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SubjectRe: [PATCH v2 3/3] x86/entry/64: Move #BP from IST to the IRQ stack
On Fri, Jul 24, 2015 at 10:57:06PM -0700, Andy Lutomirski wrote:
> There's nothing IST-worthy about #BP/int3. We don't allow kprobes
> in the small handful of places in the kernel that run at CPL0 with
> an invalid stack, and 32-bit kernels have used normal interrupt
> gates for #BP forever.
>
> Furthermore, we don't allow kprobes in places that have usergs while
> in kernel mode, so "paranoid" is also unnecessary.
>
> Signed-off-by: Andy Lutomirski <luto@kernel.org>
> ---
> arch/x86/entry/entry_64.S | 2 +-
> arch/x86/kernel/traps.c | 26 +++++++++++++-------------
> 2 files changed, 14 insertions(+), 14 deletions(-)

...

> @@ -494,7 +494,15 @@ dotraplinkage void notrace do_int3(struct pt_regs *regs, long error_code)
> if (poke_int3_handler(regs))
> return;
>
> + /*
> + * Use ist_enter despite the fact that we don't use an IST stack.
> + * We can be called from a kprobe in non-CONTEXT_KERNEL kernel
> + * mode or even during context tracking state changes.
> + *
> + * This means that we can't schedule. That's okay.
> + */
> ist_enter(regs);

Let's rename that thing. Call it atomic_ctxt_enter or whatever...

--
Regards/Gruss,
Boris.

ECO tip #101: Trim your mails when you reply.
--


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