Apparatus and method for controlling use of bounded pointers

A method of controlling use of bounded pointers within an apparatus having a plurality of bounded pointer storage elements, each bounded pointer storage element storing a bounded pointer and associated permission attributes indicative of allowed uses of the bounded pointer, the method comprising:

• providing a copy permission attribute within said associated permission attributes, the copy permission attribute indicating whether the bounded pointer is allowed to be subjected to a copy operation;
• and
• responsive to at least one instruction that specifies the copy operation, generating, from a source bounded pointer and associated permission attributes of a source bounded pointer storage element, a destination bounded pointer and associated permission attributes to be stored in a destination bounded pointer storage element, and marking the source bounded pointer storage element as storing an invalid bounded pointer dependent on whether the copy permission attribute of the source bounded pointer has a first value indicating that the source bounded pointer is to be prevented from being subjected to the copy operation, whereas when the copy permission attribute has a second value indicating that the source bounded pointer is allowed to be subjected to the copy operation, retaining the source bounded pointer storage element as storing a valid bounded pointer;
• providing each bounded pointer storage element with a validity field associated therewith to indicate whether the bounded pointer storage element stores a valid bounded pointer;
• and
• marking the source bounded pointer storage element as storing an invalid bounded pointer by updating the validity field associated with the source bounded pointer storage element to identify that the source bounded pointer is invalid.

An apparatus, comprising:

• a plurality of bounded pointer storage element means, each bounded pointer storage element means for storing a bounded pointer and associated permission attributes indicative of allowed uses of the bounded pointer, said associated permission attributes comprising a copy permission attribute indicating whether the bounded pointer is allowed to be subjected to a copy operation;
• and
• processing means for generating from a source bounded pointer and associated permission attributes of a source bounded pointer storage element means, in response to at least one instruction that specifies the copy operation, a destination bounded pointer and associated permission attributes to be stored in a destination bounded pointer storage element means, and for marking the source bounded pointer storage element means as storing an invalid bounded pointer dependent on whether the copy permission attribute of the source bounded pointer has a first value indicating that the source bounded pointer is to be prevented from being subjected to the copy operation, whereas when the copy permission attribute has a second value indicating that the source bounded pointer is allowed to be subjected to the copy operation, the processing means is arranged to retain the source bounded pointer storage element means as storing a valid bounded pointer;
• wherein
• each bounded pointer storage element means has a validity field associated therewith to indicate whether the bounded pointer storage element means stores a valid bounded pointer, and the processing means is arranged to mark the source bounded pointer storage element means as storing an invalid bounded pointer by updating the validity field associated with the source bounded pointer storage element means to identify that the source bounded pointer is invalid.