Re: [Xen-devel] [PATCH 6 of 8] Xen: remove run_in_exception_handler() and recode its only caller

[Tim Deegan <Tim.Deegan@xxxxxxxxxx>]

At 15:15 +0000 on 07 Mar (1299510944), Keir Fraser wrote:
> On 07/03/2011 15:05, "Keir Fraser" <keir.xen@xxxxxxxxx> wrote:
> 
> > On 07/03/2011 11:26, "Tim Deegan" <Tim.Deegan@xxxxxxxxxx> wrote:
> > 
> >> (dump_execution_state()) as its own bug-trap.
> >> 
> >> This is needed to compile xen with clang, which can't handle using a
> >> function name in an asm immediate.
> > 
> > Actually run_in_exception_handler() does have another user, in ns16550.c.
> > Although non-essential, it makes the 'd' debug key much more useful when
> > running the UART in polled mode.
> > 
> > So I suggest we keep run_in_exception_handler but modify it to pass the
> > function pointer in (say) rAX.
> 
> Like the attached patch (against latest tip).

Sorry, I had missed that other user.  I'll see if I can find a way to
make clang use the function address directly; if not, I'd be inclined to 
have dump_execution_state have its own ID anyway, to keep %rax valid(er)
in BUG()s.

Tim.

> > I think we won't easily be able to use
> > BUG_STR() logic but r_i_e_h is only used (directly or indirectly) in a few
> > places so the BUG_STR optimisation is unimportant. The only other
> > disadvantage is that rAX is less interesting in the state dump, but any
> > value the function pointer displaces can still be found in the stack dump,
> > albeit with likely a little extra effort.
> > 
> > Sound good?
> > 
> >  -- Keir 
> > 
> >> Signed-off-by: Tim Deegan <Tim.Deegan@xxxxxxxxxx>
> >> 
> >> 
> >> _______________________________________________
> >> Xen-devel mailing list
> >> Xen-devel@xxxxxxxxxxxxxxxxxxx
> >> http://lists.xensource.com/xen-devel
> > 
> > 
> 



-- 
Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Principal Software Engineer, Xen Platform Team
Citrix Systems UK Ltd.  (Company #02937203, SL9 0BG)

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