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

On 04/06/17 13:00, Yury Norov wrote:
> From: Andrew Pinski <apinski@cavium.com>
>
> 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

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