Subject: [PATCH 14/20] arm64: ilp32: add sys_ilp32.c and a separate table (in entry.S) to use it

From: [email-masked] (James Morse)
Date: Thu, 08 Jun 2017 16:05:36 +0100

Hi Yury,

On 04/06/17 13:00, Yury Norov wrote:
> From: Andrew Pinski <[email-masked]>
> 
> Add a separate syscall-table for ILP32, which dispatches either to native
> LP64 system call implementation or to compat-syscalls, as appropriate.

(I'm still reading through this series trying to understand it, but spotted this: )

> diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
> index 279bc2ab10c3..7d52fe1ec6bd 100644
> --- a/arch/arm64/kernel/entry.S
> +++ b/arch/arm64/kernel/entry.S
> @@ -577,6 +594,7 @@ el0_svc_compat:
>  	 * AArch32 syscall handling
>  	 */
>  	adrp	stbl, compat_sys_call_table	// load compat syscall table pointer
> +	ldr     x16, [tsk, #TSK_TI_FLAGS]
>  	uxtw	scno, w7			// syscall number in w7 (r7)
>  	mov     sc_nr, #__NR_compat_syscalls
>  	b	el0_svc_naked
> @@ -798,15 +816,21 @@ ENDPROC(ret_from_fork)
>  	.align	6
>  el0_svc:
>  	adrp	stbl, sys_call_table		// load syscall table pointer
> +	ldr	x16, [tsk, #TSK_TI_FLAGS]
>  	uxtw	scno, w8			// syscall number in w8
>  	mov	sc_nr, #__NR_syscalls
> +#ifdef CONFIG_ARM64_ILP32
> +	tst	x16, #_TIF_32BIT_AARCH64
> +	b.eq	el0_svc_naked			// We are using LP64  syscall table
> +	adrp	stbl, sys_call_ilp32_table	// load ilp32 syscall table pointer
> +	delouse_input_regs
> +#endif
>  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, #TSK_TI_FLAGS]	// check for syscall hooks

If built with CONFIG_CONTEXT_TRACKING, ct_user_exit will call
context_tracking_user_exit(), this will clobber x16 which you depend on not
changing below:

> -	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

Thanks,

James