JPS63282542A - Virtual space managing device - Google Patents

Abstract

PURPOSE:To switch virtual spaces in nonprivileged without spoiling a protecting function among the virtual spaces by providing a means which has plural candidates to be employed as the value of a register stored with information of an address conversion table and which selects a candidate to be employed in nonprivileged mode. CONSTITUTION:Address conversion tables AT8 and AT9 are provided and a register (ATBR) table 10 determines which is used. Namely, a CPU which has the nonprivileged mode has plural candidates to be employed as the value of the register stored with the information of the address conversion tables and selects a candidate to be employed in the nonprivileged mode. Therefore, the AT8 or AT9 is selected as the address conversion table (AT) in the nonprivileged mode by changing an ATBR table pointer 11. Consequently, the virtual spaces can be switched and variation to an optional value is not possible in the nonprivileged mode, so the protecting function for other user programs and the virtual space of an OS is not lost.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a virtual space management device, and in particular, in an operating system that provides a plurality of virtual spaces, virtual space switching can be performed while remaining in a non-privileged mode. This invention relates to a virtual space management device that can be realized.

[Conventional technology]

Some information processing systems use a memory management unit (hereinafter referred to as MMU) to convert an address (virtual address) recognized by a CPU into an address (physical address) in a storage device.

In a conventional MMU, a register (hereinafter also referred to as ATBR) in which information of an address translation table (hereinafter also referred to as AT) is stored can only be changed in a privileged mode.

Here, the privileged mode is a mode in which all registers of the MMU are allowed to be referenced or modified (on the other hand, a non-privileged mode is a mode in which the registers in which address translation table information is stored cannot be referenced or modified). mode).

The above points will be further explained using FIG. Figure 4 is a conceptual diagram showing the conversion process in a conventional address conversion device.
MMU is field 4 indicating ATBR of virtual address 1
The ATBR table 10 is determined from the ATBR table 10, the position of the AT8 is determined from the ATBR table 10, and the entry in the ATB is determined from the field 3 indicating the offset within the AT. By locating physical page 6 from this entry and obtaining the address within this page, i.e. physical address 7, in field 2 indicating the offset within the physical page,
Conversion is being performed from virtual address 1 to physical address 7.

In addition, in FIG. 4, 5 indicates a physical address space.

Using such an MMU, the operating system (
(hereinafter referred to as O8), in order to prevent a certain user program from changing the contents of the ATBR table 10 and destroying the virtual space of other user programs and the virtual space of O8, this user program must be placed in non-privileged mode. That is, the program is executed in a mode in which it is not possible to refer to or change the register in which address translation table information is stored.

[Problems to be Solved by the Invention] However, in implementing O8 using the conventional MMU described above, one user program is basically allocated only to one virtual space. If one user program has multiple virtual spaces and this user program switches between them, a mode is required for virtual space switching (the same virtual address is translated to a different physical address). must be switched to the privileged mode as described above, and cannot be done in the non-privileged mode, and the overhead associated with this mode change has the disadvantage that high-speed virtual space switching cannot be achieved.

An object of the present invention is to provide a virtual space management device that can realize virtual space switching in non-privileged mode without impairing the protection function between virtual spaces.

[Means for solving problems]

The present invention is a virtual space management device for an information processing system that has a memory management device that converts an address recognized by a CPU into an address in a storage device, and has a privileged mode and a non-privileged mode as running modes. The present invention is characterized in that it has a plurality of candidates that can be taken as the value of the register in which the information of the conversion table is stored, and also includes means that can select the candidate to be adopted in a non-privileged mode.

[Effect]

The virtual space management device of the present invention has a plurality of candidates that can be taken as the value of the register in which address translation table information is stored, and selects the candidate to be adopted in the non-privileged mode. You can switch between virtual spaces with the touch of a button.

Virtual space switching can be done without changing the mode to privileged mode as in the past, increasing speed and not compromising the protection function between virtual spaces.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 shows an embodiment of the virtual space management device of the present invention, and shows the process of converting a virtual address into a physical address.

As shown in FIG. 1, this virtual space management device has AT8 and AT9 as address translation tables, and the ATBR table 10 determines which one to use.

In the illustrated case, AT8 is in use, and AT9 is in an unused state.

In the conventional MMU, there is only one ATBR table 10, which is an ATBR candidate, but in this virtual space management device, a plurality of candidates can be stored here. An ATBR table pointer 11 is newly provided as a storage area for specifying which candidate i to use, and can be changed in non-privileged mode.

Note that the other components in FIG. 1 are the same as those in FIG.
3.4, and numerals 5 to 7 indicate a physical address space, a physical page, and a physical address, respectively.

As described above, this virtual space management device includes an MMU that provides a mechanism for converting an address (virtual address) recognized by the CPU into an address (physical address) in the storage room;
In a CPU that has a privileged mode in which all registers of the MMU are allowed to be referenced or changed, and a non-privileged mode in which reference to or changes to registers storing address translation table information are not allowed as running modes,
It has a plurality of candidates that can be taken as the value of the register in which address conversion table information is stored, and the candidate to be adopted can be selected in non-privileged mode.

In this embodiment, by changing the ATBR table pointer 11, the address translation table (AT) is
AT8 or AT9 can be selected as the virtual space, thereby realizing virtual space switching. Furthermore, since it is not possible to change the value to an arbitrary value in non-privileged mode, the protection function of other user programs and the virtual space of O8 is not lost.

In this way, this virtual space management device can provide virtual space switching in non-privileged mode. The advantages resulting from this will be explained in more detail using FIG. 2.

Generally, when implementing programs that call each other (hereinafter referred to as cortins), O8 is
It is necessary to prepare a Chin-specific stack.

In the case of FIG. 2, there are user virtual spaces I and (2), the former being executed and referenced by cortin A, and the latter being executed and referred to by cortin B. The stack virtual space 13 is used by Cortin A, and the stack virtual space 14 is used by Cortin B. In addition, cortin-specific cortin A5 is running, cortin A7 is suspended, and cortin
Assume that cortin B6 is suspended and cortin B8 is running.

Assuming that cortin A5 is currently being executed in this state, when a mutual call is made, the above-mentioned virtual space management device can quickly switch the cortin stack, and the user virtual space I and ■ can be switched while remaining in non-privileged mode.

That is, at this time, cortin A5 determines cortin B to which control should be transferred next and transfers control to it. As a result, cortin B starts to move as cortin B8. At this time, the current stack 13 is changed to the stack 14 of this cortin B8.
must be switched to. Furthermore, since switching between the virtual spaces I and (2) is performed frequently, it is necessary to perform the switching at high speed. Here, by using the management device according to the present invention, stack switching can be performed in a non-privileged mode, so speeding up can be achieved, and protection of virtual spaces can also be realized.

Figure 3 is an application of Figure 1, in which virtual address 1 has a field that functions as an ATBR table pointer, and in this way, field 12 indicating the offset in the ATBR table is used. There may be.

[Effects of the Invention] As explained above, according to the present invention, switching between multiple virtual spaces can be realized in non-privileged mode, and high-speed switching is possible because switching can be performed in non-privileged mode. This can be done without compromising the protection functions of the system.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an address conversion method by a device according to an embodiment of the present invention, FIG. 2 is a diagram showing a state of high-speed stack switching by a virtual space management device according to the present invention, and FIG. FIG. 4, which is a diagram showing another embodiment, is a diagram showing a conversion process in a conventional address conversion device. 1...Virtual address 2...Field 3 indicating the offset within the physical page...Field 4 indicating the offset within the AT...Field 5 indicating the ATBR...・Physical address space 6...Physical page 7...Physical addresses 8, 9...AT 10...ATBR table 11...ATBR table pointer 12...
- Field indicating the offset in the ATBR table 13... Stack virtual space (used by Colchin A) 14... Stack virtual space (used by Colchin B) A5... Cortin A (in progress) AT...Corin A (suspended) B6...Corin B (in progress) B8...Corin B (in progress) 1, If・・・User virtual space agent Patent attorney Yoshiyuki Iwasa

Claims (1)

[Claims] (1) A virtual space management device for an information processing system that has a memory management device that converts an address recognized by a CPU into an address in a storage device, and has a privileged mode and a non-privileged mode as running modes, the address conversion A virtual space management device characterized by having a plurality of candidates that can be taken as values of a register in which table information is stored, and comprising means for selecting a candidate to be adopted in a non-privileged mode.