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by kaushiks
3675 days ago
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LGDT is an instruction that Loads the Global Descriptor Table [1]. The CPU doesn't know about the persistence of local state in that it doesn't know (in this case), the significance of anything that is being pushed onto / restored from a frame around a call. It knows that a "PUSH R9" writes the value of R9 onto the region in the stack being currently pointed to by the stack pointer (RSP). It however doesn't know that this is being done because, the current frame has a live value in R9, which, per the ABI, the function being called is allowed to trash, as it is considered a volatile, callee saved register. Like I'd said earlier, these are just agreed upon conventions that might even change across compilers. I'd used the term "naked" the way the VC++ compiler uses it. A "naked" function is one without a prolog or an epilog [2]. [1] https://pdos.csail.mit.edu/6.828/2008/readings/i386/LGDT.htm [2] https://msdn.microsoft.com/en-us/library/21d5kd3a.aspx |
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