KR20040051017A - Method For Tracing Memory Alternate In Multi-Task System - Google Patents

Abstract

PURPOSE: A method for tracing the memory change on a multitask system is provided to trace the abnormal memory change through a memory protecting function of an MMU(Memory Management Unit) by setting a memory change trace function with use of a memory address and a data value stored in the address when the data value of the memory address is abnormally changed in the multitask system. CONSTITUTION: In case that the data value stored in the memory address is changed by the unauthorized task execution, the memory change trace function is set by using the memory address and the data value stored in the address(S32). In the case that the task execution having the set memory address and the data value is detected from the MMU, the task information and the task work information are stored in a register(S34). The abnormal memory change trace information including the task information and the task work information stored in the register are informed to a system operator(S35).

Description

Method for Tracing Memory Alternate In Multi-Task System}

The present invention relates to a memory change tracking function in a multitask system. In particular, when a data value stored at a specific address of a memory used by each task is abnormally changed by another task, the system can be tracked by such a memory change. The present invention relates to a memory change tracking method in a multitasking system that can notify an operator.

In a general system, a basic unit of a program controlled by an operating system is called a task. Most operating systems support multitasking in which a plurality of tasks are executed at the same time. Use by dividing by a certain area.

Each task includes a text area in which its program contents are stored, a global variable used in the text area, and the like, as shown in FIG. 1. In the text area, the program content, that is, the code that defines what task is to be performed, is stored in the text area. Therefore, it should be read-only because it should be protected without change by random access.

However, the data area should be able to be read and written because the variable value should be changed according to the task execution, but the data area used for each task should not be changed by the access of other tasks.

In this case, the function to prevent the data area from being changed by the access of another task should be supported by the kernel of the operating system. However, in the case of a kernel that does not support this, other data areas other than its own data area may be executed during the task execution. There is a case where a value of a specific memory address is changed by write access, and in this case, there is a problem that it is impossible to keep track of which task has changed the value.

That is, in a conventional multitasking environment, a task in which abnormal data processing or a logical error occurs may access a data area of a task other than its own data area, and at this time, a write operation may be performed in the data area of another task. If a specific value is modified by executing, there is a problem that normal operation cannot be performed due to the modified value when executing a task that actually has access to the data area.

In addition, in this case, the system operator cannot easily track which task has changed the data area of the task in which the current problem occurs, which makes debugging difficult.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to change a memory using a corresponding memory address and a data value to be stored at the address when a data value of a specific memory address is abnormally changed in a multitask system. By setting the tracking function, it is possible to track the corresponding abnormal memory change by using the memory protection function of the memory management unit.

Another object of the present invention is to notify the system operator of abnormal memory change tracking information tracked using the memory protection function of the memory management unit, whereby the system operator can know that the memory has been abnormally changed by executing some task of a task. The purpose of this is to enable efficient debugging.

1 is a diagram illustrating a memory partition state used by each task in a general multitasking system.

2 is a diagram illustrating a software system configuration for performing a memory change tracking function in a multitasking system according to the present invention.

3 is a flow chart illustrating a memory change tracking operation in a multitask system in accordance with the present invention.

FIG. 4 is an operational flow diagram for setting a memory address for which memory change is to be tracked and a data value to be stored at that address in FIG.

FIG. 5 is a diagram illustrating a connection structure of a supervisory structure and a data supervisory structure for managing a memory address set by FIG. 4 and a data value to be stored at the address; FIG.

FIG. 6 is a flowchart illustrating an operation of tracking a data value change for a memory address set in FIG. 4. FIG.

A feature of the present invention for achieving the object described above is that memory change tracking using the memory address and the data value to be stored at that address if the data value stored at a particular memory address is changed by an unauthorized task execution. Setting a function; Storing a corresponding task information and task task information in a register when a task execution having the memory address and data value set in the memory management unit is detected; The present invention provides a memory change tracking method in a multitask system including notifying a system operator of abnormal memory change tracking information including task information and task work information stored in the register.

The setting of the memory change tracking function may include requesting data change tracking for a corresponding memory address using an abnormally changed memory address and a data value to be stored at the address; After calculating a page number using the memory address, checking whether a watch structure having a page number corresponding to a data watch list exists; And if there is a supervisor structure having a corresponding page number, recording the memory address and data values to be stored at the new data supervisor structure, and then connecting the supervisor structure in a linked list manner.

Changing a read-only state of a page including a corresponding memory address if a supervisor structure having a page number calculated using the memory address does not exist; And allocating a new watch structure to record the page number, and then linking the data watch list to the data watch list in a linked list manner.

The storing of the task information and task task information in a register may include analyzing a command executed by a task to extract a memory address to be accessed by the task, a data value to be stored at the address, and a size thereof; ; Calculating a page number using the extracted memory address and checking whether a data monitoring structure having the extracted memory address and data value exists among data monitoring structures connected to the monitoring structure having a corresponding page number; Storing a task information for accessing the memory address and a task information of the task in a register when a data monitoring structure having the extracted memory address and data value exists.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In a system having a multitask environment according to the present invention, when a value stored in a specific data area of a memory is changed by another task execution, a memory protection function of a memory management unit is used for efficient debugging. The corresponding memory change is tracked and notified to the system operator. The software system configuration for this is shown in FIG. 2, in which a plurality of tasks are assigned a specific allocation area of memory through the kernel and the memory management unit. A memory management unit implemented between the kernel and the memory may have a specific data area in memory due to abnormal access of other tasks that are not allowed according to the memory change tracking request set by the system operator. To track changes The memory change tracking information is stored in a register.

At this time, when the data value stored in a specific memory address is abnormally changed, the system operator presets an address of a specific data area of a corresponding memory and a data value to be stored at the address through an interface provided by the kernel. By requesting data change tracking for a memory address, it is possible to track changes in the data value of a particular memory address to another value.

That is, in the memory management unit, when another unauthorized task accesses an address of a predetermined data area and records a different value, abnormal memory access occurs while a task is performing a task according to a memory change tracking request from a system operator. The memory change tracking information is stored in a register by tracking whether it has occurred, and the kernel notifies the system operator of abnormal memory change tracking information stored in a register by using a dynamic skeleton interface (DSI) exception processing function.

An abnormal memory change tracking operation in a multitask system having such a configuration will be described with reference to FIG. 3. First, in a memory management unit, when a data value stored in a specific memory address is changed by another task execution, The memory change tracking function is set by receiving a memory address and a data value to be stored at the address (steps S31 and S32).

When the memory change tracking function is set in this way, the memory management unit uses the memory protection function to determine whether a task execution with the previously set memory address and data value occurs, that is, an unauthorized task accesses the previously set memory address and the data value. (Step S33), if a task execution having a corresponding memory address and data value is detected, the task information and task task information, that is, a memory address corresponding to which task is executing any task The tracking information as to whether the data value of the data has been changed is stored in the register (step S34).

Thereafter, the kernel notifies the system operator of abnormal memory change tracking information including the task information and the task task information stored in the register so that efficient debugging can be performed (step S35).

In more detail, the above-described memory change tracking function may generate a lot of load when performing the entire address areas of the memory. Therefore, the memory change tracking function may be limited to a specific data area preset by the system operator. In this case, the system operator sets an address of a specific data area of a memory to be monitored and a data value to be stored in the address through an interface provided by the kernel through the procedure as shown in FIG. 4.

In other words, if the data value of a specific memory address is changed due to abnormal memory access when the task is executed, the system operator uses the abnormally changed memory address and the data value to be stored at the address when the task is executed for debugging. The data change tracking is requested (step S41).

Then, the kernel first checks whether the data monitoring function has been previously set, that is, whether the DSI exception processing function using the memory protection function of the memory management unit is registered (step S42).

At this time, when the DSI exception handling function using the memory protection function is registered, an empty data watcher structure (datawatcher_t) is set to set an address (that is, a specific memory address) and a value to be stored in the data area to be monitored. ) Is imported (step S43).

However, if the DSI exception handling function using the memory protection function is not registered, a new DSI exception handling function may be used to track data changes to a specific memory address set by the system operator using the memory management function of the memory management unit. After registration (step S42-1), an empty data monitoring structure is obtained (step S43).

After the empty data monitoring structure is obtained, a page number is calculated by using a memory address that the system operator wants to monitor (step S44). For example, assuming that the memory size is 10 Mbytes and the size of one page serving as the memory management unit is 1 Mbyte, the page number is calculated within the range of 1 to 10.

Subsequently, a watch list (watcher_t list) implemented in the kernel is searched to determine whether a page number calculated above exists, that is, a watch structure having the calculated page number exists (step S45).

At this time, if the page number calculated using the memory address to be monitored by the current system operator does not exist in the data monitoring list, it means that there is no watch structure having the corresponding page number. Change the page containing the read-only state (step S46), allocate an empty watch structure (watcher_t), record the corresponding page number, and then use the linked list method in the data watch list structure. It connects (step S47).

After connecting the watch structure having the page number including the memory address to be monitored to the data watch list structure, the specific memory address that the current system operator wants to monitor and the data value to be stored in the data watch structure obtained earlier And the data size are recorded together with the identifier information (step S48), and the corresponding data monitoring structure is connected to the previously connected monitoring structure using the linked list method (step S49).

However, if the page number calculated using the specific memory address that the current system operator wants to monitor in step S45 exists in the data monitoring list, the monitoring structure having the corresponding page number is already allocated and the specific monitoring target Since the page to which the memory address belongs is already changed to read-only state, the data monitoring structure obtained in step S43 indicates the specific memory address that the current system operator wants to monitor, and the data value and data size to be stored at the address together with the identifier information. After recording (step S48), the corresponding data monitoring structure is connected to the monitoring structure having the page number calculated above by the linked list method (step S49).

As described above, the system operator writes a specific memory address to be monitored and the data value to be stored in the memory address in the data monitoring structure, and connects it to the page-specific monitoring structure to which the corresponding memory address belongs in a linked list manner. Because of abnormal memory access of, you can set the monitoring function for the changed memory address, that is, the memory change tracking function for the specific memory address.

Meanwhile, the connection structure of the above-described supervisory structure and the data supervisory structure can be described with reference to FIG. 5, which is attached to a specific memory address set by the system operator in the kernel to track a memory change and the address. This figure shows the structure that manages data values to be stored.It divides memory into page units for efficient management and manages it as a monitoring structure, and the specific memory address set by the system operator for each page and the data to be stored in the address The data monitoring structures in which values are recorded are managed by linking list method.

Next, after setting the specific memory address, which is the address of the specific data area for which the system operator wants to track the memory change, and the data value to be stored at the address, the memory management unit tracks the memory access of each task to the system operator. When a data value of a specific memory address set by the controller is changed, a series of memory change tracking operations for notifying the system operator are performed. This will be described in detail with reference to FIG. 6.

When a task executed in the above-described system executes a predetermined instruction, the memory management unit analyzes the instruction of the task to store a memory address (i.e., store a specific data value) that is to be accessed. The memory address to be accessed), the data value to be stored at the address, and its size (steps S61 and S62).

After calculating the page number to which the memory address belongs, using the memory address to which the task currently accesses among the memory access related information extracted earlier (step S63), the data monitoring list shown in FIG. 4 is searched to find the same page number. It is checked whether or not a data monitoring structure having a memory address and a data value that the task currently wants to access exists among the data monitoring structures connected to the monitoring structure having (step S64).

In this case, when there is no watch structure having a page number calculated using a memory address that the task wants to access, or a data watch structure having a memory address and a data value that the task wants to access does not exist Since it is not an access to the memory address to be monitored, the memory is accessed in accordance with a normal task instruction execution procedure to perform data processing (step S65), and then waits for execution of the next instruction of the task.

However, if there is a data monitoring structure with the memory address and data value that the task wants to access, it means that the task has changed the data value by abnormally accessing a specific memory address assigned to another task. The task information for accessing the memory address to be stored and the task task information for which a specific data value is to be stored in the corresponding memory address while the task is performing the task are stored in the register (step S66).

Then, the kernel uses the DSI exception handling function to notify the system operator of abnormal memory change tracking information including task information and task operation information stored in registers (step S67), and the system operator uses abnormal memory change tracking information. This allows for quick and accurate debugging.

Also, the kernel that notified the memory change tracking information to the system operator suspends the execution of the task, and when the kernel operator receives the exit (exit, quit) command from the system operator that checks the memory change tracking information, the kernel pauses. It will return from and continue the task execution.

On the other hand, the embodiment according to the present invention is not limited to the above, it can be carried out by various alternatives, modifications and changes within the scope apparent to those skilled in the art with respect to the present invention.

As described above, according to the present invention, when the data value of a specific memory address is abnormally changed in a multitask system, the memory change tracking function is set by using a corresponding memory address and a data value to be stored at the address. By using the memory protection function, it is possible to track the corresponding abnormal memory change, and by notifying the system operator with this abnormal memory change tracking information, it is possible to know that the memory has been abnormally changed by the execution of any task of a task, so that efficient debugging can be performed. It can be done.

Claims (4)

Setting a memory change tracking function using the memory address and the data value to be stored at the address when a data value stored at a specific memory address is changed by an unauthorized task execution; Storing a corresponding task information and task task information in a register when a task execution having the memory address and data value set in the memory management unit is detected; And notifying the system operator of abnormal memory change tracking information including task information and task operation information stored in the register. The method of claim 1, The setting of the memory change tracking function may include requesting data change tracking for a corresponding memory address using an abnormally changed memory address and a data value to be stored at the address; After calculating a page number using the memory address, checking whether a watch structure having a page number corresponding to a data watch list exists; If there is a supervisor structure having a corresponding page number, recording the memory address and data values to be stored at the new data supervisor structure, and then connecting the supervisor structure in a linked list manner. How to track memory changes on task systems. The method of claim 2, Changing a read-only state of a page including a corresponding memory address when a monitoring structure having a page number calculated by using the memory address does not exist; And allocating a new watch structure to record the page number, and then linking the data watch list to the data watch list in a linked list manner. The method of claim 1, The storing of the task information and task task information in a register may include analyzing a command executed by a task to extract a memory address to be accessed by the task, a data value to be stored at the address, and a size thereof; Calculating a page number using the extracted memory address and checking whether a data monitoring structure having the extracted memory address and data value exists among data monitoring structures connected to the monitoring structure having a corresponding page number; Storing a task information for accessing the memory address and a task information of the task in a register when the data monitoring structure having the extracted memory address and data value exists. How to track memory changes.