space 5 that can be referenced by application programs
Entry table 1 in the service program 41
-43 entrance addresses 11-13 are stored. When calling the service program 42 from the application program 3 in this address space 5, the calling procedure 2 follows the block flowchart of the second section and reads the contents of the entry address 12 in the entry table storing the entry address of the service program 42. Assign to variable X, then transfer control to the address indicated by variable X using a jump instruction or call instruction. Note that the jump instruction or call instruction in this case is the same instruction that is used when calling a subroutine within the application.
Privilege mode does not change. Since an application program is normally executed in a non-privileged mode, the service program executed by the above call will perform processing in a non-privileged mode.

〔Effect of the invention〕

As explained above, the present invention can execute a service program that can be executed in a non-privileged mode in a non-privileged mode, and by using an entry table,
This has the advantage that there is no need to perform static or dynamic linking for address resolution between the service program and the application program, and no special CPU function is required for calling the service program.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an address space for explaining one embodiment of the present invention, and FIG. 2 is a block flowchart of the application program calling procedure of FIG. 1... Entry table, 2... Calling procedure, 3
...Application program, 5.Address space that can be referenced by the application program, 11.
...Entrance address of service program 41, 12...
- Entrance address of service program 42, 3... Entrance address of service program 43, 4 1 to 4 3... Service program.

Claims (1)

[Claims] an entry table that stores the entry address of a service program that can be executed in a non-privileged mode among service programs prepared by the operating system and is located at a specific address in an address space that can be referenced by an application program; A service program calling method comprising a calling procedure for transferring control to an entry address of the service program stored in the entry table by a jump instruction or a call instruction in order to call a service program executed in a non-privileged mode.