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

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Message-ID: <20160425184740.GA2559@yury-N73SV>
Date:	Mon, 25 Apr 2016 21:47:40 +0300
From:	Yury Norov <ynorov@...iumnetworks.com>
To:	Catalin Marinas <catalin.marinas@....com>
CC:	<arnd@...db.de>, <linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>, <linux-arch@...r.kernel.org>,
	<linux-s390@...r.kernel.org>, <pinskia@...il.com>,
	<Prasun.Kapoor@...iumnetworks.com>, <schwab@...e.de>,
	<broonie@...nel.org>, <linux-doc@...r.kernel.org>,
	<heiko.carstens@...ibm.com>, <agraf@...e.de>,
	<klimov.linux@...il.com>,
	Andrew Pinski <Andrew.Pinski@...iumnetworks.com>,
	<bamvor.zhangjian@...wei.com>, Andrew Pinski <apinski@...ium.com>,
	<schwidefsky@...ibm.com>, <Nathan_Lynch@...tor.com>,
	<joseph@...esourcery.com>,
	<christoph.muellner@...obroma-systems.com>
Subject: Re: [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