Messages in this thread | | | Date | Sat, 11 Apr 2015 01:18:31 +0200 | From | Andi Kleen <> | Subject | Re: [PATCH 4/8] x86: Add support for rd/wr fs/gs base |
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On Fri, Apr 10, 2015 at 04:15:39PM -0700, Andy Lutomirski wrote: > On Fri, Apr 10, 2015 at 4:05 PM, Andi Kleen <andi@firstfloor.org> wrote: > >> One might argue that this code serves no purpose, but it's there, so > >> we had better keep our per-invocation usage of DEBUG_STACK within 4k. > > > > Only if you run NKLD. I doubt KDB or GDB support nesting. > > We can ask Jan if he still uses it. > > You can trigger these things in various ways with kprobes, > single-stepping, and user-space watchpoints. These things can > definitely nest in interesting ways. Whether or not the IST shift > mechanism is involved if they nest is a complicated question, because > there's also the "debug" IDT in play.
Yes we need it for (old style) kprobes in those paths.
For user space it shouldn't matter.
-Andi
-- ak@linux.intel.com -- Speaking for myself only.
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