Re: [PATCH 2/2] alpha/ptrace: Add missing switch_stack frames

[Al Viro <viro@xxxxxxxxxxxxxxxxxx>]

On Wed, Jun 16, 2021 at 01:32:50PM -0500, Eric W. Biederman wrote:

> -.macro	fork_like name
> +.macro	allregs name
>  	.align	4
>  	.globl	alpha_\name
>  	.ent	alpha_\name
> +	.cfi_startproc
>  alpha_\name:
>  	.prologue 0
> -	bsr	$1, do_switch_stack
> +	SAVE_SWITCH_STACK
>  	jsr	$26, sys_\name
> -	ldq	$26, 56($sp)
> -	lda	$sp, SWITCH_STACK_SIZE($sp)
> +	RESTORE_SWITCH_STACK

	No.  You've just added one hell of an overhead to fork(2),
for no reason whatsoever.  sys_fork() et.al. does *NOT* modify the
callee-saved registers; it's plain C.  So this change is complete
BS.

> +allregs exit
> +allregs exit_group

	Details, please - what exactly makes exit(2) different from
e.g. open(2)?