ModR/M byte and placement of control register contents
"A D" <[email protected]> Sat, 16 Jun 2007 17:20:17 -0400
| Newsgroups | org.kernel.vger.linux-assembly |
|---|---|
| Message-ID | <[email protected]> |
I'm a bit confused about the mov instruction that moves from or to control register to or from general purpose register. In intel's x86 manual it says: "At the opcode level, the reg field within the ModR/M byte specifies which of the control registers is loaded or read. The 2 bits in the mod field are always 11B. The r/m field specifies the general-purpose register loaded or read." So you can clearly see that segment register is specified by reg field and general purpose register is specified by r/m field. My question is how processor knows looking at the intel instruction that now if i mov the contents of control register to general purpose register(with the mov instruction), the processor now has to read contents from control register(not load to control register) and write to(not read from) general purpose register? Is there any special bit in the instruction format that speciefies it? Thanks. _________________________________________________________________ Windows Live Hotmail gives you the control you need to help you keep your e-mail private, safe and secure. See for yourself! www.newhotmail.ca?icid=WLHMENCA147