linux-kernel - Re: [PATCH 3/8] x86/mce: Provide method to find out the type of exception handle

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Date:   Tue, 15 Sep 2020 09:24:55 -0700
From:   "Luck, Tony" <tony.luck@...el.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Youquan Song <youquan.song@...el.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/8] x86/mce: Provide method to find out the type of
 exception handle

On Tue, Sep 15, 2020 at 11:11:32AM +0200, Borislav Petkov wrote:
> On Tue, Sep 08, 2020 at 10:55:14AM -0700, Tony Luck wrote:
> > Avoid a proliferation of ex_has_*_handler() functions by having just
> > one function that returns the type of the handler (if any).
> > 
> > Signed-off-by: Tony Luck <tony.luck@...el.com>
> > ---
> >  arch/x86/include/asm/extable.h     |  9 ++++++++-
> >  arch/x86/kernel/cpu/mce/severity.c |  5 ++++-
> >  arch/x86/mm/extable.c              | 12 ++++++++----
> >  3 files changed, 20 insertions(+), 6 deletions(-)
> > 
> > diff --git a/arch/x86/include/asm/extable.h b/arch/x86/include/asm/extable.h
> > index d8c2198d543b..56ec02e024ad 100644
> > --- a/arch/x86/include/asm/extable.h
> > +++ b/arch/x86/include/asm/extable.h
> > @@ -29,10 +29,17 @@ struct pt_regs;
> >  		(b)->handler = (tmp).handler - (delta);		\
> >  	} while (0)
> >  
> > +enum handler_type {
> > +	HANDLER_NONE,
> > +	HANDLER_FAULT,
> > +	HANDLER_UACCESS,
> > +	HANDLER_OTHER
> 
> EX_HANDLER_* I guess - HANDLER is too generic.

Yup. Will change.

> > @@ -125,17 +125,21 @@ __visible bool ex_handler_clear_fs(const struct exception_table_entry *fixup,
> >  }
> >  EXPORT_SYMBOL(ex_handler_clear_fs);
> >  
> > -__visible bool ex_has_fault_handler(unsigned long ip)
> > +__visible enum handler_type ex_fault_handler_type(unsigned long ip)
> 
> Why __visible?

I didn't look that hard at this. Just kept the same because the
function I was replacing was also __visible.

But it looks like this commit:

  80a3e3949b8f ("x86/extable: Mark exception handler functions visible")

shouldn't have touched this function. This one is only called from C code,
not from assembler like the others.

Will drop the __visible (and note in commit comment)

Thanks

-Tony