| 摘要 |
Embodiments of the present invention provide full benefit of the cover instruction provided by the Intel IA-64 architecture to code running at less than highest privilege level. In one embodiment of the present invention, prior to execution of a cover instruction by non-privileged code, the code obtains and stores the contents of the current-frame-marker register in memory. Then, the code executes a cover instruction to obtain a new, empty register stack frame and to relegate the registers of previously allocated stack frames to the dirty-register status. Subsequently, the processor state represented by the register values of the stack frame that was current when the cover instruction was executed can be recovered by first executing another cover instruction, computing a previous-frame-marker-register value and placing the computed value into the previous-frame-marker register, executing a first branch (br.ret) return instruction, moving the saved contents of the current-frame-marker register from memory into the previous-frame-marker register, and executing a second branch return instruction.
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