Messages in this thread | | | Date | Mon, 29 Sep 2014 21:33:58 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: [PATCH] x86 : Ensure X86_FLAGS_NT is cleared on syscall entry |
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On Mon, 29 Sep 2014, Sebastian Lackner wrote: > On 29.09.2014 19:40, Andy Lutomirski wrote: > Well, the best documentation I've found is something like > http://www.fermimn.gov.it/linux/quarta/x86/int.htm > > which states: > > --- snip --- > INTERRUPT-TO-INNER-PRIVILEGE: > [...] > TF := 0; > NT := 0; > --- snip --- > (Doesn't say anything about HW interrupts though) > > This also makes sense at my opinion, since the interrupt handler has > to know if it should return to the previous task (when NT=1) or to > the same task (when NT=0).
No, it does not. Simply because Linux does not support nested tasks at all, because the TSS is not accessible and the TSS.back_link is sturdily NULL. So even if it would not explode with a #GP in IA-32e mode it would explode while trying to execute the instruction at NULL.
> That might be possible. It probably makes sense to review other > parts of the code, for similar issues.
What's the issue? Stupid user space programs segfaulting?
Thanks,
tglx
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