Al Viro <viro@xxxxxxxxxxxxxxxxxx> writes: > On Wed, Jun 16, 2021 at 08:25:35PM +0000, Al Viro wrote: >> 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)? > > Ah... PTRACE_EVENT_EXIT garbage, fortunately having no counterparts in case of > open(2)... Still, WTF would you want to restore callee-saved registers for > in case of exit(2)? Someone might want or try to read them in the case of exit. Which without some change will result in a read of other kernel stack content on alpha. Plus there are coredumps which definitely want to read everything. Although admittedly that case no longer matters. Eric
