Messages in this thread | | | Date | Thu, 6 Sep 2018 11:50:05 +0200 | From | Borislav Petkov <> | Subject | Re: [PATCH v2 1/3] x86/entry/64: Document idtentry |
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On Mon, Sep 03, 2018 at 03:59:42PM -0700, Andy Lutomirski wrote: > The idtentry macro is complicated and magical. Document what it > does to help future readers and to allow future patches to adjust > the code and docs at the same time. > > Signed-off-by: Andy Lutomirski <luto@kernel.org> > --- > arch/x86/entry/entry_64.S | 35 +++++++++++++++++++++++++++++++++++ > arch/x86/kernel/traps.c | 4 ++++ > 2 files changed, 39 insertions(+) > > diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S > index 957dfb693ecc..1796c42e08af 100644 > --- a/arch/x86/entry/entry_64.S > +++ b/arch/x86/entry/entry_64.S > @@ -900,6 +900,41 @@ apicinterrupt IRQ_WORK_VECTOR irq_work_interrupt smp_irq_work_interrupt > */ > #define CPU_TSS_IST(x) PER_CPU_VAR(cpu_tss_rw) + (TSS_ist + ((x) - 1) * 8) > > +/** > + * idtentry - Generate an IDT entry stub > + * @sym: Name of the generated entry point > + * @do_sym: C function to be called > + * @has_error_code: True if this IDT vector has an error code on the stack > + * @paranoid: non-zero means that this vector may be invoked from kernel > + * mode with user GSBASE and/or user CR3. 2 is special -- see below. > + * @shift_ist: Set to an IST index if entries from kernel mode should > + * decrement the IST stack so that nested entries get a fresh > + * stack. (This is for #DB, which has a nasty habit of > + * recursing.) > + * > + * idtentry generates an IDT stub that sets up a usable kernel context, > + * creates struct pt_regs, and calls @do_sym. The stub has the following > + * special behaviors: > + * > + * On an entry from user mode, the stub switches from the trampoline or > + * IST stack to the normal thread stack. On an exit to user mode, the > + * normal exit-to-usermode path is invoked. > + * > + * On an exit to kernel mode, if paranoid == 0, we check for preemption,
@paranoid
Otherwise, documenting our entry maze is always a good idea!
Reviewed-by: Borislav Petkov <bp@suse.de>
-- Regards/Gruss, Boris.
Good mailing practices for 400: avoid top-posting and trim the reply.
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