JPH01288943A - Memory protective system - Google Patents

Abstract

PURPOSE:To refer to the prescribed address contents of a program by providing a routine which sets an access level in a control table at an access key as an exception processing routine when the access key does not correspond to a memory key and prescribed conditions are satisfied. CONSTITUTION:When a program 1 refers to a prescribed address 6 in a reference page 5 in a memory 4, whether or not a memory key 7 coincides with an access key 3 in a program condition word 2 is checked. When the coincide the reference to the prescribed address of the program 1 is permitted. When they do not coincide whether or not an access key (i) is smaller than a memory key (j) is checked. When the condition of (i)<=(j) is satisfied, an exception processing routine 8 substitutes the value of an access level in a control table 9 for the value of the key 3 in the condition word 2. Here, the value of the key 3 coincides with the memory key 7, and the reference to the prescribed address of the program is permitted.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention provides a method for referring to a predetermined address in a memory, when the storage key of the reference page to which the predetermined address belongs matches the access key of the program in the busy state. Concerning a memory protection method that allows only reference.

[Conventional technology]

FIG. 3 is a schematic diagram for explaining a conventional memory protection method. In the figure, 1 is a program, 2 is a program status word indicating the status of program 1, 3 is an access key in the program status busy state, and 4 is a main 5 is a reference page to which a predetermined address in the memory 4 belongs; 6 is a predetermined address in the reference page 5; 7 is the reference page 5.
This is the memory key set to .

Next, the operation will be explained.

When program 1 refers to the contents of reference address 6 in reference page 5 on memory 4, the access key set in program status word 2 at that time; 3 is set corresponding to reference page 5. It is checked whether or not the stored key 7 matches. If the access key 3 and the storage key 7 match, the program 2-gram 2 can refer to the contents of the predetermined address 6.

Also, if access key 3 and memory key 7 do not match,
An internal interrupt is generated as a memory protection exception, and reference to the predetermined address 6 is prohibited.

[Problem to be solved by the invention]

Conventional memory protection systems are structured as explained above, so programs and memory are layered, and programs above a certain level cannot access memory below that level. This poses a problem in that processing performance deteriorates because it cannot be controlled and the access key must be reset in the storage key each time it is accessed.

This invention was made to solve the above-mentioned problems, and it flexibly deals with the problem so that even if the access key and the storage key do not match, a predetermined address can be referenced if a predetermined condition is met. The purpose is to improve processing performance.

[Means to solve the problem]

In the storage protection system according to the present invention, although the access key 3 and the storage key 7 do not match with the management table 9 for managing program access levels, if a predetermined condition is met, the access level in the management table 9 is The present invention is characterized in that an exception handling routine 8 for setting IO to the access key 3 is provided, and reference to a predetermined address 6 in the reference page 5 is permitted under the predetermined conditions.

[Effect]

The exception handling routine 8 in this invention is the access key 3
If the stored keys 7 and 7 do not match, it is checked whether predetermined conditions are met.

If the predetermined conditions are met, sets the access level 10 in the management table 9 to the access key 3. As a result, the access key and memory key match, and the program can refer to the contents of the predetermined address.

On the other hand, if a predetermined condition is not met, the program is prohibited from referencing the contents of the predetermined address.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. Components that are the same as those in the prior art are given the same numbers and their explanations are omitted. FIG. If not, an exception handling routine that processes an internal interrupt that occurs by checking a predetermined condition, such as whether access key 3 of program 1 is smaller than storage key 7; 9 manages information that manages program 1; Management table, IO is management table 9
This is the access level set within.

Next, the operation will be explained.

Here, access key i is iSj for storage key j.
An example of implementing a ring protection function that allows access when .

FIG. 2 shows the operational flow of the present invention at this time. As shown in the figure, program l attempts to refer to a predetermined address 6 of reference page 5 in memory 4 (step St
), it is checked whether the storage key 7 of the reference page 5 to which the predetermined address 6 belongs matches the access key 3 in the program status word 2 (step S2).

If they match, reference to the predetermined address of program 1 is permitted (step S6).

If they do not match, access key i is memory key j
It is checked whether (iSj) is smaller than (step S3
). If the condition of iSj is satisfied in the judgment in step S3, the access level 10 in the management table 9 is
The value of is substituted into the value of access key 3 of program status word 2 (step S5), and the process returns to step S2. In this case, the SP routine is the exception handling routine.

Here, the value of the access key 3 matches the memory key 7, and reference to the predetermined address of the program 1 is permitted (step 7').

Further, in the judgment in step S3, if the condition iSj is not satisfied, reference to the predetermined address in the reference page 5 of the program 1 is prohibited.

Although the above embodiment shows a method of changing the access key in the memory protection exception handling routine, only steps 83 to S5 of the flowchart are realized by hardware or a microprogram, and an internal interrupt of the memory protection exception is generated. It may be realized by adding it to a part.

〔Effect of the invention〕

As explained above, the present invention provides a management table for managing the access level of a program, and when the access key and the storage key do not match and a predetermined condition is met, the access level in the management table is changed to the access key. An exception handling routine is set up to allow reference to a specified address in the reference page under the above specified conditions, so even if the access key and storage key do not match, if the specified conditions are met, the specified address of the program will be updated. Since reference to the r address is allowed, flexible handling is possible, which has the effect of improving processing capacity.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an embodiment of the present invention, FIG. 2 is a flowchart showing the operation of the present invention, and FIG. 3 is a schematic diagram showing a conventional storage protection system. ■...Program, 2...Program status word, 3.
...Access key, 4...Memory, 5...Reference page, 6...Reference address, 7...Memory key, 8...
- Exception handling routine, 9. ...Management table, 10.
...Access level. Agent Masuo Oiwa (and 2 others) Procedural amendment (voluntary)

Claims (1)

[Claims] When a program attempts to refer to a predetermined address in a reference page in memory, check whether the access key in the program status indicating the state of the program matches the memory key set for the reference page. In a memory protection method that allows reference to a predetermined address in the reference page only when they match, a management table that manages the access level of the program and the access key and the storage key do not match, but under a predetermined condition. A memory protection system characterized by providing an exception handling routine that sets an access level in the management table to the access key when the following is satisfied, and allowing reference to a predetermined address in the reference page under the predetermined conditions.