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
