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

Al Viro
2021-06-16T20:25:55Z

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)?