linux-kernel - Re: [PATCH v2] powerpc: Wire up clone3 syscall

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Date:   Wed, 24 Jul 2019 16:21:57 +0200
From:   Christian Brauner <christian@...uner.io>
To:     Michael Ellerman <mpe@...erman.id.au>
Cc:     linuxppc-dev@...abs.org, linux-kernel@...r.kernel.org,
        asolokha@...kras.ru
Subject: Re: [PATCH v2] powerpc: Wire up clone3 syscall

On Thu, Jul 25, 2019 at 12:02:59AM +1000, Michael Ellerman wrote:
> Wire up the new clone3 syscall added in commit 7f192e3cd316 ("fork:
> add clone3").
> 
> This requires a ppc_clone3 wrapper, in order to save the non-volatile
> GPRs before calling into the generic syscall code. Otherwise we hit
> the BUG_ON in CHECK_FULL_REGS in copy_thread().
> 
> Lightly tested using Christian's test code on a Power8 LE VM.
> 
> Signed-off-by: Michael Ellerman <mpe@...erman.id.au>

Acked-by: Christian Brauner <christian@...uner.io>

> ---
>  arch/powerpc/include/asm/unistd.h        | 1 +
>  arch/powerpc/kernel/entry_32.S           | 8 ++++++++
>  arch/powerpc/kernel/entry_64.S           | 5 +++++
>  arch/powerpc/kernel/syscalls/syscall.tbl | 1 +
>  4 files changed, 15 insertions(+)
> 
> v2: Add the wrapper for 32-bit as well, don't allow SPU programs to call
>     clone3 (switch ABI to nospu).
> 
> v1: https://lore.kernel.org/r/20190722132231.10169-1-mpe@ellerman.id.au
> 
> diff --git a/arch/powerpc/include/asm/unistd.h b/arch/powerpc/include/asm/unistd.h
> index 68473c3c471c..b0720c7c3fcf 100644
> --- a/arch/powerpc/include/asm/unistd.h
> +++ b/arch/powerpc/include/asm/unistd.h
> @@ -49,6 +49,7 @@
>  #define __ARCH_WANT_SYS_FORK
>  #define __ARCH_WANT_SYS_VFORK
>  #define __ARCH_WANT_SYS_CLONE
> +#define __ARCH_WANT_SYS_CLONE3
>  
>  #endif		/* __ASSEMBLY__ */
>  #endif /* _ASM_POWERPC_UNISTD_H_ */
> diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
> index 85fdb6d879f1..54fab22c9a43 100644
> --- a/arch/powerpc/kernel/entry_32.S
> +++ b/arch/powerpc/kernel/entry_32.S
> @@ -597,6 +597,14 @@ END_FTR_SECTION_IFSET(CPU_FTR_NEED_PAIRED_STWCX)
>  	stw	r0,_TRAP(r1)		/* register set saved */
>  	b	sys_clone
>  
> +	.globl	ppc_clone3
> +ppc_clone3:
> +	SAVE_NVGPRS(r1)
> +	lwz	r0,_TRAP(r1)
> +	rlwinm	r0,r0,0,0,30		/* clear LSB to indicate full */
> +	stw	r0,_TRAP(r1)		/* register set saved */
> +	b	sys_clone3
> +
>  	.globl	ppc_swapcontext
>  ppc_swapcontext:
>  	SAVE_NVGPRS(r1)
> diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
> index d9105fcf4021..0a0b5310f54a 100644
> --- a/arch/powerpc/kernel/entry_64.S
> +++ b/arch/powerpc/kernel/entry_64.S
> @@ -487,6 +487,11 @@ _GLOBAL(ppc_clone)
>  	bl	sys_clone
>  	b	.Lsyscall_exit
>  
> +_GLOBAL(ppc_clone3)
> +       bl      save_nvgprs
> +       bl      sys_clone3
> +       b       .Lsyscall_exit
> +
>  _GLOBAL(ppc32_swapcontext)
>  	bl	save_nvgprs
>  	bl	compat_sys_swapcontext
> diff --git a/arch/powerpc/kernel/syscalls/syscall.tbl b/arch/powerpc/kernel/syscalls/syscall.tbl
> index f2c3bda2d39f..43f736ed47f2 100644
> --- a/arch/powerpc/kernel/syscalls/syscall.tbl
> +++ b/arch/powerpc/kernel/syscalls/syscall.tbl
> @@ -516,3 +516,4 @@
>  432	common	fsmount				sys_fsmount
>  433	common	fspick				sys_fspick
>  434	common	pidfd_open			sys_pidfd_open
> +435	nospu	clone3				ppc_clone3
> -- 
> 2.20.1
>