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SubjectRe: [PATCH 20/25] arm64:ilp32: add sys_ilp32.c and a separate table (in entry.S) to use it
On Mon, Apr 25, 2016 at 09:19:13PM +0300, Yury Norov wrote:
> 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.

Now it's better, I think


diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index cf4d1ae..21312bb 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -715,16 +715,22 @@ 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
+ ldr x16, [tsk, #TI_FLAGS]
+#ifdef CONFIG_ARM64_ILP32
+ tbz x16, #TIF_32BIT_AARCH64, el0_lp64_svc // We are using ILP32
+ adrp stbl, sys_call_ilp32_table // load ilp32 syscall table pointer
+ b el0_svc_naked
+el0_lp64_svc:
+#endif
+ 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
ct_user_exit 1

- ldr x16, [tsk, #TI_FLAGS] // check for syscall hooks
- tst x16, #_TIF_SYSCALL_WORK
+ tst x16, #_TIF_SYSCALL_WORK // check for syscall hooks
b.ne __sys_trace
cmp scno, sc_nr // check upper syscall limit
b.hs ni_sys
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