Re: [PATCH 2/2] ARC: run child from the separate start block in __clone

[Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>]

On 02/03/23 13:10, Pavel Kozlov via Libc-alpha wrote:
> From: Pavel Kozlov <pavel.kozlov@synopsys.com>
> 
> For better debug experience use separate code block with extra
> cfi_* directives to run child (same as in __clone3).

LGTM, thanks.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

> ---
>  sysdeps/unix/sysv/linux/arc/clone.S | 40 ++++++++++++++++++-----------
>  1 file changed, 25 insertions(+), 15 deletions(-)
> 
> diff --git a/sysdeps/unix/sysv/linux/arc/clone.S b/sysdeps/unix/sysv/linux/arc/clone.S
> index 766649625658..0029aaeb8170 100644
> --- a/sysdeps/unix/sysv/linux/arc/clone.S
> +++ b/sysdeps/unix/sysv/linux/arc/clone.S
> @@ -20,9 +20,6 @@
>  #include <sysdep.h>
>  #define _ERRNO_H	1
>  #include <bits/errno.h>
> -#include <tcb-offsets.h>
> -
> -#define CLONE_SETTLS		0x00080000
>  
>  /* int clone(int (*fn)(void *), void *child_stack,
>             int flags, void *arg, ...
> @@ -63,19 +60,9 @@ ENTRY (__clone)
>  	ARC_TRAP_INSN
>  
>  	cmp	r0, 0		/* return code : 0 new process, !0 parent.  */
> +	beq	thread_start_clone
>  	blt	L (__sys_err2)	/* < 0 (signed) error.  */
> -	jnz	[blink]		/* Parent returns.  */
> -
> -	/* child jumps off to @fn with @arg as argument
> -           TP register already set by kernel.  */
> -	jl.d	[r10]
> -	mov	r0, r11
> -
> -	/* exit() with result from @fn (already in r0).  */
> -	mov	r8, __NR_exit
> -	ARC_TRAP_INSN
> -	/* In case it ever came back.  */
> -	flag	1
> +	j	[blink]		/* Parent returns.  */
>  
>  L (__sys_err):
>  	mov	r0, -EINVAL
> @@ -89,5 +76,28 @@ L (__sys_err2):
>  	       position independent.  */
>  	b   __syscall_error
>  PSEUDO_END (__clone)
> +
> +
> +	.align 4
> +	.type thread_start_clone, %function
> +thread_start_clone:
> +	cfi_startproc
> +	/* Terminate call stack by noting ra is undefined.  */
> +	cfi_undefined (blink)
> +
> +	/* Child jumps off to @fn with @arg as argument.  */
> +	jl.d	[r10]
> +	mov	r0, r11
> +
> +	/* exit() with result from @fn (already in r0).  */
> +	mov	r8, __NR_exit
> +	ARC_TRAP_INSN
> +
> +	/* In case it ever came back.  */
> +	flag	1
> +
> +	cfi_endproc
> +	.size thread_start_clone, .-thread_start_clone
> +
>  libc_hidden_def (__clone)
>  weak_alias (__clone, clone)