Re: [PATCH 02/15] arm: __NR_syscalls fix

[Russell King - ARM Linux]

On Fri, Apr 11, 2014 at 01:50:50PM +0200, Miklos Szeredi wrote:
> On Fri, Apr 11, 2014 at 12:33 PM, Russell King - ARM Linux
> <linux@xxxxxxxxxxxxxxxx> wrote:
> > On Fri, Apr 11, 2014 at 12:25:38PM +0200, Miklos Szeredi wrote:
> >> From: Miklos Szeredi <mszeredi@xxxxxxx>
> >>
> >> Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxx>
> >> Cc: Russell King <linux@xxxxxxxxxxxxxxxx>
> >> ---
> >
> > This has me wondering...
> >
> > (a) what you think it fixes
> > (b) whether you tried to build-test this
> >
> > The ARM instruction set supports 8-bit immediate constants with an even
> > power of two shift.  384 fits that (0x180), 382 does not (0x17e), and
> > in your following patch, 383 definitely doesn't (0x17f).
> >
> > Having this constant larger than necessary does not cause any problem
> > for the syscall table: we explicitly pad it with calls to sys_ni_syscall
> > to make up the difference.
> 
> Yes, and the padding will be of wrong length if NR_syscalls is
> incorrect (which may be Oopsable?).  At least that is my impression
> from a casual glance.

Please explain.

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