User-level re-initialization instruction interception
A data processing system comprising an operating system for supporting processes, such that the process are associated with one or more resources and the operating system being arranged to police the accessing by processes of resources so as to inhibit a process from accessing resources with which it is not associated. Part of this system is an interface for interfacing between each process and the operating system and a memory for storing state information for at least one process. The interface may be arranged to analyze instructions from the processes to the operating system, and upon detecting an instruction to re-initialize a process cause state information corresponding to that pre-existing state information to be stored in the memory as state information for the re-initialized process and to be associated with the resource.
1. A data processing system comprising:
an operating system for supporting processes, each process being associated with one or more resources each identifiable by a file descriptor, the operating system being arranged to police the accessing by processes of resources so as to inhibit a process from accessing resources with which it is not associated, and being responsive to instructions of a certain type to re-initialize a process;
a user-level library for interfacing between each process and the operating system; and
a memory shared between the operating system and the user-level library for storing state information for at least one process, the state information being associated with a resource;
wherein the user-level library is arranged to intercept and analyze instructions from the processes to the operating system, and:
on detecting an instruction to re-initialize a process associated with a resource that is managed by the user-level library, cause state information equivalent to the pre-existing state information associated with said resource to be stored in the memory as state information for the re-initialized process and to be associated with the resource;
on detecting an instruction to re-initialize a process so as to be associated with a resource that is associated with pre-existing state information, store a record of that instruction and then pass the instruction to the operating system; and
on being called to configure state information for a process to check whether it has a record of there having been an instruction to re-initialize that process so as to be associated with a resource that is associated with pre-existing state information and:
if so, cause state information corresponding to that pre-existing state information to be stored in the memory as state information for the process and to be associated with the resource; and
otherwise generate fresh state information for the process.
2. A data processing system as claimed in claim 1 , wherein the said instructions include exec( )instructions.
3. A data processing system as claimed in claim 1 , wherein the user-level library is arranged to, when two or more resources are associated with the process, cause the said state information corresponding to the said pre-existing state information to be associated with the resource in response to an attempt to access the resource.
4. A data processing system as claimed in claim 1 , wherein the operating system is responsive to instructions of another type to duplicate a process.
5. A data processing system as claimed in claim 4 , wherein the said instructions of another type include fork( ) instructions.
6. A data processing system as claimed in claim 1 , wherein the resource with which the state information is associated is a memory area storing data for transmission and/or reception by the data processing system.
7. A data processing system as claimed in claim 6 , wherein the state information is one or more of: data transmission information, reception state information, information defining a virtual hardware interface, TCP windows, information defining unacknowledged buffers and information defining timeout values.
8. A data processing system as claimed in claim 1 , wherein the system is arranged to be capable of using the state information to form a memory mapping onto the resource.
9. A data processing system as claimed in claim 1 , wherein the operating system has a table indicating which state information is associated with which resource.
10. A data processing system as claimed in claim 1 , wherein the right of a process to access a resource is enabled by allocating a file descriptor associated with the resource to the process.
11. A data processing system as claimed in claim 1 , wherein a resource can be identifiable by multiple file descriptors.
12. A data processing system as claimed in claim 11 , wherein the operating system is arranged to, in response to instructions to re-initialize a process and allocate a new file descriptor to that process, preferentially allocate a new resource to that process, identifiable by the new file descriptor.
13. A non-transitory computer readable medium including a user-level library for use by a data processing system comprising an operating system for supporting processes, each process being associated with one or more resources each identifiable by a file descriptor, the operating system being arranged to police the accessing by processes of resources so as to inhibit a process from accessing resources with which it is not associated, and being responsive to instructions of a certain type to re-initialize a process and a memory shared between the operating system and the user-level library for storing state information for at least one process, the state information being associated with a resource;
wherein the user-level library is for interfacing between each process and the operating system and is arranged to intercept and analyze instructions from the processes to the operating system, the user-level library being arranged to:
on detecting an instruction to re-initialize a process associated with a resource that is managed by the user-level library, cause state information equivalent to that pre-existing state information associated with said resource to be stored in the memory as state information for the re-initialized process and to be associated with the resource;
on detecting an instruction to re-initialize a process so as to be associated with a resource that is associated with pre-existing state information, store a record of that instruction and then pass the instruction to the operating system; and
on being called to configure state information for a process to check whether it has a record of there having been an instruction to re-initialize that process so as to be associated with a resource that is associated with pre-existing state information and:
if so, cause state information corresponding to that pre-existing state information to be stored in the memory as state information for the process and to be associated with the resource; and
otherwise generate fresh state information for the process.
14. A method for processing instructions in a data processing system comprising: an operating system for supporting processes, each process being associated with one or more resources each identifiable by a file descriptor, the operating system being arranged to police the accessing by processes of resources so as to inhibit a process from accessing resources with which it is not associated, and being responsive to instructions of a certain type to re-initialize a process; a user-level library for interfacing between each process and the operating system; and a memory shared between the operating system and the user-level library for storing state information for at least one process, the state information being associated with a resource; the method comprising the steps of:
intercepting and analyzing instructions from the processes to the operating system; and
on detecting an instruction to re-initialize a process associated with a resource that is managed by the user-level library, causing state information equivalent to that pre-existing state information associated with said resource to be stored in the memory as state information for the re-initialize process and to be associated with the resource;
on detecting an instruction to re-initialize a process so as to be associated with a resource that is associated with pre-existing state information, storing a record of that instruction and then passing the instruction to the operating system; and
on being called to configure state information for a process to check whether it has a record of there having been an instruction to re-initialize that process so as to be associated with a resource that is associated with pre-existing state information and:
if so, causing state information corresponding to that pre-existing state information to be stored in the memory as state information for the process and to be associated with the resource; and
otherwise generating fresh state information for the process.