[PATCH 20/25] arm64:ilp32: add sys_ilp32.c and a separate table (in entry.S) to use it

Yury Norov
2016-04-25T18:19:13Z

On Mon, Apr 25, 2016 at 06:26:56PM +0100, Catalin Marinas wrote:
> On Wed, Apr 06, 2016 at 01:08:42AM +0300, Yury Norov wrote:
> > --- a/arch/arm64/kernel/entry.S
> > +++ b/arch/arm64/kernel/entry.S
> > @@ -715,9 +715,13 @@ ENDPROC(ret_from_fork)
> > */
> > .align 6
> > el0_svc:
> > - adrp stbl, sys_call_table // load syscall table pointer
> > uxtw scno, w8 // syscall number in w8
> > mov sc_nr, #__NR_syscalls
> > +#ifdef CONFIG_ARM64_ILP32
> > + ldr x16, [tsk, #TI_FLAGS]
> > + tbnz x16, #TIF_32BIT_AARCH64, el0_ilp32_svc // We are using ILP32
> > +#endif
>
> There is another ldr x16, [tsk, #TI_FLAGS] load further down in the
> el0_svc_naked block. We should rework these a bit to avoid loading the
> same location twice unnecessarily. E.g. move the ldr x16 just before
> el0_svc_naked and branch one line after in case of the ILP32 syscall.
>

Yes, I thiks we can refactor it. Thanks for a catch.

> > + adrp stbl, sys_call_table // load syscall table pointer
> > el0_svc_naked: // compat entry point
> > stp x0, scno, [sp, #S_ORIG_X0] // save the original x0 and syscall number
> > enable_dbg_and_irq
> > @@ -737,6 +741,12 @@ ni_sys:
> > b ret_fast_syscall
> > ENDPROC(el0_svc)
> >
> > +#ifdef CONFIG_ARM64_ILP32
> > +el0_ilp32_svc:
> > + adrp stbl, sys_call_ilp32_table // load syscall table pointer
> > + b el0_svc_naked
> > +#endif
> > +
> > /*
> > * This is the really slow path. We're going to be doing context
> > * switches, and waiting for our parent to respond.
>
> --
> Catalin