Messages in this thread | | | Date | Thu, 7 Apr 2005 13:17:28 -0400 (EDT) | From | "Richard B. Johnson" <> | Subject | Re: crash in entry.S restore_all, 2.6.12-rc2, x86, PAGEALLOC |
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On Thu, 7 Apr 2005, Dave Jones wrote:
> On Thu, Apr 07, 2005 at 07:47:41AM -0700, Linus Torvalds wrote: > > > So the sysenter sequence might as well look like > > > > pushl $(__USER_DS) > > pushl %ebp > > sti > > pushfl > > .. > > > > which actually does three protected pushes thanks to the one-instruction > > "interrupt shadow" after an sti. > > Is this guaranteed on every x86 variant (or rather, every one > that has SEP). ? > > Dave
The i486 book says that if the next instruction lets the IF flag remain enabled, then any interrupts pending occur after the next instruction. If the next instruction is CLI, no interrupts will occur. There is a note:
"In case of an NM1, trap, or fault following ST1, the interrupt will be taken before executing the next sequential instruction in the code." The use of "NM1" and "ST1" is (sic). I don't know what NM1 is, it can't be NMI because, by definition NMI is not maskable so CLI and STI could not affect this pin.
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