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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 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.

> + 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

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